Monitoring and Movements of the Preble's Meadow Jumping Mouse

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Monitoring and Movements of the

Preble’s Meadow Jumping Mouse (Zapus hudsonius preblei)

in Montane Drainages of the

Pike National Forest, Colorado.

CRAIG MCDOWELL HANSEN

B.A., Bowdoin College, 2002.

A thesis submitted to the Graduate Faculty of the

University of Colorado at Colorado Springs

in partial fulfillment of the

requirements for the degree of

Master of Science

Department of Biology

2006

This thesis for the Master of Science degree by

Craig McDowell Hansen

has been approved for the

Department of Biology

______Dr. Jon Pigage

______Dr. Karen Newell

______Dr. Tom Wolkow

______Date

DEDICATED TO:

Denny Bohon, United States Forest Service Wildlife Biologist, for the generous grant that made this three-year study possible and for her guidance and support throughout the project.

AND IN MEMORY OF:

Professor Paul Nyhus, Bowdoin College, an inspiring mentor.

CHAPTER 1

INTRODUCTION

Zapus hudsonius preblei, the Preble’s meadow jumping mouse (henceforth-

Preble’s), distinguished by its specialized ecological requirements and unique morphologic traits, is a rare subspecies of Zapus hudsonius. As a collective species, meadow jumping mice are broadly distributed across the upper latitudes of North

America (Krutzch 1954, Hafner 1981). They thrive throughout Canada and southern

Alaska and also along the East Coast from Maine into Georgia (Hafner 1981). However, due to its natural history (Armstrong et al. 1994), the Preble’s remains a habitat specialist

(Bellows 2001, Trainor 2004) representing the southwestern extent of the meadow jumping mice in Colorado and Wyoming (USFWS 2005).

Although its northern relatives enjoy a wide distribution, the Preble’s subspecies exists only in Colorado and Wyoming. When mapped, the Preble’s range appears geographically equivalent to a narrow ellipse, linking the midpoints of the two states

(Figure 1). Extending from east-central Wyoming, south into Colorado Springs,

Colorado, the Preble’s range stands as a slender corridor abutting the foothills of the

Front Range in Colorado (USFWS 2005). The harsh Rocky Mountains and the dry eastern border of the Great Plains sandwich this thin segment to the west and to the east, preventing expansion in either direction. Both the eastern and western flanks of this corridor lack the habitat components needed to support viable Preble’s populations

(Armstrong et al. 1994). As a habitat specialist (Bellows 2001, Trainor 2004), Preble’s 2

exhibit a strict affinity for moist, semi-aquatic lowlands near streams, rather than mesic

uplands or wooded forests (Quimby 1951, Whittaker 1972, Armstrong et al. 1994).

Therefore, the severity of the Rocky Mountain winters and the aridity of the eastern plains preclude both regions as suitable habitats for the Preble’s.

Figure 1 = The approximate range of the Preble’s meadow jumping mouse (highlighted in green) in Colorado and Wyoming. (Adapted from USFWS 2005.)

In the past, the Preble’s range likely extended beyond today’s limited boundaries.

During the Pleistocene, the eastern plains imposed a less restrictive barrier resulting in a broader distribution to the east. In Colorado, valley glaciers breached the alpine and moved eastward, descending to elevations as low as 2.6 kilometers (Mutel 1992). Pushed eastward by the advancing glacial front, animals dispersed, seeking refuge from the 3

encroaching ice sheets (Cox 2000). A colder and wetter climate accompanied the ice age

glaciers, creating forests and grasslands in areas now covered by desert shrubland

(Jennings 2003). Meadow jumping mice and other mammals relocated to expanded habitats in the eastern plains. Subsequently, the Pleistocene Preble’s were likely more widespread throughout this region, thriving on the eastern tallgrass prairies and savannas

(Armstrong et al. 1994, Bakeman 1997). However, as the ice sheets retreated and the climate dried, the eastern boundary of semi-arid, shortgrass prairie restricted the Preble’s range to the few remaining riparian corridors in Wyoming and the Colorado Piedmont

(Armstrong et al. 1994, Clippenger 2002, USFWS 2005).

Furthermore, at the end of the last glacial period, the Preble’s failed to adapt to the drying environment. As a probable Pleistocene relict, the mouse retained its specialized ecological requirements, despite environmental change (Armstrong et al.

1994, Bakeman 1997, Meaney et al. 2003). Therefore as a result of its natural history, the Preble’s remains a riparian obligate in the semi-arid Colorado Piedmont (Meaney et al. 2003).

The viability of Zapus hudsonius preblei is intricately tied to its habitat. The

Preble’s preferred habitat consists of lush, green vegetation that parallels perennial waterways or the dense, herbaceous understories that blanket wooded areas (Quimby

1951, Whittaker 1972, Armstrong et al. 1994). These specialized habitats supply a readily available source of food including: seed, fruit, fungi or insects critical to Preble’s survival (Armstrong et al. 1994). When seasonal or climatic variations drain the moisture from the riparian habitats, these energetic resources diminish. In response, meadow jumping mice tend to wander in search of suitable habitat with the requisite food supplies 4

(Quimby 1951, Armstrong et al. 1994, Shenk 1999). Furthermore, the dense vegetation of riparian habitats provides protective cover from predators (Clippinger 2002). Thus, movement outside the riparian zone exposes the Preble’s to exacting environments and predation. Therefore, the dense, vegetative cover typical of riparian ecosystems remains essential to Preble’s sustainability (Clark and Stromberg 1987, Bakeman 1997).

Furthermore, quality habitat plays a critical role in regulating Preble’s survival during hibernation (Meaney et al. 2003). Meadow jumping mice are profound hibernators (Babcock 1914, Whitaker 1963, Ryon 1995), remaining approximately eight months, between September and May, in underground hibernacula (USFWS 2005). Food is not cached inside the hibernacula (Whitaker 1963, Armstrong et al 1994, Bain and

Shenk 2002, USFWS 2005) and meadow jumping mice do not feed during periodic arousals (Storey et al. 1994). Therefore, pre-hibernation hyperphagia is necessary to boost the brown-fat reserves. Individuals experience a 100 percent gain in body weight toward the end of summer, prior to immergence (Armstrong et al. 1994). Quality habitat, providing substantial energetic resources at this specific time of year, remains crucial to

Preble’s survival during hibernation.

The natural history and its specialized ecological requirements restrict the

Preble’s range to the narrow riparian corridor sandwiched between the mountains and eastern plains in Colorado. However, these few remaining corridors fail to provide the fluid, continuous riparian ecosystems essential to Preble’s sustainability. Urbanization along the Front Range fragments and isolates meadow jumping mice populations. The greater Denver and Colorado Springs metropolitan areas function as geographical barriers, obstructing movement between Preble’s populations in northern and southern 5

Colorado. The US Fish and Wildlife Service granted “block exclusions” to these

sprawling urban corridors (USFWS 2005), thereby acknowledging the loss of Preble’s

habitat in these regions.

Encroaching real estate development in response to Colorado’s burgeoning

population through the 1990s further exacerbated Zapus hudsonius preblei habitat loss.

The dramatic loss of meadow jumping mice habitat, due to land development, prompted the Colorado Division of Wildlife to commission a study in 1995 to assess Preble’s populations. Tom Ryon (1995) failed to capture a single meadow jumping mouse in historical capture sites once known to support Preble’s throughout the Front Range urban corridor. In the following ten years, additional studies underscored the disappearance of

Preble’s populations: meadow jumping mice are likely gone from previously inhabited

regions, including Fort Collins, Loveland, Greeley, Semper, Croke’s Lake, in other

words, the extensive Front Range urban corridor (Armstrong 2006).

The documentation of dwindling populations and the unchecked destruction of

riparian corridors, led to Z.h. preblei’s listing as a threatened subspecies under the

Endangered Species Act (1998). Federal statues created a 91.4-meter buffer protection

zone for riparian ecosystems designated as critical Preble’s habitat. The federal

recognition of the Preble’s rarity and vulnerability to extinction supposedly slowed the

homogenization of the sparse riparian corridors exacted by developers’ land conversion

along the Front Range in Colorado.

In the Pike National Forest, the South Platte River and its tributaries provide the

only fluid expanses of riparian habitat in a landscape dominated by mountainous terrain.

However, at these intermediate altitudinal zones, an imposing topography of precipitous, 6 rocky ridges and buttes fragment and isolate Preble’s populations, supplanting the urban barriers of the eastern plains. The river corridors in the Pike National Forest are narrow and the riparian vegetation boxed-in by steep inclines of decomposing granite abutting the perennial creek banks. These sparse, montane riparian ecosystems, confined by steep, granite slopes and isolated by extensive canyon-like walls of dry coniferous forest, afford the only suitable Preble’s habitat in the Pike National Forest.

In addition to the limitations imposed by uncompromising topography, wildfires ravaged the Preble’s habitat in the Pike National Forest. Abetted by drought in the summer of 2002, the Hayman Fire burned roughly 138,000 acres. The fire’s high intensity burn jumped the creeks and its scorching flames decimated riparian corridors.

Black soot and charred granite soils clogged the South Platte River and its tributaries.

Noxious weeds usurped the creek bank’s lush, moist vegetation. Powerful floods and erosion adversely impacted the hydrology of the river corridor, precluding the regrowth of Preble’s habitat three years later.

In addition to wildfire, floods and erosion, anthropogenic intrusion into the Pike

National Forest further reduces Preble’s habitat. Housing developments unnaturally dissect riparian systems, disrupting the fluidity of the creeks and surrounding ecosystems.

Heavily-trafficked ATV motocross tracks, hiking trails, and popular camping grounds destroy and degrade riparian vegetation. As a result of the mountainous terrain, with its geographical confinements and subsequent habitat fragmentation, compounded by wildfires, floods, and human encroachment, Preble’s are effectively restricted to minimal patches of undisturbed riparian habitat in the montane drainages of the Pike National

Forest. The loss and fragmentation of riparian habitats along the Front Range urban 7 corridor and in the Pike National Forest places Preble’s populations at risk. The Preble’s is the “canary in the coal mine” and its expiration signals the loss of the complex, biodiversity of the riparian ecosystems throughout Colorado (Armstrong 2006).

PURPOSE OF THIS STUDY:

The documentation of Preble’s montane populations in the Pike National Forest relies on short-term, presence or absence surveys conducted by environmental contractors between 1999 and 2002. Historical data collectively evidenced the low trap success rates for meadow jumping mice, despite intense trapping efforts along montane creeks exhibiting suitable riparian habitats (Bohon et al. 2005). These historical surveys occurred before the 2002 Hayman Fire. Additionally, no data exits relative to meadow jumping mice utilization of upland, forested regions outside the riparian corridors.

Commissioned by the US Forest Service, this three-year study strove to augment the available knowledge of the Preble’s beyond mere capture data. The study was designed to be a comprehensive survey and analysis of the meadow jumping mice populations in the montane drainages of the Pike National Forest and to monitor their use of upland slopes outside the riparian corridors. The Preble’s utilization of the forested upland slopes would thereby determine the relevance of the 91.4 meter buffer zone delineating critical Preble’s habitat, imposed by the Endangered Species Act (1998).

CHAPTER 2

SPECIES DESCRIPTION AND LITERATURE REVIEW

The taxonomic history of the North American jumping mice, or the Zapodid

rodents, is complex. The family is nearly 40 million years old (Armstrong et al. 1994)

and since its first official description by Pennant and Zimmerman at the end of the 18th century (Quimby 1951), multiple taxonomic revisions modified the family and its species. Based on morphologic similarities, Zimmerman originally grouped the North

American jumping mice as con-generics of the Old World jerboas under the Family

Dipodidae (Preble 1899). Many researchers continue to recognize North American jumping mice as a subfamily of the Dipodidae (Klingener 1984, Shenk and Bain 2002,

ITIS 2006). However, the Family Zapodidae generally defines Zapus (Klingener 1963,

Jones 1981, Armstrong et al. 1994, Ryon 1998).

One genus and two species of jumping mice occur in Colorado (Armstrong et al.

1994). The meadow jumping mouse (Zapus hudsonius) and the western jumping mouse

(Zapus princeps, common name Princeps) share similar morphologic features, rendering

the species difficult to distinguish in the field (Conner and Shenk 2003). Additionally,

the two species - and their subspecies - share similar ecological characteristics and

coexist throughout their range (Meaney et al. 1997). The subspecies congeners (Z.h preblei and Z.p.princeps) are sympatric at the intermediate elevations of the Pike

National Forest (Schorr 1999, Meaney 2001, Bohon et al. 2005). Weights or elevations 9

of capture function to quickly differentiate species in the field. Although parameters vary widely, weights exceeding 28 grams usually indicate a western jumping mouse (Bakeman

2001). Zapus captures below 2.3 kilometers identify a Preble’s meadow jumping mouse

(Bohon et al. 2005). However, cranial morphometrics and molar toothfold analysis of voucher specimens, in conjunction with genetic identification, are required to accurately class an animal. The western jumping mouse is not federally listed and surveys are easily complicated by its presence.

There is very little literature specific to the Preble’s meadow jumping mouse in

Colorado. Most of the literature assumes the form of technical reports submitted to various land management agencies. Therefore, a review of the literature includes references specific to Zapus hudsonius while acknowledging that the information may not specifically apply to the Colorado Preble’s. The literature is especially sparse for

Zapus populations in montane environments similar to the Pike National Forest.

Therefore, when similar traits and features, not directly related to the study purpose, were observed in montane drainages, they are denoted as personal observations.

DESCRIPTION AND ECOLOGY:

Jumping mice in Colorado appear similar to other rodents that share its riparian

habitat. Body measurements for Z.hudsonius vary with a total body length averaging 187 to 255 millimeters (Armstrong et al. 1994). Z.hudsonius body size roughly equates to that of the deer mouse (Peromyscus maniculatus) and the two rodents are easily confused by inexperienced mammal trappers (Figure 2). In the field, the similar coloration of both mice leads to misidentifications. When nestled inside dark traps, both animals’ fur

exudes a rusty-brown hue. However, upon closer examination, deer mice adults are either orange or gray and the fur is noticeably dull. Jumping mice, on the other hand,

have longer, shiny body hairs that are yellow-brown, particularly on the sides. These lustrous, yellowish hairs are interspersed with streaks of darker, black tipped hairs

(Figure 3). The black hairs culminate on the dorsum as a shadowy mid-dorsal band or stripe. The venter of jumping mice is white, contrasting sharply with the darker pelage of the dorsum. The dorsal pelage blends perfectly with the decomposing leaves and dark soil that blanket the riparian understory. Additionally, deer mice pinnae are prominent with the ears protruding upwards from the cranium. Jumping mice pinnae are smaller and less distinct (Armstrong et al. 1994, personal observations).

Figure 2 = Zapus (A) and deer mouse (B) from Trout Creek at North Rainbow Falls. Upon initial capture, the two species are often difficult to distinguish simply on body size and pelage. 11

Figure 3 = Zapus from Trout Creek at North Rainbow Falls exhibiting rusty-yellow coloration on the sides punctuated by a distinct, dark band on the dorsum. Yellowish hairs are interspersed by shiny, black hairs.

Although body size and pelage are relatively similar to other rodents, the

exceptional tail distinguishes jumping mice (Figure 4). The bicolored tail is

disproportionately long and accounts for over 60 percent of the total body length

(Quimby 1951, Armstrong et al. 1994, USFWS 2004, personal observations). The tail is sparsely covered with hair and reptilian in appearance, with scaly skin covering a thin snake-like frame. When fully enclosed inside a trap or secured inside a day-nest or hibernacula, the tail curls naturally around the body. On occasion when entering a large

Sherman trap, the tail fails to clear the snapped door and may accidentally be clipped.

The elongated tail provides balance during jumping and if the tail is inadvertently shortened, stability is greatly impaired (Preble 1899). During jumping, the tail is violently whipped like a rudder, facilitating midair superhero-like changes in direction

(Armstrong et al. 1994, personal observations). Zapus are capable swimmers, but the tail

does not function to enhance swimming (Quimby 1951).

Figure 4 = Zapus from Trout Creek at North Rainbow Falls illustrating the elongated tail relative to the overall body size. On average, the tail accounts for 60 percent of the total body length.

The hindlegs of jumping mice are as extraordinary and equally disproportionate as the long tail when juxtaposed to the body trunk and the short forelegs (Figure 5). The tail provides balance while jumping, but the hindlegs afford the mouse its prodigious jumping ability. The scientific literature debates the maximum horizontal distance that

Zapus are capable of jumping and disputes recorded distances. In his observations,

Preble recorded jump distances greater than 2.4 meters (1899). Quimby argues that

Preble overestimated, with maximum jump distances closer to one meter (1951).

Regardless of scientific disagreements, this acrobatic mouse excels as an expert jumper, and with a single leap easily scales horizontal and vertical distances in excess of one- meter (personal observations). These long leaps function as a perfect escape mechanism.

When disturbed, jumping mice forcefully spring away from their predator and then remain motionless and undetected in the shadows – a strategy termed “bound and sit”

(Jones 1981). When not threatened, they move with short hops or crawl along the understory vegetation (Quimby 1951, Armstrong et al. 1994, personal observations).

Figure 5 = Zapus possess greatly enlarged hindlegs and hindfeet that enable their incredible jumping ability. Photo is of a 14 gram male juvenile captured at Trout Creek, North Rainbow Falls, August 2005.

Jumping mice are solitary rodents (Whittaker 1963, Armstrong et al. 1994).

Quimby observed minimal intraspecific aggression between individuals in captivity

(1951). Jones recorded communal intraspecific interactions in El Paso County, Colorado

(1985). But in the riparian vegetation of the Pike National Forest, jumping mice share their preferred habitat with several other rodent species with whom they interspecifically compete. Deer mice, voles, and woodrats are the three most common cohabitants (Figure

6). As extreme habitat generalists, deer mice and voles are the most ubiquitous members of these montane riparian systems. Jumping mice and deer mice share food and feeding habits – both feed on seeds and insects - and compete directly for these energetic resources (Nichols 1981, as cited in Boonstra and Hoyle 1986).

Figure 6 = Voles, deer mice and woodrats share the riparian habitat of the Preble’s. (A) Meadow vole (Microtus pennsylvanicus) from Upper Trout Creek. (B) Meadow vole from Tout Creek at North Rainbow Falls. (C) Deer mouse from Trout Creek. (D) Mexican woodrat (Neotoma mexicana) from Trout Creek.

Conversely, voles are herbivores and feed on plant material, not seeds (Armstrong et al. 1994). Voles compete with jumping mice for space exhibiting high reproductive rates and large populations. They also compete for resources by “cropping grasses and herbs” and thus reducing “the potential for seed-fall” – the meadow jumping mouse’s primary food source (Boonstra and Hoyle 1986). In the grasslands of southern Ontario,

Canada, Boonstra and Hoyle observed competition between Microtus pennsylvanicus and

Z. hudsonius and determined that Microtus significantly reduced the abundance of

Z.hudsonius. According to Boonstra and Hoyle, the competition and its detrimental effects on Zapus are typical throughout the two species’ ranges (1986). Additionally, the extent to which jumping mice frequent or avoid the runways of other rodents remains unclear (Armstrong et al. 1994).

Unique among their riparian cohabitants, meadow jumping mice are profound hibernators and remain in hibernation longer than most other hibernating mammals

(Babcock 1914, Whitaker 1963, Ryon 1998). Jumping mice spend approximately eight months, between September and May (USFWS 2004), in underground hibernacula that they dig themselves (Shenk and Bain 2002). In Minnesota, Z.hudsonius emerged late

April through the second week in May and immerged at the end of September into early

October (Quimby 1951). Immergence and emergence were similarly timed in Michigan

(Muchlinski 1988), upstate New York (Whitaker 1963) and Colorado (Bakeman 1997).

In Colorado, 5 May stands as the earliest recorded emergence from hibernation and the inclusive end dates, 1 May through 31 October, delineate the active period

(Bakeman 1997). In Bakeman’s opinion, mid-September is a more realistic cutoff date for immergence (1997). At the higher elevations of the Pike National Forest, winters

compress the active period’s duration, and animals prepare for hibernation in early

August. They emerge in late May or early June. In spring, males emerge first, followed by females. In autumn, the seasonal newborns enter the hibernacula last in order to

increase fat stores needed to sustain life through hibernation (Quimby 1951, Whitaker

1963, Bakeman 1997).

Food is not cached inside the hibernacula (Whitaker 1963, Armstrong et al. 1994,

Bain and Shenk 2002, USFWS 2004) and meadow jumping mice do not feed during

periodic arousals (Storey et al. 1994). At the molecular level, concentrations of

glycogenolytic enzymes effectively suppress metabolic processes in the hibernating

meadow jumping mice (Storey et al. 1994). Therefore, pre-hibernation hyperphagia is

necessary to boost the brown-fat reserves required to survive the winter. Subsequently as

summer ends, the amount of secured body fat determines the immergence date (Quimby

1951, Whitaker 1963). The composition of body fat approximates 20 percent (Bakeman

1997) with mice gaining a 100 percent increase of their original body weight before

entering hibernation (Armstrong et al. 1994). The fattening is readily observed toward the end of the summer as the mice scramble to gain weight (Ryon 1998, personal observations).

A critical correlation exists between body fat and the date of immergence.

Weights increase dramatically in the two weeks preceding hibernation (Quimby 1951).

Additionally, air temperature and photoperiod work in conjunction with the accumulation of fat to determine the exact point of immergence (Quimby 1951, Muchlinski 1978,

Armstrong et al. 1994). Cold summer nights may force jumping mice into torpor aboveground (Figure 7), exposing the animal to predation or death from hypothermia

(Shenk 2000, personal observations). Captive meadow jumping mice kept in cold cages tend to enter hibernation sooner than mice in warm cages (Whitaker 1963). The shorter photoperiods of autumn may also stimulate the mice to prepare for hibernation

(Muchlinski 1978). All of these factors contribute to immergence for hibernation.

Figure 7 = A Preble’s meadow jumping mouse from Monument Creek, Colorado, on the Air Force Academy. The mouse was captured in a torpid state, pushed into torpor by cold, overnight temperatures. After ambient air temperature increased, the mouse slowly revived.

Jumping mice hibernate in underground nests made of grass or dead leaves

(Quimby 1951). The nests are inside holes, usually 0.5 meter to one meter below the ground surface (Preble 1899, Quimby 1951). Hibernal chambers are found in a variety of soil substrates including sandy banks (Quimby 1951), compacted wood ash and tilled soil

(Bakeman 1997). Unfortunately, very little is known about jumping mice hibernacula

specific to Colorado or montane habitats. Wunder at Rocky Flats, Colorado, successfully

located a Preble’s hibernaculum in a leaf litter nest approximately 0.3 meter underground

on a north facing slope (Wunder 1995 as cited in Bakeman 1997). This hibernaculum

was nine meters above the creek bed (Wunder 1995 as cited in Bakeman 1997).

However, the extent to which surrounding topography and stream character dictate hibernacula site selection remains unclear, especially for those sites in montane environments. The three-year study by Meaney et al. in Boulder County, Colorado, stresses that quality habitat for hibernation is a critical factor regulating Preble’s survival

(2003).

Breeding immediately follows spring emergence and there are two to three breeding cycles per year (Quimby 1951, Ryon 1998). In Colorado, reproduction occurs in early June and mid-August (Armstrong et al. 1994). During the active season, jumping mice are primarily nocturnal and spend the day resting in day-nests (Quimby 1951).

Day-nests are approximately eight to 10 centimeters in diameter; “globular”; shaped like an oval; and constructed of grass or other vegetation (Figure 8) with a small opening on the side (Preble 1899, Quimby 1951, Ryon 2001, personal observations). Day-nests are aboveground, but maternal nests are usually underground in protected chambers or hollow logs. Maternal nests are more solidly constructed than aboveground day-nests

(Quimby 1951, Ryon 2001).

Figure 8 = Red circle indicates a Zapus day-nest located in Trout Creek at North Rainbow Falls. The nest was constructed from the surrounding vegetation, primarily grasses. The jumping mouse used the day-nest during the day. Sharpie permanent-marker included for scale (marker equals 13.5 centimeters).

Again, there is very little available literature specific to Preble’s day-nests in

Colorado and there is no literature pertaining to day-nests in montane habitats. On the plains, Ryon located several day-nests at Rocky Flats, Colorado (2001); Bain and Shenk

located 23 aboveground day-nests in the Plum Creek watershed of Douglas County,

Colorado (2002). Ryon, Bain and Shenk determined that Colorado day-nests share many

of the characteristics described for Midwestern and eastern jumping mice (2001, 2002).

At Rocky Flats, jumping mice wove nests from nearby riparian vegetation and built them

near streams or wetlands. Shrubs or dense grasses surrounded all day-nests. Single

20 individuals occupied a nest up to three weeks and then abandoned it for a new nest (Ryon

2001). At Plum Creek, most day-nests were located within 30 meters of standing water

(Bain and Shenk 2002). It is apparent that day-nests function as daytime retreats in the summer. However, it is less clear how sites are selected in relation to the riparian ecosystem as a whole.

Since days are spent resting inside nests, foraging and feeding are primarily nocturnal activities. Jumping mice feed by holding their food in the front feet while reclining on their hindlegs. The mice gnaw through the seed head while rotating and moving it along a horizontal plane, a smooth motion that mimics the eating of a corn cob

(Quimby 1951, personal observations). While foraging, jumping mice chew off stalks of grass and then bite off the seed heads, leaving behind small piles of grass stems (Bailey

1926 as cited in Quimby 1951). Quimby also noted that jumping mice rarely consume all parts of the seed head and after feeding, deposit “characteristic little piles [that contain] seeds and other parts of the spikelet” on the ground (1951). Voles and deer mice do not make these distinctive feeding piles. Therefore, their presence indicates active jumping mice (Quimby 1951). In general, jumping mice exhibit site fidelity to their nesting and feeding sites (Shenk 2000).

Estimates of the home ranges of meadow jumping mice approximate 0.20 to 0.86 acres with males enjoying larger ranges than females (Quimby 1951, Armstrong et al.

1994). During the active season, jumping mice move more than 1.6 kilometers per year, with seasonal shifts in movement patterns (Shenk 1999). Seasonal movements may be triggered by the drying of habitat (Quimby 1951, Armstrong et al. 1994) or by specific seasonal dietary needs (Shenk 1999). At the Air Force Academy along Monument

Creek, Colorado, Schorr (2003) documented movements ranging from 13 meters to 968 meters with an average distance of 362 meters. At Rocky Flats, Ryon recorded maximum travel distances of 1.16 kilometers with monthly averages of 526 meters

(1999). Movement data at Plum Creek determined that jumping mice venture into upland

habitats outside of the immediate riparian system (Shenk 2000). Jumping mice also

frequented perennial and intermittent tributaries adjacent to the main capture drainage

(Shenk 2000).

At Plum Creek, Preble’s were tracked inside and outside of the 91.4 meter buffer

protection zone for riparian systems (Shenk 1999). This data questions the validity of the

USFWS-imposed restriction as part of the ESA listing (Shenk 1999). However,

movement data for Preble’s is difficult to obtain, due to their minute size and concealing

habitat. Furthermore, Schorr stresses that the intrusion of telemetry collars and

accompanying researchers, tend to impact the mouse’s natural movements and hence

distort the data (2002). Additionally, seasonal movements or migrations are difficult to track because transmitter batteries discharge after two to four weeks (Schorr 2002).

Trapping data for recaptures functions as a reliable alternative to difficult radio telelmetry to gauge jumping mice movement (Schorr personal communication).

The ecology of the Preble’s meadow jumping mouse is intricately tied to its habitat. The habitat in turn governs the mouse’s ability to secure energetic or spatial resources needed to reproduce and hibernate. Over-wintering mortality of meadow jumping mice approaches 70 percent, a probable result of extreme weight loss experienced during winter hibernation (Armstrong et al. 1994). Therefore, as habitat vanishes, food sources and suitable hibernation sites concurrently diminish, and the

probability of over-wintering mortality increases (Bain and Shenk 2002). The rapid

disappearance of riparian habitat throughout Colorado indicates that the Preble’s meadow

jumping mouse, with its specialized ecological characteristics and unique morphologic

traits, is at risk.

SURVEY HISTORY IN THE PIKE NATIONAL FOREST:

Prior to this study, environmental contractors surveyed 12 sites in the Pike

National Forest for the presence or absence of the Preble’s meadow jumping mouse

(Table 1). Nine of the survey sites were below 2.3 kilometers, the cutoff distinguishing

Preble’s from Princeps (Bohon et al. 2005). Between 1999 and 2002, 46 total jumping mice were captured in the Pike National Forest. Five of the 12 surveyed sites were designated Preble’s positive based on cranial morphometrics and molar toothfold analysis of voucher skulls (Bohon et al. 2005). Ruggles (2000) classified Bear Creek as Preble’s

positive based on capture weights (17-23 grams) and elevation (2.3 kilometers).

Surveyors trapped three different sections of Trout Creek: Upper Trout Creek

(Bakeman 2001); Trout Creek at Rainbow Falls, near the Teller County Line (Meaney

2001); and Trout Creek at North Rainbow Falls (Schorr 1999 and 2001). With the exception of Kelsey Creek, trapped in August 2002, all surveys were conducted before the Hayman Fire. Meaney trapped the burn-free, upper reaches of Kelsey Creek (2002).

Schorr conducted the single survey along the South Platte River near the Ouzel

Campground, a popular and overused recreation area (1999).

Table 1 = Preble’s meadow jumping mouse (Z.h.preblei) survey sites, Pike National Forest, Colorado, from 1999 to 2000. Site names in red indicate positive Z.h.preblei capture for that site. (*) = ZAPUS represents total Zapus captures during the survey period, V indicates take of voucher specimen. (**) = PREBLEI Represents verification results of Zapus capture as Preble’s instead of the western jumping mouse congener, Zapus princeps princeps. Text indicates verification technique as either “weight elev,” meaning weights and elevation data were used in the identification, or “voucher” indicating AMF analysis of m1 and cranial morphometrics were used (Adapted from Bohon et al. 2005).

SITE NAME DATES SURVEYOR ELEV ZAPUS* PREBLEI** WEIGHT Wigwam Creek Cmpgd 9-11 Sept 2000 Meaney 6660 ft 1 (V) NO, voucher Phantom Creek 5-9 July 2001 Schorr 8320 ft 7 (V) NO, voucher 24 g YES, weight Bear Creek 4-7 July 2000 Ruggles 7470 ft 5 17-23 g elev Trail Creek 9-13 July 2001 Meaney 7900 ft 5 (V) NO, voucher 21-29 g Unnamed at Trumbull 1-4 June 2002 Bakeman 6840 ft 1 (V) YES, voucher 18 g Kelsey Creek 19-22 Aug 2002 Meaney 7470 ft 0 Surprising lack Indian Creek 2000 Schorr 7000 ft 1(V) YES, voucher 17.0 g Ouzel Cmpgd-Oxyoke 2000 Schorr 6200 ft 2 (V) YES, voucher 20-26 g Upper Trout Creek Bakeman – 27June-1July 01 7996 ft 42 (V) NO, voucher 22.2 g avg (Teller County) Site 3 Unnamed Monument 25Aug-1Sep ’99 Schorr 7040 ft 0 Surprising lack Creek (Monument Fire) TroutCreek-Teller 30Jun-4Jul 2001 Meaney 7600 ft 8 (V) YES, voucher 17 g Line Trout Creek- 17 June 1999 Schorr 6760 ft 7 (3 V) YES, voucher 19-29 g North Rainbow Falls Schorr 5-9 July 2001 6760 ft 0 NO (Douglas County) (w/Hansen)

Historical surveys collectively documented the low trap success rates for jumping

mice in the Pike National Forest (Bohon et al. 2005). Capture rates for Zapus remain

consistently low, despite intense trapping efforts along montane creeks exhibiting

suitable riparian habitats. These low capture rates automatically invalidated population

or abundance estimates (Bohon et al. 2005). For example, Schorr’s survey at the

Monument Fire Center failed to capture a single Zapus in spite of suitable habitat and the

site’s proximity to established Preble’s populations along Monument Creek (1999).

Similarly, the 2001 survey of Trout Creek at North Rainbow Falls failed to capture a

single Zapus (Schorr 2001) in spite of seven Zapus captures in 1999 (Schorr 1999). Low

Zapus capture rates were typical throughout the Forest, regardless of trapping effort or

habitat quality. Therefore, the historical trapping data suggests that numbers of Preble’s

in the Pike National Forest, at the western fringe of their range, are very low, especially

when compared to established Preble’s populations east of the Front Range (Bohon et al.

2005).

PREBLE’S VERSUS PRINCEPS:

As historical surveys progressed, the correct quantification of Preble’s in the Pike

National Forest was complicated by the presence of the western jumping mouse (Z.p.

princeps). The Princeps shares similar ecologic and morphologic features with the

Preble’s. The Princeps often weighs more, and is generally found at higher elevations,

but the two species are impossible to distinguish in the field (Conner and Shenk 2003).

Surveyors in the Forest realized that differentiations between Princeps and Preble’s based

on weights and elevations were readily discredited by analysis of the skulls from

euthanized voucher animals. Since physical attributes like size, weight, or color failed to discriminate the species, the correct identification of live specimens in the Pike National

Forest challenged even the most skilled mammalogists (Schorr personal communication, personal observations).

Eventually, surveys along the upper and lower reaches of Trout Creek concluded that Preble’s and Princeps are sympatric at the intermediate elevations of the Pike

National Forest (Bakeman 2002), effectively eliminating the elevation criterion. Without skulls from voucher specimens or advanced genetic identification techniques, Zapus

captures from the Forest may be either Preble’s or Princeps and animals are best

identified to genus. As a result, historical capture data likely overestimated actual

Preble’s numbers in surveys dated from 1999 through 2001 (Bohon et al. 2005).

However, possible misidentifications do not negate the fact that overall capture rates for

Zapus remain consistently low in the Pike National Forest.

Verification of sympatry for Preble’s and Princeps therefore necessitated a more

reliable technique to distinguish the species and quantify their ranges and populations.

Initially, researchers accepted Klingener’s analysis of dentition as an improved method.

While researching the dental evolution of the Zapus genus, Klingener described a distinct

anteromedian fold (AMF) on the first lower molars of Z. hudsonius (1963). Klingener

also noted that the first lower molar of Z.princeps featured a concentric circle without a

fold or distinct notch (Figure 9). He concluded that the AMF serves as an identifier for

Z.hudsonius (1963). Therefore, after the Preble’s federal listing, researchers used

Klingener’s diagrams of the m1 toothfold to classify Zapus voucher specimens.

Figure 9 = Meadow jumping mice (Z.hudsonius) feature a distinct anteromedian toothfold (AMF) on the first lower molar m1. The presence of the AMF provides evidence that a specimen is Preble’s, but its absence is inconclusive (Conner and Shenk 2003). Tooth diagrams from Klingener (1963).

Unfortunately, the AMF on m1 is not a unique identifier for Z.hudsonius or

Preble’s in Colorado. By analyzing Zapus specimens in the zoology collection at the

Denver Musuem of Nature and Science, Conner and Shenk determined that the presence

1 of the m1 AMF provides “good evidence that a specimen” is Z.h.preblei (2003).

However, the absence of the AMF is uninformative (Conner and Shenk 2003). As a

1 In Conner and Shenk’s article published in the Journal of Mammalogy (2003), the anteromedian fold is incorrectly attributed to “M3”, the third upper molar. The AMF is actually on m1, the first lower molar. This mistake was verified by Dr. Carron Meaney (personal communication).

27 result, toothfold data must be analyzed in conjunction with discrete functional analysis

(DFA) of cranial measurements. Conner and Shenk concluded that cranial morphometrics reliably distinguish Preble’s from Princeps when subjected to rigorous

DFA (2003). Precision measurements of cranial features are necessary to eliminate human error which statistically leads to misclassifications (Conner and Shenk 2003).

In summation, correct delineation of Zapus in Colorado as either Preble’s or

Princeps requires a three-step approach that ideally concludes with genetic analysis.

First, voucher specimens are analyzed for the presence or absence of the m1 toothfold. If the AMF is present, the animal is probably a Preble’s, but if the AMF is absent, the results are inconclusive (Conner and Shenk 2003). Then, DFA of cranial morphometrics is required to verify the toothfold analysis. And finally, future genetic techniques, using genetic markers, not readily available at present, will accurately class Preble’s by comparing genomes rather than morphology. These three steps will ultimately function as a tripod that provides the accurate taxonomic identification of Zapus specimens

(Meaney personal communication).

Based on skull analyses from nine historical capture sites, Preble’s and Princeps are known to coexist in the Pike National Forest. However, the extent to which Zapus populations in the Pike National Forest interact with larger populations east of the foothills remains unknown. It is theorized that biogeographical barriers and habitat fragmentation limit intermixing and breeding between montane and eastern populations

(Bohon et al. 2005). The Preble’s of the Pike National Forest are isolated, and consistently exhibit low capture rates indicative of small populations.

CHAPTER 3

MATERIALS AND METHODS

OVERALL STUDY AREA AND STUDY SITES:

The United States Forest Service, Department of Agriculture, manages the Pike

National Forest as part of the “Pike, San Isabel National Forests and Comanche and

Cimarron National Grasslands”, or PSICC, system. This collective management unit

encompasses approximately three-million acres of diverse landscape, from shortgrass

prairies in Kansas and Oklahoma, to the barren alpine tundra in the Colorado mountains

(USFS 2006). Situated in the center of Colorado, the Pike National Forest spans roughly

1.3 million acres (Banks 2006) and extends north from the snowcapped peaks of Mt.

Evans, south to Pikes Peak, and west to the South Park basin. The flat grasslands of the

Great Plains adjoin the low-elevation foothills of the Rampart Range that abut the Forest to the east (Figure 10).

Figure 10 = Map of Colorado with the Pike National Forest shaded in green (USFS 1994). 29

With undulating valleys and steep mountain ridges, the Pike National Forest covers the apex of the western foothills overlooking the urban corridor that stretches between Denver and Colorado Springs. Elevations range from 1.5 kilometers in the east to more than 4.3 kilometers in the west, as montane buttes and rolling hills transition to steep, jagged mountaintops. Interspersed with grassy meadows and open mountain parks, mixed-conifer forests of ponderosa pine and Douglas fir predominate at lower elevations.

At these lower elevations, junipers thrive on dry, south-facing slopes that are flecked with patches of yucca, purple liatris and blue-gramma grass. At higher elevations, the ponderosa pine and Douglas fir communities yield to sub-alpine spruce-fir forests. As elevation increases, spruce-fir communities thin, replaced by sparse patches of bristlecone pine and barren alpine tundra. Dense stands of lodgepole pine are located along the Rampart Range and below tree line in the high-country near Mt. Evans.

In the Pike National Forest unstable slopes of decomposing Pikes Peak granite dominate the landscape (Figure 11). Decomposition is most prevalent at lower elevations and crumbling granite slopes line the banks of the South Platte River and its tributaries.

Along the river corridor, these slopes of loose granite, with steep 40 to 60 degree inclines, topographically carve mountainous ridges, valleys, and deep drainages. The rolling hills of decomposing granite are prone to erosion. Like piles of loose marbles, the granite granules fail to trap moisture in its particulate matrix. Subsequently, the soil dislodges and easily surrenders to minor hydrologic forces. The Buffalo Creek Fire of 1996 exacerbated the already erosion prone environment and massive floods swept through the town of Buffalo Creek, resulting in the loss of human life.

Figure 11 = (A) A slope of decomposing Pikes Peak granite slope at Trout Creek in the Pike National Forest. (B) A close-up of the decomposing granite soil. Decomposing granite soils are loose, unstable and especially prone to erosion.

Abetted by drought in the summer of 2002, the Hayman Fire burned roughly

138,000 acres of the Pike National Forest, making it the largest wildfire in Colorado’s

history. More than 32 percent of the fire’s burn was classified as high intensity (USFS

2002) with the scorching flames leaving behind an ashen moonscape. When viewed from

space, the burn area resembled a giant carcinoma, scarred onto the surface of the Pike

National Forest (Figure 12). Black soot and charred granite soils, unleashed by erosion,

clogged the South Platte River, its tributaries, and reservoirs (Figure 13).

Simultaneously, slick hydrophobic soils prevented the immediate regrowth of vegetation

as monocultures of invasive noxious weeds, like leafy spurge and yellow toadflax,

colonized burned soil and usurped rightful access to native plants. As Hayman slowly

cooled, the federal Burn Area Emergency Rehabilitation (BAER) team quickly

assembled to prevent a similar ecological disaster, experienced following the Buffalo

Creek fire.

Figure 12 = Satellite image of the Hayman Fire burn area (USFS 2002). The red square outlines the approximate study area. The Hayman Fire burned roughly 138,000 acres on its northern progress from Lake George, Colorado.

Figure 13 = (A) Wigwam Creek west of Deckers filled with eroded silt and lined with slick hydrophobic soils. (Branch, USFS 2002). (B) Aerial photograph of West Creek and Highway 67 toward Deckers surrounded by Hayman burn area (Whattenmaker 2002). Both creeks were filled with soot, ash and eroded granite granules resulting from the Hayman Fire 33

Fed by snowmelt, runoff, and a multitude of tributaries, the South Platte River flows through the Pike National Forest on its descent to the eastern plains (Figure 14).

Several reservoirs capture its water and the river provides the greater Denver metropolitan area with over 60 percent of its water supply (USFS 2006). The river splits into two distinct forks, the North and South Forks, after leaving its source in the

Mosquito Range above South Park. The North Fork travels east, bordering the Forest’s northern edge before rejoining the South Fork at a confluence above the Strontia Springs

Reservoir. The South Fork meanders through the center of the Forest and is collected at the Elevenmile and Cheeseman Reservoirs. Following its release from Elevenmile, the

South Fork turns northeast and passes through the small mountain towns of Deckers,

Trumbull and Oxyoke on its way to the confluence.

Figure 14 = The South Platte River runs through the Pike National Forest. The approximate boundary of the Pike National Forest is outlined in dark green (USGS 2006). The North Fork of the river is highlighted in turquoise and the South Fork in dark turquoise. The North and South Forks join at a confluence above Strontia Springs Reservoir (blue). The red square outlines the approximate study area.

Unlike riparian systems on the eastern plains, the South Platte River and its tributaries are boxed-in by steep, mountainous slopes rather than flat stretches of grassland. Eastern riparian systems, like Monument Creek or Plum Creek, are wide and expansive, in stark contrast to the narrow and confined mountainous, or montane, drainages typical of the Pike National Forest (Figure 15). On the plains, riparian corridors have wide stream and bank widths; the riparian vegetation often extends more than 30 meters outward from the creek edge (personal observation). On the flat landscape, extensive riparian ecosystems thrive beyond the area immediately defined by the creek or river bank. In contrast, the Pike National Forest’s riparian systems are confined by the mountainous slopes of dry forest (Figure 16).

Figure 15 = (A), Monument Creek on the Air Force Academy juxtaposed to (B) Sugar Creek, a steep, montane drainage in the Pike National Forest.

Figure 16 = Trout Creek at North Rainbow Falls exemplifies the riparian topography characteristic of the Pike National Forest. Creeks and their riparian vegetation are strictly delimited by steep, forested slopes of decomposing granite. The three-dimensional GIS rendition of Trout Creek and the surrounding area illustrate the confined montane drainages. The Middle trap line at Trout Creek is illustrated in both photos.

In the Pike National Forest, riparian systems are extremely narrow. Bank widths are short and often span less than 10 to 20 meters with the riparian vegetation contained by precipitous, rocky slopes. In aerial photographs, these montane riparian systems resemble thin slivers of green, snaking modestly through canyon-like valleys of steep, forested slopes (Figure 17). The riparian vegetation, and hence the Preble’s habitat, is strictly delimited by the confining slopes of decomposing granite and an imperious terrain dominated by steep rocky ridges and deep valleys.

Figure 17 = Aerial photograph of Trout Creek at North Rainbow Falls illustrating the isolated riparian system. Kilometers of dry forest and steep topography effectively separate riparian systems from one another. The Hayman burn area appears as a light scar to the southwest of Trout Creek. Photograph dated 1 August 2005.

In addition to their slight stature amidst a mountainous landscape, the montane

riparian systems of the Pike National Forest are isolated and remote. As seen in aerial

photographs, kilometers of steep mountains and buttes separate individual riparian zones

from one another (previous Figure 17). Although the tributaries are joined like

appendages of the South Platte River, they are secluded by many kilometers of

mountainous terrain and dry forest (Figure 18). For example, a 6.4 kilometer void of dry coniferous forest latitudinally separates Pine Creek from Sugar Creek. The extent to which jumping mice move between these corridors remains unclear, but it is unlikely that jumping mice venture outside their particular riparian system and trek across dry, forested wilderness in search of new riparian habitats. Additionally, jumping mice display high site fidelity (Bain and Shenk 2002), and movement between drainages is improbable, especially when these drainages are isolated by coniferous forest.

Figure 18 = Thunder Butte with Pikes Peak in the background as viewed from Saloon Gulch above Trumbull. Riparian systems are effectively secluded by dry forests and steep terrain. 38

The South Platte River and its tributaries provide the only fluid expanses of riparian habitat in a landscape dominated by steep granite slopes and dense conifer forests. Although hemmed in tightly by decomposing granite slopes, the South Platte

River supports narrow bands of willows and other riparian vegetation along its banks.

Perennial creeks connect to the river like venous capillaries, allowing the vegetation to follow the tributaries up into spur drainages. Similarly surrounded by coniferous forest, the tributaries sustain the continued growth of riparian vegetation into the wooded forests

(Figure 19). The South Platte River and its major tributaries supply the Pike National

Forest with its only worthy tracts of sustainable Preble’s habitat.

Figure 19 = Trout Creek is a secondary tributary of the South Platte River and flows first into West Creek. The creek allows riparian vegetation to grow in drainages that are surrounded by coniferous forest. Photograph illustrates the Middle trap line used at Trout Creek as the creek flows to the west.

In addition to the limitations imposed by uncompromising topography, wildfire

ravaged Preble’s habitat of the Pike National Forest. Since 1996, approximately 22,100

acres of potential Preble’s habitat burned in unexpected wildfires (Bohon et al 2005).

Another 3,100 acres burned in prescribed fires monitored by the USFS, but escaped

control (Bohon et al 2005). At Trout Creek, the Hayman Fire (2002) jumped the creek

and burned the riparian vegetation. Willow regrowth remained sparse three years later.

As a result of the fire, erosion and flooding continued to adversely impact the creek and

its ecosystem. Until regrowth methodically reestablishes a developed riparian system,

burned streams and creek banks remain unsuitable Preble’s habitat (Figure 20).

Figure 20 = The Fire trap line for Trout Creek at North Rainbow Falls in September 2003, roughly one year after the Hayman Fire jumped the creek and burned the riparian vegetation.

Already adversely impacted by wildfire, Preble’s habitat in the Pike National

Forest is further reduced and isolated by anthropogenic factors. The Forest boundary

does not delineate an untouched, pristine environment free from human intrusion.

Instead, multiple tracts of private land, outside state or federal jurisdiction, dissect the

Forest. Many of these private land holdings unnaturally divide riparian corridors,

effectively disrupting the fluidity of the creek and its riparian system. For example,

approximately two kilometers above its confluence with West Creek, the well-

established, gated, North Rainbow Falls housing development physically interrupts the

flow of Trout Creek. Dense coniferous forest surrounds North Rainbow Falls, yet the

community resembles a subdivision unnaturally stuck in the center of wilderness, with

manicured lawns replacing riparian vegetation. Nestled tightly within the Trout Creek

drainage, this community features a complex system of roads that connects sprawling homes to bridges, resident-made dams, and fishing ponds that alter the natural flow of the creek (Figure 21). To the homeowners, the Forest exists for their enjoyment, a natural extension of their private property. Dogs running at large often interrupted field work and threatened a radio-collared mouse.

Figure 21 = The North Rainbow Falls residential community features large houses, fishing ponds, roads and bridges. The community is surrounded by Forest. Trout Creek flows into the pond past the gray house immediately after crossing the private property boundary with the Pike National Forest. 41

As Trout Creek flows into North Rainbow Falls, the quality of the riparian system degrades drastically (following Figure 22). Willow densities decrease and the lush riparian vegetation noticeably thins. Vegetative diversity declines and the riparian system is homogenized after the creek enters private property. Additionally, a heavily- trafficked ATV trail parallels Trout Creek for several kilometers and even abruptly crosses the creek above the housing community. Despite Forest Service efforts to close the trail or divert ATV traffic outside the riparian system, reckless damage continues

(Figure 23). As a result of geographical limitations and habitat fragmentation, compounded by wildfires, floods, and human encroachments, Preble’s are effectively restricted to minimal patches of undisturbed riparian habitat in the montane drainages of the Pike National Forest.

Figure 23 = ATV damage at Trout Creek, North Rainbow Falls, near the Upper trap line. ATV users cross Trout Creek and destroy Zapus habitat.

Figure 22 = Aerial photograph of the North Rainbow Falls housing community dated 1 August 2005. The large residential community is surrounded by the Pike National Forest. The blue arrow indicates the flow of Trout Creek across the Forest boundary into the community. The red lines highlight the complex system of roads. The quality of the riparian system degrades dramatically once Trout Creek leaves the Forest boundary and enters the private housing community.

This study trapped small mammals at six montane drainages in the Pike National

Forest during the summer and autumn field seasons of 2003, 2004, and 2005 (Figure 24).

Pine, Sugar and Gunbarrel Creeks are primary tributaries of the South Platte River and

were trapped in 2003. Trout Creek at North Rainbow Falls is a secondary tributary of the

South Platte River, flowing first into West Creek and was trapped all three years. An

upper reach of Trout Creek next to the Manitou Experimental Forest, called Upper Trout

Creek, was trapped once in 2004. Additionally, an unnamed creek at the Monument Fire

Center, near the town of Monument, was trapped once in 2003.

Initially, geographic information system (GIS) habitat models aided the selection

of the six study sites. Developed by the USFS, these habitat models identified potentially suitable Preble’s habitat within the South Platte River basin. Next, habitat layers overlaid with riparian and creek layers, narrowed the possible choices to those sites with suitable

Preble’s habitat. And finally, field visits verified the GIS models and selected six locations as valuable trapping sites. Historical trapping data conferred particular importance to Trout Creek, Upper Trout Creek and the Monument Fire Center. Although

Gunbarrel, Pine and Sugar Creeks lacked historical trapping data, these sites were chosen to enhance understanding of the Preble’s range in the Forest. And finally, Trout Creek’s

Zapus capture history and its productive riparian system, qualified it as the most suitable

Preble’s trapping site. Therefore, Trout Creek became the focus of an intensive three- year study.

Following a summary of the trapping protocol, individual study sites are discussed in detail.

Figure 24 = Topographic overview of the six study sites trapped for the Preble’s meadow jumping mouse between 2003 and 2005 in the Pike National Forest. Gunbarrel Creek, Pine Creek, Sugar Creek and the Monument Fire Center were trapped once in 2003. Upper Trout Creek was trapped once in 2004. Trout Creek at North Rainbow Falls was trapped all three years.

SMALL MAMMAL TRAPPING PROTOCOL:

Small mammals were trapped and handled according to the guidelines outlined by

the United States Fish and Wildlife Service (1999) and the American Society of

Mammalogists (1998). Trapping was conducted under permits issued by the USFWS and the Colorado Division of Wildlife. Sherman live-traps (8 cm x 8 cm x 23 cm) were baited with either plain rolled oats or a mixture of rolled oats and peanut butter. A small ball of polyester batting was placed in each trap to provide warmth (Figure 25). Traps were set late in the evening (1700-2200), and checked early in the morning (0500-0800).

Traps were cleaned with a 10 percent bleach solution to prevent transmission of diseases between sessions and sites. After cleaning, traps were seasoned in the field before reuse.

Traps at Trout Creek were dismantled regularly and exposed to atmospheric moisture and

UV energy from the sun.

Figure 25 = Large Sherman traps (8 cm x 8 cm x 23 cm) were baited with rolled oats or a rolled oats and peanut butter mixture. A small ball of polyester batting was placed in each trap to provide warmth.

Traps were placed three to 10 meters apart along transects that followed the

respective creek at each of the six study sites. Individual traps were relocated if

topography, the curvature of the stream, or vegetative cover prevented a strict adherence

to trap spacing. Mixtures of collapsible and non-collapsible traps were used. For each

site, a minimum of two parallel transects were placed on opposite sides of the creek.

More complex trap transects and trap grids were added at Trout Creek to assess

movements within the drainage. Surveys were terminated early following positive

capture of Zapus at Gunbarrel, Sugar and Pine Creeks. Trout Creek served as the main

study site and was trapped all three years (Table 2).

Table 2 = Trapping protocol for six sites in the Pike National Forest, 2003 through 2005. There were 14,940 total trap nights of effort with 12,539 nights in Trout Creek alone. SITE NAME DATES TRAP NIGHTS TRAPPING PROTOCOL Three sections (Upper, Middle, Gunbarrel Creek 12-14 August 2003 369 Lower) with six lines. 14-15 August Three sections (Upper, Middle, Sugar Creek 240 2003 Lower), with six lines. 16-17 August One section with two parallel lines. Pine Creek 250 2003 29 Aug – 1 Sept Four sections (1, 2, 3 and 4) with Monument Fire 750 2003 parallel lines 13-19 August One section inside a cattle Upper Trout Creek 792 2004 exclosure with two parallel lines. Three primary sections (Upper, Trout Creek Sept ‘03 – Oct ‘05 12,539 Middle, Lower) and five auxiliary lines.

TOTAL 14,940 TRAP NIGHTS

SURVEY SITE DESCRIPTIONS AND PROTOCOLS:

Gunbarrel Creek ~ 12-14 August 2003:

From Highway 126 in Jefferson County, Gunbarrel Creek flows west to east into

Douglas County near its confluence with Kelsey Creek. Once in Douglas County,

Gunbarrel Creek passes a small group of old log-cabins and crosses Highway 67 before joining the South Platte River. Following the Preble’s ESA ruling in 1998, the lower reaches of Gunbarrel Creek, near the Oxyoke cabins, were classified as federally protected “critical” Preble’s habitat by the USFWS.

Three sections of Gunbarrel Creek were surveyed with 259 traps: the Upper,

Middle and Lower lines (Figure 26). Within each of these lines, there were two transects

(A and B) placed on opposite sides of the creek. Gunbarrel Creek is remote, situated in

steep canyon-like terrain, without access roads or hiking trails. Therefore, the 159 traps

were backpacked to the Upper and Middle Lines. The Upper line ended above the

Gunbarrel-Kelsey confluence, but the confluence marked the start of the Middle line.

Figure 26 = Three sections of Gunbarrel Creek were surveyed for Preble’s with three trap lines: the Upper, Middle and Lower lines. Numbers below line names indicate the number of traps used at that line. Each line featured two transects of traps (A and B) on opposite sides of the creek. 48

While moving north, the Hayman Fire of 2002 crossed Gunbarrel Creek at

multiple locations. The upper reaches of Gunbarrel Creek, above the Kelsey Creek

confluence at the Upper line, experienced high intensity burns that charred the riparian

vegetation. As the fire cooled, flooding and erosion quickly followed, plugging

Gunbarrel Creek with silt and ash, and degrading the unburned vegetation downstream.

At the time of the survey, one year after the Hayman Fire, the wildfire’s destructive impact on the surrounding ecosystem stood nakedly visible. A massive knee- high silt wall of eroded soil and rock blocked the water flow at the Gunbarrel-Kelsey confluence. Only a small trickle of water dribbled beneath the barrier wedge of erosion and ebbed through the burned, steep canyon walls of the Middle line before gaining momentum and volume above the Lower line. An estimated two weeks prior to the survey, powerful floods swept through Gunbarrel Creek, loading the creek with more silt, and uprooting the riparian vegetation (Figure 27). Enormous ponderosa pine snags,

felled by heavy snow from a March 2003 blizzard, crashed into the creek and further

impeded its flow. These snags created an obstructive maze to navigate when placing

traps and precluded uniform transect lines. The Hayman Fire and the subsequent

flooding and erosion destroyed suitable Preble’s habitat at Gunbarrel Creek.

Figure 27 = The Lower line at Gunbarrel Creek experienced heavy flooding at least two-weeks before the Preble’s survey was initiated. Flooding loaded the creek with silt and damaged the riparian vegetation.

Sugar Creek ~ 14-15 August 2003:

Sugar Creek lies directly east of Gunbarrel Creek with a westerly flow that joins

the South Platte River to the north of Oxyoke. The drainage is steep and rocky as its

narrow sides rise toward the apex of the Rampart Range. A well-developed dirt road

(Sugar Creek Road) maintained by Douglas County, parallels the entire length of Sugar

Creek. Multiple ATV trails cross the upper reaches of Sugar Creek complete with

parking areas and car-pullouts.

Three sections of Sugar Creek were trapped with 240 traps: the Upper, Middle

and Lower lines (Figure 28). Within each section, two transects of traps (A and B) were

placed on opposite sides of the creek. Traps transects were situated along stretches of

suitable habitat. Steep cliffs limited the available riparian vegetation between the Middle

and Upper lines. The trapped sections of Sugar Creek were unaffected by flood or

wildfire. Shallow beaver ponds were situated in the center of the Middle line and a small

upland meadow briefly bordered the southern edge of the riparian vegetation along the

Lower line (Figure 29).

Figure 28 = Three sections of Sugar Creek were surveyed for Preble’s with three lines: the Upper, Middle and Lower lines. Numbers above line names indicate trap quantities for that section. Each line featured two transects of traps (A and B) on opposite sides of the creek.

Figure 29 = The Lower B transect at Sugar Creek with the adjoining upland meadow and Sugar Creek Road to the south. The blue line highlights the well-developed dirt roadway (Sugar Creek Road). Pink flagging indicates trap stations.

Pine Creek ~ 16-17 August 2003:

After passing a small cluster of cabins in Sprucewood, Pine Creek flows through a

narrow mountain valley and descends along Nighthawk Hill. As the terrain eventually

flattens, and the creek approaches its confluence with the South Platte River, Pine Creek

develops a narrow band of riparian vegetation. This vegetation is bordered by montane

slopes to the south and a heavily trafficked dirt road (Pine Creek Road) to the north. Pine

Creek Road is maintained by Douglas County and parallels the creek throughout its

length.

One section of Pine Creek was trapped with 250 traps (Figure 30). Two transects

(A and B), each with 125 traps, were placed on opposite sides of the creek. Pine Creek’s

intersection with the paved South Platte River Road marked the beginning of both trap

transects.

Figure 30 = One section of Pine Creek was surveyed for Preble’s. Number indicates trap quantity. Two transects, each with 125 traps, were placed on opposite sides of the creek. The B line was on the creek’s northern bank next the edge of the dirt road.

Although untouched by wildfire or flood, Pine Creek exhibited signs of stress

from drought and vehicular traffic. Water volumes in the creek were low and flow rates

were nearly undetectable. Most of the creek was dry, except for small, stagnant puddles

of water, the aqueous remains of rain leftover from brief afternoon thundershowers

(following Figure 31). Fine gravel replaced water in the numerous dry sections of the

creek. As drivers overcompensated for sharp turns on Pine Creek Road, the loose edge of

the adjacent roadbed eroded and splattered the riparian system (Figure 32). Heavy traffic along the roadway and speeding cars disturbed the road’s gravel surface, unleashing a thick spray of dust that blanketed the willows and riparian grasses, further evidence of the detrimental anthropogenic intrusion into Preble’s habitat.

Figure 32 = Pine Creek toward the east with the adjacent Pine Creek Road. Riparian system showed stress from drought and heavy vehicular traffic.

Figure 31 = Pine Creek toward the east. During the survey, water volumes and flows were low. Small puddles of stagnant rainwater were interspersed by dry gravel banks. 54

Monument Fire Center ~ 29 August – 1 September 2003:

The Monument Fire Center is the home base for the Pike National Forest

Hotshots, an elite team of wildland firefighters and smokejumpers. The Fire Center sits

at the foot of the Rampart Range. The populous town of Monument lies directly to the

east. Houses and split-rail fences separate the Fire Center from Monument’s busy truck-

stops and fast-food restaurants. An expansive network of social trails and dirt roads

crisscross the Fire Center and its single unnamed creek.

The unnamed creek passes through the Monument Fire Center along the eastern

border separating federal property from private property. The unnamed creek originates

near Monument Rock and flows southeast along a well-used social trail (Figure 33).

After leaving the Center’s grounds, the unnamed creek intersects Monument Creek

approximately one kilometer before Monument Creek flows into Monument Lake.

Robert Schorr of the Colorado Natural Heritage Program surveyed the unnamed creek in

late August 1999 (see Chapter 2). Schorr failed to capture Zapus during his survey.

Figure 33 = The Upper trap line in the foreground at the Monument Fire Center with Monument Rock and the Rampart Range in the background.

Four sections of the unnamed creek at the Monument Fire Center were trapped in

2003 replicating Schorr’s original trap transects (Figure 34). Two transects (A and B),

each with 50 traps, were placed on opposite sides of the creek for the Upper and Middle

lines. The narrow creek bed, with its sparse vegetative cover, limited the number of traps

at the Lower line and, as a result, traps could not be placed on opposite sides of the creek.

The Lower line’s transects were separated by Mount Herman Road and a stone culvert divided the Upper and Middle lines (Figure 35).

Figure 34 = Four sections of an unnamed creek were surveyed for Preble’s at the Monument Fire Center. Number indicates trap quantity for each line. The Upper and Middle lines featured two transects (A and B), each with 50 traps placed on opposite sides of the creek. The Lower line was separated at Mount Herman Road.

Figure 35 = An old stone culvert separated the Upper and Lower trap lines at the Monument Fire Center. Pink flagging indicates trap station.

Upper Trout Creek ~ 13-19 August 2004:

The upper reaches of Trout Creek (called Upper Trout Creek) flow north along a

high elevation plain traversing the center of the Manitou Experimental Forest. The creek meanders at elevations averaging 2.4 kilometers before descending into the South Platte

Basin at Rainbow Falls and the Teller-Douglas county line. On its way to Rainbow Falls, the creek passes several large Forest Service campgrounds and parallels Highway 67.

Under USFS permits, cattle are allowed to graze along several sections of Upper Trout

Creek. The Hayman Fire approached Upper Trout Creek within 1.6 kilometers and crossed the creek below Rainbow Falls.

In 2001, Dr. Mark Bakeman of Ensight Technical Services trapped a portion of

Upper Trout Creek just to the north of the South Meadows Campground (see Chapter 2).

This section of the creek is surrounded by a barbed wire fence to the south and west in

order to exclude cattle from entering the riparian system.

Bakeman’s 2001 survey of Upper Trout Creek (site 3) was trapped again in 2004 with a single trap line of 132 traps (Figure 36). The line featured two transects (A and B) of 66 traps placed on opposite sides of the creek. The A transect followed the eastern

edge of the creek and the B line followed the western extremity. A popular social trail

connects the South Meadows Campground to Upper Trout Creek. The trail closely

paralleled the A transect within five meters before turning back into the campground.

Figure 36 = One section of Upper Trout Creek near the South Meadows Campground was surveyed for Preble’s. Number indicates trap quantity. The single line featured two transects (A and B), each with 66 traps placed on opposite sides of the creek.

Trout Creek at North Rainbow Falls ~ 2003-2005:

After leaving the high elevation corridor of Upper Trout Creek, Trout Creek looses altitude as it flows toward its confluence with West Creek. The creek contracts

considerably during its descent, squeezed by steep slopes of decomposing granite that abut the riparian edge at nearly perpendicular angles (Figure 37). These slopes confine the creek to a narrow valley and thereby limit the spread of vegetation beyond the creek

banks. Along Trout Creek, the distinct segregation between dense riparian vegetation

and dry forested slopes is noticeably dramatic. Tall willows and lush grasses thrive in the flat drainage bottom until crumbling granite slopes forcefully demarcate the riparian ecosystem from the adjacent forested ecosystem (Figure 38).

Figure 37 = Trout Creek’s banks are bordered by steep rocky slopes composed of decomposing granite. These slopes effectively restrict the growth of riparian vegetation to the flat drainage bottom.

Figure 38 = The Middle trap line at Trout Creek, North Rainbow Falls. The riparian ecosystem in the Trout Creek drainage is confined by rocky slopes and mixed conifer forest. The slopes erode easily into the creek.

Both the north and south-facing slopes bordering Trout Creek are composed of

loose granite soils. The slopes are unstable and erode easily into the creek. However, the

micro-ecosystems on the two slopes are remarkably different. North-facing slopes are

cool, wet, and support dense forests of ponderosa pine intermixed with Douglas fir. Tree

densities on the north-facing slopes approach “dog-hair” levels, with small-diameter trees

spaced tightly together, filtering out sunlight. The overcrowded tree canopy, with its

thick mats of decomposing tree-needles, impedes the growth of ground vegetation on the

north-facing slopes.

Conversely, south-facing slopes in Trout Creek are drier and receive more

sunlight. Tall, large diameter ponderosa pine trees are conservatively interspaced and

these stands resemble those of mountain parks. The open tree canopy allows light to

reach the ground vegetation. Grasses, mountain shrubs and wildflowers grow in these

upland areas underneath the pines (Figure 39). Yucca and mullen are also common.

Small upland meadows of blue gramma grass and other grasses flourish between groups

of trees.

Figure 39 = South-facing slopes in the Trout Creek drainage are dry. South-facing slopes are covered by upland grasses, like blue-gramma grass. Trees are spaced far apart and the canopy is open. Photograph of the Lower Upland trap transects.

Robert Schorr of the Colorado Natural Heritage Program trapped Trout Creek in

1999 and 2001 (see Chapter 2). Schorr used four lines in 1999 and one line in 2001.

During his first survey, Schorr captured seven Zapus in 114 trap nights. Three Zapus

voucher specimens were collected; one specimen was later identified as a Preble’s by

toothfold and cranial analysis (Schorr 2000). The other two specimens were classed as

Princeps. There were no Zapus captures in 2001.

Surveys were conducted at Trout Creek in September 2003, May-October 2004, and May-October 2005. Three main trap lines (the Lower, Middle, and Upper lines) were modeled after Schorr’s original 1999 lines (Figure 40). These three lines were established in 2003 and used consistently throughout the study. In 2004, the “Beaver” line was added between the Lower and Middle lines, linking all three lines in an approximate 1.8 kilometer continuum of trap transects. Upland lines were added in 2005 to measure the movement of Zapus beyond the riparian cooridor into more elevated, forested regions. After the Hayman Fire, Schorr’s Upper line became the “Fire” line, which was trapped in 2003 and 2005.

Figure 40 = Trap lines for Trout Creek at North Rainbow Falls. The Lower, Middle, Upper and Fire lines were used in 2003-2005. All other lines were added in 2004 or 2005. Upland lines were used to gauge movement of small mammals outside of the riparian corridor. The Red line approximates the Hayman Fire burn area.

The steep sides of the drainage controlled the placement of individual trap transects. At intermittent points along four of the lines, the granite slopes defined one bank of the creek, preventing trap placement on that respective side of the creek. As a result, transects were positioned on only one side of the creek at the Middle, Upper, Fire, and Beaver lines. The Upper and Fire lines featured two parallel transects on the northeastern side of the creek. At the Middle line, four parallel transect lines were situated on the southwestern side of the creek (Figure 41). In 2005, the Middle Upland line (a single transect of 20 traps) was added to a waterless runoff-drainage near the northern terminus of the Middle line to monitor movement within an intermittent tributary.

Figure 41 = The Middle line at Trout Creek featured four parallel transects of traps on the southwestern side of the creek. Approximate transect locations with their respective names are highlighted in green.

The Lower line featured an extensive grid of traps that fanned outwards from both banks of the creek and spanned up into the forested uplands (Figure 42). The A, B, and

G transects were on the southwestern side of the creek; the D, K, L and M transects were

on the northeastern side. Transects A, B, and D traversed dense riparian vegetation

typical of Preble’s habitat. The D transect lined the farthest edge of the riparian vegetation as the willows abruptly transitioned to forested uplands (Figure 43A). These lines paralleled the creek’s banks. The G transect bordered the southwestern edge of the riparian system in a north-facing mixed-conifer forest (Figure 43B).

The Lower Upland line, including the K, L and M transects, paralleled the Lower transects, but were located outside the riparian zone on the south-facing upland slope.

The Lower Upland transects traversed upland grasses on the slopes of an open, but dry forest of large diameter ponderosa pine (Figure 44). The edge of the M transect marked the boundary of the 91.4 meter USFWS protection zone. Sections of the understory along the Lower Upland lines sustained minimal burn damage during the Polhemus prescribed fire in October 2001. As an entire unit, the Lower grid roughly covered a 0.32 kilometers squared (32 hectares) area.

Figure 42 = The Lower and Lower Upland trap transects in detail. Transects A, B and D were situated within dense riparian vegetation. Transect G was situated at the southwestern edge of the riparian vegetation near the mixed-conifer forest. 64

Figure 43 = Two views of the Lower line trap grid at Trout Creek: facing northeast (A); facing southwest (B). Green lines approximate transect locations.

Figure 44 = Panoramaic composite of the southeastern half of the Lower Upland trap transects. The K, L, and M transects (highlighted in green) paralleled Trout Creek in the grassy, forested upland slopes immediately outside the riparian vegetation. Sections of the Lower Upland were lightly burned during the Polhemus prescribed fire in 2001.

In June 2002, the Hayman Fire crossed Trout Creek at the Fire line. The high

intensity flames decimated the riparian ecosystem and the contiguous forest (Figure 45).

The wildfire and the resultant floods and erosion degraded the environment. The

detrimental effects were readily observed throughout all three study years. For example,

brief afternoon rain showers changed Trout Creek’s normally translucent waters to a dull,

opaque gray, the creek blackened by ash and silt. The creek’s water level fluctuated

throughout the summer and autumn and rose dramatically as upstream floodwaters raced

downstream. Several beaver dams burst from the pressure of these floods, unleashing

torrents of dammed water that stripped willows from the ground. Eroded soil also

clogged the beaver ponds, beaching the lodges on islands of gravel. The floodwaters

stripped the soil of native vegetation and invasive plants quickly colonized. Canada

thistle, yellow toadflax, and mullen moved into the Lower, Middle, Upper, and Fire lines,

preventing the regrowth of the indigenous riparian plants typical of Preble’s habitat.

Populations of spiky Canada thistle dominated the flooded banks of the Lower line.

Three years after the Hayman Fire, its injurious impact still scarred the landscape and

reduced Preble’s preferred habitat (Figure 46).

The Hayman burn area defined the southern border of the study area while the

North Rainbow Falls housing community delineated its northern border. Both the burn

area and the housing development curtailed the riparian ecosystem. Therefore, the

combined factors of imposing granite slopes, blackened burn areas, floods, erosion, and

the housing development in Trout Creek, compressed the Preble’s riparian habitat to a

meager 2.1 kilometer stretch along the creek bank.

Figure 45 = The Upper trap line at Trout Creek with the Hayman burn area in the distance.

Figure 46 = The burned forest surrounding the Fire line in 2005, three years after the Hayman Fire. Willow and riparian growth was slow.

PROCESSING AND MARKING OF ZAPUS:

Handling times for Zapus were limited to five minutes. All jumping mice,

including recaptures, were weighed with a Pesola scale. Sex (male or female), age (adult

or juvenile) and reproductive condition (lactating, pregnant, scrotal, nonlactating or

nonscrotal) were documented for each mouse (Figure 47). Photographs of each Zapus and the approximate environment were taken at each capture site as historical documentation. Using tweezers, small clumps of hair were gently pulled from the dorsal pelage and stored in plastic bags or sterile PCR tubes. Hair samples, and their apical root follicles from all Zapus captures, were frozen for later genetic analysis as requested by the USFS and the USFWS.

Figure 47 = Zapus were weighed with pesola scale. Sex, reproductive condition and age were also documented. GPS coordinates were recorded at the site of capture.

Positional waypoint coordinates were recorded for every jumping mouse capture

with a portable global positioning system (GPS) receiver (Garmin eTrex Vista). Satellite

accuracy for readings ranged from three meters to 11 meters. ArcGIS computer software

(version 8.1) was used to plot each capture location on USGS topographic maps.

Jumping mice were permanently marked with Passive Integrated Transponder

(PIT) tags (Destron-Fearing) inserted subcutaneously between the scapulae on the

dorsum (Figure 48). These tags provided each mouse with a unique identification

number. A Biomark portable reader (Boise, Idaho) read the tags and identified recaptures. Additionally, the reader functioned to scan possible predators and their scat for possible Zapus mortalities. Trapped animals other than Zapus were identified to genus and released. Due to the time limitations imposed by a single field researcher

checking approximately 300 traps each day, all other captured species were not marked

for recapture.

Figure 48 = All Zapus were permanently tagged with Passive Integrated Transponder (PIT) tags injected subcutaneously between the scapulae on the dorsum. The yellow portable reader (Biomark) scanned recaptures. When electrically excited by the reader, PIT tags emit a unique radio frequency that corresponds to a 10 digit identification number. Needle and PIT tag are enlarged and not to scale.

IDENTIFICATION OF ZAPUS VOUCHER SPECIMENS:

In order to distinguish Z. h. preblei from Z. p. princeps, voucher specimens were

collected at Gunbarrel, Sugar, and Pine Creeks. At these three sites, voucher males were euthanized with carbon-dioxide. At Trout Creek, a natural mortality, partially consumed

by a predator, was collected as a voucher specimen for later analysis. A total of four

Zapus voucher specimens were collected throughout this three-year study.

Skulls of the four voucher specimens were examined for the presence or absence

of the lower anteromedian toothfold (Figure 49) by Dr. Carron Meaney at the University

of Colorado at Boulder. The eruption of m3 relative to m2 and m1 determined the age of

each animal according to Klingener (1963). Dr. Meaney also measured cranial features in duplicate according to Conner and Shenk (2003). Dr. Mary Conner (Utah State

University) completed the discrete functional analysis (DFA) on the skull morphometrics according to the protocol used by Shenk and Conner (2003).

Figure 49 = The AMF toothfold on m1 was used to identify Zapus voucher specimens as Z.h.preblei. Molar diagram from Klingener (1963). 71

MOVEMENTS, DAY-NESTS & HIBERNACULA IN TROUT CREEK:

The Upland trap transects, K, L, and M, traversed the dry, forested uplands, and

its capture data documented the use of these non-riparian regions by Zapus.

Additionally, trapping data for recaptures measured the distances mice moved between

traps and lines. Positional waypoint data for recaptures were plotted on USGS

topographic maps with ArcGIS software (version 8.1). The software also calculated

travel distances.

Radio telelmetry provided a more detailed understanding of Zapus movements,

feeding, day-nests, and hibernation within Trout Creek. Zapus were outfitted with one-

gram radio transmitters (Advanced Telemetry Systems) and followed for the duration of

the transmitter battery or until the transmitter was dislodged (Figure 50). In accordance with USFWS regulations, only male, non-reproductively active jumping mice weighing more than 18 grams were collared for telemetry. Small capture rates for Zapus limited the sample size available for radio telemetry.

Figure 50 = Photograph of radio transmitter (ATS, <1gram) and collar. Signal receiver is in the background. 72

Collared animals were tracked during the day and night (Figure 51). The diminutive size of the mouse and the thick willow beds made tracking difficult, especially in the dark. Locations were triangulated and the animal was quietly approached within sight distance. Care was taken not to disturb the animal. Positions were marked with pin flags and GPS waypoints recorded. Radio telemetry was only used at Trout Creek.

Figure 51 = Radio transmitter signals were triangulated and then exact locations were pinpointed

In 2004, radio transmitters were secured to Zapus with the wire and plastic collar

provided by ATS. The collar was bulky and difficult to secure around the incredibly small necks of the jumping mice in the allotted five minutes. The wire and tubing added weight to the transmitter and the entire collaring process caused stress to the animal.

Therefore, in 2005, radio transmitters were secured quickly to the dorsal pelage of Zapus

with small dabs of surgical-grade super glue. The antenna rested discreetly along the backside of the Zapus (Figure 52).

Figure 52 = Zapus at Trout Creek with super-glued radio transmitter (outlined by the red circle) on the dorsum.

STATISTICAL ANALYSIS:

The Statgraphics Centurion XV software package (version 15.0.08) was used to

analyze small mammal capture data. ANOVA and Tukey’s Honestly Significant

Difference (HSD) tests were used to compare standardized capture data and their

respective means. Capture rates were compared for all species throughout the three year

span and individually between years interspecifically and intraspecifcally. Tukey’s HSD method was selected as the a posteriori procedure to compare pairs of means following the ANOVA analysis (Gotelli and Ellison 2004).

CHAPTER 4

RESULTS

During the three-years and 14,940 trap nights logged in the Pike National Forest, there were 3,144 small mammal captures from eight different species. This represents an overall capture rate of 21 percent. From the six study sites, there were 58 Zapus captures with 18 recaptures, representing 40 distinct Zapus individuals captured during the study period from 2003 to 2005. The overall capture rate specific to Zapus was 0.39 percent.

Zapus were captured at all study sites except the Monument Fire Center (Figure 53)

Figure 53 = Blue diamonds are GPS coordinates for Zapus captures at six sites in the Pike National Forest. There were 58 Zapus captures between 2003 and 2005. There were no captures at the Monument Fire Center. 75

Results are arranged according to study site. Surveys at Gunbarrel Creek, Sugar

Creek, Pine Creek, Upper Trout Creek and the Monument Fire Center were presence- absence surveys. Since Trout Creek at North Rainbow Falls was the main study site, an extensive statistical analysis was conducted on its results. The chapter concludes with a statistical synthesis of the Zapus data from the six sites across all study years.

GUNBARREL CREEK:

Throughout the 369 trap nights in Gunbarrel Creek, there were 27 small mammal

captures from three different species (Table 3). Of this total there were eight jumping

mice captures with one recapture, representing seven distinct Zapus individuals. There

were also 15 deer mice and four Mexican woodrat captures. Deer mice were caught most

frequently, representing 56 percent of the total captures. Mexican woodrats and jumping

mice accounted for 15 and 30 percent of the captures respectively. The overall capture

rate for small mammals was 7.32 percent. Despite the available riparian habitat, voles

were not captured at Gunbarrel Creek.

Table 3 = Total number of small mammals captured by species, 12-14 August 2003 along Gunbarrel Creek near Oxyoke, Pike National Forest, Colorado. Parentheses for jumping mice indicate recaptures. TN indicates the number of trap nights.

% OF TOTAL SPECIES TOTAL CAPTURES TN = 369 CAPTURES Deer Mice 15 56% Peromyscus maniculatus Voles 0 - Microtus spp. Mexican Woodrats 4 15% Neotoma mexicana Shrews 0 - Sorex spp. Jumping Mice 8 (1) 30% Zapus spp. TOTAL SMALL MAMMAL CAPTURE RATE = CAPTURES 27 7.32 %

Of the seven distinct captured Zapus at Gunbarrel Creek, three were male and

four were female. All captures were adults (Table 4). Female 45255B5301 was the only

Zapus recaptured during the survey period and was lactating. This lactating female was

the only mouse that was reproductively active. Weights for jumping mice ranged from

16 to 34.5 grams with an average weight of 27.9 grams.

Table 4 = Jumping mice (Zapus spp.) data for small mammal survey in Gunbarrel Creek near Oxyoke, Pike National Forest, Colorado, 12- 14 August 2003 with 369 trap nights. NS means “non-scrotal,” NL means “non- lactating” and L means “lactating.” The 19 gram voucher specimen was later identified as a western meadow mouse (Zapus princeps princeps) by AMF toothfold analysis and DFA of cranial measurements. ‘A’ indicates adult age- class. PIT NUMBER SEX DATE WEIGHT(g) AGE SITE NAME TRAP OTHER

452464193D M 8-13-03 16 A Gunbarrel Creek Up 27A NS 4525515608 M 8-13-03 26 A Gunbarrel Creek Up 20A NS 8-13-03 34.5 A Gunbarrel Creek Up 6A L 45255B5301 F 8-14-03 34.5 A Gunbarrel Creek Up 6A L 45260A6C3D F 8-14-03 28 A Gunbarrel Creek Up 5B NL 452224725C F 8-14-03 30.5 A Gunbarrel Creek Lo 35A NL 45284E402E F 8-14-03 35 A Gunbarrel Creek Lo 32A NL VOUCHER M 8-14-03 19 A Gunbarrel Creek Lo 42B Princeps

Five jumping mice were captured along the Upper line surrounded by the Hayman burn area. Three jumping mice were captured along the Lower line within a recently flooded zone. The narrow middle line, characterized by sparse vegetation, canyon-like walls, and intense flooding, yielded no Zapus captures. Jumping mice were never captured outside the riparian corridor as evidenced by the mapped GPS coordinates

(Figure 54). Additionally, jumping mice were captured only in sites with tall willows and a dense riparian understory (Figure 55A).

Figure 54 = Mapped GPS coordinates for Zapus captures at Gunbarrel Creek, Pike National Forest, 12-14 August 2003. Blue diamonds represent capture locations. Zapus were captured only on the Upper and Lower lines (highlighted in green) next to the creek within dense riparian vegetation.

Figure 55 = (A) The Lower trap line at Gunbarrel Creek, Pike National Forest, provided three Zapus captures. The blue arrow indicates the direction of creek flow. (B) Red circle indicates the capture location of the 19 gram voucher male on the Lower line. This voucher was later identified as a Princeps.

The Gunbarrel Creek survey was terminated after two days following positive

Zapus capture. The survey ended with the removal of a voucher specimen. The voucher male was taken from the Lower line in a dense stand of tall willows (previous Figure

55B). The study skin was processed and catalogued at the UCCS museum (Figure 56).

Figure 56 = Study skin of the 19 gram Z.p. princeps voucher specimen from Gunbarrel Creek, Pike National Forest, Colorado.

This 19 gram voucher male was later identified as a Stage 3, adult western jumping mouse, or the Princeps. The first lower molar lacked a distinct AMF toothfold

(Figure 57) and DFA of repeat cranial measurements supported the identification as

Princeps. The third lower molars had erupted parallel to m1 and m2 indicating an adult

Stage 3 age class.

Figure 57 = Right lower molars of adult Z.p.princeps from Gunbarrel Creek.

SUGAR CREEK:

Twenty small mammals from three species were captured in 240 trap nights at

Sugar Creek situated to the east of Gunbarrel Creek (Table 5). The small mammal

capture rate at Sugar Creek was 8.33 percent. Deer mice dominated the captures

representing 75 percent of the total captures. There was one Mexican woodrat and four

jumping mouse captures. Jumping mice represented 20 percent of the total captures but

there were no Zapus recaptures. Additionally, there were no vole captures.

Table 5 = Small mammal trapping data for 14-15 August 2003 at Sugar Creek, Pike National Forest, Colorado. There were no jumping mouse recaptures. TN indicates number of trap nights. % OF TOTAL SPECIES TOTAL CAPTURES TN = 240 CAPTURES Deer Mice 15 75% Peromyscus maniculatus Voles 0 - Microtus spp. Mexican Woodrats 1 5% Neotoma mexicana Shrews 0 - Sorex spp. Jumping Mice 4 20% Zapus spp. TOTAL SMALL MAMMAL 20 CAPTURE RATE = CAPTURES 8.33 %

Three male jumping mice and one female jumping mouse were captured at Sugar

Creek. Weights for jumping mice ranged from 15 to 29.5 grams with an average weight

of 21.6 grams (Table 6). All captures were adults and were not reproductively active.

Table 6 = Jumping mice (Zapus spp.) data for small mammal survey at Sugar Creek, Pike National Forest, Colorado, 14-15 August 2003 with 240 trap nights. NS means “non-scrotal,” NL means “non-lactating.” The 15 gram voucher specimen was later identified as a western meadow mouse (Zapus princeps princeps) by AMF toothfold analysis and DFA of cranial measurements. ‘A’ indicates adult age-class. PIT NUMBER SEX DATE WEIGHT(g) AGE SITE NAME TRAP OTHER 452413620D F 8-15-03 19 A Sugar Creek Lo 6A NL

4523495F7D M 8-15-03 23 A Sugar Creek Mid 14A NS 45236F373D M 8-15-03 29.5 A Sugar Creek Mid 31A NS VOUCHER M 8-15-03 15 A Sugar Creek Lo 9A Princeps

Zapus were caught on only the Lower and Middle trap lines (Figure 58). There

were two Zapus captures on each line respectively. The Upper line near several ATV

trails yielded no Zapus captures. Zapus were captured solely within the confines of the

riparian system, as verified by mapping of the GPS coordinates for each capture (Figure

59A). Sugar Creek also supported a large population of garter and bull snakes that were

observed sunning along trap transects near metal Sherman traps.

Figure 58 = Mapped GPS coordinates for Zapus captures at Sugar Creek, Pike National Forest, 14-15 August 2003. Blue diamonds represent capture locations. Zapus were captured only on the Lower and Middle lines (highlighted in green) next to the creek within dense riparian vegetation. Gunbarrel Creek captures along the Lower line are also mapped.

Figure 59 = (A) The Lower trap line at Sugar Creek, Pike National Forest, provided two Zapus captures. The blue arrow indicates the direction of creek flow. (B) Red circle indicates the capture location of the 15 gram voucher male. This voucher was later identified as a Princeps. Pink flagging marks trap stations.

The survey at Sugar Creek was terminated following positive Zapus capture. The

15 gram male voucher specimen was captured in a dense stand of willows on the edge of a small beaver pond along the Lower line (previous Figure 59B). The study skin was processed and catalogued at the UCCS museum (Figure 60).

Figure 60 = Study skin of the 15 gram Z.p. princeps voucher specimen from Sugar Creek, Pike National Forest, Colorado.

The voucher male was later identified as a Stage 3 adult western jumping mouse

(Z.p.princeps), or the Princeps. The first lower molar lacked a distinct AMF toothfold

(Figure 61) and repeat cranial measurements verified the identification as Princeps. The third lower molar had erupted to level of m1 and m2, indicating an adult Stage 3 age

class.

Figure 61 = Right lower molars of Z.p.princeps from Sugar Creek.

PINE CREEK:

In 250 trap nights along two transects used in Pine Creek, there were only four small mammal captures from three species: two deer mice, one vole and one jumping mouse (Table 7). The capture rate for small mammals was 1.6 percent. All mammal captures were within 200 meters of Pine Creek’s confluence with the South Platte River.

Additionally, all captures were within the boundaries defined by the intersection of Pine

Creek Road and Highway 93, South Platte River Road (Figure 62).

Table 7 = Small mammal trapping data for 16-17 August 2003 at Pine Creek, Pike National Forest, Colorado. TN indicates number of trap nights. % OF TOTAL SPECIES TOTAL CAPTURES TN = 250 CAPTURES

Deer Mice 2 50% Peromyscus maniculatus

Voles 1 25% Microtus spp.

Mexican Woodrats 0 - Neotoma mexicana

Shrews 0 - Sorex spp. Jumping Mice 1 25% Zapus spp. TOTAL SMALL MAMMAL CAPTURE RATE = CAPTURES 4 1.6 %

Figure 62 = Small mammal captures at Pine Creek were within 200 meters of the South Platte River. Blue arrow indicates direction of creek flow. Blue line approximates the location of the South Platte River. 85

The single 17 gram Zapus from Pine Creek was captured in a dry section of the creek, but inside the riparian corridor underneath the cover of willows (Figure 63). The capture site was three meters from the edge of the dirt road near a metal road sign (Figure

64). The mouse was not reproductively active and was collected as a voucher specimen

(Table 8).

Figure 63 = Mapped GPS coordinates for Zapus captures at Pine Creek, Pike National Forest, 16-17 August 2003. Blue diamonds represent capture locations. A single Zapus was captured on the B transect near the edge of the dirt road (highlighted in green). The mouse was captured within dense riparian vegetation.

Figure 64 = Capture site for the single Zapus at Pine Creek. Red circle indicates the capture location, which was three meters from a metal road sign and the edge of Pine Creek Road.

Table 8 = Jumping mice (Zapus spp.) data for small mammal survey at Pine Creek, Pike National Forest, Colorado, 16-17 August 2003 with 250 trap nights. The sole 16 gram voucher specimen was later identified as a Preble’s meadow jumping mouse (Z. hudsonius preblei) by AMF toothfold analysis and DFA of cranial measurements. The Preble’s mouse was a Stage 3 adult based on the eruption of the lower molars.

PIT NUMBER SEX DATE WEIGHT AGE SITE NAME TRAP OTHER VOUCHER M 8-17-03 16 A Pine Creek 40B Preble’s

The study skin of the Pine Creek voucher male was processed and catalogued at the

UCCS museum (Figure 65).

Figure 65 = Study skin of the 16 gram Z.h.preblei voucher specimen from Sugar Creek, Pike National Forest, Colorado.

The jumping mouse from Pine Creek was identified as a Preble’s meadow jumping mouse (Z.h. preblei) following an analysis of the AMF toothfold and DFA of cranial measurements. The AMF toothfold was clearly present on m1 as a distinct notch on the anterior edge of the tooth (Figure 66). DFA of repeated cranial measurements supported the AMF identification of the mouse as a Preble’s. The mouse was aged as a

Stage 3 adult because m3 had erupted exactly to the horizontal level of m2 and m1.

Figure 66 = Right lower three molars from Z.h.preblei collected at Pine Creek. Photograph is enlarged to show detail. The anteromedian toothfold on m1 was clearly visible, suggesting identification as Preble’s. DFA of cranial measurements confirmed the toothfold analysis. This Preble’s was a Stage 3 adult because m3 had erupted parallel to m2 and m1.

MONUMENT FIRE CENTER:

In 750 trap nights spaced over three nights in the unnamed creek at the Monument

Fire Center, there were 46 small mammal captures from two species (Table 9). There

were 27 deer mice and 19 vole captures, comprising 59 percent and 41 percent of the total captures respectively. The capture rate for small mammals was 6.13 percent.

Trapping results were comparable to Rob Schorr’s survey data dated September

1999: Zapus were not captured at the Monument Fire Center in 2003 or in 1999 along identical trap transects. The absence of jumping mice was notable because suitable habitat was available during both surveys (Figure 67), especially considering the site’s proximity to nearby Monument Creek and its established Preble’s populations. Major portions of the creek were dry and without consistent water flow during both the 1999 and 2003 surveys.

Table 9 = Small mammal trapping data for 29 August – 1 September 2003 along an unnamed Creek at the Monument Fire Center, Pike National Forest, Colorado. TN indicates trap nights

% OF TOTAL SPECIES TOTAL CAPTURES TN = 750 CAPTURES Deer Mice 27 59% Peromyscus maniculatus Voles 19 41% Microtus spp. Mexican Woodrats 0 - Neotoma mexicana

Shrews 0 - Sorex spp.

Jumping Mice 0 - Zapus spp. TOTAL SMALL MAMMAL CAPTURE RATE = CAPTURES 46 6.13 %

Figure 67 = The Middle line along an unnamed creek at the Monument Fire Center: (A) facing east; (B) facing west. Zapus were not captured during the survey despite the available riparian habitat and the creek’s close proximity to Monument Creek. Pink flagging marks trap stations.

Heavy vandalism complicated trapping at the Monument Fire Center. Raccoons

and domestic dogs were the most frequent culprits. Many domestic dogs ran at large

during the survey period, allowed off-leash by owners walking the nearby social trails.

Raccoon prints were also located near the survey lines.

Shorr’s trapping data were standardized to 100 trap nights to facilitate comparison

between the two survey years (Table 10). Captures for all small mammals decreased

from 1999 to 2003. The capture rate for small mammals decreased by 38.4 percent between 1999 and 2003. Shrews were captured in 1999 but not in 2003. Zapus were not captured during either survey.

Table 10 = Standardized small mammal captures for Preble’s surveys along an unnamed creek at the Monument Fire Center. Numbers of captures were standardized to 100 trap nights, as indicated by “STN”. SPECIES SCHORR 1999 HANSEN 2003 STN = 100 STN = 100 Deer Mice 27.4 3.6 Peromyscus maniculatus Voles 16.8 2.5 Microtus spp. Mexican Woodrats 0 0 Neotoma mexicana Shrews .32 0 Sorex spp. Jumping Mice 0 0 Zapus spp. TOTAL SMALL MAMMAL 6.1 CAPTURES (STANDARDIZED) 44.5

UPPER TROUT CREEK:

In 792 trap nights in Upper Trout Creek at the Manitou Experimental Forest, there were 450 small mammal captures from four different species (Table 11). The overall

capture rate for small mammals was 57 percent. With 156 captures, deer mice accounted

for 35 percent of the total captures. Voles were trapped the most frequently at Upper

Trout Creek with 284 captures, representing 63 percent of the total captures. Five Zapus

and five shrews were captured, each representing little more than one percent of the total

captures.

Table 11 = Small mammal trapping data for 13-19 August 2004 along Upper Trout Creek at the Manitou Experimental Forest, Pike National Forest, Colorado, Bakeman Site 3. TN indicates trap nights. Parentheses indicate recaptures for jumping mice. % OF TOTAL SPECIES TOTAL CAPTURES TN = 792 CAPTURES Deer Mice 156 35% Peromyscus maniculatus Voles 284 63% Microtus spp. Mexican Woodrats 0 - Neotoma mexicana Shrews 5 1.1% Sorex spp. Jumping Mice 5 (1) 1.1% Zapus spp. TOTAL SMALL MAMMAL CAPTURE RATE = CAPTURES 450 57 %

There was one jumping mouse recapture out of the five total Zapus captures, representing four distinct Zapus individuals (Table 12). From this group, there were two males and two females. Weights for jumping mice were on the high end of all study sites and ranged from 24 to 35 grams with a mean weight of 28.9 grams. None of the jumping mice were reproductively active. A voucher specimen was not collected at Upper Trout

Creek.

Table 12 = Zapus captures at Upper Trout Creek (Bakeman Site 3), Pike National Forest, Colorado, 13-19 August 2004. There was one recapture.

PIT NUMBER SEX DATE WEIGHT AGE SITE NAME TRAP OTHER 452A274A1E M 8-15-04 35 A Up Trout Creek 48B NS 4461521570 M 8-15-04 24.5 A Up Trout Creek 49B NS 8-17-04 24 A Up Trout Creek 32B NL 4461414051 F 8-19-04 - A Up Trout Creek 30B NL 45311E0C4E F 8-17-04 32 A Up Trout Creek 45B NL

Zapus were captured only on the B trap transect on the western side of the creek.

There were no Zapus captures on the A transect which followed the South Meadows

Campground hiking trail. Furthermore, Zapus were captured exclusively along a short

section of the B transect between trap stations 24 and 35, representing a distance of

approximately 55 meters (Figure 68).

Figure 68 = Mapped GPS coordinates for Zapus captures at Upper Trout Creek, Pike National Forest, 13-19 August 2004. Blue diamonds represent capture locations. Zapus were captured only on the B transect (highlighted in green) within dense riparian vegetation.

The high percentage of voles captured in 2004 (63 percent of the total captures) contrasted sharply to Bakeman’s trapping results from 2001. During his survey,

Bakeman did not capture meadow voles and he noted that their absence was unusual, especially considering the large capture rate for Zapus (2001). During Bakeman’s survey, Zapus accounted for 88 percent of the total captures. This capture rate was atypically large since, on average, Preble’s comprise only five percent of the small mammal community (Bakeman 1997).

Despite Bakeman’s high capture rate for Zapus, the overall capture rate for small mammals was 4 percent (Table 13). Conversely, the capture rate for small mammals was approximately 57 percent in 2004 but Zapus accounted for only 1.1 percent of the total captures. When standardized to 100 trap nights, vole captures were roughly 36 percent greater in 2004 and Zapus captures decreased by approximately three percent.

Table 13 = Standardized small mammal captures for Preble’s surveys along Upper Trout Creek. Numbers of captures were standardized to 100 trap nights, as indicated by “STN”. SPECIES BAKEMAN 2001 HANSEN 2004 STN = 100 STN = 100 Deer Mice 0.5 19.7 Peromyscus maniculatus Voles 0 35.9 Microtus spp. Mexican Woodrats 0 0 Neotoma mexicana Shrews 0.08 0.63 Sorex spp. Jumping Mice 3.5 0.63 Zapus spp. TOTAL SMALL MAMMAL 56.8 CAPTURES (STANDARDIZED) 4.1

TROUT CREEK AT NORTH RAINBOW FALLS:

Over three years and 12,539 trap nights in Trout Creek at North Rainbow Falls,

2,597 small mammals from eight different species were captured (Table 14). This

represents an overall small mammal capture rate of 20.7 percent. Deer mice, voles and

Mexican woodrats were the most commonly captured small mammals, representing 48

percent, 41 percent and 7.4 percent of the total captures respectively. Jumping mice

accounted for only 1.5 percent of the total captures with 40 captures and 16 recaptures,

representing a total of 24 distinct individuals. The capture rate specific to Zapus was

0.32 percent.

Table 14 = Total number of small mammals captured by species for 2003-2005 along Trout Creek at North Rainbow Falls, Pike National Forest, Colorado. Zapus were the only mammals tagged for recapture so all values represent total captures. Parentheses for Zapus indicate recaptures. TN indicates the number of trap nights and YR indicates trapping year. % of TOTAL SPECIES YR 2003 YR 2004 YR 2005 TOTAL TN = 1,070 TN = 5,887 TN = 5,582 TN = 12,539 CAPTURES Deer Mice 53 611 586 1,250 48 Peromyscus maniculatus Voles 18 833 215 1,066 41 Microtus spp. Mexican Woodrats 1 76 114 191 7.4 Neotoma mexicana Jumping Mice 1 17 (6) 22 (10) 40 (16) 1.5 Zapus spp. W. Harvest Mice Reithrodontomys 0 11 0 11 < 1 megalotis Shrews 1 7 9 17 < 1 Sorex spp. Desert Cottontails 0 3 10 13 < 1 Sylvilagus audubonii Least Chipmunks 0 3 6 9 < 1 Tamias minimus TOTAL SMALL 74 1561 962 2597 MAMMAL CAPTURES

Shrews (Sorex spp.), western harvest mice (Reithrodontomys megalotis), desert

cottontails (Sylvilagus audubonii) and least chipmunks (Tamias minimus) each

represented less than one percent of the total captures. Although not identified to species, voles were likely meadow voles (Microtus pennsylvanicus) and shrews the masked shrew

(Sorex cinereus, Figure 69).

Figure 69 = Shrew (Sorex spp.) captured in trap 2D of the Upper line at Trout Creek, North Rainbow Falls in September 2005.

In Trout Creek, small mammal capture rates increased from 2003 to 2004 as trap

nights increased. The small mammal capture rate was 6.9 percent in 2003, 26.5 percent in 2004 and 17.2 percent in 2005 (Table 15). Between 2004 and 2005, the capture rate decreased by 9.3 percent.

Table 15 = Total overall and yearly capture rates for small mammals during trapping in Trout Creek at North Rainbow Falls, Pike National Forest, Colorado, 2003 through 2005. YR 2003 YR 2004 YR 2005 TOTAL

TOTAL SMALL 74 1561 962 2,597 MAMMAL CAPTURES

TOTAL TRAP NIGHTS 1,070 5,887 5,582 12,539

OVERALL CAPTURE RATE 6.9 % 26.5 % 17.2 % 20.7 %

All trap lines in Trout Creek yielded small mammal captures. However, Zapus were captured only on the Lower, Middle, and Upper lines. The Lower and Middle lines yielded nearly equal numbers of Zapus captures, with 16 and 15 captures respectively.

The Upper line provided nine Zapus captures. Zapus captures occurred exclusively within the riparian system, as evidenced by the mapped GPS data and were excluded from the Upland lines and the Hayman Fire zone (Figure 70).

The capture data specific to Zapus is analyzed following a statistical analysis of captures for the four most commonly trapped small mammals.

Figure 70 = Mapped GPS coordinates for Zapus captures at Trout Creek at North Rainbow Falls, Pike National Forest, 2003-2004. Blue diamonds represent capture locations, including locations of recaptures. Zapus were captured only on the Lower, Middle and Upper lines (highlighted in green) next to the creek within dense riparian vegetation. Mice were never captured outside of the riparian corridor in the Upland grids.

Analysis of Total Small Mammal Captures at Trout Creek by Year:

Trapping data for Trout Creek was divided into smaller replication segments to statistically analyze differences in small mammal captures between years. Daily small

mammal captures were standardized to 100 trap nights and the means calculated for each

year. There were five replicates in 2003 (N2003 = 5), 35 replicates in 2004, and 35 replicates in 2005 (N2004 = 35, N2005 = 35). Next, the standardized yearly averages were

compared as a group with Fisher’s Analysis of Variance (ANOVA). The ANOVA null-

hypothesis concluded that there was no difference in small mammal captures between

years, and variance could be attributed completely to chance.

ANOVA rejected the null-hypothesis at the 95 percent confidence level.

Therefore, ANOVA indicated a significant difference between the yearly means, and

furthermore, the difference could not be attributed to chance. In other words, the mean

number of small mammals captured per 100 trap nights was significantly different

between the three study years.

A further statistical analysis using Tukey’s HSD method at the 95 percent

confidence level was performed to identify the significant difference for the yearly means

as suggested by ANOVA. Tukey’s HSD revealed significant difference between small

mammal captures for year 2004 and the other two years. There was no significant

difference in captures between 2003 and 2005 (Figure 71). Therefore, the 2004 capture spike was significant and significantly more small mammals were caught in 2004 than in

2003 or 2005. The results of the Tukey’s HSD analysis were graphically verified with 95 percent confidence intervals (Figure 72).

30 *

5 Mean Small Mammal Captures / 100 Trap Nights 100 Trap / Captures Mammal Mean Small 0 YEAR 2003 YEAR 2004 YEAR 2005

Figure 71 = Yearly means for total small mammal captures per 100 trap nights for 2003, 2004 and 2005 in Trout Creek, Pike National Forest, Colorado. ANOVA revealed significant differences between the group means. Tukey’s HSD revealed that numbers of small mammal captures in 2004 were significantly greater than captures in 2003 and 2005. Asterix indicates significant difference.

Figure 72 = Plot of standardized means for small mammal captures per 100 trap nights by year with Tukey HSD intervals. At the 95 confidence level, Tukey’s HSD revealed a significant difference in capture rates for Year 2004 compared to Years 2003 and 2005. Capture rates for 2003 and 2005 were not significantly different.

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Interspecific Analysis of Small Mammal Captures at Trout Creek:

To compare capture rates between the four most commonly caught small mammal

species, daily captures for deer mice, voles, woodrats and jumping mice were

standardized to 100 trap nights. Captures between years were combined yielding equal

sample sizes, or observations, for all four species (N = 75). The ANOVA null-hypothesis concluded that there was no difference between capture means for the four species during the entire study, 2003 to 2005.

ANOVA rejected the null-hypothesis at the 95 percent confidence level and suggested a significant difference between species captures as an entire group. Tukey’s

HSD analysis of the means at the 95 percent confidence level identified two homogenous

groups of significant difference: deer mice and voles; Mexican woodrats and jumping mice (Figure 73). There was no significant difference between the two members of each homogenous group. In other words, there was no significant difference between deer mice and voles or between Mexican woodrats and jumping mice. During the three-years in Tout Creek, jumping mice captures were significantly less than deer mice or vole captures, but not significantly different from woodrat captures. Graphical representation of Tukey’s HSD analysis supported these conclusions (Figure 74).

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12 *

Mean Captures / 100 Trap Nights 100 Trap / Mean Captures 2

0 Deer Mice Voles Mexican Woodrats Jumping Mice

Figure 73 = Mean number of captures per 100 trap nights for the four most commonly caught small mammals at Trout Creek, North Rainbow Falls, years 2003 through 2005. ANOVA revealed significant differences within the group. Tukey’s HSD revealed significant differences between two homogenous groups: deer mice and voles; woodrats and jumping mice. Error bars are Tukey’s HSD limits.

Deer Mice Voles Woodrats Zapus

Figure 74 = Plot of standardized means for small mammal captures per 100 trap nights by species with Tukey HSD intervals. At the 95 confidence level, Tukey’s HSD revealed a significant difference in capture rates for two homogenous groups. Deer mice and vole captures were significantly greater than woodrat and Zapus captures during the three-year study.

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Significance was further defined between species for each year. Standardized

captures were arranged into yearly samples, with five observations for each species in

2003 (N2003 = 5) and 35 observations for each species in 2004 and 2005 (N2004 = 35,

N2005 = 35). At the 95 percent confidence level, ANOVA indicated significant

interspecific differences between the mean captures for all three years.

Further statistical analysis with Tukey’s HSD revealed significant differences

between several species within years (Figure 75). In 2003, Tukey’s HSD analysis

identified a significant difference between the mean captures of deer mice and the other

three species. Therefore deer mice were captured significantly more than woodrats, voles

or jumping mice in 2003. However, there was no significant difference between vole,

woodrat or jumping mice captures.

In 2004, there were two homogenous groups demonstrating significant difference: deer mice and voles; woodrats and jumping mice. Although voles were the most numerous, there was no significant difference between vole and deer mouse captures in

2004. As a homogenous group, woodrat and jumping mouse captures were significantly less than vole and deer mouse captures. There was no significant difference between woodrats and jumping mice. In other words, mean captures of jumping mouse were significantly less than vole or deer mouse captures in 2004. However, jumping mouse captures were not significantly different from woodrat captures in 2004.

In 2005, there were four groups of significant difference. Mean captures for all species were significantly different from one another. Deer mouse captures were significantly greater than all other captures. Additionally, vole captures were significantly greater than woodrat or jumping mouse captures, but significantly less than

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deer mouse captures. Conversely, in 2005, Zapus captures were significantly less than

deer mouse, woodrat and vole captures. The analysis was verified graphically with

Tukey’s HSD intervals (Figure 76).

18 Deer Mice (1) * Voles (2) 16 Mexican Woodrats (3) Jumping Mice (4) 14

12 * 10

6 *

Mean Captures / 100 Trap Nights 4 * *

2 * *

0 * 1 2 3 4 1 2 3 4 1 2 3 4 YEAR 2003 YEAR 2004 YEAR 2005

Figure 75 = Mean captures for small mammals arranged by year for capture data from Trout Creek. ANOVA determined significant differences within each yearly group at the 95 percent confidence level. Tukey’s HSD identified significance within groups. Asterix indicates a significant difference. Brackets group homogenous data sets. In 2003, mean deer mouse captures per 100 trap nights were significantly greater than mean captures for the other three species. In 2004, there were two groups of homogenous difference: deer mouse and vole captures were significantly greater than woodrat and Zapus captures. However, there was no significant difference between deer mice and voles or woodrats and Zapus in 2004. In 2005, there was significant difference between all four species. Deer mice captures were significantly greater than the other three species. Conversely, Zapus captures were significantly less than deer mouse, vole and woodrat captures in 2005.

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Deer Mice Voles Woodrats Zapus

Deer Mice Voles Woodrats Zapus Figure 76 = Insterspecific means plot of capture rates by species for Years 2003 (top), Year 2004 (middle), and Year 2005 (bottom) with Tukey HSD intervals. In 2003, deer mouse captures were significantly greater than all other species. In 2004, deer mouse and vole captures were greater than woodrat and Zapus captures. In 2005, capture rates for all four species were significantly different. 105

In summation, significantly more small mammals were captured in 2004 than in

2003 or 2005. Small mammal captures increased significantly from 2003 to 2004 as

more trap nights were completed. However, capture rates decreased significantly

between 2004 and 2005 when trap nights were nearly equal. Throughout the three study

years, deer mouse and vole captures were significantly greater than Mexican woodrat or

jumping mouse captures. But between years, deer mouse captures were significantly

greater than captures for all other species in 2003 and 2005. In 2004, vole captures increased, but were not significantly different from deer mouse captures. Vole captures decreased significantly in 2005. Zapus captures were significantly less than all other species in 2005. However, Zapus captures were not significantly different from woodrats in 2004 and 2003 or from voles in 2003.

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Intraspecific Analysis of Small Mammal Captures at Trout Creek by Year:

In accord with field observations and before statistical analysis, the standardized

capture rates for the four most commonly captured small mammals at Trout Creek

suggested that vole captures peaked in 2004 (Table 16). Similar reasoning suggested that deer mouse captures increased in 2004 but remained steady from 2004 to 2005. Woodrat captures increased steadily during the three years while jumping mouse captures increased slightly in 2004 and again in 2005.

Table 16 = Standardized captures for the four most commonly trapped small mammal species in Trout Creek. Yearly species captures were standardized to 100 trap nights. S TN indicates the number of standardized trap nights and YR indicates year.

SPECIES YR 2003 YR 2004 YR 2005 S TN = 100 S TN = 100 S TN = 100

Deer Mice 4.95 10.4 10.5 Peromyscus maniculatus

Voles 1.68 14.1 3.85 Microtus spp. Mexican Woodrats 0.0935 1.29 2.04 Neotoma mexicana Jumping Mice 0.0935 0.289 0.394 Zapus spp.

In order to statistically compare captures for the four most commonly trapped small mammals between the three study years, the standardized captures per 100 trap nights for each trapping period were calculated. ANOVA revealed significant differences for voles and woodrats at the 95 percent confidence level. However, ANOVA did not identify differences for deer mice or jumping mice and accepted the null-hypotheses for these two species. Differences in capture rates for deer mice and jumping mice resulted from chance.

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Following ANOVA’s rejection of the null hypothesis for voles and woodrats,

Tukey’s HSD analysis of the means further revealed significant differences between each year for voles. Vole captures were significantly the greatest in 2004. Similarly, Mexican woodrat captures were greatest in 2005, but significance was not detected between 2004 and 2005 (Figure 77).

ANOVA accepted the null-hypothesis that differences between the capture means for jumping mice were insignificant. Instead, ANOVA accepted the null-hypothesis and determined no significant difference in yearly capture means for Zapus at the 95 percent confidence level. Tukey’s HSD supported the results of ANOVA. Therefore, differences in the mean captures for Zapus between 2003, 2004, and 2005 were insignificant (Figure

77).

As indicated by the yearly comparison for Zapus, ANOVA for deer mice captures accepted the null-hypothesis at the 95 percent confidence level. ANOVA suggested no significant difference between the yearly means for deer mice (Fratio = 3.0028, P = 0.056).

However, the F ratio was close to F critical (Fcrit = 3.12) and the probability value, P, close to the 95 percent cutoff, warranting “a posteriori” analysis. At the 95 percent confidence level, Tukey’s HSD determined that deer mice captures were significantly less in 2003 than in 2004 or 2005. There was no significant difference in mean captures for deer mice between 2004 and 2005 as graphically represented with Tukey HSD intervals (Figure 78).

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18 YEAR 2003 16 * YEAR 2004 14 YEAR 2005

6 *

4 Mean Captures / 100 Trap Nights 2 *

0 Deer Mice Voles Mexican Woodrats Jumping Mice Figure 77 = Yearly mean captures for the four most commonly trapped small mammals for years 2003, 2004 and 2005 at Trout Creek. ANOVA suggested significant in-group differences for voles and woodrats. ANOVA did not find a significant difference for deer mice or jumping mice.

Figure 78 = Intraspecific mean plots with 95 percent Tukey HSD intervals for deer mice, voles, woodrats and Zapus captures by year at Trout Creek.

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In summation, significant intraspecific differences in capture means were detected by ANOVA and Tukey’s HSD. Vole captures peaked significantly in 2004 and woodrat captures were significantly greatest in 2005. ANOVA suggested no significant difference between years for deer mice captures, but Tukey’s HSD suggested that deer mice captures were significantly less in 2003 than 2004 and 2005.

Although captures for other small mammals fluctuated significantly between study years, jumping mouse captures were consistent. ANOVA accepted the null- hypothesis for jumping mice and variations in mean Zapus captures between years were attributed to chance. Group analysis with Tukey’s HSD supported the results of

ANOVA. Therefore, differences in mean Zapus captures between years 2003, 2004, and

2005 were insignificant.

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Jumping Mice Captures in Trout Creek:

Despite the enormous trapping effort at Trout Creek at North Rainbow Falls, there were only 40 Zapus captures with 16 recaptures throughout the three-year study period.

This represents 24 distinct individuals captured between 2003 and 2005 (Table 17).

Zapus accounted for only 1.5 percent of the total small mammal captures and the capture rate specific to Zapus was 0.32 percent. At Trout Creek, there was no significant difference in the mean Zapus captures between years.

Out of the 24 individual Zapus captured at Trout Creek, four were female and 20 were male. The sex ratio was skewed in favor of males, with one female captured for every five males. Females accounted for only 14 percent of all Zapus captures, but males accounted for 86 percent. Although males dominated the Zapus catch, females were recaptured more frequently than males. Females assumed 56 percent of the total recaptures.

Only three individuals were recaptured between years after winter hibernation.

Females 4531286A0A, 4523737D01 and male 4523593337 were captured in 2004 and then again in 2005. Female 4523737D01 was captured twice as a non-reproductive juvenile in 2004 and recaptured as a lactating adult two more times in July 2005.

Despite an 82 percent increase in trap nights after 2003, the single 25 gram female captured on 3 September 2003 (45296A221F) was never recaptured.

Four captured Zapus were juveniles and the remaining were adults. Weights for

Zapus ranged from 14 grams to 43 grams. The average weight was 21.5 grams. Average weights for males and females were 21.9 grams and 29.1 grams respectively. On average, females weighed 7.2 grams more than males Female 4523737D01’s average

111 weight as a juvenile increased by 5.7 grams as the mouse transitioned from a low-weight juvenile into a reproductively active female.

One voucher specimen was collected at Trout Creek. After two weeks of radio telemetry, Male 45312F7657, with its radio collar intact, was found dead. The pelage was scarred and the right femur was dislocated, indicating predation. Skull analysis revealed the presence of the AMF toothfold, and coupled with DFA of cranial measurements, the mouse was identified as a Preble’s. The mouse was age classed as a late Stage 2 adult based on the nearly parallel eruption of m3 to m2. This Preble’s was at least one year old.

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Table 17 = Jumping mice capture data for Trout Creek at North Rainbow Falls, Pike National Forest, Colorado, 2003 through 2005. There were 40 Zapus spp. captures with 16 recaptures for a total of 24 individuals. ‘A’ indicates adult, ‘JV’ indicates juvenile. NS = non-scrotal, S = scrotal, NL = non-lactating, L = lactating, Preg = pregnant. Red PIT tag identification numbers indicate that the mouse was followed with radio telemetry. PIT NUMBER SEX DATE WEIGHT(g) AGE SITE NAME TRAP OTHER 45296A221F F 9-3-03 25 A Trout Creek Mid 22B 5-21-04 25.5 A Trout Creek Mid 24B NS 4527605878 M 6-5-04 23 A Trout Creek Mid 15B NS 6-27-04 20.5 A Trout Creek Lo 13B S 45274A3257 M 5-25-04 27.5 A Trout Creek Up 12A NS 4529324411 M 5-25-04 20.5 A Trout Creek Mid 29B 6-5-04 21 A Trout Creek Up 12A 45240D3640 M 7-23-04 18 A Trout Creek Mid 20A 6-27-04 28 A Trout Creek Mid 22A S 7-1-04 29.5 A Trout Creek Mid 35A S 4523593337 M 7-23-05 30.5 A Trout Creek Up 13B S Freq 424 4531345428 M 7-1-04 16.5 A Trout Creek Mid 14A S 7-3-04 19 JV Trout Creek Lo 20A NL 7-21-04 18 JV Trout Creek Lo 3B NL 6-30-05 21 A Trout Creek Lo 5A NL 4523737D01 F 7-1-05 - A Trout Creek Lo 18A NL 7-9-05 26 A Trout Creek Lo 17A L 7-15-05 25.5 A Trout Creek Lo 10A L 45295D5B7A F 7-11-04 28.5 A Trout Creek Mid 31A L 7-21-04 20 A Mid Trout Creek S 35BC 4526426057 M 7-22-04 17.5 A Mid Trout Creek S 18BC 9-12-04 41 A Trout Creek Up 11B NL 6-23-05 40 A Trout Creek Up 8A 4531286A0A F 7-9-05 - A Trout Creek Lo 19A L, Preg 8-8-05 33 A Trout Creek Up 4B NL 8-20-05 43 A Trout Creek Mid 17B L, Preg 9-30-04 18 A Trout Creek Lo 11A NS 45312F7657 M Freq 443 Preble’s 6-23-05 26 A Mid 4531432053 M Trout Creek 18BC 6-29-05 U15A M 6-29-05 16 A Trout Creek Up 15A No tag 445C772E34 M 6-30-05 19 A Trout Creek Up 9A S 453142487B M 7-1-05 19.5 A Trout Creek Lo 16A S 4531446B04 M 7-1-05 22 A Trout Creek Lo 9B S 446159114E M 7-10-05 23 A Trout Creek Lo 8A S 7-10-05 M17B M 7-10-05 25 A Trout Creek Mid 17B S,No tag 7-10-05 20.5 A Trout Creek Mid 7A S 45312D155D M 7-15-05 20.5 A Trout Creek Lo 16A S 453152521B M 7-17-05 19.5 A Trout Creek Lo 10A S 45315B0552 M 8-13-05 14 JV Trout Creek Lo 11D NS 4461215A2B M 8-25-05 14 JV Trout Creek Lo 12D NS 8-31-05 37.5 A Trout Creek Up 5A NS 45311F2B54 M Freq 385

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During trapping sessions, it was apparent that Zapus captures were more numerous in July. In 2004 there were eight captures and in 2005 there were 12 captures, for a total of 20 Zapus captures in July (Table 18). Capture rates seemed to decrease in

August and September as nighttime temperatures cooled, signaling winter’s approach.

However, when monthly capture rates for Zapus were standardized to 100 trap nights and the means statistically analyzed by ANOVA and Tukey’s HSD, no statistical difference was detected for Zapus captures between months (Figure 79). Differences in mean capture rates between months were insignificant and attributed to chance. Tukey’s HSD intervals at the 95 percent confidence level supported the analysis (Figure 80).

Table 18 = Zapus captures by month for Trout Creek, Pike National Forest, Colorado, 2003-2004. Values are not standardized to equal trap nights. YEAR MAY JUNE JULY AUGUST SEPTEMBER TOTAL 2003 - - - - 1 1

2004 3 4 8 0 2 17 2005 - 5 12 4 1 22

TOTAL 3 9 20 4 4 40

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1.6

1.4

1.2

0.8

Nights 100 Trap per Captures 0.6

0.4 Zapus spp. Zapus 0.2

Mean 0 M AY JUNE JULY AUGUST SEPTEMBER M ONTH Figure 79 = Mean Zapus capture rates standardized to 100 trap nights by month. N = 1 for May, N = 2 for June, July and August, and N = 3 for September. Although means were close, differences between months were insignificant (ANOVA and Tukey’s HSD).

Figure 80 = Mean plot of Zapus captures in Trout Creek by month with Tukey HSD intervals. Differences in capture rates for Zapus were insignificant between each month.

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Movement in Trout Creek:

The trapping data provided insight into movements of Zapus within the Trout

Creek drainage. The GPS readings for the 16 recaptures detected movement between

individual trap stations and between lines. Recaptures never returned to traps from a

previous capture, but they were recaptured on the same transect within 10 meters of a

previous capture.

With the positional GPS data recorded for each of these recaptures, ArcGIS

software (version 8.1) calculated maximum distances traveled by each mouse between trap stations. The creek layer guided distance measurements and digital elevation models

(DEMs) accounted for elevational change. Travel distances for Zapus ranged from 241.4 meters to 836.9 meters and the average distance moved between trap stations was 413.9 meters (Table 19).

Table 19 = Maximum distance measurements of Zapus between trap stations at Trout Creek. NUMBER OF MAXIMUM Zapus I.D. SEX LINES OF CAPTURE CAPTURES DISTANCE (m) 4527605878 M 3 Lower, Middle 563.3

45240D3640 M 2 Middle, Upper 241.4 4523593337 M 3 Upper, Middle 257.5 4523737D01 F 6 Lower 370.2 4531286A0A F 5 Lower, Middle, Upper 836.9 45312D155D M 2 Lower, Middle 563.3 4526426057 M 2 Middle 64.37 AVERAGE DISTANCE = 413.9

Females 4523737D01 (hereafter 7D01) and 4531286A0A (hereafter 6A0A) were captured six and five times respectively during the three year study. Both females

survived the 2004 winter and were captured again in the summer of 2005. Of all the

recaptures, Female 6A0A moved the farthest between trap stations (836.9 meters),

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traveling between the Lower, Middle, and Upper lines (Figure 81). During two seasonal

pregnancies in 2005, Female 6A0A moved from the Lower line to the Upper line and then returned to the Middle line. The Upper line yielded three of Female 6A0A’s five captures. The mouse was captured once on the Lower and Middle lines.

Figure 81 = Blue diamonds represent GPS coordinates of capture locations for Zapus female 4531286A0A (6A0A) between 2004 and 2005 in Trout Creek. The mouse moved a maximum distance of 836.9 meters between the Upper and Lower trap lines. The Upper line yielded three captures. The Zapus was captured once on the Middle and Lower lines.

Female 7D01 was captured twice as a juvenile in July 2004 and recaptured a total of six times. Following the winter of 2004, the mouse was recaptured as an adult on 30

June 2005. Lactation was observed on 9 July and 15 July 2005, and during this

reproductive period, Female 7D01 moved between trap stations 17A and 10A of the

Lower line. The mouse was captured exclusively on the Lower line, moving a maximum

370 meters between trap 3B and 20A (Figure 82). The mouse was only captured once on

the B transect and the five other captures were on the A transect bordering the edge of the

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creek. For roughly two weeks in July 2005, Female 7D01 exhibited site fidelity at the

Lower line, with captures in traps 18A, 17A, and 10A. However, this mouse was never

recaptured after 15 July 2005.

Figure 82 = Blue diamonds represent GPS coordinates of capture locations for Zapus female 4523737D01 (7D01) between 2004 and 2005 in Trout Creek. The mouse moved a maximum distance of 370.2 meters exclusively within the Lower trap line. The mouse was captured once on the B transect and five times on the A transect nearest the creek edge.

Zapus captures were limited to those traps and lines inside the riparian system.

Jumping mice were never captured in the Upland slope transects beyond the riparian

vegetation in the forested uplands. The Lower Upland line, composed of transects K, L,

and M, yielded only captures of deer mice. The Lower D transect, at the fringe of the

riparian system next to the upland K transect, yielded only two juvenile Zapus captures.

All other Zapus captures on the Lower trap grid occurred on transects A and B next to the southwestern creek bank. Deer mice, woodrats and voles were the sole species captured along the Middle Upland line inside the runoff drainage perpendicular to Trout Creek.

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Jumping mouse male 45312F7657 (hereafter 7657) was captured on 30

September 2004 and fitted with a radio transmitter (ATS, frequency 164.443 Hz), secured

by a wire collar. Dr. Joseph Merritt assisted the collaring and the mouse was monitored

in a clear Tupperware before its release. Movements, especially jumping, and respiration

appeared unhindered by the radio collar. The mouse was captured on the Lower line at

trap station 11A, less than 0.5 meter from the southwestern bank of Trout Creek near a

large woodrat midden (Figure 83). The mouse was released, with the collar intact, at the

exact capture site, trap station 11A. Subsequent toothfold and skull analysis classified male 7657 as a Preble’s meadow jumping mouse, a Stage 2 adult.

Figure 83 = Capture and release site for 18 gram male Preble’s mouse, 45312F7657 (7567) fitted with radio transmitter frequency 164.443 Hz. Upon release, the mouse remained motionless under the cover of the willows and dead sticks of the woodrat midden for three hours. The blue line highlights the bank edge of Trout Creek. The red circle identifies the capture and release site within the willows, Lower trap station 11A. Photograph of 7567 at the time of capture is reproduced in the upper right hand corner.

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Upon release, 7657 retreated into the adjacent willow thicket and woodrat

midden. Concealed by the willow branches and the midden’s sticks, the mouse remained

motionless for approximately three hours, from 1300 to 1604. Then, flushed from his

cover by two barking dogs running through the willow thicket, the Preble’s scurried to

the east along the creek bank. The homeowner from North Rainbow Falls was instructed

to control his dogs and leave the area. At 1613, the radio telemetry signal located

Preble’s 7657 in an open patch of grass and short willow stubs near Lower trap 14A. The

Preble’s moved downstream and finally retreated into a day-nest (DN-7657-A, discussed in the following section), located between Lower trap stations 12A and 13A, for approximately 40 minutes. This day-nest lay 5.0 meters from the water’s edge. After a brief rain shower, at 1659, the Preble’s traveled approximately seven meters between traps 14A and 15A. He remained stationary for 30 minutes until 1731.

At 1731, the radio signal pinpointed the Preble’s, affording visual confirmation of

the mouse inside a second day-nest (DN-7657-B, discussed in the following section).

This day-nest lay 3.6 meters from the edge of Trout Creek’s bank; 6.9 meters from the

edge of the water; and 3.0 meters from the Lower trap station 14A (Figure 84). The mouse remained in this second day-nest for 93 minutes until 1824. Sequestered in the day-nest, the Preble’s was observed sleeping with its eyes closed. While resting, the mouse changed positions several times, moving deeper into the nest or reorienting the direction of his head relative to the nest’s opening. At one point, its long tail protruded outside the day-nest’s opening hole. At other intervals, the radio transmitter antenna jutted through the opening hole. As the sun retreated behind the mountains and darkness

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enveloped Trout Creek, the mouse abruptly awoke and hurriedly exited the second-day

nest at 1824.

Figure 84 = Day-nest two for 18 gram male Preble’s mouse (45312F7657) near Lower trap station 14A within 5.0 meters of the water’s edge. The mouse rested in this day-nest for 93 minutes, awakened at 1824 after sunset and left the nest.

Shrouded by darkness at 1824, Preble’s 7657 vacated the second day-nest and

returned directly to the first day-nest (DN-7657-A). The mouse remained motionless inside this nest for 31 minutes. At 1855, the mouse suddenly bolted northwest into a patch of densely packed willows with a three-meter tall canopy. The Preble’s scrambled north through the willow thicket to Lower trap 6B. Here, the Preble’s approached the outer fringe of the riparian corridor, moving within 8.3 meters of the ponderosa pine forest on the contingent, north-facing granite slope. At 1924, the transmitter signal

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disappeared, suggesting that the Preble’s crossed the creek. Due to the cold temperature

(-1ºC), and the difficulty of navigating the willow thicket in the dark encumbered by the

bulky receiver antenna, monitoring ceased until the next morning.

On 1 October 2004 at 0830, the Preble’s signal emanated from a willow clump

covered by thick vines of hops, near Lower trap station 7D, situated on the northeast

bank, across Trout Creek from the previous sighting at Lower trap 6B. Between 0925

and 1340, the signal unexpectedly disappeared. Three tests with an unused transmitter

indicated that the receiver and antenna were still functional. At 1340, radio contact

placed the Preble’s near the same willow clump adjacent to trap 7D. Multiple

triangulations of the signal positioned the mouse underneath the willow and hops, at least

0.3 meters underground (Figure 85). The signal remained stationary for approximately

eight more hours. Monitoring for the day ended at 2130.

Figure 85 = Willow clump surrounded by vines of hops where Preble’s male (45312F7657) was located on 1 October 2003 between 0830 and 2130. The strongest signal was 0.85 meters above the water level and 0.3 meters underground beneath the willow bush. 122

From 1 October through 10 October 2004, the Preble’s location, 0.3 meter beneath the small willow bush on the northeastern bank of Trout Creek, remained unchanged. The strong radio signal emanating from the same precise location throughout this 10-day period, suggested that the Preble’s was hibernating in an underground hibernaculum. Small fluctuations in the signal frequency and gain recorded movement of the transmitter antenna on the mouse. This in turn documented the Preble’s movement inside the internal chamber. Monitoring sessions started early in the morning and lasted all day until after nightfall. The Lower, Middle, and Upper trap transects were also set during this period

During this 10-day period of hibernation, nighttime temperatures fell to -6.6ºC.

Thick frost blanketed the willow leaves and Sherman traps at early morning trap checks

(Figure 86). The ground’s surface was wet and cold, with daytime temperatures averaging 4.4ºC. Then, typical of Colorado’s fickle weather, the temperature rose to

18.3ºC, punctuated by severe thunderstorms and lightning.

Figure 86 = Sherman trap covered by a think layer of frost, typical of early morning trap checks in October at Trout Creek.

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On a warm autumn day, 11 October at 1530, the 10-day stationary signal, located

continuously beneath the willow clump inside the creek bank, ceased. Instead, the

triangulated signal transitioned north of the hiberniculum along the creek bank. At 1600,

the signal emanated from a willow patch at the borderline between Forest and private

property. Here, the Preble’s with its radio collar intact, was visually identified at 1619.

Then, at 1623, the Preble’s scurried into a willow clump located directly below the green

gate that artificially separates Preble’s habitat in the Pike National Forest from privately

owned habitat in the North Rainbow Falls housing development (Figure 87). Next, at

1723, the signal shifted northwest, indicating that the Preble’s traversed the creek onto

private property. And finally, at 1810, the triangulated signal placed the Preble’s on private land outside Forest jurisdiction. As a result, monitoring terminated.

Figure 87 = Positive sighting location of Preble’s (45312F7657) on 11 October 2004 after 10 days of hibernation in an underground chamber. The brown line highlights the parking area in North Rainbow Falls next to the green gate that separates private property form Forest.

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The next morning, 12 October at 0930, Preble’s 7657 was again located directly below the green gate separating Forest from private property. As the researcher walked toward the most recent sighting location, the mouse was flushed from its willow cover, substantiating Schorr’s observations that researcher intrusion affects the mouse’s movement (2003). However, the Preble’s arousal afforded a third visual identification.

Without warning, the well-habituated red fox, fed by homeowners, suddenly appeared.

The red fox elicited immediate concern for the Preble’s safety. As a result, the area was quickly vacated to avoid leading this tame predator to the mouse. Returning to the site at

1130, radio telemetry failed to locate the Preble’s. Finally, after four hours of searching, at 1300, the carcass of Preble’s 7657 was found floating at the bottom of shallow pond next to the bridge and boat dock inside the housing community (Figure 88).

Figure 88 = Preble’s 45312F7657 emerged from hibernation on 11 October and was positively identified twice on the 11th and 12th. At 1300 on 12 October, the carcass of 7657 was found in a shallow pool within the North Rainbow Falls housing community, visibly scarred.

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Upon retrieval of the carcass, the radio collar remained around the Preble’s neck, but his body was visibly scarred and bloodied. Teeth marks marred the dorsal pelage and the right femur was dislocated. A post-mortem analysis determined that the Preble’s was most likely a victim of predation. Because the red fox appeared immediately following visual identification of the mouse moving through the willows, it is probable that the fox killed the Preble’s. The predator dislocated the right femur during capture. The Preble’s was likely partially consumed by the red fox before the metal collar and antenna disrupted mastication, and the carcass was discarded into the creek. The carcass of

Preble’s 7657 moved with the current and sank to the bottom of the small pool.

Preble’s 7657 moved a maximum distance of 708 meters between the second day- nest (DN-7657-B) and the last sighting location directly below the green gate (Figure 89).

All of the Preble’s movements were confined to the riparian system. The mouse did not venture outside of the riparian vegetation into the upland slopes to feed. Additionally, the

Preble’s two day-nests and hibernaculum were within the riparian system. All of the

Preble’s activity occurred within seven meters of the creek bank and 8.3 meters from an adjacent upland slope.

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Figure 89 = Movements for Preble’s 45312F7657 at the Lower line recorded with radio telemetry. The mouse was captured and released at Lower trap station 11A. Two day-nests and a hibernaculum were locatednear the release site. Blue line highlights Trout Creek. The Preble’s mouse traveled a maximum of 708 meters between its second day-nest and the last sighting.

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Jumping mouse male 4523593337 (hereafter 3337) was first captured on 27 June

and once more 1 July 2004. The mouse survived the winter of 2004 and was recaptured

the morning of 23 July 2005. As evidenced at all three captures, the mouse was an adult,

with an average capture weight of 29.3 grams. Additionally, the Zapus was visibly

scrotal at all three captures. In 2005, a radio transmitter was affixed to the dorsal pelage

of 3337 with surgical-grade super glue (ATS, Frequency 164.424 Hz, Figure 90). The collar was stable and movement appeared unhindered. The efficient collaring process required less than two minutes of handling time.

Figure 90 = Male 4523593337 at the time of capture on 23 July 2005 and following its release with an affixed radio transmitter (ATS, Frequency 164.424 Hz). The mouse was scrotal and weighed 30.5 grams.

Zapus male 3337 was released with its radio transmitter at 0925 on 23 July 2005

adjacent to its capture site, trap station 13B on the Upper line, 10.3 meters from the edge

of Trout Creek (Figure 91). During approximately four hours of monitoring, the mouse

remained stationary under the willows adjacent to trap 13B. Then at 1330, the mouse

moved northeast to a different patch of willows nearby, distinguished by the presence of

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a tall willow with a large diameter trunk. Monitoring was interrupted at 1400 due to rain

and lightning strikes. At 2000, the radio transmitter dislodged from the mouse and was

found inside a small day-nest (DN-3337-A). This small, globular day-nest, composed of dead willow leaves, lay within 0.5 meter of the last sighting near the base of the distinctively tall willow. Several hairs stuck to the transmitter and residual dried glue.

Zapus 3337 used its large hindlegs to obstruct collaring and most likely the hindlegs

succeeded in prying the transmitter from the dorsal pelage.

Figure 91 = Capture and release site for male 452359333 at Upper line trap station 13B.

The radio transmitter was removed after approximately 10 hours, but a day-nest

was successfully located for Zapus male 3337. Throughout the 10 hours of radio

telemetry, the mouse moved minimally, venturing a maximum of 10 meters from the

129 capture/release point at Upper trap 13B. Its day-nest lay 7.2 meters to the northeast of the release site. The mouse never left the riparian system during monitoring (Figure 92).

Figure 92 = Movements for male 452359333 at the Upper line recorded with radio telemetry. The mouse was captured and released at Upper trap station 13B. A day-nest was located 7.2 meters to the northeast of the release site. Blue line highlights Trout Creek.

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Jumping mouse male 45311F2B54 (hereafter 2B54) was captured in trap 5A of the Upper line on 31 August 2005. The Zapus weighed 37.5 grams, a noticeably heavy capture (Figure 93). A radio transmitter was glued to the dorsal pelage (ATS, Frequency

164.385 Hz). The mouse was released at 0815 at its capture site near Upper trap 5A and followed for 15 hours. Overnight monitoring on 31 August terminated prematurely at

2200 after a violent thunderstorm with heavy rain and lighting strikes moved above the drainage.

Figure 93 = Male 45311F2B54 at the time of capture on 31 August 2005. The mouse was nonscrotal and weighed 37.5 grams.

At 0830 on 31 August, Zapus 2B54 moved northwest from the capture site and crossed Trout Creek. The mouse then retreated into an area of thick willows near the

Forest Service post-and-cable bordering the ATV trail (Figure 94A). Two hours later at

1030, the mouse was flushed from a large day-nest (DN-2B54-A, discussed in the following section), in spite of the researcher’s cautionary approach. The mouse with its affixed radio transmitter, jumped out of the day-nest and remained motionless next to tall

131 willows and patch of Canada thistle (Figure 94B). The mouse had traveled 11 meters from trap station 5A to this day-nest.

Figure 94 = (A) Mouse 45311F2B54’s day-nest and feeding pile in relation to the upland forest and post-and-cable ATV fence. (B) The mouse with affixed radio transmitter after jumping out of the day-nest as the Biomark reader was passed overhead. 132

Careful attenuation of the radio receiver indicated that the Zapus had returned to

its day-nest by 1048. The mouse remained in the day-nest for approximately two more

hours. At 1305, a scan of the day-nest with the Biomark PIT tag reader startled the

concealed mouse and it jumped out of the day-nest and landed 0.3 meter away. This

enabled visual identification of the Zapus. The collar remained firmly affixed to the dorsal pelage and movements were unhindered by the radio transmitter. The mouse hid

underneath dense vegetation, but was easily observed breathing and the Zapus eventually fell asleep outside the day-nest. At 1324, the mouse slowly crawled back inside the day-

nest. At 1750, a second scan of the day-nest with the Biomark reader again flushed the

mouse out of the day-nest. After 10 minutes, the mouse returned to the day-nest, where it

remained to the end of the monitoring session at 2200 due to the thunderstorms.

Therefore, despite three unnatural movements caused by researcher intrusions, the mouse

remained in the day-nest for 13.5 hours.

The next morning at 0900, Zapus 2B54 was not in its day-nest. A Biomark scan

of the nest elicited no response. At 1210, the radio transmitter, dislodged from the Zapus,

was located next to a small feeding pile at the edge of the tall willows (feeding pile

discussed in the following section). Small clippings of Canada thistle and riparian

grasses were situated next to the discarded transmitter. During the telemetry monitoring

period, male 2B54 never ventured outside the riparian system (Figure 95). The mouse

remained in its day-nest during the day and after dark. It fed on thistle and grasses from

the riparian system, but did not feed on the adjacent upland slopes.

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In spite of continued trapping effort, neither Zapus male 3337 or 2B54 were recaptured. Therefore, the absence of voucher specimens precluded the identification of these Zapus as Princeps or Preble’s.

Figure 95 = Movements for male 45311F2B54 at the Upper line recorded with radio telemetry. The mouse was captured and released at Upper trap station 5A. A day-nest was located 11 meters to the northwest of the release site on the opposite side of the creek. Blue line highlights Trout Creek.

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Day Nests and Feeding Piles in Trout Creek:

Radio telemetry of two Zapus and one Preble’s located four active day-nests and one feeding pile in the Trout Creek drainage. Preble’s 7657 used two day-nests during monitoring with radio telemetry. The first day-nest (DN-7657-A) was 2.1 meters from the bank edge and 5.0 meters from the water between Lower traps 12A and 13A. The second day-nest (DN-7657-B) was 3.6 meters from the bank edge and 6.9 meters from the water’s edge, near Lower trap 14A (Figure 96). The Preble’s mouse frequented both nests on 30 September 2004. A 6.7 meter stretch of riparian vegetation separated the two

nests. Both nests were outside the creek floodplain but within the willows.

Figure 96 = Locations of two day-nests used by Preble’s 45312F7657 in relation to Trout Creek, Lower line trap stations and the site of release and capture.

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The first day-nest (DN-7657-A) used by Preble’s 7657 was situated at the base of an old willow. Beaver previously chewed the lower branches of this willow, leaving behind sharply pointed branches that protruded above the riparian grasses. Compared to the surrounding vegetation, this particular willow was short, approximately one meter tall. The day-nest was nestled against the base of the willow and well protected by the thick, overhanging willow branches (Figure 97).

Day-nest DN-7657-A was constructed of dead grasses, typical of the surrounding vegetation. The grasses were tightly woven, but an opening hole leading into the day- nest was not readily visible. The intricate weave of the dead grasses distinguished the nest from the adjacent riparian vegetation. The nest was circular with a domed top rising approximately seven centimeters above ground level. The diameter of the day-nest was approximately 15.5 centimeters. Following its initial release, Preble’s 7657 spent 40 minutes inside this nest.

Figure 97 = Day-nest (DN-7657-A) used by Preble’s mouse 45312F7657 during radio tracking on 30 September 2004. The pen provides scale. The brown line highlights the outside edge of the nest. 136

Preble’s 7657 eventually left its first day-nest and traveled between Lower trap stations 14A and 15A before retiring to a second day-nest (DN-7657-B). This nest featured a well-defined circular opening hole and the Preble’s was clearly visible sleeping inside the day-nest (Figure 98). The antenna from the radio transmitter jutted outside the day-nest’s perfectly rounded entrance. The mouse shifted positions several times inside the day-nest, and at one point, its long tail protruded from the opening hole as the

Preble’s oriented its head toward the back of the day-nest (Figure 99). Similarly constructed from dead riparian grasses as DN-7657-A, the day-nest rested flush against a small-diameter willow stump. Preble’s 7657 remained in this nest for 93 minutes until sundown.

Figure 98 = Preble’s 45312F7657’s inside its second day-nest (DN-7657-B) with the radio transmitter antenna protruding from the opening. The mouse slept in this nest for 93 minutes after leacing its first day-nest (DN-7657-A). The mouse awakened at sundown and left the nest.

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Figure 99 = Preble’s 45312F7657’s long tail sticking out of the small opening of its second day-nest (DN-7657-B) after reorienting its head toward the back of the nest.

Following its release from Upper trap 5A, Zapus male 2B54 crossed Trout Creek

and retreated to a day-nest (Figure 100). This nest was seven meters from the edge of

Trout Creek below a dense stand of tall willows. Surrounded by thick, herbaceous vegetation, the day-nest lay on the ground near the trunk of a thin willow. A small patch of Canada thistle grew nearby. The nest was constructed of dead grasses weaved tightly into a globular structure. An opening hole leading inside was not readily visible.

However, when startled, the mouse jumped out of the nest without disturbing its construction, suggesting the presence of a concealed opening. The day-nest’s diameter was 15 centimeters and the nest was six centimeters tall, the top shaped like a rounded dome. Male 2B54 remained inside the nest for 13.5 hours.

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Figure 100 = Day-nest (DN-2B54-A) for Zapus 45311F2B54. The diameter was approximately 15 centimeters. The mouse remained in this nest for 13.5 hours. Sharpie marker pictured for scale reference.

Of the four observed day-nests, Zapus male 2B54’s day-nest was situated farthest from the edge of Trout Creek and nearest the adjacent forested uplands. Although nestled within tall, dense willows and riparian grasses, the day-nest was only one meter from the edge of a steep, 40 degree incline of loose, decomposing granite (Figure 101).

However, radio telemetry verified that the mouse did not venture into the uplands at night or day.

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Figure 101 = Location of day-nest used by Zapus male 45311F2B54 in relation to the adjacent 40 degree granite slope. The day-nest was one meter from the edge of the slope beneath a dense willow canopy.

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Radio telemetry located a feeding pile, indicative of Zapus presence, used by

mouse 2B54. The feeding pile was positioned six meters northeast of the day-nest (DN-

2B54-A), near the edge of the tall willows, approximately four meters from the creek bank and concealed by dense riparian vegetation. Well-traversed vole runways passed within 15 centimeters of the feeding pile. Clipped Canada thistles lay next to the feeding pile while the discarded thistle leaves were inside the feeding pile (Figure 102). The thistle leaves in the feeding pile were verified by Dr. Janet Hardin of Colorado State

University.

Figure 102 = Feeding pile of Zapus 45311F2B54. The mouse clipped adjacent Canada thistle and ate the fleshy stems, discarding the leaves in the pile. The feeding pile was six meters from a day-nest. Pen illustrates scale.

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Underneath the willow canopy, Canada thistle generally do not flower or seed and resemble dandelion greens (Hardin personal communication). In contrast, the thistle outside the willow canopy seed with purple flower heads and the leaves are spiked.

Zapus 2B54 foraged on slender, non-seeding thistles growing beneath the willow canopy.

The mouse clipped the thistles close to the ground and the stems were noticeably missing.

The leaves from the consumed stems were discarded inside the feeding pile. Therefore, the feeding pile documented that Zapus feed on the fleshy stems of Canada thistle. The feeding pile resembled Quimby’s description for Z.hudonius in the Midwest (1951).

Furthermore, Zapus 2B54’s radio transmitter was located within the feeding pile next to the discarded thistle leaves.

Hibernacula in Trout Creek:

Radio telemetry of Preble’s 7657 located one hibernal chamber in the Trout Creek drainage. The Preble’s mouse entered the hibernaculum on 1 October 2004 and unexpectedly emerged on 11 October 2004. The unchanged, continuously strong radio signal pinpointed the hibernaculum’s position underground. Buried inside a south-facing creek bank approximately 0.85 meter above the water line, the soil surrounding the

Preble’s hibernaculum appeared moist, loosely compacted like rich, black potting dirt.

Relative to the slope and surface of the creek bank, the Preble’s placed his hibernaculum at the vertex of a 90º triangle with roughly equilateral sides: 0.3 meter from the hypotenuse-forming slope and 0.3 meter below the surface underground (Figure 103).

Due to Forest Service restrictions, the chamber could not be excavated the following year.

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Figure 103 = Location of hibernaculum for Preble’s 7657 relative to the Lower line and Trout Creek. Based on radio signals, the chamber was 0.85 meter above the water and 0.3 meter underground.

Hibernation and Breeding in Trout Creek:

Throughout the three-year in Trout Creek, Zapus capture data supported the generalized hibernation timeline for jumping mice in Colorado. For example, male

4527605878 represented the earliest Zapus capture on 21 May 2004 and weighed 25.5 grams (Table 19). Preble’s 7657 represented the last Zapus capture on 30 September

2004 and weighed 18 grams. Zapus were never captured in October, but Preble’s 7657 emerged from hibernation on 11 October 2004. Additionally, only deer mice, not Zapus, were captured during an unseasonably warm spring break trapping session on the Lower,

Middle, and Upper lines, 26-28 March 2004. Therefore, Zapus emergence and immergence dates in Trout Creek are approximated at: late May and late September respectively.

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Although no jumping mice were captured in Trout Creek during October, Zapus may remain active into October in order to boost fat reserves prior to hibernation as evidenced by the Preble’s 7657 emergence on 11 October 2004. As previously stated, statistical analysis detected no significant difference in mean Zapus captures as photoperiods shortened and night temperatures fell, corresponding to expected immergence. Regardless of the season, spring, summer, or autumn, ANOVA and

Tukey’s HSD detected no significant difference for mean Zapus captures between all months. Furthermore, at the four selected survey sites in the Pike National Forest, the difference between the monthly average weights for all Zapus captures remained insignificant even in the months of observed pre-hibernation weight gain (discussed in the following section).

Table 19 = Earliest and latest dates of Zapus capture in Trout Creek with the weight of the respective jumping mouse capture. FIRST FIRST Zapus LAST LAST Zapus YEAR WEIGHT WEIGHT TRAP DATE CAPTURE TRAP DATE CAPTURE

2003 2 September 3 September 25 g 8 September 3 September 25 g 2004 20 May 21 May 25.5 g 14 October 30 September 18 g 2005 1 June 23 June 40 g 1 October 31 August 37.5 g

In spite of cold, overnight temperatures typical of late summer or fall in the

Colorado mountains, Zapus were never captured or observed in torpor during the entire three-year study period. In addition, only three individuals out of the 11 distinct Zapus captures in 2004 were recaptured in 2005. Therefore, 73 percent of the Zapus captured in

2004 were never recaptured in 2005, suggesting they succumbed to over-wintering mortality or perhaps predation.

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Evidence of reproductively active jumping mice, as indicated by enlarged

mammae, pregnancy, or descended testicles (Figure 104), was documented as early as 27

June and as late as 20 August. Scrotal males were captured between 27 June and 23 July

and lactating females between 9 July and 20 August. During the three years, 20 August

2005 remains the latest capture date for a pregnant female. In the July surveys

encompassing all three years, 80 percent of the total Zapus captures were reproductively

active, compared to 30 percent and 20 percent in June and August respectively for the

combined years (Figure 105). Furthermore, the first two weeks in July yielded the most

captures of reproductively active Zapus. Female 6A0A provided evidence that Zapus in

Trout Creek experienced two breeding cycles during the active season: 6A0A was pregnant on 9 July 2005; non-lactating on 8 August 2005; and pregnant again on 20

August 2005. Therefore, Zapus breeding periods in Trout Creek were approximated to

late June through early July, followed by a second breeding period in late August.

Figure 104 = Reproductively active Zapus in Trout Creek: pregnant and lactating female 4531286A0A and scrotal male 445C772E34. Two breeding cycles were observed, early July and late August. 145

25 Total Captures Reproductive Captures 20

Number of Zapus Captures Zapus of Number 5

0 May June July August September October MONTH

Figure 105 = In July, 80 percent of the Zapus captures were reproductively active. In June and August, 30 percent and 20 percent of the Zapus captures were reproductively active respectively. Reproductively active Zapus were not captured in May or September.

The capture data for female Zapus 7D01 suggest that female juveniles in Trout

Creek did not breed during their first year. For example, Zapus 7D01 was captured twice in July 2004 as a low weight, 18 to 19 gram, non-reproductive juvenile. Though recaptured on 30 June 2005, within the approximate breeding period, female 7D01 remained a non-reproductive adult weighing 21 grams. However, nine days later on 7

July 2005, 7D01 was captured as a 26 gram lactating adult. Furthermore, males

45315B0552 and 4461215A2B were captured late in the season, on 13 and 25 August

2005 respectively, as extremely low weight juveniles, both 14 grams. The mice were not reproductively active, suggesting that males born late in the season do not breed. Instead, energetic resources are likely used for pre-immergence feeding.

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Wildlife, Predation, Anthropogenic Factors, and Floods Impacting Trout Creek:

Throughout the three-year study, several carnivore species were observed

foraging in the Zapus habitat near the trap lines. Coyote (Canis latrans) and red fox

(Vulpes vulpes) fed regularly on large desert cottontails, which thrived along the banks of

Trout Creek. Coyote hunted for prey in the dense riparian vegetation, but retreated back

into the adjacent forest to feed. The numerous red fox were well habituated to the nearby

housing community. Frequently the tame animals approached the homes scavenging for

garbage or begging the owners for food in broad daylight. Homeowners admitted feeding the fox. Additionally, raccoon (Procyon lotor) and striped skunk (Mephitis mephitis) were observed near the trap lines. Black bear (Ursus americanus) roamed through Tout

Creek and brazenly flattened several Sherman traps while greedily extracting the peanut butter and oats. The presence of mountain lions (Felis concolor) was documented by the homeowner’s reports to the Division of Wildlife, detailing mountain lion invasions inside their homes. Furthermore, mountain lion deer kills were found farther up the Trout Creek drainage adjacent to the Hayman burn area.

Figure 106 = Well-habituated red fox (Vulpes vulpes) frequented the housing development and the Lower trap line.

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Mule deer (Odocoileus hemionus) and elk (Cervus elaphus) foraged along the banks and drank from Trout Creek. These large ungulates probably used the interconnected drainage systems as an efficient movement corridor, possibly disrupting

Zapus habitat and behavior. For example, mule deer waded into the creek and traveled through the aqueous corridor connecting Trout Creek and West Creek. Scat from both species littered the hiking trail paralleling Trout Creek and the grounds adjacent to trap stations. Additionally, several Sherman traps were bent with artiodactyl hoof prints embossed onto the metal finish and the vegetation trampled. Each year, at the official start of hunting season, rifle shots reverberated from the burn area upstream, further categorizing Trout Creek as popular mule deer and elk habitat and underscoring anthropogenic intrusion into Zapus habitat.

Beaver (Castor canadensis) and muskrat (Ondatra zibethicus) actively moved throughout the Trout Creek waterway, from the resident-made ponds in the housing community to the shallow pools in the burn area. Three large beavers regularly sunned in the early morning like beached walruses, their large bodies framed by the steam rising off the cold creek waters. Dams and lodges dotted the waterway and shifted locations between years. A lodge below the Middle trap line was active in 2003 and 2004, but remained inactive in 2005. Its supporting dam was breached by floodwaters and the lodge, now choked by silt instead of water, was abandoned. The lodge was discarded and left like a vacant island surrounded by dry mud and young willows. This area remained inactive until late August 2005. Then a new dam was meticulously constructed upstream from this vacated lodge. To build this new damn, the beavers felled the willows, ruining

148

the riparian habitat. The beaver dam flooded the riparian vegetation and thus eliminated

the first ten trap stations of the Middle line and destroyed Zapus habitat.

Non-mammalian species were also inadvertently trapped in Trout Creek including

several songbirds and a garter snake (Thamnophis elegans). Small songbirds abruptly

flew out of the traps, rendering identification impossible. In July 2005, a fat, four-foot

long bull snake (Pituophis catenifer) meandered slowly out of the riparian brush and

retreated into the upland, forested slopes. A slowly executed scan of the docile snake

with the Biomark reader failed to produce any PIT tag readings, eliminating the fear that

the snake swallowed a tagged jumping mouse (Figure 107).

Figure 107 = Large bull snake leaving the riparian system on 22 July 2005. The snake was scanned with the Biomark reader, but PIT tags were not elicited.

Garter snakes of varying sizes actively slithered along the trap lines and the banks of the creek, especially on sunny, hot summer mornings. Turkey vultures (Cathartes aura) perched in tall rotting snags above Trout Creek, enjoying the morning sun, stretching their wings and lazily watching the running of trap lines (Figure 108). The mournful hoots of multiple great horned owls echoed through the drainage during numerous late night trapping or telemetry sessions. An owl pair nested downstream from

149 the Lower line and the chatter from the fledglings disturbed the night silence in early

July.

Figure 108 = Turkey vultures watching the early-morning opening of traps in Trout Creek, I July 2005.

In addition to mule deer and elk scat, scat from other species lined the hiking trail and marked individual trap stations. Coyote and red fox deposited their feces on top of

Sherman traps, as though marking their territory, and urine coated several traps of the

Lower Upland transects, indicative of predator proximity to the trap lines. Piles of owl pellets outlined by thick whitewash lay underneath several large diameter ponderosa pine roost trees. Upon dissection, owl pellets contained many small mammal bones, primarily the fragmented skeletons of voles. Coyote and fox scat were densely packed with vole and rabbit bones and fur. All scat and raptor pellets were scanned with the Biomark reader, however PIT tags were never activated, negating the presence of tagged jumping mice within the scat. The extent of predation on jumping mice by owl, snake, fox, and coyote in Trout Creek remains unclear. However, it is probable that a red fox attempted

150 to eat Preble’s 45312F7657 while the mouse wore a radio collar. After biting down on the hard transmitter, metal antenna and metal collar, the fox subsequently discarded its prey and the Preble’s was located as a visibly abused carcass.

As a result of the high-intensity forest fire burn upstream, and the unstable decomposing granite soils, flooding in Trout Creek frequently occurred with noticeable detriment to Zapus habitat. Flooding caused repeated beaver dam blowouts and severe erosion of the creek banks and adjoining slopes, with heavy sediment loading the creek, degrading the riparian system. Beaver dams and flooding remarkably impacted the hydrology of the creek between years and surrounding trap lines. Seasonal variations in water flow and bank heights were observed, with high flows typically predominating early in the season. Flows and depths even increased after minor rainfall, the water volumes augmented by runoff from the damaged hydrophobic soils left by the Hayman

Fire. Flooding compounded with erosion and the cyclical destruction and regrowth of riparian vegetation may have profoundly affected the Preble’s population in Trout Creek.

SYNTHESIS OF Zapus DATA FOR THE PIKE NATIONAL FOREST 2003-2005:

In the years 2003 through 2005, the five surveys sites in the Pike National Forest with positive Zapus captures included Gunbarrel Creek, Sugar Creek, Pine Creek, Upper

Trout Creek, and Trout Creek at North Rainbow Falls. The overall capture rate for small mammals at the six survey sites was 21 percent. Deer mice, voles, and woodrats accounted for 47 percent, 44 percent, and 6.2 percent of the total captures respectively

(Figure 109). Out of 3,144 total small mammal captures, Zapus represented only 1.8

151

percent of the captures. The capture rate specific to Zapus was 0.39 percent. There were

58 Zapus captures and 18 recaptures in the Pike National Forest, representing 40 distinct

Zapus individuals captured during the three-year study at five survey sites with positive

Zapus captures.

Figure 109 = Capture percentages for small mammals of 3,144 total small mammal captures at six sites in the Pike National Forest, 2003-2005.

The 18 Zapus recaptures out of 58 total Zapus captures, represented a 31 percent recapture rate. Zapus recaptures occurred exclusively in the drainage of the original capture. Furthermore, jumping mice captured at one particular survey site were never recaptured at a different survey site. Additionally, those Zapus marked with PIT tags

during historical surveys in the Pike National Forest were never recaptured between 2003

and 2005. For example, none of the 31 Zapus tagged by Bakeman in 2001 were

152 recaptured in 2004 at Upper Trout Creek. Furthermore, the four Zapus tagged and released by Schorr in Trout Creek in 1999 were never recaptured in 2003-2005.

At Trout Creek, Zapus moved a maximum of 836.9 meters between trap stations.

The average movement distance remained 413.9 meters. At the five survey sites in the

Pike National Forest, Zapus were never trapped or observed beyond the riparian perimeter into the forested upland slopes. At Trout Creek, the Lower and Middle Upland trap lines, stationed outside the riparian corridor, yielded no Zapus captures. The closest a Zapus approached a forested slope was approximately one meter. Four day-nests, one feeding pile, and one hibernaculum, located in Trout Creek, were within ten meters of the creek bank, well within the riparian corridor. Furthermore, at Gunbarrel Creek and Trout

Creek, mice were never captured or observed in flooded zones or wildfire burn areas.

The weights and monthly captures for all sites were consolidated and statistically analyzed per ANOVA and Tukey’s HSD as one comprehensive unit. Because Zapus were not captured at the Monument Fire Center, that survey was excluded from the analysis. Additionally, Pine Creek’s single Zapus was removed from the statistical analyses that required a mean.

Weights, Elevation, and Season:

Elevations for the five study sites with positive Zapus captures ranged from 1.9 kilometers at Pine Creek to 2.4 kilometers at Upper Trout Creek. The elevation at Trout

Creek at North Rainbow Falls approximated 2.0 kilometers. Upper Trout Creek represented the highest elevation of positive Zapus capture, above the 2.3 kilometer elevational cutoff used to distinguish Princeps from Preble’s. Additionally, captures at

153

Upper Trout Creek yielded the greatest average weight of capture: 28.9 grams. However, statistical comparison revealed that differences in mean weights between the four survey sites were insignificant (Figure 110). Additionally, Sugar Creek and Gunbarrel Creek yielded 15 gram and 19 gram Stage 3 adult Princeps respectively, both survey sites at 2.1 kilometers, below the altitudinal cutoff historically demarcating the range of Princeps.

35 2.1 km 2.4 km 30 (g) 2.1 km 2.0 km 25

Zapus Zapus 20

of Weight Mean 5

0 GUNBARREL CREEK SUGAR CREEK UPPER TROUT CREEK TROUT CREEK N = 8 N = 4 N = 4 N = 38 SURVEY SITE Figure 110 = Mean weights in grams of Zapus for the five survey sites in the Pike National Forest. Differences between sites are insignificant as determined by ANOVA and verified with Tukey’s HSD method. N represents the sample size for each study site. Pine Creek was not included in the statistical analysis because N=1. Elevations for each site are printed in italics above each bar. 54 weights used in the analysis.

Means and 95.0 Percent Tukey HSD Intervals

Mean Zapus Mean Weight (g) 18

Sugar Gunbarrel TroutCreek Trout Creek 154

When Zapus weights were compared by month, averages appeared to increase toward the end of the trapping season. Mean weights were greatest in August and

September, at 26.5 grams and 28 grams respectively. From July to August, average

Zapus weights increased by 4.3 grams and recaptures visibly gained weight as autumn

approached. For example, female 6A0A’s weight peaked at 43 grams in late August: the

Zapus gained ten grams between 8 and 20 August 2005. However, when grouped by

month and the means calculated, there was no significant difference in mean weights

between all capture months (Figure 111). ANOVA revealed that differences in mean

weights of Zapus between months were insignificant, as supported by Tukey’s HSD

analysis. Therefore, even as Zapus prepared for hibernation and weight gain was readily observed in the field, there was no significant increase in mean weights between months.

40 35

(g) 30

apus 25

10 Mean Weight of Z of Weight Mean 5

0 MAY JUNE JULY AUGUST SEPTEMBER N = 3 N = 9 N = 18 N = 22 N = 3 MONTH Figure 111 = Combined mean weights of Zapus in grams for five sites in the Pike National Forest per capture month. Differences between years were insignificant according to ANOVA. N represents the number of samples per month used in the analysis. 55 weights used in the analysis.

155

Mean Weights by Month with 95% Tukey HSD Intervals

Mean Zapus Mean Weight (g) 20

16 May June July August September

CHAPTER 5

DISCUSSION

This three-year study in the Pike National Forest augmented the available knowledge of the Preble’s meadow jumping mouse beyond short-term capture data. The results provided an analysis of Preble’s populations in montane drainages and their utilization of upland forested slopes outside the riparian corridors. The historical data between 1999 and 2002 collectively evidenced the low trap success rates for meadow jumping mice (Bohon et al. 2005) and the results from this endeavor validate the historical findings. Throughout this study, there were 40 distinct Zapus captures between

2003 and 2005, representing only 1.8 percent of the 3,144 total small mammal captures in the Pike National Forest. More importantly, the capture rate specific to Zapus remained equally low, at a mere 0.39 percent. In spite of an extensive three-year trapping effort, the data documented an extremely low capture rate specific to Zapus (0.39 percent) and subsequently limited the available sample size used to monitor Preble’s populations.

The fundamental premise interwoven throughout the results, evidenced by the conclusive data and statistical analysis, documented that the Preble’s remains a habitat specialist confined to the riparian corridors in the Pike National Forest. The capture data and radio telemetry succinctly demonstrated that the Preble’s meadow jumping mouse never ventured beyond its specialized habitat of lush, dense, herbaceous riparian vegetation. Additionally, there was no evidence of Zapus movement between drainages or utilization of the forested upland slopes adjacent to the riparian ecosystem. 156

Furthermore, none of the Hayman Fire burn areas, flood zones, or developed land regions yielded a single jumping mouse capture. Therefore, as a result of the mountainous terrain, with its geographical confinements of precipitous, rocky ridges and granite slopes, compounded by wildfires, floods, and anthropogenic intrusions, Preble’s are restricted to minimal patches of undisturbed riparian habitat in the montane drainages of the Pike National Forest. The results depict a small population of montane Zapus, restricted to fragmented and isolated riparian corridors at the western extent of the

Preble’s range in Colorado. Similar to meadow jumping mice on the eastern plains, the

Preble’s in the Pike National Forest exhibited its specialized ecological requirements as a riparian obligate, underscoring the importance of the sparse, montane riparian ecosystem to its viability.

Travel Distances and Home Ranges in Montane Corridors:

The trapping data for recaptures at Trout Creek detected linear movements of

Zapus between trap stations and trap lines. Zapus recaptures traveled an average distance of 413.9 meters between trap stations. Female 6A0A traveled 836.9 meters between the

Lower, Middle, and Upper trap lines, the longest recorded individual movement for

Zapus in Trout Creek. Radio tracked Zapus 3337 and 2B54, however, traveled short distances: 7.2 meters and 11 meters respectively, from the sites of capture to their respective day-nests. Likewise, radio tracking of Preble’s 7657 measured similarly short movements, totaling 6.9 meters, between two day-nests during the active period before immergence on 1 October. However, on 11 October, following an unexpected emergence from hibernation, the Preble’s traveled 708 meters downstream. This 157

exceptionally long downstream movement suggested that the Preble’s searched for food

resources that the dry October vegetation precluded. The recapture data and radio

telemetry verified that all movements occurred within the riparian corridor.

Movements recorded for Preble’s east of the Front Range in flat, prairie habitats

closely approximated the average travel distance for Zapus in Trout Creek, 413.9 meters.

Ryon at Rocky Flats recorded monthly averages for Preble’s movements of 526 meters

(1999), greater than Trout Creek by 112.1 meters. At the Air Force Academy, Schorr

documented average movement distances of 362 meters (2003), 51.9 meters less than the

average distance at Trout Creek. Therefore, montane Zapus in the Pike National Forest

exhibited similar average travel distances to those of eastern Preble’s populations.

The average Zapus movement distance, 413.9 meters, and the average width of

the riparian corridor, 10 meters, calculated the home range estimates. The fact that Zapus

never moved into the upland slopes effectively made the canyon-like walls the outer limit of riparian vegetation, or a 10-20 meter expanse. As a result, the approximated average

home range size for Zapus in Trout Creek was 1.02 acres. Previous estimates

approximated the home range size for meadow jumping mice at 0.20 to 0.86 acres

(Armstrong et al. 1994). Therefore, the average home range for Zapus in Trout Creek was slightly larger than the accepted range for meadow jumping mice on the eastern plains. However, the average distance component of the home range estimate was

calculated from only seven Zapus, due to the low 0.32 percent capture rate at Trout

Creek. A larger sample size would perhaps enable a more definitive home range estimate. Again, the forested upland slopes confined the home ranges of Zapus in Trout

Creek strictly to the riparian ecosystem. 158

Meadow jumping in the eastern plains displayed site fidelity (Shenk 2000).

Similarly, Zapus in the Pike National Forest exhibited site fidelity at both macro and micro scales. At the macro scale, recaptures occurred exclusively in the original capture drainage inside that specific riparian corridor. Migration of recaptures between drainages

or study sites was never documented. For example, consecutive surveys in Gunbarrel

Creek and Sugar Creek, their Lower trap stations separated by 1.1 kilometers of dry

forest, Highway 67, and Oxyoke, failed to detect movement of Zapus between these two

creeks. Fragmentation or geographic separation between Gunbarrel Creek and Sugar

Creek may have precluded migration between these drainages. Even more importantly,

mice tagged at Kelsey Creek by Meaney (2002), just upstream from the Gunbarrel Creek

trap lines, were never recaptured, despite their close proximity. Zapus captured and

tagged at one creek were never recaptured at a different creek, substantiating that

meadow jumping mice did not leave their specific riparian corridor and cross exacting

environments to other systems. Therefore, the data showed that Zapus illustrated site

fidelity for specific creeks. The absence of migration between drainages underscored the

threat posed by habitat loss: if one riparian corridor is destroyed, the existent Zapus

population at that site likely suffers.

At the micro level, individual Zapus displayed fidelity for definite areas within

the riparian ecosystem of their capture drainage. For example, female Zapus 7D01 was

captured six times exclusively on the Lower line in both years of capture, 2004 and 2005.

This Zapus moved 370.2 meters between trap stations: five captures on the A transect

bordering the creek bank and one capture on the B transect approximately ten meters 159

from the creek’s edge. Therefore, Zapus 7D01’s movements remained confined to the

Lower line on the southwestern side of the creek, demonstrating the mouse’s site fidelity.

Similarly, Preble’s 7657 was captured on the Lower A transect, 0.5 meter from

the edge of Trout Creek. Upon release, the Preble’s immediately retreated to the

protective cover of the adjacent willows and woodrat midden. Shortly thereafter,

Preble’s 7657 moved to its first day-nest, only seven meters from its release site along the

Lower line between trap stations 12A and 13A. Next, the mouse traveled only 6.7 meters to a second day-nest, also along the A transect between stations 14A and 15A. The

Preble’s hibernal chamber was approximately eight meters from its first day-nest. This movement and capture data, and location of day-nests and the hibernaculum substantiated the Preble’s micro scale site fidelity.

In addition, Zapus 2B54 moved 11 meters across Trout Creek from the capture site to its day-nest, where it remained for more than 13 hours. The location of its feeding pile, only six meters from the day-nest, suggested that the mouse fed in the immediate vicinity of capture. Therefore, the data showed that Zapus illustrated site fidelity for specific, small-scale sections of the riparian corridor. This further substantiates the gravity of habitat loss to montane Zapus populations.

At Plum Creek east of the Front Range, Preble’s moved beyond the immediate riparian system and ventured into the adjacent uplands and tributaries (Shenk 2000). In sharp contrast, Zapus at five sites in the Pike National Forest were captured only on trap transects within ten meters of the creek bank. Captures were limited to those trap stations situated beneath dense riparian vegetation and surrounded by grasses and a thick herbaceous understory. The Lower Upland trap transects at Trout Creek, situated on 160

decomposing granite slopes surrounded by upland grasses and ponderosa pine, yielded no

Zapus, only deer mice captures. Similarly, Zapus were not captured on the Middle

Upland line that followed a small, intermittent tributary into the forested uplands.

Therefore, trapping data at Trout Creek suggested that Zapus never left the confines of the linear, well-developed riparian system.

Furthermore, radio telemetry of two Zapus and one Preble’s at Trout Creek provided additional evidence that Zapus avoided the montane upland slopes. Radio tracked Zapus never ventured onto the upland slopes, during the day or night. All Zapus movements were restricted exclusively to the riparian corridor. Additionally, four day- nests, one feeding pile, and one hiberniculum were situated in close proximity to the creek bank, well within the dense riparian vegetation, not on the decomposing granite slopes of the abutting forest. In addition, when released from capture or flushed from day-nests by anthropogenic intrusion, Zapus fled deeper into the protective cover of the thick willows and herbaceous understory. Zapus did not, in spite of measured movements within one meter of the upland forest, ever retreat to the atypical habitat of the forested slopes.

In conclusion, both the trapping and radio telemetry data documented that Zapus never left the riparian system, and therefore never utilized the forested uplands. This fact suggests that the upland slopes lacked the necessary habitat components needed to support Zapus populations. These habitat components included energetic food sources, cover from predators, suitable soil substrates for hibernacula construction, and the riparian grasses woven into day-nests. All of these data further demonstrated Preble’s 161

specialized ecological requirements as a riparian obligate that avoided the dry, upland

slopes of the coniferous forest.

At Plum Creek, jumping mice moved beyond the USFWS imposed 91.4 meter

buffer protection zone for riparian ecosystems designated as critical Preble’s habitat

(Shenk 1999). At this eastern plains location, the riparian vegetation extended beyond

the 91.4 meter buffer zone, questioning the buffer zone’s effectiveness to protect critical

Preble’s habitat (Shenk 1999). In sharp contrast to the riparian systems on the eastern plains, the South Platte River and its tributaries are confined by steep inclines of forested

uplands and decomposing granite. Bank widths in the Pike National Forest are narrow

and often span less than 10 to 20 meters, with the riparian vegetation contained by the

precipitous, rocky slopes. Therefore, the buffer zone in the montane drainages extended

into the forested uplands, which Zapus never utilized. The buffer zone reached an

average 70 meters beyond the riparian corridor, the exclusive site of Zapus activity, as

verified by GIS analysis (Figure 112). In Trout Creek, the three transects of the Lower

Upland grid thoroughly trapped the buffer zone up to the 91.4 meter cutoff and yielded no Zapus captures on the K, L, or M transects. Even the Lower D transect on the northeastern bank of Trout Creek, situated directly at the edge of the riparian system, within the riparian vegetation, yielded only two juvenile Zapus captures. Therefore, all jumping mice activity in the Pike National Forest, occurred well within the 91.4 meter buffer zone, confined by the abutting mountainous slopes. This questions the application of such a wide buffer zone in montane drainages.

162

Figure 112 = The 91.4 meter USFWS buffer protection zone for Preble’s critical habitat (yellow) extended outside the riparian corridor, the exclusive site of Zapus activity in montane drainages.

Eastern meadow jumping mice are relatively vagile for small mammals (Meaney et al. 2003). Comparable average movement distances at Trout Creek evidenced that montane Zapus were also relatively vagile. However, as previously discussed, Zapus movement in the Pike National Forest remained restricted to their specific riparian system and Zapus never utilized the surrounding upland forests. As a result, the minimal patches of undisturbed riparian vegetation afford the only suitable Preble’s habitat in the montane drainages. But these sparse habitat resources were further fragmented, isolated, and destroyed by wildfire. The Hayman Fire crossed Trout Creek at the Fire trap line, decimating the riparian vegetation and the adjacent forest. Capture and telemetry data documented that Zapus never entered the Hayman Fire burn area. During the study period, the Fire line at Trout Creek, characterized by scorched willows and mullen 163

infestations, yielded no jumping mice captures. Three years after the fire, the riparian

ecosystem remained unsuitable Zapus habitat. The loss of critical Preble’s habitat to wildfires in the Pike National Forest further threatens Preble’s sustainability.

As a result of upstream, high-intensity forest fire burn areas, and the prevalent

unstable decomposing granite slopes, coupled with hydrophobic soils resulting from the

Hayman Fire, Trout Creek and Gunbarrel Creek experienced intense flooding. At both

sites, flooding caused noticeable detriment to Zapus habitat, stripping the soil of native vegetation, to be quickly replaced by invasive noxious weeds. The Middle line at

Gunbarrel Creek, characterized by severe flooding and erosion, yielded no Zapus captures. Similarly, the washed-out sections of Gunbarrel Creek’s Lower line yielded no

Zapus captures. Flooding, compounded with erosion and the cyclical destruction and regrowth of riparian vegetation may have adversely affected the Preble’s population in

Trout Creek and Gunbarrel Creek by exacerbating habitat loss.

Already adversely impacted by wildfire, anthropogenic factors further reduced and fragmented Preble’s preferred habitat in the Pike National Forest. For example, the fluidity of Trout Creek was disrupted by the populous North Rainbow Falls housing development. Vegetative diversity declined and manicured lawns replaced the riparian vegetation as private land holdings artificially disrupted Preble’s habitat. During radio telemetry, the private landholdings precluded tracking of Preble’s 7657’s movement within the development. Additionally, at Upper Trout Creek, no Zapus were captured on the A transect that paralleled a heavily trafficked hiking trail from the South Meadows

Campground. This suggests that anthropogenic intrusions may further threaten Preble’s viability in montane drainages. 164

Ecological Traits: Day-Nests, Hibernacula, Hibernation, and Feeding Piles:

Prior to this study, there was no data specific to Preble’s day-nests, hibernacula, or feeding piles in montane riparian ecosystems. As previously discussed, the four day- nests, one hiberniculum, and one feeding pile located in Trout Creek remained well within the riparian system. The narrow riparian perimeter dictated the locations of the day-nests, within 10 meters of the creek bank. In contrast, at Plum Creek, with its broad eastern riparian corridor, day-nests spanned 30 meters away from the creek bank (Bain and Shenk 2002). The construction and location of day-nests shared many of the characteristics of Midwestern and eastern jumping mice. For example, montane Zapus also tightly wove the surrounding grasses into globular structures with similar forms and dimensions. Furthermore, the day-nests were expertly concealed within the grassy riparian understory and placed flush against willow trunks. The day-nests’ camouflage prohibited visual identification without radio telemetry. As evidenced by radio telemetry, montane Zapus used day-nests as daytime retreats, hidden and secluded from predators.

Therefore, day-nests are an additional indication of the specialized ecological requirements of Preble’s and the criticality of habitat to the Preble’s survival in montane ecosystems.

Furthermore, Preble’s survival during hibernation depends on quality habitat. In

Trout Creek, the hiberniculum of Preble’s 7657 was positioned inside a south-facing creek bank, 0.85 meter above the water level and 0.3 meter underground. The hibernaculum lay inside the creek bank, placed above the flood plain, buried in moist, loosely compacted dirt with willows, snowberry, and riparian grasses growing from the top and sides of the bank. The soil quality, similar to rich potting soil, dictated the 165

placement of the hiberniculum within the riparian perimeter and concurrently excluded it

from the decomposing granite of the forested upland slopes.

In addition, Preble’s are profound hibernators, spending approximately eight

months in hibernation (USFWS 2005). Therefore, rich energetic food sources are

required to sustain jumping mice during the extended hibernation period. Before

hibernation, the body weight increases by 100 percent (Armstrong et al. 1994). Radio

tracked Zapus fed exclusively in the riparian corridor and never entered the forested

upland slopes. Therefore, the upland slopes likely lacked the requisite food sources for

pre-immergence hyperphagia needed to boost fat reserves. However, the data at Trout

Creek revealed no statistical difference in weight gain between all months, particularly

for those months correlated to pre-immergence weight gain. The low capture rate

specific to Zapus may have skewed the results. Nevertheless, this does not negate the

Preble’s need for quality habitat that provides adequate food resources in order to prevent

over-wintering mortalities.

During the active season, numerous torpid Zapus were captured at low elevations

along Monument Creek and Plum Creek (Schorr personal communication, Shenk 1999).

The colder temperatures of the mountainous Pike National Forest would expectantly also

force active mice into torpor during the entire active period. However, throughout the

three study years at the higher elevations, Zapus were never captured or observed in

states of torpor. Furthermore, emergence and immergence dates approximated the

timeline for eastern Zapus as late May and late September respectively regardless of

cooler temperatures in the Pike National Forest. Therefore, this suggests that montane

Zapus were better acclimated to their mountainous environment with its wide ranges and 166

fluctuations in temperature. However, a definitive emergence date required earlier

capture data in April.

Additionally, Zapus 2B54 in the Pike National Forest left behind a characteristic

feeding pile of uneaten seeds and discarded plant material similar to Midwestern jumping

mice (Quimby 1951). The feeding pile was well-concealed by riparian vegetation and

located within the linear riparian system. The feeding pile lay within six meters of its

day-nest and not on the decomposing granite slopes. Male Zapus 2B54 fed on the

nearby, fleshy stems of Canada thistle, while discarding the leaves inside the feeding pile.

Although Canada thistle is a potent noxious weed that outcompetes native vegetation by fostering thick monocultures, thistle stems may be an important food source for montane

Zapus. Therefore, the fleshy stems of thistles may provide additional fats required for winter hibernation.

MONITORING OF MONTANE PREBLE’S:

The overall capture rate for small mammals during the three years in the Pike

National Forest was 21 percent. With 58 total captures of 40 distinct Zapus individuals in

the Forest between 2003 and 2005, the capture rate for Zapus was only 0.39 percent. The

capture rate for Zapus at Trout Creek was 0.32 percent. Comparatively, during a three-

year study at Boulder Creek east of the Front Range, Meaney et al. captured 352

individual meadow jumping mice, representing a Zapus capture rate of 3.4 percent

(2003), roughly three percent greater than the Zapus capture rate in the montane

drainages of the Forest. However, the overall capture rate for small mammals at Boulder 167

Creek was 15 percent (2003), six percent less than the 21 percent capture rate recorded for the Pike National Forest between 2003 and 2005. Therefore, the montane drainages of the Pike National Forest yielded slightly more small mammal captures than Boulder

Creek, but the capture rate for Zapus was considerably less.

Deer mice and voles compete directly with meadow jumping mice for spatial and energetic resources (Boonstra and Hoyle 1986). In the Pike National Forest, continuous captures of voles and deer mice during the entire three-year study overshadowed the few

Zapus captures. Deer mice and voles dominated the small mammal catch, constituting 47 percent and 44 percent of the total small mammal captures respectively. Zapus, on the other hand, accounted for only 1.8 percent of the total small mammal captures. Specific capture rates for deer mice and voles, 9.8 percent and 9.2 percent respectively, greatly exceeded the 0.39 percent capture rate for Zapus. Deer mice and voles exhibited significantly greater capture rates than Zapus, regardless of yearly fluctuations in intraspecific capture rates. These two habitat generalists, with their large capture rates and burgeoning populations, may have directly limited the abundance of Zapus in montane drainages by competing with Zapus for habitat resources. Interspecific competition for commodities essential to Preble’s survival, already limited to the sparse riparian systems in montane drainages, further documents the fragility of Zapus populations in the Pike National Forest due to habitat constraints.

At Trout Creek, significantly more small mammals were captured in 2004 than in either 2003 or 2005. The capture rate for small mammals in 2004 was 26.5 percent, compared to 6.9 percent in 2003 and 17.2 percent in 2005. The small mammal capture rate significantly decreased by 9.3 percent from 2004 to 2005, coinciding with a mere 168

305 reduction in trap nights between the two years. This slight decrease in trapping effort

failed to reasonably explain the significant spike in small mammal captures observed in

2004. However, vole captures were significantly greatest in 2004, accounting for the

significant spike for small mammal captures in 2004. The capture rate for voles

increased by 12.3 percent in 2004 and voles represented 53 percent of the small mammal

catch. Voles represented only 1.7 percent of the captures in 2003. From 2004 to 2005,

vole captures decreased by 10.1 percent and voles assumed only 22 percent of the small

mammal catch in 2005. Therefore, the 2004 significant spike in vole captures, not the

305 reduction in trap nights, contributed to the significant spike in small mammal

captures observed in 2004. Furthermore, voles exhibit two to four-year population cycles

(Krebs and Myers 1974) and the significant decrease in vole captures in 2005 perhaps

signaled the end of a population cycle for voles. An analysis of vole population cycles

and its impact on Zapus populations requires additional survey years in Trout Creek.

Voles compete directly with meadow jumping mice for space, exhibiting high

reproductive rates and large populations (Boonstra and Hoyle 1986). Additionally,

Microtus crop grasses and herbs, reducing the potential for seed-fall, the meadow

jumping mouse’s primary food resource (Boonstra and Hoyle 1986). In the grasslands of

southern Ontario, Boonstra and Hoyle determined that Microtus significantly reduced the abundance of Z.hudsonius and this is typical throughout the two species’ ranges (1986).

Therefore, because vole captures at Trout Creek were significantly greatest in 2004,

Zapus captures would be significantly less in 2004. Greater numbers of voles would

result in fewer Zapus captures due to increased interspecific competition between the two

species. 169

The data at Trout Creek documents that Microtus out-competed Zapus. For example, in 2004 there were only 17 Zapus captures corresponding to the significant spike in vole captures. Furthermore, in 2005, there were 22 Zapus captures, five more than in 2004, coinciding with the 10.1 percent decrease in vole captures. Additionally,

Bakeman’s 2001 survey of Upper Trout Creek evidenced no vole captures, whereas

Zapus accounted for 88 percent of the total captures. In 2004 at Upper Trout Creek, however, vole captures increased by 36 percent and the Zapus capture rate decreased by approximately three percent. Therefore, before statistical analysis, it would appear that voles directly limited Zapus abundance by out-competing jumping mice for spatial and energetic resources.

However, ANOVA and Tukey’s HSD detected no significant difference for

Zapus captures between years and the five-capture increase from 2004 to 2005 was insignificant. Therefore, while undoubtedly a contributing factor to low Zapus abundance in 2004, competition with voles did not significantly alter the Zapus population between years according to statistical analysis. Instead, the combined detrimental effects of interspecific competition with the large populations of deer mice and voles limited the Zapus catch, and hence Preble’s populations, during the three-year study period.

Variances in capture rates for Zapus between years or months at Trout Creek were insignificant. Zapus capture rates remained consistently low throughout the entire study period. The large capture rates for deer mice and voles, indicative of thriving populations, possibly contributed to the low abundance of Zapus in montane drainages, as the two habitat generalists, deer mice and voles, out-competed Zapus for food and 170

resources. The underlying fact that the low Zapus capture rates at all six sites in the Pike

National Forest affirmed the low abundance of jumping mice. In spite of the 12,539 trap nights logged in Trout Creek, the Zapus specific capture rate remained a low 0.32

percent. Even the addition of trap lines, relocating trap stations, or altering the ratio of

peanut butter to the bait, failed to produce a significant increase in Zapus captures.

Additionally, Zapus were completely absent from the unnamed creek at the Monument

Fire Center despite the availability of suitable riparian habitat and the creek’s proximity

to nearby Preble’s populations. Therefore, the suppressed capture rates for Zapus in the

Forest perhaps resulted from an overall population depression as part of a broader population cycle typical of jumping mice. Ten or more years of monitoring may be required to adequately assess population cycles of meadow jumping mice (Meaney et al.

2003). The observation of a Zapus population cycle necessitates additional survey years in Trout Creek.

Over-wintering Survival, Predation, and Recaptures:

At Trout Creek, only three Zapus were recaptured between years following emergence from winter hibernation in the spring. Zapus 6A0A, 7D01, and 3337 were the

only jumping mice captured in 2004 and recaptured in 2005. Therefore, 73 percent of the

Zapus individuals captured in 2004 were never recaptured in 2005. This percentage of

failed recaptures approached Armstrong et al’s 70 percent estimate for over-wintering mortalities (1994). This suggests that Zapus in the Pike National Forest died during

hibernation, possibly as a result of the premature depletion of fat stores. An early depletion of fat stores perhaps resulted from an insufficient accrual of fats prior to 171

hibernation. Pre-hibernation hyperphagia is essential to the survival of Zapus during

winter hibernation, but the accumulation of fats in turn depends on the availability of

food within the Preble’s habitat. Subsequently, lack of energetic resources within the

habitat likely contributed to the low over-winter recapture rate for Zapus. Again, quality

habitat is essential to Preble’s sustainability throughout hibernation.

This study documented the unexpected emergence of a Preble’s following

approximately two weeks of underground hibernation. Radio collared Preble’s 7657

immerged on 1 October as a low-weight 18 gram, late Stage 2 adult, and emerged from

its hibernal chamber on 11 October. Following the emergence, the Preble’s moved 708

meters downstream, possibly in search of food. Although the frequency of pre-

emergence in montane drainages remains unclear, unexpected emergence exposed the

Preble’s to unfavorable environmental conditions. In general, Zapus that emerge

prematurely in winter or spring, face a leafless willow understory devoid of lush, green

herbaceous vegetation. The dormant riparian vegetation provides no energetic resources

and very little cover, thereby increasing the probability of predation, which was observed with Preble’s 7657. Premature emergence may have contributed to over-wintering mortalities of Zapus in the montane drainages of the Pike National Forest, thus limiting the number of recaptures and the total Zapus catch.

The recapture rate for Zapus in Trout Creek was 40 percent, implying that the majority of Zapus captured and tagged were never recaptured. In 2005, 11 of the 22 total

Zapus captures, or 50 percent of the capture total, were never recaptured. In 2004, four of the 17 Zapus captures, or 24 percent of the capture total, were never recaptured.

Jumping mice that were never recaptured following their initial release may have 172 succumbed to predation during the active season. Numerous mammalian, reptilian, and avian predators frequented the riparian corridors in the Pike National Forest, like coyote, snake, owls, and fox. Scans with the Biomark reader of predators and their scat or pellets failed to elicit PIT tags. However, predation of Preble’s 7657 occurred following its unexpected emergence from hibernation. Therefore, predation likely contributed to the low capture rate for Zapus in the montane riparian systems of the Pike National Forest.

The marginal recapture rate at Trout Creek, 40 percent, coupled with the low capture rate specific to Zapus, 0.32 percent, indicated that jumping mice were disappearing from the capture pool during the active season. These Zapus may have dispersed outside of the riparian corridor, negating the possibility of their recapture, by exposing them to exacting, hostile environments. In Trout Creek, females were recaptured more frequently than males, suggesting that males may have vacated the drainage in search of food or mating opportunities. However, the movement data failed to recognize dispersal and all activity remained confined to individual drainages.

Furthermore, trapping and telemetry documented that jumping mice avoided the upland slopes, their movements and home ranges restricted to the linear riparian corridor.

Therefore, the low capture and recapture rates likely resulted from a low overall Zapus population and not from dispersal away from the trap lines. A low population of Zapus in the Pike National Forest effectively limited capture rates, and thereby the numbers of recaptures, in spite of the trapping effort.

Preble’s and Princeps in the Pike National Forest: 173

Historical surveys developed weight and elevational parameters to distinguish

Preble’s from Princeps quickly in the field. According to these parameters, Zapus

captures below 2.3 kilometers signified a Preble’s (Bohon et al. 2005) while weights

exceeding 28 grams indicated a western jumping mouse (Bakeman 2001). However,

toothfold analysis and cranial morphometrics of voucher specimens from Gunbarrel and

Sugar Creeks invalidated these accepted guidelines and their application in the Pike

National Forest.

Captures of low-weight, Stage 3 adult Princeps occurred at Gunbarrel and Sugar

Creeks in late August, both creeks situated 0.2 kilometers below the 2.3 kilometer elevational cutoff used to differentiate Preble’s from Princeps. Toothfold analysis and morphometrics concluded that the small, 15 gram male Zapus voucher specimen from

Sugar Creek, situated at 2.1 kilometers, was a Stage 3 adult Princeps. In addition, the 19 gram voucher male from Gunbarrel Creek, also altitudinally situated at 2.1 kilometers, was classified as a Stage 3 adult Princeps. These extremely low-weight, adult, western jumping mice invalidated the convention that adult Princeps, especially those in montane environments at intermediate elevations, are larger and heavier than the Preble’s meadow

jumping mouse. Therefore, neither the mouse’s weight nor the elevation of capture

accurately distinguishes a Preble’s from a Princeps in the montane drainages of the Pike

National Forest.

174

CONCLUSION:

This three-year study conclusively documents the specialized ecological requirements of the Preble’s meadow jumping mouse as a riparian obligate. The Preble’s never utilized the upland forests outside of the riparian ecosystem. However, the Preble’s preferred riparian habitat remains depleted and fragmented by wildfire, floods, and anthropogenic intrusions and further isolated by a mountainous terrain. Continued habitat loss places an already low population at risk. The expiration of the Preble’s along the Front Range or in the Pike National Forest signals the loss of the complex biodiversity of riparian ecosystems throughout Colorado. 1

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