Medium-Sized Mammal Resources in the Hells Canyon Study Area

Natalie J. S. Turley Wildlife Technician

Anthonie M. A. Holthuijzen Wildlife Ecologist

Technical Report Appendix E.3.2-25 January 2001 Revised July 2003 Hells Canyon Complex FERC No. 1971 Copyright © 2003 by Idaho Power Company

Idaho Power Company Medium-Sized Mammal Resources

TABLE OF CONTENTS

Table of Contents ...... i

List of Tables...... iii

List of Figures ...... iii

List of Appendices ...... iii

Abstract ...... 1

1. Introduction ...... 2

2. Study Area...... 3

2.1. Location...... 3

2.2. Physiography...... 4

2.3. Land Features and Geology...... 5

2.4. Soils...... 5

2.5. Climate ...... 6

2.6. Vegetation ...... 6

2.7. Land Use ...... 8

2.8. Plant Operations ...... 8

3. Methods...... 9

3.1. Survey Technique...... 9

3.2. Sampling Design ...... 10

3.3. Survey Protocol...... 11

3.4. Data Analysis ...... 11

4. Results ...... 11

5. Discussion ...... 12

6. Summary and Conclusions...... 14

Hells Canyon Complex Page i Medium-Sized Mammal Resources Idaho Power Company

7. Acknowledgments...... 15

8. Literature Cited ...... 15

Page ii Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

LIST OF TABLES

Table 1. Medium-sized mammals potentially occurring in the Hells Canyon Study Area and vicinity...... 21

Table 2. Cover-types (acreage and percentages) present in the Hells Canyon Study Area...... 22

Table 3. Number of surveys conducted in spring, summer, fall, and winter in upland and riparian habitats, Hells Canyon Study Area, 1995–1999...... 23

Table 4. Observations of medium-sized mammals during point-count surveys, Hells Canyon Study Area, 1995–1999...... 24

Table 5. Red squirrel density (number/ha) by cover-type and season, Hells Canyon Study Area, 1995–1999...... 24

Table 6. Medium-sized mammal densities (n/ha) along various reaches of the Snake River, Idaho...... 25

LIST OF FIGURES

Figure 1. Location of the Hells Canyon Study Area and mammal survey points...... 27

Figure 2. Köppen climate diagrams for the Weiser, Richland, Brownlee, and Lewiston weather stations, Hells Canyon Study Area, Idaho–Oregon border...... 29

LIST OF APPENDICES

Appendix 1. Criteria and definitions used to identify cover-types in the Hells Canyon Study Area...... 31

Hells Canyon Complex Page iii

Idaho Power Company Medium-Sized Mammal Resources

ABSTRACT

Idaho Power Company (IPC) investigated the medium-sized mammal community in the Hells Canyon Study Area between 1995 and 1999. The objective was to determine the presence and relative abundance of these animals. Four-hundred forty-two points were established and monitored. Of these, 288 were riparian points and 154 were upland points. Surveys were conducted during four seasonal periods: spring (May), summer (June), fall (late September through early October), and winter (late January). Five species were observed during point-count surveys. The red squirrel (Tamiasciurus hudsonicus) was the most common species, followed by coyote (Canis latrans), mountain cottontail (Sylvilagus nuttallii), badger (Taxidea taxus), and beaver (Castor canadensis). Fifteen other medium-sized mammal species were observed incidental to other IPC studies.

The density of medium-sized mammals that serve as prey for coyotes, raptors, and other predators was very low for upland and riparian habitats, with the exception of red squirrel in riparian habitats. The black-tailed jackrabbit (Lepus californicus) was only observed on one occasion. Even though the mountain cottontail was observed throughout the study area, densities were low (< 0.01/ha in upland and riparian habitat) compared with their densities in other areas along the Snake River (C.J. Strike: 0.02 to 0.34/ha, Sunderman et al. 1998; Hagerman Valley: 0.05 to 0.18/ha, Holthuijzen 1995). The red squirrel was observed in riparian and wooded upland cover-types in moderately high densities throughout the study area. The highest density was reported for fall (1.24/ha), which was significantly higher than those for summer (0.24/ha), winter (0.18/ha), or spring (0.15/ha). In general, highest densities were observed in the Forested Wetland (0.17 to 1.52/ha) and Forested Upland (0.00 to 1.37/ha) cover-types. However, significant differences were found only in fall when the Forested Wetland cover-type had higher densities than the Mountain Shrub cover-type did.

Most species—including red squirrel, mountain cottontail, coyote, bobcat (Lynx rufus), and raccoon (Procyon lotor)—were observed throughout the study area. However, several species had more restricted distributions. The mink (Mustela vison) and muskrat (Ondatra zibethica) were limited by the lack of extensive riparian habitats throughout most of the study area. The red fox (Vulpes vulpes) was only observed in the southern portion of the study area along Brownlee Reservoir and above Cobb Rapids. Red fox are most abundant in areas with a mixture of croplands, grasslands, and woodlands (Verts and Carraway 1998). Thus, the absence of agriculture in the northern portion of the study area may explain the red fox distribution.

Hells Canyon Complex Page 1 Medium-Sized Mammal Resources Idaho Power Company

1. INTRODUCTION

Medium-sized mammals serve as prey, animals for hunting, indicators of habitat quality, and models for ecological research (Chapman and Willner 1986). A diverse group of animals— including lagomorphs, rodents, and carnivores with varied functional roles in ecosystems—are classified as medium-sized mammals.

Twenty-seven medium-sized mammal species may occur in the Hells Canyon Study Area (Table 1). This report focuses on information about medium-sized mammals of the orders Lagomorpha and Rodentia collected during point-count surveys. Information on the furbearer and carnivore community is found in another report focusing on data collected with scent-station surveys and camera detection systems (Edelmann 2001).

In general, lagomorphs have high reproductive rates and are short-lived. Population levels are regulated by mortality and dispersal. The quality of the plant community within their habitats is critical for their survival (Steenhof and Kochert 1988). Mountain cottontail (Sylvilagus nuttallii), pygmy rabbit (Brachylagus idahoensis), black-tailed jackrabbit (Lepus californicus), white-tailed jackrabbit (Lepus townsendii), and snowshoe hare (Lepus americanus) may occur in the study area. Mountain cottontail, snowshoe hare, and pygmy rabbit are classified as game animals, while the black-tailed jackrabbit and white-tailed jackrabbit are categorized as predatory wildlife in Idaho. Rabbits are classified as predatory wildlife in Oregon.

Mountain cottontails, which are widely distributed in Idaho, occur in their highest densities when cover-types are highly dispersed (IDFG 1990). However, population data are not available for this species (IDFG 1990). Black-tailed jackrabbits are widely distributed in the southern half of the state. Their populations are cyclic, with 7- to 12-year cycles (Johnson and Peek 1984). Densities peaked in the Snake River Birds of Prey Area (SRBOPA) in southwestern Idaho in 1980 and in 1990 (Knick 1991).

The pygmy rabbit, endemic to the Great Basin and adjacent intermountain areas of the western United States, is designated a species of special concern in Idaho and Oregon (IDCDC 1999). Populations of pygmy rabbits do not seem to be as cyclic as populations of other leporids are. Reproductively, they seem unable to respond quickly to favorable environmental conditions (Wilde 1978, Green and Flinders 1980). Though they also occupy greasewood stands (Davis 1939), pygmy rabbits are closely associated with dense or clumped stands of big sagebrush growing in deep, loose soils (Green and Flinders 1980 Weiss and Verts 1984). Here they exhibit the unique behavior of digging shallow burrows. The pygmy rabbit depends on the big sagebrush for cover and, to a large extent, for food (Wilde 1978; Flinders and Green 1980, White et al. 1982). This dependency may pose a threat to the species: fragmentation of these sagebrush communities will ultimately affect existing populations.

Asherin and Claar (1976) reported that the mountain cottontail was abundant throughout the Hells Canyon Study Area, particularly in shrub-steppe plant communities and riparian areas. Pygmy rabbits were not noted in the Hells Canyon Study Area, although the species was

Page 2 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources suspected to occur in the shrub-steppe at the upper end of Brownlee Reservoir. Likewise, though the black-tailed jackrabbit was expected in the general area, it was never observed.

The order Rodentia includes a wide variety of mammals. The yellow-bellied marmot (Marmota flaviventris), beaver (Castor canadensis), red squirrel (Tamiasciurus hudsonicus), fox squirrel (Sciurus niger), muskrat (Ondatra zibethica), and porcupine (Erethizon dorsatum) may be found in the study area. When Asherin and Claar (1976) censused medium-sized mammals in the Hells Canyon Study Area, they recorded their observations of tracks, scat, and other signs to supplement trapping efforts. Yellow-bellied marmots, found along the entire river corridor, were most abundant along Oxbow and Hells Canyon reservoirs and in other places where rock piles were available. Porcupines were also noted in the Hells Canyon Study Area, but in low numbers.

The general objective of the study was to describe existing medium-sized mammal resources in the Hells Canyon Study Area. The specific objective was to determine presence and relative abundance of medium-sized mammals. The results of this descriptive study will enable IPC in meeting Federal Energy Regulatory Commission (FERC) requirements to describe wildlife resources of the Hells Canyon Project and its vicinity. Medium-sized mammals are considered important under FERC regulations for their ecological, recreational, and sensitive status qualities. This study was proposed in IPC’s Formal Consultation Package for Relicensing: Hells Canyon Project (IPC 1997). In addition, updated study plans were made available in July 1999 (IPC 1999).

2. STUDY AREA

2.1. Location

The Hells Canyon Reach of the Snake River is situated in west-central Idaho and northeastern Oregon (Figure 1). The Hells Canyon Study Area is located between the city of Weiser and the confluence of the Salmon and the Snake rivers (from approximately RM 351 to RM 188). The Snake River, a major tributary to the Columbia River, is the focal point of Hells Canyon. Its generally northward flow forms part of the boundary between Idaho and Oregon. The Hells Canyon Hydroelectric Complex is located on the Snake River in the southern portion of Hells Canyon and includes three reservoirs—Brownlee, Oxbow, and Hells Canyon. The reach below Hells Canyon Dam is unimpounded, although the three-dam complex controls flows.

Federal agencies, including the Bureau of Land Management (BLM) and the U.S. Forest Service (USFS), are responsible for managing the majority of public land in Hells Canyon. These areas fall within the jurisdictional boundaries of the Wallowa–Whitman National Forest, Oregon; Payette National Forest, Idaho; Nez Perce National Forest, Idaho; Cascade Resource Area (RA) of the Boise District, BLM–Idaho; Cottonwood RA of the Coeur d’Alene District, BLM–Idaho; Baker RA of the Vale District, BLM–Oregon; and Northern Malheur RA of the Vale District, BLM–Oregon. Other agencies with natural resource jurisdiction in the greater project area include the USDI National Marine Fisheries Service (NMFS), USDI Bureau of Indian Affairs (BIA), USDI Fish and Wildlife Service (USFWS), and state agencies from Idaho and Oregon.

Hells Canyon Complex Page 3 Medium-Sized Mammal Resources Idaho Power Company

The area upstream and downstream of Hells Canyon Dam can be broadly divided into five reaches, based on distinct geomorphic features, river characteristics, and legal project boundaries:

• Upstream of Brownlee Reservoir to the Weiser Bridge (approximately 12 mi; RM 351.2 to 339.2).

• Brownlee Reservoir (approximately 55 mi; RM 339.2 to 284.6).

• Oxbow Reservoir (approximately 12 mi; RM 284.6 to 272.2).

• Hells Canyon Reservoir (approximately 25 mi; RM 272.2 to 247.0).

• Downstream of Hells Canyon Dam to the confluence of the Snake and Salmon rivers (approximately 59 mi, RM 247.0 to 188.2).

Generally, the lateral extent of these reaches includes all land within 0.5 mi of each shoreline above Hells Canyon Dam and all land within 0.25 mi of each shoreline below Hells Canyon Dam. However, the lateral extent of the study area can vary depending on which resources are being studied. The study area below Hells Canyon Dam is extremely difficult to access. In the upstream reach, the Snake River can be characterized as a low-gradient (0.2 to 0.4 m/km) river, with several island complexes. Agricultural impacts are apparent with high amounts of irrigation returns causing high turbidities and increased nutrient loading. Farmland and rural development on flat to gentle topography surround this reach. Brownlee Reservoir is a steep- sided reservoir with a maximum depth approaching 300 ft near the dam. Large rock outcrops occur throughout the entire length. Oxbow Reservoir is a small re-regulating reservoir surrounded by moderate to steep topography (20 to 75% slopes). Shorelines are primarily basalt outcrops and talus, except for alluvial fans created by small tributaries. Hells Canyon Reservoir is a re-regulating reservoir with maximum depths approaching 200 ft. Shorelines in the reservoir are generally very steep, and substrates are primarily composed of basalt outcrops and talus slopes. The Snake River in the downstream reach is a high-gradient river (1.8 m/km) with a wide diversity of aquatic habitat, including numerous large rapids, shallow riffles, and deep pools. Substrates are highly diverse, ranging from large basalt outcrops and boulders to cobble/sand bars. This unimpounded reach of the Hells Canyon is considered to be the deepest gorge in North America. The Hells Canyon Reach is surrounded at the upstream end by nearly vertical cliff faces.

2.2. Physiography

Hells Canyon is the deepest and one of the most rugged river gorges in the continental United States. It ranges between 2000 and 3000 ft in depth from Weiser to Oxbow Dam. Below Oxbow Dam, the river enters a narrow, steep-sided chasm measuring up to 5500 ft deep. From the confluence with the Grande Ronde River, the Snake River then flows into a lava-filled basin and through a much shallower canyon to Lewiston, Idaho (DOE 1985). The elevation of the Snake River near Weiser, Idaho, is about 2090 ft mean sea level (msl), descending to about 910 ft msl at the confluence of the Salmon River about 59 mi below Hells Canyon Dam.

Page 4 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Throughout the canyon, topography is generally steep and broken with slopes often dominated by rock outcrops and talus slopes. At the deepest points of the canyon, the walls rise almost vertically. Canyon walls are deeply dissected by numerous side canyons with tributaries to the Snake River. The Seven Devils Mountains to the east and the Wallowa Mountains to the west form the upper reaches of the canyon walls. These mountains form a series of jagged peaks reaching almost 10,000 ft, with subalpine and alpine conditions (USDA 1990) to the west.

2.3. Land Features and Geology

Hells Canyon consists of a series of folded and faulted metamorphosed sediments and volcanics overlain unconformably by nearly horizontal flows of Columbia River basalt. This basalt group covered much of eastern Washington, northern Oregon, and adjacent parts of Idaho (Bush and Seward 1992). The older rocks in the series are Permian to Jurassic in age and represent at least two episodes of island arc volcanism and adjacent marine sedimentation similar to those found today in the Aleutian Islands west of Alaska. These rock units represent old island arc chains that were sequentially “welded” to the west coast of North America during the late Paleozoic and early to mid-Mesozoic eras by subduction of a tectonic plate beneath the North American continental tectonic plate (Asherin and Claar 1976, USDA 1994).

In more recent geologic time, Hells Canyon was formed through erosion, by the Snake River, of the Blue Mountains in Oregon and Seven Devils Mountains in Idaho (DOE 1985). The Snake River has existed since the Pliocene and probably cut to its present level during the Pleistocene. During the Pleistocene, glacial meltwater provided abundant runoff for down- cutting, while regional uplifting created weak points in the 2000- to 3000-foot-thick basalt plateau that overlaid the Blue and Seven Devils mountains. Resulting erosion formed the currently observed drainage pattern that established the Snake River (DOE 1985). Northeast- trending, high-angle fault patterns characterize the extensive Snake River fault system running throughout the study area (Fitzgerald 1982).

Besides basalt, other rock types are also present within the study area. Extensive limestone outcrops are found in some tributary drainage areas, and local granitic outcrops also occur.

2.4. Soils

The soils throughout Hells Canyon are derived primarily from Columbia River basalt, covered in most areas with a thin mantle of residual soils from weathered native rock. Isolated areas contain deposits of windblown silt. Unconsolidated materials include ash-loess from the Mount Mazama eruption 6900 years ago, river sands and gravel deposited during the Bonneville floods 15,000 years ago, and colluvium and talus deposited more recently. The amount of soil cover declines northward through Hells Canyon. Near Hells Canyon Dam (RM 247), most rock faces are nearly vertical with little soil cover (USDA 1994).

Most soil complexes are well drained and vary from very shallow to moderately deep. Loams are the dominant textural class and vary from very stony to silty, often with a clay subsoil component (NRCS 1995).

Hells Canyon Complex Page 5 Medium-Sized Mammal Resources Idaho Power Company

2.5. Climate

From late fall to early spring, the climate of west-central Idaho and eastern Oregon is typically influenced by cool and moist Pacific maritime air. Periodically this westerly flow is interrupted by outbreaks of cold, dry continental air from the north, which is normally blocked by mountain ranges to the east. During the summer, a Pacific high-pressure system dominates weather patterns, resulting in minimal precipitation and more continental climatic conditions overall (Ross and Savage 1967). Hells Canyon, located in the High Desert region, is significantly influenced by the rain shadow of the Cascade Mountains to the west.

Climatological information is summarized for Weiser, Richland, Brownlee Dam, and Lewiston (Figure 2). Average annual precipitation is lowest at the southern end of the study area (Weiser, 286 mm), increases northward (Richland, 298 mm), peaks around Brownlee Dam (445 mm), and declines towards Lewiston (326 mm). The average annual precipitation ranges from about 380 to 500 mm (15 to 20 inches), depending on elevation. Nearly 45% of the average annual precipitation at Brownlee Dam (445 mm [17.8 inches]) falls from November through January, which strongly contrasts with the 9% average recorded for July through September. Thus, most precipitation occurs in the spring and winter (Tisdale et al. 1969,Tisdale 1986, Johnson and Simon 1987), and little or no precipitation falls during the hottest months of summer. Average annual evapotranspiration is estimated to be about 1300 mm (52 inches).

Mean annual temperatures are similar among the four weather stations. Generally, the climate tends to become drier and warmer downstream of Brownlee Dam. Climatological information from Brownlee Dam (RM 284.6) is probably characteristic of the central section of the study area and is discussed in more detail here. The canyon bottom area is dry with seasonal temperatures ranging from lows of about –5 °C in January to highs of about 35 °C in July (Figure 2). Temperatures below freezing are normally experienced from mid-November through mid-April. As a rule, winters in the canyons are mild, while summers on the canyon floor may be hot. Mean temperatures above 2000 m (6562 ft msl) elevation range from –9 °C in January to 13 °C in July. By contrast, mean temperatures below 1000 m (3281 ft msl) elevation range from 0 °C in January to between 28 °C and 33 °C in July (Johnson and Simon 1987).

2.6. Vegetation

The types of vegetation growing along the canyon slopes of the middle Snake River are the result of three primary ecological factors: topography, soils, and climate. Climate exerts the strongest influence on the development of plant life. The relatively mild winters below the canyon rim have allowed the development of disjunct species such as hackberry (Celtis reticulata), which is most often found in the southwestern states, though it commonly occurs in the middle and lower Snake River area (Tisdale 1979, DeBolt 1992).

Within the context of regional climate, topography is a major influence on the development and distribution of vegetation (Tisdale et al. 1969; Tisdale 1979, 1986). The topographical complexity of Hells Canyon has produced a mosaic of vegetation types (Tisdale 1979, BPA 1984, USDI 1987). Grassland, shrubland, riparian, and coniferous forest communities exist in

Page 6 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources close proximity. Interfingering of grassland and forest, for example, occurs at a number of sites throughout the canyon due to variations in aspect (Tisdale 1979).

Twenty-six cover-types were identified along the Snake River in the Hells Canyon Study Area (Holmstead 2001). The area that was classified covered up to approximately one-half mile on both sides of the Snake River or associated reservoirs. The dominant cover-types were Grassland (35.5%), Shrub Savanna (21.0%), Lotic (16.1%), Shrubland (6.6%), and Cliff/Talus (5.6%). Each remaining cover-type covered less than 5% of the area classified.

Wetland and Riparian CommunitiesInformation is limited on wetland and riparian communities in Hells Canyon (Huschle 1975, Asherin and Claar 1976, Miller 1976, Miller and Johnson 1976, DeBolt 1992). Emergent wetland communities are composed mostly of common cattail (Typha latifolia), narrowleaf cattail (Typha angustifolia), American bulrush (Scirpus americanus), and common spikerush (Eleocharis palustris). Willows are sparsely represented, and various forbs grow on the shoreline side of these stands (Asherin and Claar 1976). A narrow band of diverse riparian communities follows the course of the Snake River and its many tributaries. Although it is limited in geographic area, this riparian zone is vital because of the biological diversity it provides (USDI 1987). Predominant tree species in riparian areas include white alder (Alnus rhombifolia), water birch (Betula occidentalis), and black cottonwood (Populus trichocarpa). Predominant shrub species in riparian areas include syringa (Philadelphus lewisii), netleaf hackberry (Celtis reticulata), chokecherry (Prunus virginiana), black hawthorn (Crataegus douglasii), and poison ivy (Toxicodendron radicans).

There is no riparian vegetation along many shoreline sections. Rather, upland vegetation on steep canyon slopes simply meets the rocky shoreline. Grassland communities are also common along the Snake River and its tributaries. Where these grassland communities occur, such as on the canyon slopes, the dominant species are bluebunch wheatgrass (Pseudoroegneria spicata), cheatgrass (Bromus tectorum), and Idaho fescue (Festuca idahoensis) (Asherin and Claar 1976).

Herbaceous-Dominated Vegetation TypesThe dry climate and typically stony, shallow soils of the canyon have favored the development of grassland steppe communities at the lower and middle elevations (Tisdale 1979, 1986). Commonly occurring grass species in the study area include bunchgrasses such as bluebunch wheatgrass, Sandberg bluegrass (Poa secunda), and Idaho fescue (Garrison et al. 1977, BPA 1984, Tisdale 1986, Franklin and Dyrness 1988). Sand dropseed (Sporobolus cryptandrus) and red threeawn (Aristida longiseta) are also common and, at times, dominant (BPA 1984, Tisdale 1986).

Habitat types in which bluebunch wheatgrass is dominant occur throughout the study area and occupy over half of its grassland area (Tisdale 1986). Bluebunch wheatgrass flourishes on deep, loamy soils but adapts to coarser and shallower soils as well. Generally, it is associated with Idaho fescue on deeper soils and with Sandberg’s bluegrass on shallower soils.

Shrub-Dominated Vegetation TypesShrub species comprise a large segment of the canyon’s overall vegetation composition. Shrub-steppe vegetation types occur at mid-elevations in the Hells Canyon Study Area, especially in the southern region of the study area. For example, big sagebrush (Artemisia tridentata) is a dominant species in the southern sector of the study area, particularly in the area around Brownlee Reservoir (BPA 1984). Commonly occurring shrubs

Hells Canyon Complex Page 7 Medium-Sized Mammal Resources Idaho Power Company include big sagebrush, antelope bitterbrush (Purshia tridentata), hackberry, serviceberry (Amelanchier alnifolia), and bitter cherry (Prunus emarginata) (BPA 1984, Tisdale 1986). Other species of sagebrush are also present, including low sagebrush (Artemisia arbuscula), stiff sagebrush (Artemisia rigida), and silver sagebrush (Artemisia cana) (Tisdale and Hironaka 1981, Franklin and Dyrness 1988). For the most part, sagebrush stands are limited to the area around Brownlee Reservoir. In these stands, the herbaceous layer is dominated by Sandberg bluegrass, with a variety of forbs also occurring.

Stands of hackberry can be found throughout the study area, either on lower slopes with rocky residual/colluvial soil or on alluvial terraces with sandy soil (Tisdale 1986). In these stands, hackberry is often mixed with a number of other shrub and tree species, including antelope bitterbrush, blue elderberry (Sambucus cerulea), and ponderosa pine (BPA 1984). The herbaceous layer is most often dominated by bluebunch wheatgrass, with cheatgrass and sand dropseed dominant in those areas that have been heavily disturbed by the grazing and trampling of cattle.

Tree-Dominated Vegetation Types—Although coniferous forest communities are generally restricted to the higher elevations of steep canyon slopes, they do reach down to the Snake River in certain locations of the study area. The predominant forest community is a ponderosa pine (Pinus ponderosa)/bluebunch wheatgrass plant association, which extends to the river on north- facing slopes at sites along Oxbow and Hells Canyon reservoirs (Asherin and Claar 1976, Bonneville Power Administration 1984). This association typically occurs as a savanna of ponderosa pine trees distributed over a grassland steppe dominated by bluebunch wheatgrass. Shrubs are almost completely absent, except for sparsely distributed, drought-resistant species such as antelope bitterbrush and serviceberry (Garrison et al. 1977, Johnson and Simon 1987). A ponderosa pine/hackberry type may also extend down to the river in this area. Hackberry dominates the shrub layer in moderate density, and poison ivy is also abundant (Asherin and Claar 1976).

2.7. Land Use

The study area and vicinity is still dominated by the land-use patterns established at the turn of the century: irrigated and nonirrigated agriculture, livestock grazing, mining, large areas of open space, scattered rural development, and rapidly growing recreational activities. The bottomlands adjacent to the reservoirs are generally used for grazing, some farming, and recreation.

2.8. Plant Operations

Hells Canyon, on the Oregon–Idaho border, is the deepest canyon in North America and home to IPC’s largest hydroelectric generating complex, the HCC. The HCC includes the Brownlee, Oxbow, and Hells Canyon dams, reservoirs, and power plants. Operations of the three projects of the complex are closely coordinated to generate electricity and to serve many other public purposes.

Page 8 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

IPC operates the complex to comply with the FERC license, as well as to accommodate other concerns, such as recreational use, environmental conditions and voluntary arrangements. Among these arrangements are the 1980 Hells Canyon Settlement Agreement, the Fall Chinook Recovery Plan adopted in 1991, and, between 1995 and 2001, the cooperative arrangement that IPC had with federal interests in implementing portions of the Federal Columbia River Power System (FCRPS) biological opinion flow augmentation, which is intended to avoid jeopardy of the FCRPS operations below the HCC.

Brownlee Reservoir is the only one of the three HCC facilities—and IPC’s only project—with significant storage. It has 101 vertical feet of active storage capacity, which equals approximately 1 million acre-feet of water. On the other hand, Oxbow and Hells Canyon reservoirs have significantly smaller active storage capacities—approximately 0.5 and 1.0% of Brownlee Reservoir’s volume, respectively.

Brownlee Dam’s hydraulic capacity is also the largest of the three projects. Its powerhouse capacity is approximately 35,000 cubic feet per second (cfs), while the Oxbow and Hells Canyon powerhouses have hydraulic capacities of 28,000 and 30,500 cfs, respectively.

Target elevations for Brownlee Reservoir define the flow through the HCC. However, when flows exceed powerhouse capacity for any of the projects, water is released over the spillways at those projects. When flows through the HCC are below hydraulic capacity, all three projects operate closely together to re-regulate flows through the Oxbow and Hells Canyon projects so that they remain within the 1-foot per hour ramp rate requirement (measured at Johnson Bar below Hells Canyon Dam) and meet daily peak load demands.

In addition to maintaining the ramp rate, IPC maintains minimum flow rates in the Snake River downstream of Hells Canyon Dam. These minimum flow rates are for navigation purposes and IPC’s compliance with article 43 of the existing license. Neither the Brownlee Project nor the Oxbow Project has a minimum flow requirement below its powerhouse. However, because of the Oxbow Project’s unique configuration, a flow of 100 cfs is maintained through the bypassed reach of the Snake River below the dam (a segment called the Oxbow Bypass).

3. METHODS

3.1. Survey Technique

Line transects and point counts have been used extensively during wildlife surveys to estimate population densities (Franzreb 1981, Bibby et al. 1992). Determining the basic line transect involves walking a predetermined straight line, or a series of straight lines, and recording detections of individuals along both sides of the transect line. Line-transect counts are best applied in large areas that are relatively homogenous and can be used throughout the year (Franzreb 1981, Wakely 1987a; Bibby et al. 1992, Buckland et al. 1993). Point counts are basically line-transect counts conducted at zero speed (Buckland et al. 1993). Point counts are particularly applicable where habitat to be sampled is patchy, fragmented, or irregularly sloped,

Hells Canyon Complex Page 9 Medium-Sized Mammal Resources Idaho Power Company or where rough terrain makes transects difficult to establish and follow (Dawson 1981, Wakely 1987b, Bibby et al. 1992, Buckland et al. 1993).

Because of the patchy and linear nature of riparian habitat in the study area, circular plots were chosen for sampling of riparian habitat. A pilot study, conducted in 1995, compared the efficiencies of using line transects and circular plots for sampling upland habitats of Hells Canyon. This study was designed to determine which method was more appropriate based on: 1) sampling variance, 2) efficiency of data collection, 3) ease of field application, 4) minimum violation of critical assumptions, and 5) ability to detect a larger number of species. Results of the pilot study indicated that several of the assumptions critical to the line-transect method were violated. Line transects were often difficult to traverse, with observers spending more time negotiating the survey route than actually conducting the survey. Variable topography made distance estimation difficult, and habitats existed in patchy and irregularly distributed clumps or bands. Therefore, it was determined that point counts were the most appropriate method for sampling.

3.2. Sampling Design

Tributaries to the Snake River between Farewell Bend and Hells Canyon Dam were inventoried in 1994 to determine their accessibility and suitability for circular-plot surveys. The sampling design was based on two criteria. First, sample points had to be evenly distributed across the study area. Second, the probability of selecting a particular sample point had to be the same across the study area. The study area was divided into 5-mile segments with equal probability for all segments. Thus, a stratified random design was employed with a fixed sampling fraction per stratum. Surveys of medium-sized mammals were conducted concurrently with nongame bird surveys. A pilot study conducted in 1994 indicated that approximately 180 circular plots were required to achieve a 25% coefficient of variation for an abundance estimate of the avian population. Based on this design, an estimated 200 circular plots were available to be sampled. Tributaries were clustered as much as possible to optimize sampling time and minimize travel. Although probability theory suggests that a valid estimate of the sampling variance could only be obtained from a random sample (Bibby et al. 1992), the remote and rugged landscape of the Hells Canyon Study Area precludes a random assignment. Therefore, riparian areas that were accessible by automobile, all-terrain vehicle, or boat were selected to increase sampling efficiency. These areas were delineated on topographic maps and assumed to be independent. Thus, they were treated as sampling units (that is, replicates). To improve sampling time and efficiency, upland sample sites were clustered near riparian sample sites. Therefore, the selection of sampling sites was constrained by availability of appropriate habitat and logistics.

Most riparian habitat in the study area is patchy, linearly oriented, and fragmented. Upland habitat is also patchy, consisting of Grassland, Shrub Savanna and Shrubland clumps. Survey points were located in homogeneous patches of upland or riparian vegetation. At the time of installation, points were subjectively classified by vegetation cover-type. However, final cover-type classification was based on vegetation data collected at each point. Four hundred forty-two points were established and monitored (Figure 1). Of these, 288 were riparian points and 154 were upland points. Each point count was classified into a standard vegetation cover- type (Appendix 1). The center of each plot was marked with rebar. Upland points were

Page 10 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources established within homogenous habitat patches that could contain a 50-m radius plot. Riparian points were established in riparian zones that were at least 30 m wide, resulting in 15-m radius plots. However, we preferred and, in most cases, used points that were 40 m wide, resulting in 20-m radius plots. Riparian plots had smaller radii due to the general narrowness of the riparian corridor and reduced visibility.

3.3. Survey Protocol

Surveys of medium-sized mammals were conducted concurrently with nongame bird surveys during four seasonal periods: spring (May), summer (June), fall (late September through early October), and winter (late January through early February). The number of surveys conducted each season is reported in Table 3. Surveys began up to 30 minutes before sunrise and were completed no later than 5 hours after sunrise, except in winter when surveys were conducted throughout the day. The sample period at each point was 8 minutes. All medium-sized mammals observed were recorded, and their distance from the center of the plot was estimated.

All incidental observations of medium-sized mammals reported during other IPC field activities occurring from 1995 through 1999 were also recorded and mapped on USGS topographical maps. A complete list of medium-sized mammals was then compiled based on data from medium-sized mammal surveys and incidental observations, and from information collected on the furbearer community at stations equipped with scent posts or remote cameras. Detailed methods for the latter two techniques are described in Edelmann and Pope (2001).

3.4. Data Analysis

Medium-sized mammal densities per hectare (ha) were calculated for each year, season, and vegetation cover-type for all species that were observed more than 20 times. Differences in densities among years, seasons, and cover-types were investigated using Analysis-of-Variance (ANOVA) procedures (PROC GLM, SAS Institute Inc. 1988). Differences among seasons were tested using the overall residual mean square error term to test the season and cover- type × season interaction effect. The type III mean square was used with survey point nested in cover-type as the error term to test the cover-type effect, whereas overall residual mean square error served as the error term to test the year and cover-type × year interaction effect. If no differences in mammal densities were found among years or the same direction of response was found (that is, the cover-type × year interaction term was not significant), years were combined. Duncan’s multiple-range test was used to evaluate differences among cover-types.

4. RESULTS

From 1995 through 1999, 2995 point-count surveys were conducted in riparian habitat, and 992 point-count surveys were conducted in upland habitat in the Hells Canyon Study Area (Table 3). Five species of medium-sized mammals were observed during point-count surveys (Table 4). The red squirrel was the most common species, followed by coyote (Canis latrans), mountain

Hells Canyon Complex Page 11 Medium-Sized Mammal Resources Idaho Power Company cottontail, badger (Taxidea taxus), and beaver. Fourteen species of medium-sized mammals were observed incidentally, during scent-post surveys, or at remote camera stations: yellow-bellied marmot, black-tailed jackrabbit, white-tailed jackrabbit, striped skunk (Mephitis mephitis), long-tailed weasel (Mustela frenata), raccoon (Procyon lotor), red fox (Vulpes vulpes), river otter (Lutra canadensis), bobcat (Lynx rufus), snowshoe hare, muskrat, mink (Mustela vison), porcupine, and spotted skunk (Spilogale gracilis) (Table 1). The wolverine (Gulo gulo) and marten (Martes americana) were observed in the vicinity of the Hells Canyon Study Area (at Seven Devils Mountains and Cuddy Mountain, respectively).

Most species—including red squirrel, mountain cottontail, coyote, bobcat, and raccoon—were observed throughout the study area. However, several species had more restricted distributions. For example, the muskrat was only observed near the Powder River pool, whereas the red fox was only observed in the southern portion of the study area along Brownlee Reservoir and above Cobb Rapids. Snowshoe hare tracks were observed in January along Dukes Creek, a tributary to the Snake River.

Density estimates were calculated for each species; however, only red squirrel estimates were analyzed with ANOVA because of insufficient data for the other species. All other species had average densities less than 0.01/ha and were observed at very few points. Red squirrel densities differed among seasons (ANOVA, F = 31.8, df = 3, P = 0.01). Highest densities were reported for fall (1.24/ha), which were significantly higher than densities for summer (0.24/ha), winter (0.0.18/ha), or spring (0.15/ha). Red squirrel were observed in Forested Wetland, Forested Upland, Scrub-Shrub Wetland, Tree Savanna, Mountain Shrub, and Shrub Savanna cover-types. In general, highest densities were observed in the Forested Wetland (0.17 to 1.52/ha) and Forested Upland (0.00 to 1.37/ha) cover-types. However, significant differences were found only in fall, when the Forested Wetland cover-type had higher densities than the Mountain Shrub cover-type did (Table 5).

5. DISCUSSION

The density of medium-sized mammals that serve as prey species for coyotes, raptors, and other predators was very low in upland and riparian habitats, with the exception of the red squirrel in riparian habitats. Along other portions of the Snake River, including C.J. Strike Reservoir and the Hagerman Valley, the mountain cottontail was the most abundant species in riparian habitat, while the black-tailed jackrabbit was the most common species in upland habitat (Table 6). Black-tailed jackrabbits use a variety of habitats and have extremely variable diets (Johnson and Anderson 1984). They require abundant forage and cover (Johnson and Peek 1984) and herbaceous cover that has high diversity and biomass (Flinders and Hansen 1972). In Idaho, the black-tailed jackrabbit occurs on the sagebrush steppe throughout the southern portion of the state (Johnson and Peek 1984). However, only one black-tailed jackrabbit was observed in Hells Canyon in March 2001. Asherin and Claar (1976) did not report the presence of black-tailed jackrabbits in the study area. Its rarity in the southern portion of the study area, where big sagebrush and rabbitbrush are common, is somewhat surprising. Fragmentation and degradation of sagebrush habitat may be a factor (Knick and Dyer 1997). In the unimpounded reach above Brownlee Reservoir, agriculture, grazing, roads, and fire have all fragmented the

Page 12 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources shrub habitat. And although Shrubland and Shrub Savanna constitute 28% of the land area along Brownlee Reservoir, shrub polygons were generally small and interspersed with grassland. Thus, very little high-quality shrub habitat is available in Hells Canyon. The black-tailed jackrabbit was apparently at low population densities during the period of study. Black-tailed jackrabbit populations are cyclic, with 7- to 12-year cycles (Johnson and Peek 1984). Densities peaked in the Snake River Birds of Prey Area in 1979 and again from 1990 through 1992 (Watts and Knick 1994). The black-tailed jackrabbit observation in 2001 indicates that populations may be increasing but are still at very low levels.

Distributed throughout Idaho, mountain cottontails occur in highest densities where cover-types are widely dispersed (IDFG 1990). Mountain cottontails, often associated with rocky ravines and sagebrush-covered hills, show a preference for willows along river bottoms (Chapman and Feldhamer 1982). These requirements appear to be met in the Hells Canyon Study Area. Mountain cottontails were observed throughout the study area in both riparian and upland habitat, but were observed at low densities (< 0.01/ha in upland and riparian habitat) compared with densities for other areas along the Snake River (C.J. Strike: 0.02 to 0.34/ha, Sunderman et al. 1998; Hagerman Valley: 0.05 to 0.18/ha, Holthuijzen 1995). The low densities of mountain cottontail found in the study area may correspond to an overall low population level. Incidental observations of the species were low from 1995 to 1997, but increased in 1998, indicating that the population may have been increasing. Information on population densities of the mountain cottontail is more limited than for the black-tailed jackrabbit. The Snake River Birds of Prey Area reported the highest number of observations of mountain cottontail in 1990 with much lower counts in subsequent years (Knick 1993, Watts and Knick 1994).

The pygmy rabbit was not observed in the Hells Canyon Study Area during any IPC survey. Likewise, Asherin and Claar (1976) did not observe the species in the area but suspected that the species might occur in the southern portion of the study area. Similarly, the pygmy rabbit was not observed in the C.J. Strike Study Area (Sunderman et al. 1998) and occur only at low densities in the Snake River Birds of Prey Area (Knick 1993). The species probably does not occur in the study area (with the possible exception of the area near the Oregon side of Farewell Bend), based on the predicted distribution of the pygmy rabbit (Csuti et al. 1997, Groves et al. 1997).

The white-tailed jackrabbit was observed in shrub habitat south of the Powder River Arm near the summit above Brownlee Reservoir. This species is very rare in the study area.

Yellow-bellied marmots are commonly found near rocky talus slopes (Chapman and Feldhamer 1982, Holthuijzen 1997), typically above about 2000 m (Groves et al. 1997). However, yellow-bellied marmots were found in low densities along the entire river corridor at much lower elevations (1500–2000 ft). The species was nearly always found close to rocky outcroppings. Asherin and Claar (1976) noted that yellow-bellied marmots were most abundant along Oxbow and Hells Canyon reservoirs and other places where rock rip-rap was available along roads.

Several medium-sized mammals have limited distributions in the study area. The mink and muskrat were limited by the lack of extensive riparian habitats throughout most of the study area. Muskrat were observed by IPC personnel only at the confluence of the Powder River and Eagle

Hells Canyon Complex Page 13 Medium-Sized Mammal Resources Idaho Power Company

Creek. Asherin and Claar (1976) also observed muskrat on the upper pool of Brownlee Reservoir and just below Oxbow Dam. Mink were observed incidentally in similar areas—just below Oxbow Dam and along the Wildhorse River, a tributary entering the Snake River just below Brownlee Dam. Asherin and Claar (1976) also noted mink sign along the upper pool of Brownlee Reservoir. These observations correspond to areas with a more developed riparian zone. The red fox was observed only in the southern portion of the study area along Brownlee Reservoir and above Cobb Rapids. Red fox are most abundant in areas with a mixture of croplands, grasslands, and woodlands (Verts and Carraway 1998). Thus, the absence of agriculture in the northern portion of the study area may explain the red fox distribution.

Density estimates for red squirrel populations on logged and unlogged plots (Douglas fir [Pseudotsuga menziesii] and ponderosa pine) in west-central Idaho ranged from 0.1 to 0.7/ha in logged plots and from 2.2 to 3.1/ha in unlogged plots (Medin 1986). Elsewhere within the range of the red squirrel, densities were estimated between 0.21 and 0.63/ha in white spruce (Picea glauca) forests in Alaska (Smith 1968). In Alberta, densities were between 0.31 and 0.39/ha in aspen (Populus tremuloides)/balsam poplar (Populus balsamifera) and between 0.54 and 0.59/ha in jackpine (Pinus bandsiana)/alder (Alnus crispa) (Kemp and Keith 1970). Red squirrel densities in the Hells Canyon Study Area were at the lower end of this range of densities (summer, Forested Wetland: 0.36/ha; Forested Upland: 0.29). Because the red squirrel prefers conifers and mixed forests, the low to medium densities found likely result from the relatively low coniferous component in the study area.

6. SUMMARY AND CONCLUSIONS

Twenty-seven medium-sized mammal species may occur in the Hells Canyon Study Area. Five species of medium-sized mammals were observed during point-count surveys. The red squirrel was the most common species, followed by coyote, mountain cottontail, badger, and beaver. Fourteen species of medium-sized mammals were observed incidentally during surveys, during scent-post surveys, or at remote camera stations: yellow-bellied marmot, striped skunk, long-tailed weasel, raccoon, red fox, river otter, bobcat, snowshoe hare, black-tailed jackrabbit, white-tailed jackrabbit, muskrat, mink, porcupine, and spotted skunk.

The density of medium-sized mammals that serve as prey species for coyotes, raptors, and other predators was very low for upland and riparian habitats, with the exception of the red squirrel in riparian habitats. Along other portions of the Snake River, including C.J. Strike Reservoir and the Hagerman Valley, the mountain cottontail was the most abundant species in riparian habitat, while the black-tailed jackrabbit was the most common species in upland habitat. In Hells Canyon, however, black-tailed jackrabbits were only observed on one occasion. Mountain cottontails were observed throughout the study area in both riparian and upland habitat but at low densities (< 0.01/ha in upland and riparian habitat) compared with densities for other areas along the Snake River (C.J. Strike: 0.02 to 0.34/ha, Sunderman et al. 1998; Hagerman Valley: 0.05 to 0.18/ha, Holthuijzen 1995). The red squirrel was observed in riparian and wooded upland cover- types in moderately high densities throughout the study area. The highest density was reported for fall (1.24/ha), which was significantly higher than those for summer (0.24/ha), winter (0.0.18/ha), or spring (0.15/ha). In general, highest densities were observed in the Forested

Page 14 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Wetland (0.17 to 1.52/ha) and Forested Upland (0.00 to 0.1.37/ha) cover-types. However, significant differences were found only in fall when the Forested Wetland cover-type had higher densities than the Mountain Shrub cover-type did.

7. ACKNOWLEDGMENTS

Thanks go to Kelly Wilde and Von Pope for organizing the fieldwork for this study. We would also like to thank all the field assistants for their efforts. Thanks also go to Mike Butler of IPC’s Geographic Information Services for GIS support. Von Pope provided valuable comments on earlier drafts. Natalie Chavez edited the draft manuscript. Corporate Publishing, IPC, formatted the manuscript.

8. LITERATURE CITED

Asherin, D. A., and J. J. Claar. 1976. Inventory of riparian habitats and associated wildlife along the Columbia and Snake rivers. Volume IIIA. College of Forestry, Wildlife and Range Sciences, Univ. of Idaho, Moscow, ID. 556p.

Bibby, C. J., N. D. Burgess, and D. A. Hill. 1992. Bird census techniques. Academic Press, New York, N.Y. 257p.

Bonneville Power Administration (BPA). 1984. Hells Canyon environmental investigation. Prepared by CH2M-Hill, Boise, ID. 300p.

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: estimating abundance of biological populations. Chapman and Hall, New York, N.Y. 446p.

Bush, J. H., and W. P. Seward. 1992. Geologic field guide to the Columbia River Basalt, northern Idaho and southeastern Washington. Information Circular 49. Idaho Geographical Survey, Univ. of Idaho, Moscow, ID. 35p.

Chapman, J. A., and G. A. Feldhamer. 1982. Wild mammals of North America. Johns Hopkins Univ. Press, Baltimore, MD. 1147p.

Chapman, J. A., and G. R. Willner. 1986. Lagomorphs. Pages 453-473 in A. Y. Cooperrider, R. J. Boyd, and H. R. Stuart, eds. Inventory and monitoring of wildlife. U.S. Dept. Inter., Bur. Land Manage., Serv. Center, Denver, CO.

Csuti, B., A. J. Kimerling, T. A. O’Neil, M. M. Shaugnessy, E. P. Gaines, and M. M. P. Huso. 1997. Atlas of Oregon wildlife: distribution, habitat, and natural history. Oregon State Univ. Press, Corvallis, OR. 492p.

Davis, W. B. 1939. The recent mammals of Idaho. Caxton Printers Ltd., Caldwell, ID. 400p.

Hells Canyon Complex Page 15 Medium-Sized Mammal Resources Idaho Power Company

Dawson, D. G. 1981. Experimental design when counting birds. Stud. Avian Biol. 6:392-398.

DeBolt, A. 1992. The ecology of Celtis reticulata Torr. (Netleaf Hackberry) in Idaho. M.Sc. Thesis, Oregon State Univ., Corvallis, OR. 166p.

Department of Energy (DOE). 1985. Hells Canyon environmental investigation. Final report. U.S. Department of Energy, Bonneville Power Administration, Office of Power and Resource Management. DOE/BP-11548-1.

Edelmann, F., and V. R. Pope. 2001. Distribution and relative abundance of mammalian carnivores and furbearers in Hells Canyon. In License Application for the Hells Canyon Hydroelectric Complex. Technical Report E.3.2-28. 50p.

Fitzgerald, J. F. 1982. Geology and basalt stratigraphy of the Weiser Embayment, west-central Idaho. Pages 137-141 in B. Bonnichsen, and R.M. Breckenridge, eds. Cenozoic geology of Idaho. Idaho Bureau of Mines and Geology, Univ. of Idaho, Moscow, ID.

Flinders, J. T., and R. M. Hansen. 1972. Diets and habitats of jackrabbits in northeastern Colorado. Range Sci. Dept., Colorado State Univ. Science Ser. 12.

Franklin, J. F., and C. T. Dyrness. 1988. Natural vegetation of Oregon and Washington. Oregon State Univ. Press, Corvallis, OR. 452p.

Franzreb, K. E. 1981. The determination of avian densities using the variable-strip and fixed- width transect surveying methods. Sud. Avian Biol. 6:139-145.

Garrison, G. A., A. J. Bjugstad, D. A. Duncan, M. E. Lewis, and D. R. Smith. 1977. Vegetation and environmental features of forest and range ecosystems. U.S. Dept. Agric., For. Serv., Agric. Handb. No. 475. 68p.

Green, J. S., and J. T. Flinders. 1980. Habitat and dietary relationships of the pygmy rabbit. J. Range Manage. 33:136-142.

Groves, C. R., B. Butterfield, A. Lippincott, B. Csuti, and J. M. Scott. 1997. Atlas of Idaho’s wildlife: integrating gap analysis and Natural Heritage information. Idaho Dept. Fish and Game, Nongame and Endangered Wildlife Program, Boise, ID. 372p.

Holthuijzen, A. M. A. 1995. An investigation of medium-sized mammals in the Hagerman Study Area. In License application for the Upper Salmon Falls, Lower Salmon Falls, and Bliss hydroelectric projects. Vol. 3, Technical Report E.3.2-I. Idaho Power, Boise, ID. 17p.

Holthuijzen, A. M. A. 1997. An investigation of medium-sized mammals in the Shoshone Falls study area. In License application for the Shoshone Falls project. Vol. 2, Technical Report E.3.2-G, Idaho Power, Boise, ID. 21p.

Huschle, G. 1975. Analysis of the vegetation along the middle and lower Snake River. M.Sc. Thesis, Univ. of Idaho, Moscow, ID. 268p.

Page 16 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Idaho Conservation Data Center (CDC). 1994. Rare, threatened and endangered plants and animals of Idaho. Third ed. Idaho Dept. Fish and Game, Boise, ID. 39p.

[IDCDC] Idaho Conservation Data Center. 2000. Pygmy rabbit. http://www2.state.id.us/fishgame/birds.htm. Updated [April 2000].

Idaho Department of Fish and Game (IDFG). 1990. Upland game species management plan 1991-1995. Idaho Dept. Fish and Game, Boise, ID. 102p.

Idaho Power Company (IPC). 1997. Formal consultation package for relicensing Hells Canyon hydroelectric project, FERC. No. 1971. Idaho Power Co., Boise, ID. 819p.

Idaho Power Company (IPC). July 1999. Detailed Final Study Plans Terrestrial Section, Phase II, for Relicensing the Hells Canyon Complex (FERC No. 1971). Idaho Power Co., Boise, ID.

Johnson, R. D., and J. E. Anderson. 1984. Diets of black-tailed jack rabbits in relation to population density and vegetation. J. Range Manage. 37:79-83.

Johnson, D. R., and J. M. Peek. 1984. The black-tailed jackrabbit in Idaho: life history, population dynamics and control. Bull. 637. Univ. of Idaho Coll. Agric. Coop. Ext. Serv. 16p.

Johnson, C. G. Jr., and S. A. Simon. 1987. Plant associations of the Wallowa-Snake province, Wallowa-Whitman National Forest. U.S. Dept. Agric. For. Serv. PNR. R-6 ECOL-TP- 225A-86. 272p.

Kemp, G. A. and L. B. Keith. 1970. Dynamics and regulation of red squirrel (Tamiasciurus hudsonicus) population. Ecology 51:763-779.

Knick, S. T. 1991. Habitat classification and the ability of habitats to support populations of Townsend’s ground squirrels and black-tailed jackrabbits. In K. Steenhof, ed. Snake River Birds of Prey Area research and monitoring annual report 1991. U.S. Dept. Inter., Bur. Land Manage., Boise Distr., Boise, ID.

Knick, S. T. 1993. Habitat classification and the ability of habitats to support populations of Townsend’s ground squirrels and black-tailed jackrabbits. In K. Steenhof, ed. Snake River Birds of Prey Area research and monitoring annual report 1992. U.S. Dept. Inter., Bur. Land Manage., Boise Distr., Boise, ID.

Knick, S. T., and D. L. Dyer. 1997. Distribution of black-tailed jackrabbit habitat determined by GIS in southwestern Idaho. J. Wildl. Manage. 61:75-85.

Marshall, D. B. 1986. Oregon nongame wildlife management plan. Oregon Dept. Fish Wildl., Portland, OR.

Hells Canyon Complex Page 17 Medium-Sized Mammal Resources Idaho Power Company

Medin, D. E. 1986. The impact of logging on red squirrels in an Idaho conifer forest. West. J. Appl. Forest. 1: 73-76.

Miller, T. B. 1976. Ecology of riparian communities dominated by white alder in western Idaho. M.Sc. Thesis, Univ. of Idaho, Moscow, ID. 154p.

Miller, T. B., and F. D. Johnson. 1976. Ecology of riparian communities dominated by white alder in western Idaho. Pages 11-123 in Proc. terrestrial and aquatic vegetation. E. Wash. State Coll., Cheney, WA.

Natural Resources Conservation Service (NRCS). 1995. Soil survey for Adams and Washington counties, Idaho. Weiser, ID. Draft 1995.

Ross, S. H., and C. N. Savage. 1967. Idaho earth science: Geology, fossils, climate, water, and soils. Idaho Bureau of Mines and Geology, Earth Science Series No. 1, Moscow, ID. 271p.

SAS Institute, Inc. 1988. SAS/STAT user’s guide, release 6.03 ed. SAS Institute. Cary, N.C. 1028p.

Smith, M. C. 1968. Red squirrel responses to spruce cone failure in interior Alaska. J. Wildl. Manage. 32:305-317.

Steenhof, K., and M. N. Kochert. 1988. Dietary responses of three raptor species to changing prey densities in a natural environment. J. Anim. Ecol. 57:37-48.

Sunderman, N. J., F. B. Edelmann, and A. M. A. Holthuijzen. 1998. Presence and relative abundance of medium-sized mammals in the C.J. Strike study area. In License application for the C.J. Strike project. Vol. 2, Technical Report E.3.2-H, Idaho Power, Boise, ID. 32p.

Tisdale, E. W. 1979. A preliminary classification of Snake River canyon grasslands in Idaho. For., Wildl. and Range Exp. Sta., Univ. of Idaho, Moscow, ID. 8p.

Tisdale, E. W. 1986. Canyon grasslands and associated shrublands of west central Idaho and adjacent areas. For., Wildl and Range Exp. Sta. Bull. No. 40. Univ. of Idaho, Moscow, ID. 42p.

Tisdale, E. W., and M. Hironaka. 1981. The sagebrush-grass region: a review of the ecological literature. For., Wildl. and Range Exp. Sta., Univ. of Idaho. Moscow, ID. 31p.

Tisdale, E. W., M. Hironaka, and M. A. Fosberg 1969. The sagebrush region in Idaho: a problem in range resource management. Ag. Exp. Sta. Bull. 512, Univ. of Idaho, Moscow, ID. 12p.

Turley, N. J. S., and A. M. A. Holthuijzen. 2001. Composition and relative abundance of the small and medium-sized mammal community in the upper and lower Malad Study Area.

Page 18 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

In License application for the Upper and Lower Malad hydroelectric project. Vol. 2. Technical Report E. 3.2-D. Idaho Power, Boise, ID. 25p.

U.S. Dept. Agriculture (USDA). 1990. Final environmental impact statement and land resource management plan: Wallowa–Whitman National Forest. U.S. Dept. Agric. For. Serv., Pac. Northwest Region, Baker, OR. 367p.

U.S. Dept. Agriculture (USDA) 1994. Final environmental impact statement: Wild and scenic Snake River recreation management plan. U.S. Dept. Agric. For. Serv., Hells Canyon Nat. Rec. Area, Wallowa-Whitman Nat. For., Pac. Northwest Region, Baker, OR. 243p.

U.S. Department of the Interior (USDI). 1987. Proposed resource management plan and final environmental impact statement: Cascade Resource Area. U.S. Dept. Inter., Bur. Land Manage., Boise Distr., Boise, ID.

Verts, B. J., and L. N. Carraway. 1998. Land mammals of Oregon. Univ. of California Press, Berkley, CA. 668p.

Wakely, J. S. 1987a. Avian line-transect methods. Section 6.3.2., U.S. Army Corps of Engineers wildlife resource management manual. Tech. Rep. EL-87-5. U.S. Army Waterways Exp. Sta., Vicksburg, MS.

Wakely, J. S. 1987b. Avian plot methods. Section 6.3.3., U.S. Army Corps of Engineers wildlife resource management manual. Tech. Rep. EL-87-6. U.S. Army Waterways Exp. Sta., Vicksburg, MS.

Watts, S. E., and S. T. Knick. 1994. Habitat classification and the ability of habitats to support populations of Townsend’s ground squirrels and black-tailed jackrabbits. In K. Steenhof, ed. Snake River Birds of Prey Area research and monitoring annual report 1994. U.S. Dept. Inter., Bur. Land Manage., Boise Distr., Boise, ID.

Weiss, N. T., and B. J. Verts. 1984. Habitat and distribution of pygmy rabbits (Sylvilagus idahoensis) in Oregon. Great Basin Nat. 44:563-571.

White, S. M., J. T. Flinders, and B. L. Welch. 1982. Preference of pygmy rabbits (Brachylagus idahoensis) for various populations of big sagebrush (Artemisia tridentata). J. Range Manage. 35:724-726.

Wilde, D. B. 1978. A population analysis of the pygmy rabbit (Sylvilagus idahoensis) on the INEL site. Ph.D. Dissertation, Idaho State Univ., Pocatello, ID. 172p.

Hells Canyon Complex Page 19 Medium-Sized Mammal Resources Idaho Power Company

This page left blank intentionally.

Page 20 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Table 1. Medium-sized mammals potentially occurring in the Hells Canyon Study Area and vicinity.

Marshall (1986) Groves et al. Asherin and This Study Common Name Scientific Name Blue Mnts. (1997) Idaho Claar (1976) (1995–1999)

Pygmy rabbit Brachylagus idahoensis Da Vicinity

Mountain cottontail Sylvilagus nuttallii W Study Area Present Present

Snowshoe hare Lepus americanus D Vicinity Present

White-tailed jackrabbit Lepus townsendii D Study Area Present

Black-tailed jackrabbit Lepus californicus D Study Area Present

Yellow-bellied marmot Marmota flaviventris D Study Area Present Present

Fox squirrel Sciurus niger L Present

Red squirrel Tamiasciurus hudsonicus W Study Area Present Present

Northern flying squirrel Glaucomys sabrinus W Vicinity

Porcupine Erethizon dorsatum W Study Area Present Present

Mink Mustela vison W Study Area Present Present

River otter Lutra canadensis D Study Area Present Present

Beaver Castor canadensis W Study Area Present Present

Muskrat Ondatra zibethica W Study Area Present Present

Coyote Canis latrans W Study Area Present Present

Red fox Vulpes vulpes D Study Area Present Present

Raccoon Procyon lotor D Study Area Present Present

Marten Martes americana W Vicinity Vicinityb

Fisher Martes pennanti D Vicinity

Ermine Mustela erminea W Study Area

Long-tailed weasel Mustela frenata W Study Area Present Present

Wolverine Gulo gulo L Vicinity Vicinityc

Badger Taxidea taxus D Study Area Present Present

Striped skunk Mephitis mephitis D Study Area Present Present

Spotted skunk Spilogale gracilis – Study Area Present

Lynx Lynx canadensis D Vicinity

Bobcat Lynx rufus W Study Area Present Present a W–Widespread, D–Discontinuous Distribution, L–Local Population, – Not Observed b Observed on Cuddy Mountain, Idaho c Observed in Seven Devils Mountains, Idaho

Hells Canyon Complex Page 21 Medium-Sized Mammal Resources Idaho Power Company

Table 2. Cover-types (acreage and percentages) present in the Hells Canyon Study Area.

Vegetation Cover-type Acreage (acres) Percentage Agriculture 6019 5.0 Barrenland 131 < 1.0 Cliff/Talus 6729 5.6 Desertic Herbland 870 < 1.0 Desertic Shrubland 1362 1.1 Disturbed 109 < 1.0 Emergent Herbaceous Wetland 534 < 1.0 Forbland 376 < 1.0 Forested Upland 179 < 1.0 Forested Wetland 963 < 1.0 Forested/Orchard 18 < 1.0 Grassland 42,484 35.5 Grazing Land 1435 1.2 Industrial 467 < 1.0 Lentic 24 < 1.0 Lotic 19,252 16.1 Parks and Recreation 234 < 1.0 Residential 524 < 1.0 Roads 5 < 1.0 Scrub-Shrub Wetland 2033 1.7 Shore & Bottomland Wetland 2220 1.8 Shrub Savanna 25,092 21.0 Shrubland 7895 6.6 Tree Savanna 570 < 1.0 119,534

Page 22 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Table 3. Number of surveys conducted in spring, summer, fall, and winter in upland and riparian habitats, Hells Canyon Study Area, 1995–1999.

Season Brownlee Oxbow Hells Canyon HC Below Combined Riparian Points Spring 1995 26 15 23 - 64 1996 73 46 83 - 202 1997 74 47 58 - 179 1998 74 48 89 - 211 Summer 1995 70 48 79 - 197 1996 74 48 89 - 211 1997 70 48 89 95 302 1998 74 47 89 95 305 Fall 1995 71 48 79 - 198 1996 72 48 89 95 304 1997 74 48 89 96 307 1998 74 48 89 96 307 Winter 1997 35 17 47 - 99 1998 37 16 56 - 109 1999 37 19 57 - 113

Combined 898 572 1048 477 2995

Upland Spring 1995 - - - - 0 1996 6 - - - 6 1997 67 5 29 - 101 1998 67 5 29 - 101 Summer 1995 - - - - 0 1996 67 5 23 95 95 1997 67 5 29 118 118 1998 67 5 29 121 121 Fall 1995 - - - 0 0 1996 67 5 29 121 121 1997 67 5 29 118 118 1998 66 5 29 120 120 Winter 1997 22 5 18 45 45 1998 22 5 18 45 45 1999 20 5 17 42 42

Combined 586 50 262 94 992

Hells Canyon Complex Page 23 Medium-Sized Mammal Resources Idaho Power Company

Table 4. Observations of medium-sized mammals during point-count surveys, Hells Canyon Study Area, 1995–1999.

Species 1995 1996 1997 1998 1999a

Red squirrel 15 120 34 65 2 Coyote 0 0 9 7 0 Mountain cottontail 1 2 1 6 0 Beaver 0 0 1 0 0 Badger 0 1 0 0 0

a Surveys conducted only in winter 1999

Table 5. Red squirrel density (number/ha) by cover-type and season, Hells Canyon Study Area, 1995–1999.

Cover-typea Springb Summer Fall Winter

FW 0.17A 0.36A 1.52A 0.26A FU 0.00A 0.29A 1.37AB 0.00A MS 0.22A 0.00A 0.00B 0.00A SSW 0.13A 0.00A 0.88AB 0.09A TS 0.00A 0.26A 0.50AB 0.00A

P-value 0.97 0.54 0.03 0.77

a Cover-types: FW–Forested Wetland, FU–Forested Upland, MS–Mountain Shrub, SSW–Scrub-Shrub Wetland, and TS–Tree Savanna. b Mean abundances within a season followed by the same letter are not different at P < 0.05 based on Duncan’s multiple-range test.

Page 24 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Table 6. Medium-sized mammal densities (n/ha) along various reaches of the Snake River, Idaho.

Source Location Habitat BTJA MOCO RESQ YBMA

Holthuijzen Hagerman (1995) Valley Riparian 0.01 0.18 - 0.08 Upland 0.28 0.05 - < 0.01

Holthuijzen Shoshone (1997) Falls Riparian - Low - Medium Upland - Low - Medium

Sunderman et al. (1998) C.J. Strike Riparian 0–0.02 0.07–0.34 - Low Upland 0.07–0.30 0.02–0.16 - Low

Sunderman and Holthuijzen (2001) Malad River - - Low - Medium

Asherin and Claar (1976) Hells Canyon - - Medium Low Medium

This study Hells Canyon Ripariana - < 0.01 0.61 < 0.01 Uplandb - < 0.01 0.00 < 0.01

BTJA–black-tailed jackrabbit, MOCO–mountain cottontail, RESQ–red squirrel, YBMA–yellow-bellied marmot a Includes Scrub-Shrub Wetland and Forested Wetland cover-types b Includes shrub-steppe cover-types

Hells Canyon Complex Page 25 Medium-Sized Mammal Resources Idaho Power Company

This page left blank intentionally.

Page 26 Hells Canyon Complex Nez Per Theme: i:\relic\hellscan\terr\mammal.aml Created: February 21, 2001 OREGON R Plotfile: mammal.gra Plotting Scale: 570000 i v e r Grangeville

n o m Sal

Imnaha

Salmon

Enterprise Riggins

Joseph

Idaho County Adams County Hells Canyon Dam

River Wallowa County r

e

v i

R

Imnaha

Union County Baker County

New Meadows Oxbow Dam Mc Call

Halfway

Powder Brownlee Dam River Richland

Donnelly Council

Cascade

Res.

Durkee Snake Cambridge

Cascade

Midvale

Baker County Malheur County Farewell q Bend Weiser

Features Legend Figure 1 hington Vicinity Map Hells Canyon Complex Primary Route Montana Secondary Route Transmission Lines Location of the Hells Rim- to- Rim Study Area egon Canyon Study Area and Idaho Mammal Survey Points Wyom Mammal Survey Points Idaho Power Facility City or Town Nevada Utah IDAHO POWER COMPANY BOISE, IDAHO

52.5 0 5 10 MILES

Scale = 1:570000 Medium-Sized Mammal Resources Idaho Power Company

This page left blank intentionally.

Page 28 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Weiser 2 SEa (641m)b 10.1d 286mme Richlanda (675m)b 10.6d 298mme 60 60 60 60 55 55 55 55 50 47, 47c 50 50 49, 49c 50 45 45 45 45 42.8i 42.8i 40 40 40 l 40 35 35 35 35 33.4h 33.8h 30 n l 30 30 n 30 25 25 25 25 20 20 20 20 15.7j 17.3j 15 15 15 15 10 10 10 m 10 5 5 5 k 5 k m (mm) PRECIPITATION (mm) PRECIPITATION 0 0

DEGREES CENTIGRADE 0 0 DEGREES CENTIGRADE -5 -5 -5 -6.8f -7.7f JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC -32.8g -33.9g o MONTHS o o MONTHS o

Brownleea (562m)b 12.3d 445mme Lewiston WSO APa (438m)b 11.3d 326mme 60 60 60 60 55 33, 33 55 55 55 c 51, 51 50 n 50 50 c 50 46.1i 45i 45 45 45 45 40 l 40 40 40 39.4h 35 35 35 n 35 34.7h l 30 30 30 30 27.4j 25 25 25 25 20 20 20 20 15 15 13.1j 15 15 10 m 10 m k 10 10 PRECIPITATION (mm) PRECIPITATION 5 5 (mm) PRECIPITATION 5 k 5 DEGREES CENTIGRADE 0 0 CENTIGRADE DEGREES 0 0 -5 -5 -5 -5 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC -13.3f JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC o MONTHS o -30g o MONTHS o

a: Station b: Elevation c: Number of years of observation (temperature, precipitation) d: Mean annual temperature in °C e: Mean annual precipitation in millimeters f: Mean daily minimum of the coldest month g: Lowest recorded temperature h: Mean daily maximum of the hottest month i: Highest recorded temperature j: Mean daily temperature range k: Monthly means of temperature in °C l: Monthly means of precipitation in millimeters m: Arid period (horizontal hatched) n: Humid period (vertical hatched) o: Months with an absolute minimum below 0 °C

Figure 2. Köppen climate diagrams for the Weiser, Richland, Brownlee, and Lewiston weather stations, Hells Canyon Study Area, Idaho–Oregon border.

Hells Canyon Complex Page 29 Medium-Sized Mammal Resources Idaho Power Company

This page left blank intentionally.

Page 30 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Appendix 1. Criteria and definitions used to identify cover-types in the Hells Canyon Study Area.

1. EHW Emergent Herbaceous Wetland—is dominated by emergent, erect, rooted and herbaceous hydrophytes excluding mosses and lichens. This vegetation is present for most of the growing season in most years and is usually dominated by perennial plants. It has less than 30% cover of woody vegetation and a total vegetation cover of at least 30%. The lands in this cover-type are usually saturated with or covered by water at least for part of the growing season. However, because of the difficulties in distinguishing between species and interpreting hydrologic indicators during remote sensing activities, some lands in this cover-type may be dominated by upland species (FAC, FAC-, and UPL hydrologic indicator status) and located in areas without the necessary hydrologic regime to be considered "jurisdictional wetlands" by the U.S. Army Corps of Engineers. Actual extent of jurisdictional boundaries are not indicated on cover-type maps and must be determined on the ground through formal wetland delineation techniques.

3. SBW Shore & Bottomland Wetland—may consist of bare sand, gravel, or rocky areas along the riparian zone. If vegetation is present, its cover is less than 30%. Examples of this cover-type include Rock Bottom, Unconsolidated Bottom, Streambed, Rocky Shore, and Unconsolidated Shore, as defined by Cowardin (1979). Actual extent of jurisdictional boundaries are not indicated on cover-type maps and must be determined on the ground through formal wetland delineation techniques.

4. SSW Scrub-Shrub Wetland—is dominated by woody wetland vegetation less than 6 m (20 feet) tall. It has a total vegetation cover of at least 30% and at least 30% cover of woody vegetation. Because of the difficulties in distinguishing between species and interpreting hydrologic indicators during remote sensing activities, some lands in this cover-type are dominated by upland species (FAC, FAC-, and UPL hydrologic indicator status) and located in areas without the necessary hydrologic regime to be considered "jurisdictional wetlands" by the U.S. Army Corps of Engineers. Actual extent of jurisdictional boundaries are not indicated on cover-type maps and must be determined on the ground through formal wetland delineation techniques.

5. FW Forested Wetland—is dominated by woody wetland vegetation that is 6 m (20 feet) tall or taller. It has a total vegetation cover of at least 30% and at least 30% cover of woody vegetation. Because of the difficulties in distinguishing between species and interpreting hydrologic indicators during remote sensing activities, some lands in this cover-type are dominated by upland species (FAC, FAC-, and UPL hydrologic indicator status) and located in areas without the necessary hydrologic regime to be considered "jurisdictional wetlands" by the U.S. Army Corps of Engineers. Actual extent of jurisdictional boundaries are not indicated on cover-type maps and must be determined on the ground through formal wetland delineation techniques.

6. LS Lentic (Standing Water)—is non-moving open water habitat such as ponds and lakes.

Hells Canyon Complex Page 31 Medium-Sized Mammal Resources Idaho Power Company

Appendix 1. (continued)

7. LM Lotic (Moving Water)—is moving open water habitat such as rivers and streams.

8. FU Forested Upland—is dominated by trees (taller than 5 m) and has a tree canopy cover of at least 25%.

9. S Shrubland—is an upland vegetation community dominated by shrubs (including small trees shorter than 5 m) and having a shrub canopy cover of at least 25%. Total vegetation cover is greater than 25%.

11. SS Shrub Savanna—is an upland community with a canopy cover of shrubs (including small trees shorter than 5 m) between 5% and 25%. This cover-type has a total vegetation cover of at least 25%. The area between shrubs is typically dominated by grasses or other herbaceous vegetation.

13. DS Desertic Shrubland—is an upland community, with 1 to 25% total vegetation cover and shrubs (and small trees shorter than 5 m) forming the dominant vegetation stratum. This cover-type includes sparsely vegetated habitats in non-desert areas.

14. DH Desertic Herbland—is an upland community with 1 to 25% total vegetation cover and non-woody plants (including lichens and mosses) forming the dominant vegetation stratum. It includes sparsely vegetated types in non-desert areas.

15. G Grassland—is an upland community with a total vegetation cover of at least 25% dominated by non-woody plants (including lichens and mosses), of which grasses (native or introduced) are dominant. This cover-type may include prairies, rangeland, and upland subalpine meadows.

16. F Forbland—is an upland community with a total vegetation cover of at least 25% dominated by non-woody plants (including lichens and mosses), of which forbs (native or introduced) are dominant. This cover-type includes many weedy fields, old fields, and other types in early successional stages.

18. CTS Cliff/Talus Slope—consists of nearly vertical rock or bare soil faces or slopes of unconsolidated rock material with a total vegetation cover of 5% or less.

19. D Disturbed—is land with more than 50% of the area disturbed by human activities and a total vegetation cover of less than 15%. This cover-type may include off-road vehicle areas, rural trash dumps, and soil barrow pits.

23. R Residential—is land principally associated with human housing. This cover-type may include homes, garages, yards, gardens, sidewalks, driveways, and small livestock pens and pastures (1 to 2 acres).

Page 32 Hells Canyon Complex Idaho Power Company Medium-Sized Mammal Resources

Appendix 1. (continued)

24. I Industrial—is land principally used for larger businesses and corporations, such as office complexes, manufacturing plants, and warehouses.

25. PR Parks/Recreation—is cultivated landscape principally used for human recreation such as city or county roadside rest areas and picnic areas.

Hells Canyon Complex Page 33 Medium-Sized Mammal Resources Idaho Power Company

This page left blank intentionally.

Page 34 Hells Canyon Complex