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Home , American pika, Great Basin

Western North American Naturalist 77(2), © 2017, pp. 252–268

A SURPRISING ISCOVERY OF AMERICAN SITES IN THE NORTHWESTERN

Mackenzie R. Jeffress1, K. Jane Van Gunst2, and Constance I. Millar3

ABSTRACT.—Although the (Ochotona princeps) continues to receive attention due to documented declines and range retractions, particularly in the Great Basin, thorough range inventories have yet to be completed in many parts of the . Here we report on recently discovered populations in northwestern in areas not suspected to support pika activity under current climate regimes. We describe 238 new locations (“sites”) with evidence of past or current occupancy by which cluster into 31 locales, which we interpret as metapopulations or “demes,” in 15 distinct mountain ranges or geographic areas. We documented twice as many relict sites (sites with evidence of former pika occupancy) as currently occupied sites, a result that supports previous observations of local range retraction and site losses within the pika’s range. In the overall site data, median elevation and water year were higher and minimum and maximum July temperatures were lower for occupied sites than for relict sites. This pattern was repeated in most, but not all, of the 7 mountain ranges where both occupied and relict sites were found. Occupied sites were more likely to be found in areas with a narrow range of water year precipitation, in cooler climates, and on more mesic-facing aspects, but many of these environmental descriptors also describe relict sites. The apparent extirpa- tion of pikas from the range with the highest elevation and lowest temperatures (Black Rock Range) and the continued persistence in some of the lowest and hottest areas of our survey (Home Camp Range) are particularly noteworthy. Since pikas were known from only a handful of early 20th century records in the area, these surveys greatly expand our understanding of both current and historic pika distributions in the northwestern Great Basin and shed light on patterns of pika persistence and extirpation in a region typified by harsher climates respective to other areas with extant pika populations. Furthermore, our results emphasize the importance of conducting spatially extensive fieldwork to better understand site extirpations and species range retractions.

RESUMEN.—Aunque la pica americana (Ochotona princeps) continúa recibiendo atención debido a su declive docu- mentado y a su gama de retracciones, en particular en la Gran Cuenca (Great Basin), aún resta completar los inventarios sobre su rango de distribución en muchas partes de la región. Aquí reportamos poblaciones recientemente descubiertas en el noroeste de Nevada, en áreas en las que no se pensaba que las picas estuviesen activas bajo las condiciones climá- ticas actuales. escribimos 238 nuevos lugares (“sitios”) con evidencia de ocupación pasada o actual de las picas que se agrupan en 31 sitios, los cuales interpretamos como metapoblaciones o “demes,” en 15 montañas o áreas geográficas distintas. ocumentamos el doble de sitios relicto (sitios que justifican la ocupación histórica de picas) que los sitios habitados actualmente; respaldando observaciones previas de retracción del rango local y la pérdida de sitios dentro del rango de las picas. Al observar los datos generales del lugar, tanto la elevación media como las precipitaciones anuales fueron más altas, y las temperaturas mínimas y máximas en julio fueron más bajas en los sitios habitados actualmente que en los sitios relicto. Este patrón se repitió en la mayoría, pero no en todos, de los siete sitios montañosos en donde se encontraron sitios ocupados y sitios relicto de pica. Los sitios ocupados fueron más propensos a encontrarse entre el límite inferior y el límite superior de precipitaciones anuales, en climas más fríos y en condiciones más mésicas, pero muchas de estas características ambientales también describen sitios relicto. Es particularmente significativa la aparente desaparición de las picas de las montañas con mayor elevación y con temperaturas más bajas (cordillera Black Rock), y su persistencia en algunas de las áreas más bajas y más cálidas de nuestra investigación (cordillera Home Camp). ado que las picas sólo eran conocidas por unos cuantos registros pertenecientes a principios del siglo XX en el área, estos monitoreos amplían enormemente nuestra comprensión tanto de su distribución actual como de su distribución histó- rica en la Gran Cuenca del noroeste y clarifican sobre los patrones de persistencia y de desaparición de las picas en una región tipificada por climas más severos con respecto a otras áreas con poblaciones de pica. Además, nuestros resultados hacen hincapié en la importancia de llevar a cabo extensas investigaciones de campo para comprender mejor las desapa- riciones en ciertos sitios y las retracciones de estas especies.

American pikas (Ochotona princeps) are western (Smith and Weston small related to and are 1990). Limits to thermoregulation combined patchily distributed in broken rock landforms with specific habitat requirements and (e.g., talus and lava flows) of mountainous metapopulation dynamics suggest that pikas

1Nevada epartment of Wildlife, 60 Youth Center Road, Elko, NV 89801. E-mail: [email protected] 2Nevada epartment of Wildlife, 815 E. Fourth St., Winnemucca, NV 89445. 3US A Forest Service, Pacific Southwest Research Station, Albany, CA 94710.

252 2017] RECENTLY ISCOVERE GREAT BASIN PIKA SITES 253 could be vulnerable to . For old evidence of pikas, suggesting extirpation example, pikas appear to be in decline in some (Beever et al. 2011 [App. V], Millar et al. 2014). low-elevation locations of the Great Basin, and Conversely, Collins and Bauman (2012) docu- potential stressors, including decreased snow- mented newly discovered populations on the pack and warming summer months, are impli- Sheldon National Wildlife Refuge (NWR), in cated in these declines (Beever et al. 2003, areas just north and west of Hall’s Summit 2010, 2011). However, pikas continue to be Lake site and in nearby southern ’s Hart found outside of described bioclimatic Mountains, and Beever et al. (2008) found a envelopes, and the species does not often fit small extant population of pikas in Boulder well within species niche models (Martínez- Canyon in the , Nevada Meyer et al. 2004). Previously undocumented (Fig. 1). Additionally, Millar et al. (2013) docu- populations have recently been found in new mented nearby populations to the west in areas, including lower-elevation, non-talus, northern Great Basin portions of , and anthropogenic sites (Beever et al. 2008, above the Madeline Plain, and in the South Simpson 2009, Rodhouse et al. 2010, Collins . Interestingly, Hall (1946) and Bauman 2012, Millar et al. 2013, Varner noted that pikas “are much more widely dis- and earing 2014a, Shinderman 2015). Fur- tributed in northwestern Nevada than our thermore, for several populations across the records indicate.” Yet, aside from these few pika’s range, species distribution models and areas mentioned, this region has not been projections that account for current and antici- extensively surveyed until now. The northwest- pated climate change and habitat connectivity ern portion of the Great Basin is atypical com- suggest that the impacts on pikas will vary pared to the mountainous (“alpine”) landscapes by place (Jeffress et al. 2013, Schwalm et al. associated with much of the species’ range. The 2016). Resilience also appears to relate to area is at a lower elevation that is warmer and pikas’ habitat dependence on broken rock more xeric than expected given its latitude, landforms, which develop thermal regimes at providing an opportunity to understand how least partially decoupled from surface temper- a species vulnerable to heat stress persists in a atures and thereby mitigate seasonal tempera- warmer and drier environment. Furthermore, ture stresses on pikas (e.g., Varner and earing the region is at the edge of the range for the 2014b, Hall et al. 2016, Millar et al. 2016). subspecies (O. p. schisticeps; Therefore, generalizations about pika extirpa- Hafner and Smith 2010). In the context of tions at regional and species-wide scales might under standing climate change impacts, examin- be inaccurate, and place-based assessments ing populations at the range periphery provides relying on extensive surveys over multiple years valuable insight into a species’ adaptive poten- are needed (Jeffress et al. 2013). tial, especially for species like pika, which are Pikas are a Nevada Species of Conservation dispersal-limited habitat specialists, with low- Priority and the Nevada Wildlife Action Plan ered ability to avoid or adapt to changes in their calls for a thorough statewide inventory of the environment (Thomas et al. 2001, Parmesan species (Wildlife Action Plan Team 2012). 2006, Morueta-Holme et al. 2010). Though much of Nevada has been surveyed for The goal of our study was to conduct a pikas, little was known about pika distribution, more complete and spatially extensive survey potential connectivity among sites, and site of potential pika habitat in northwestern characteristics of both currently occupied and Nevada to better understand the current and seemingly relict sites across the northwestern historic distribution in the area. Here, we portion of the Great Basin, making that region document numerous pika sites over a 2-year particularly important for conservation of the survey period and present our results at mul- American pika. The area has recently docu- tiple scales, from the smaller “site” level to a mented extirpated sites, as well as newly dis- snapshot of potentially connected population covered occupied sites. Early 1900s naturalist centers (or “demes”) to larger mountain ranges. E.R. Hall (1946) captured pikas in the area of At these scales, we describe climatic and envi- Barrel Springs (near the California border), ronmental variables in multiple occupancy near Summit Lake, and in the Pine Forest categories to provide insight into factors asso- Mountains. However, resurveys of these sites, ciated with pika persistence and extirpation starting in the 1990s, have documented only within the region. Our hope is that our survey 254 WESTERN NORTH AMERICAN NATURALIST [Volume 77

EG ON O R EGO N NE VADA Bl SPFflNG TAB!.e

~-----l

✓ / ) J. ,z < l o,; 0 I ~ ~ "' ~- z u ,, Summit l •"-• lndlan lltJ MB OI tl 1 Rli,1ewiit10n ,• \\"AS/ JOE

Source: Hall (1946) and/or Beever et al. (2003, 20081 * Occupied / * Relict b Source: Collin• and Bauman (201 2) 1111 Occupied \ ~ Relict (Previously Occupied) 0 r.·::::J No Detection f ;; ~ '----,,--;------i(~ ,6 ~;o,• 700 1,400 km I

Fig. 1. Sites in northwestern Nevada documented prior to 2014 as American pika habitat (noted as occupied or relict at the time of observation): (a) Barrel Springs/Fort Bidwell, occupied in 1941 (Hall 1946) but since extirpated (i.e., relict; Beever et al. 2003); (b) Boulder Canyon in the Hays Canyon Range first documented as occupied in 2002 (Beever et al. 2008); (c) mix of occupied and recently extirpated sites, first documented in 2009, on and near the Sheldon National Wildlife Refuge (Collins and Bauman 2012); (d) N Summit Lake, occupied in 1936 (Hall 1946) but since extirpated (Beever et al. 2003); and (e) uffer Peak in the Pine Forest, occupied in 1935 (Hall 1946) but since extirpated (Beever et al. 2003). results and insights will refine characteriza- do not fall into named mountain ranges, such tions of the pika’s ecological niche and further as the Crooks Lake Hills. These upland areas a comprehensive understanding of population are part of the Black Rock Plateau and sites dynamics and associated conservation needs were dominated by basaltic rock. Upland for American pikas in the Great Basin. vegetation primarily consisted of mountain big sagebrush ( vaseyana), METHO S big sagebrush (Artemisia tridentata wyomingensis), and bitterbrush (Purshia tri- Study Area dentata), with a perennial grass and forb Surveys were restricted to northwestern understory. Some of our sites also had but the study area had no other precon- ( Juniperus occidentalis) and cheat- ceived boundaries; rather, areas were surveyed grass () in the vicinity. All opportunistically, as access and the availability sites surveyed were on public land adminis- of personnel allowed. Mountain ranges sur- tered by the epartment of the Interior veyed included the Black Rock Range, Hays Bureau of Land Management. Canyon Range, Home Camp Range, Little High Rock Mountains, Massacre Range, Mos- Surveys quito Mountains, Painted Point Range, and We visited potentially suitable locations Nut Mountain, as well as upland that (i.e., talus, broken lava, and coarse rock matrix 2017] RECENTLY ISCOVERE GREAT BASIN PIKA SITES 255 landforms) that had been identified via aerial effects on detection). However, previous stud- imagery or preliminary ground inspection, ies have found high detection probabilities and assessed these for pika presence in 2014 (≥0.90) using these survey methodologies and 2015. We surveyed a single potential (Beever et al. 2008, 2010, Rodhouse et al. habitat patch for at least 30 person-minutes 2010, Erb et al. 2011, Moyer-Horner et al. 2012, and documented evidence of current or past Ray et al. 2016), and given our use of multiple pika occurrence. We also noted when a site sources of conspicuous and persistent sign and was surveyed but no evidence of pika pres- trained observers, we used the detection of ence was found. Survey sites and evidence current pika presence to indicate that a site encountered were often further documented was occupied (as was done in Jeffress et al. by collecting pellets and taking photos. As 2013). This allowed us to focus our resources pika sign tends to be clustered in small areas, on increasing survey coverage. Nevertheless, we combined all detection records within 50 we acknowledge that multiple surveys of an m of each other into a single “site.” Therefore, area are needed to confirm true extirpation or a site could contain one to several pika territo- absence and encourage the classification of ries (Smith and Weston 1990) and could be relict and no-detection sites to be interpreted considered representative of a habitat area or with a level of prudence. patch. To evaluate pika occurrence at a coarser Analysis scale, we combined detections that were within 3 km of each other (which is greater To help describe our sites, we used several than the cited average maximum dispersal environmental variables (e.g., elevation, slope, distance of 2 km; Smith and Weston 1990) and and aspect) extracted from a 10-m igital called these clusters “demes” (as in Millar et Elevation Model ( EM) and a 30-m pixel al. 2013). These demes are meant to present a landform dataset that derived landform posi- snapshot of potentially connected populations. tion classes based on (1) a refined and adjusted Finally, we examined results by mountain Topographic Relative Moisture Index (TRMI; ranges and distinct geographic areas defined accounting for slope position and angle, slope by Charlet (unpublished data). shape, and slope aspect), (2) landform position Occupied sites were identified by one or from valley flats to steep slopes, and (3) climatic more detections of hay piles containing cur- zone stratification based on the Soil Adjusted rent year vegetation, pika calls, and pika sight- Vegetation Index, a measure derived from ings. Possibly occupied sites were identified remote sensing (see table 1 in Manis et al. by the detection of questionably fresh hay [2001] for the slope limits and TRMI values (limited green material) or fresh-appearing that define each of the landform position scat (green and perched but not abundant or classes). Aspect was binned into one of eight associated with distinctly fresh hay). Relict 45° ordinal classes (e.g., NE, S, SW). We also sites were identified by one or more detec- calculated total daily solar radiation (both tions of hay pile remnants (brown and decom- diffuse and direct) using the solar radiation posing vegetation) and old scat (brown or tool in ArcMap (Fu and Rich 1999). The solar moldy, dry, and no longer perched). Sites analyst tool uses aspect and slope from a 30-m where only pika-like urine staining on rocks EM to derive a measure of clear-sky radiation was found were described as possibly relict; over the single-day period of 15 August, however, there is currently no way to confirm thereby representing the total amount of insola- these stains as pika-created. Areas surveyed tion (indicating heat load from direct sunlight) that had neither current nor historic evidence and total solar irradiance during peak summer of pika presence were also recorded, with conditions (Fu and Rich 1999, 2002). coordinates taken at the center of the area We present our results by occupancy status searched and annotated at the same scales as and at multiple scales including site, deme, described above. With this single-visit rapid and mountain range. In addition to the envi- assessment survey methodology, the potential ronmental variables, we examined several for false negative results can be high, particu- candidate climatic variables including maxi- larly when considering possible detectability mum and minimum January temperature as a issues (e.g., sites that might have had old sign measure of wintertime stress and maximum that we were unable to locate or seasonal and minimum July temperature as a measure 256 WESTERN NORTH AMERICAN NATURALIST [Volume 77 of summertime stress (Beever et al. 2011, the environmental variables and climate Wilkening et al. 2011). The 800-m PRISM variables derived at our study sites. A classifi- normals from 1981 to 2010 ( aly et al. 2008) cation tree is a type of machine-learning tool were used to derive temperature variables (as that makes hierarchical binary splits in a done in Schwalm et al. 2016). We derived dataset based on a drop in deviance ( e’ath average water year precipitation over the and Fabricius 2000). We restricted the tree to 1981–2010 period from gridded monthly those sites where definitive sign of current or PRISM precipitation data. Water year pre- historic pika occupancy was found. We used cipitation is widely used to describe climate water year precipitation, both July tempera- and changes in climatic trends in the interior ture variables, solar radiation, and the binned western , such as changes in aspect variable for this analysis. The tree was snowpack, snowmelt, seasonal shifts in vegeta- not pruned but several controls were used in tion, and vegetation growing period (Regonda fitting the tree. These controls were as follows: et al. 2005, Wilkening et al. 2011). Water pre- (1) 20 observations needed to exist before a cipitation is derived from the October through split was attempted, (2) at least 10 observa- September period and captures both the season tions needed to exist in any terminal node, of high precipitation input (late fall to early and (3) each split needed to increase the spring), as well as dry periods (late spring to overall fit by 0.05 (e.g., a complexity parame- early fall). ter). These limitations were imposed to ensure Because many of these variables are highly parsimony by identifying the most important correlated (e.g., elevation is highly correlated splits in our dataset. with precipitation and with winter and summer maximum temperatures), we restricted inclu- RESULTS sion of variables to those that have Pearson’s product-moment correlation scores between Surveys occurred in September 2014 and −0.7 and 0.7. For example, for our analysis we March through October 2015, with most only used the median maximum and minimum 2015 surveys occurring in August or later. July temperature with the knowledge that Raw detections of pikas totaled 977, and an these variables are highly correlated with additional 21 sites were surveyed for a mini- analogous variables from January. We pre- mum of 30 person-minutes, but no evidence sented the results of the landform variable in of pikas was found. The raw detections were order to describe the overall environmental clustered into 238 sites, constituting 31 context for these sites, and we included analy- demes in 15 mountain ranges and distinct sis of elevation due to its common use in other geographic areas (Fig. 2). studies. However, neither landform nor eleva- Sites tion was used in our regression tree analyses because of their correlation with other envi- Fifty-six (23.5%) of the sites were occupied, ronmental and climate variables. Because of 12 (5.0%) were possibly occupied, 117 (49.2%) the novel settings of many of these locations, it were relict, 32 were possibly relict (13.4%), is unclear exactly how these variables influence and 21 (8.8%) had no detected evidence of pika occurrence and how that influence changes pika occurrence. No currently occupied or depending on differences in macro- and possibly occupied sites fell within habitat microsites, differences in the talus structure, predicted to be occupied by the GAP species and differences in pika population demograph- distribution model (USGS Gap Analysis Pro- ics. Nonetheless, we present these variables gram 2013). Over our study area, only the because they are important in explaining pika relict Black Rock Range sites fell within GAP- occurrence elsewhere and it seems clear that predicted occupied habitat (n = 4). Most sites climatic stress is important in describing both were located on gently sloping ridges and hills, pika occupancy and extirpation in many areas moderately moist steep slopes, and moderately (Beever et al. 2003, Wilkening et al. 2011). dry slopes (Fig. 3). The highest percentage of We used a classification tree derived in the occupied sites (42.8%) were on moderately R statistical program (R evelopment Core moist steep slopes, while the highest percent- Team 2016) using the “rpart” and “rattle” age of relict sites (36.7%) were on moderately libraries to describe the hierarchical nature of dry slopes and moderately moist steep slopes 2017] RECENTLY ISCOVERE GREAT BASIN PIKA SITES 257

Overview rc~:~r- ---r- ---....J----~ OREG'ON ,,. r osquito Mins , Coleman Rim ----NlsADA

"w'1 if) Sheldon National • Wildlife Refuge Mosquito Mountain oC>

Painted Point Range

BJ.ACK ROCK .9894ft D~SERT r~ ~ B 0 5 10 20 km 3 6 1~ km I I II I I II I ...... _._ ...... _._ ...... , -.l~ut Mountain

Hays Canyon Range 0® Black Rock Range High Rock Canyon Hills

Site Occupancy Status Deme Occupancy Status * Occupied - Occupied * Possibly Occupied Possibly Occupied ,A. Relict c::) Relict D_ Possibly Relict f;~,:'{J Possibly Relict Little High Rock Mountains X No Detection c:J No Detection / 0 ~ 21/.'85 17 l(m

Fig. 2. Map of 2014–2015 pika survey sites and demes, indicated by occupancy status, and associated mountain ranges in northwestern Nevada. P nel A: The northwest portion of the study area including the Mosquito Mountains, Crooks Lake Hills, northern Hays Canyon Range, and Coleman and Massacre Rim. P nel B: The southwestern portion of the study area, from the Hays Canyon Range (furthest west) to the High Rock Canyon Hills and Badger Mountains (to the east). P nel C: The southeastern portion of the study area encompassing the Black Rock Range. A reference map for the panels is provided in the upper left and titled Overview.

45 40 35 30 - -- 25 Occupied 20 s f- ·-1 s  Possibly occupied 15 ~. I - IS] 10 ~ ~ " Relict I ~. I~  occupancy category 5 _.- Possibly relict Im I •s --amrt~ · 0 ~ Percentage of sites in each ·~ Ill " No detections valley flats toe slopes, gently sloping nearly level very moist moderately moderately very dry bottoms, and ridges and plateaus or steep slopes moist steep dry slopes steep slopes swales hills terrace slopes

Landform types

Fig 3. Percent of sites binned by American pika occupancy status and landform.

(35.9%). We found relict-only sites on almost characterized by moderate positions on either all landform types, while over 90% of occu- slope, moisture gradients, or both. Relict sites pied sites were found on 3 landform types can be found in those places as well but they 258 WESTERN NORTH AMERICAN NATURALIST [Volume 77

45

40

35

30

25  Occupied  20 Possibly occupied 51 Relict 15

occupancy category  Possibly relict 10

Percentage of sites in each EH No detections 5

0 N NE E SE S SW W NW

Aspect

Fig 4. Number of sites binned by American pika occupancy status and aspect. dominate the drier landform types. Thirty-nine Median maximum and minimum July tempera- percent of occupied sites were on west-facing tures of possibly occupied sites were about slopes and 16% were on northwest-facing slopes 0.2 °C warmer than occupied sites. Outliers of (Fig. 4). Forty percent of currently occupied both high and low temperatures were noted sites were distributed over northerly aspects at several relict sites. Cold minimum July (north- and northeast-facing together account temperatures of <7.1 °C were found at occu- for 25%), and approximately 15% of occupied pied and relict sites in the Home Camp areas were found on south- and east-facing Range and the Hays Canyon Range, at one slopes. The highest percentage of relict sites occupied site in the Massacre Range, and at were on southwest-facing slopes (24.7%), fol- relict sites in the Black Rock Range. Some, lowed by west-facing (22.2%) and northwest- but not all, of these sites were also colder as facing (18.8%) slopes. However, occupied and defined by a median maximum July tempera- relict sites were found throughout all aspect ture <25.5 °C. Three of the relict Black Rock categories. Median elevation was highest for Range sites were also the hottest sites of the occupied sites (1920 m) and lowest for sites survey area using minimum July temperature where no current or historic sign was detected as the measure. Median total radiation was (1828 m). Median elevation of definitively highest for sites where pika sign was not occupied sites was 29 m higher than that of found (7125 watt-hours [Wh]/m2) and lowest relict sites. for possibly occupied sites (5076 Wh/m2). Median water year precipitation was high- efinitively occupied sites received much est for occupied sites (311.3 mm) and lowest more solar radiation (median = 6927 Wh/m2) for possibly relict sites (297.3 mm). For relict than relict sites (median = 6138 Wh/m2). sites, median water year precipitation was 14.2 mm less than for currently occupied sites; emes and Mountain Ranges although, as with elevation, relict sites in the Eight (25.8%) of the demes were occupied, Black Rock Range had the highest water year 2 (6.5%) were possibly occupied, 14 (45.2%) precipitation of all sites in the survey region. were relict, 3 (9.7%) were possibly relict, and Currently occupied sites had the lowest 4 (12.9%) had no detected evidence of pika median maximum July temperature (26.5 °C) occurrence. Overall, the occupied demes were and lowest median minimum July temperature found more in the western part of our study (8.3 °C) of all occupancy status categories in area (Fig. 2). Five demes contained only one our survey area (Fig. 5). Sites without evidence site (7.3 km2), whereas the largest deme of current or historic pika occupation were the (Carter Reservoir, 74.0 km2) contained 32 sites, warmest in our survey area, having the high- was occupied, and was in close proximity to est maximum July temperature (27.0 °C) and 2 other occupied demes. Our results indicate highest minimum July temperature (9.0 °C). 4 population centers in our survey region: 2017] RECENTLY ISCOVERE GREAT BASIN PIKA SITES 259

0

I 28 . .

26 +T$ ~• . . . .

Minimum July Temperature (ºC) Minimum July Temperature . . 24 .

Occupied Possibly occupied Relict Possibly relict No detection Site Occup ncy

11 C) º 10

9

8 Minimum July Temperature ( Minimum July Temperature

7

Occupied Possibly occupied Relict Possibly relict No detection Site Occup ncy

Fig. 5. Boxplots of median maximum (top) and minimum (bottom) July temperature by site occupancy status.

(1) Crooks Lake, Carter Reservoir, and South- (Fig. 7), and Nut Mountain demes (45 sites, ern Vya Rim (Fig. 6) demes (96 sites, 16.7% 56.8% occupied), and (4) the Massacre Rim occupied), (2) Boulder Canyon and southern deme (Fig. 8; 3 sites, 66.7% occupied). Hays Canyon demes (24 sites, 54.2% occu- Although we attempted to survey as much pied), (3) Massacre Ranch and Grassy Canyon of the study area as possible, we cannot go 260 WESTERN NORTH AMERICAN NATURALIST [Volume 77

Fig. 6. Vya Rim looking toward the Carter Reservoir deme, which includes the Mosquito Rim area. The broken rim- rock in these demes contains a mix of occupied and relict sites. The habitat is sagebrush-steppe and scattered western juniper, and the view is north. This site had many hay piles and fresh scat and was one of the most densly occupied sites that we visited.

Fig 7. The Grassy Canyon deme in the Massacre Range. Several patches of pika-occupied basalt outcrops are visible here and continue down into the canyon. Sagebrush steppe dominates the deme, and the view here is to the southwest. beyond speculation about the potential for may once have been connected via the Pinto habitat and connectivity across unsurveyed Peak deme, but this area is now likely extir- areas. Our surveys indicate that the extant pated. It is also possible that the Boulder Boulder Canyon and Grassy Canyon demes Canyon deme was once connected throughout 2017] RECENTLY ISCOVERE GREAT BASIN PIKA SITES 261

Fig. 8. The Massacre Rim deme in the Painted Point Range. This area was occupied throughout, and although not extensively surveyed as part of this study, the rim has similar and likely connected habitat for several miles to the north and south. the Hays Canyon Range north to the Carter Mountains Piedmont North, and the Yellow Reservoir deme, but surveys that documented Hills). Only 7 of the 11 ranges had sites with relict demes inbetween, such as at Forty-niner current occupation, and in only 2 of those Mountain, suggest another possible and recent ranges, the Home Camp Range and Massacre break in connectivity. The Massacre Rim Range, more sites with current occupation deme is likely much larger than the area we were found than relict sites. To examine dif- were able to document due to limited survey ferences between occupied and relict sites, time (see Fig. 8 for photo of habitat that is rep- we summarize elevation and maximum July resentative of unsurveyed rim areas to north temperature in these 7 ranges. and south), but our results do indicate that the Sites in the Black Rock Range and on Little Massacre Rim Wilderness Study Area to the Hat Mountain in the Hays Canyon Range southeast of the rim is now likely extirpated. were the highest-elevation survey sites, and The potential for connectivity of these demes only historical evidence was found at these to the previously documented Sheldon sites sites (Fig. 10). Median elevation of occupied (Collins and Bauman 2012, Castillo et al. sites was higher than that of relict sites in 3 of 2016) needs further exploration. Furthermore, the 7 ranges and was roughly equal between the relict Black Rock demes (Fig. 9) were likely the 2 occupancy categories in the Hays at one point connected to each other and pos- Canyon Range. In 3 of the 7 ranges (Home sibly to the early 20th century–occupied Pine Camp Range, Massacre Range, and Painted Forest Range to the north and the currently Point Range), median elevation of relict sites occupied Sheldon NWR to the west. was higher than that of occupied sites. The Our surveys covered 15 mountain ranges Home Camp Range had the lowest median and distinct geographic areas in northwestern elevation and Painted Point the second lowest Nevada, 8 of which had ≥10 survey sites per of the 7 ranges; here, pikas were more likely range. We found definitive sign of relict or to be found at the lower elevational limits current occupation in 11 of these ranges, with (but see comments below about potential no conclusive evidence of historic occupation confounding survey effort in the Painted Point in the remaining 4 ranges (i.e., Badger Moun- Range). In the Hays Canyon Range, the highest tains, Little High Rock Mountains, Mosquito median elevation in our study area, median 262 WESTERN NORTH AMERICAN NATURALIST [Volume 77

Fig. 9. A deme in the Black Rock Range. Although this was one of the highest elevation areas surveyed, only relict sites were documented in the demes throughout the range. The view is to the south toward the Colman River drainage.

Crooks Lake Hills* Hays Canyon Range Home Camp Range 2000 2200 2200

1950 2100 2100 1900 1850 2000 ~ B 2000 1800 ~ 1900 ~ Occupied Relict Occupied Relict Occupied Relict Massacre Range Mosquito Mountain Nut Mountain 2100 1950 1900

1850 1900 i 2000 C: .£! 15 1800 1850 > Q) w 1900 1750 9 1800

1700 8 ~ Occupied Relict Occupied Relict Occupied Relict Painted Point Range  1900

1850

1800

Occupied Relict

Site Occupancy

Fig. 10. Elevational boxplots for the 7 ranges (Crooks Lake Hills, Hays Canyon Range, Home Camp Range, Massacre Range, Mosquito Mountain, Nut Mountain, and Painted Point Range) where both occupied and relict sites were detected. 2017] RECENTLY ISCOVERE GREAT BASIN PIKA SITES 263

1 Relict . 2 .68 100% 2 LJ WYPPT >= 292 Relict c::Jyes no .45 .55 66% 4 0 Occupied .54 .46 54% 8 aspBnd = N,NE,NW,SE ,W Occupied .62 . 8 042% WYPPT < 359 16 1 9 5 3 Occupied Relict Relict Relict Relict .67 . . 0 .70 .25 .75 .05 .95 .08 .92 0 6% 06% 012% 12% 4%

Fig. 11. The classification tree for the variables examined for all the occupied and relict sites in the dataset (n = 173; WYPPT = average water year precipitation [mm], aspBnd = aspect, JulyTmin = median minimum July temperature [°C]). The tree can be read as a series of hierarchical characteristics resulting in a terminal node or leaf. Leaves show the designation of each site (either “occupied” or “relict”) and the probability of membership in each class, with “occupied” as the first class (on the left) and “relict” as the second class (on the right). Lastly, each leaf presents the percentage of total observations used in each “branch.” For example, when water year precipitation is under 292 mm, then there is a 92% probability that the sites are relict and an 8% probability that the sites are occupied. There are 59 observations (34% of 173) falling into this leaf. elevation of occupied sites was just slightly Because of this area’s close proximity to the higher than that of relict sites. Sheldon NWR and observations made nearby Occupied sites had higher median July by other researchers (Collins and Bauman temperatures in the Home Camp Range and 2012, Castillo et al. 2016), we did not survey Painted Point Range than relict sites. For all this likely extensive population; thus, results other ranges, occupied sites were cooler and presented for this range may change when characterized by lower maximum July tem- the area is surveyed more fully. espite its peratures than relict sites. At Massacre Range, relatively lower elevation and hotter cli- although occupied sites tended to be at lower mates, the Home Camp Range received the elevations than relict sites, they were often highest median precipitation, which may mit- in cooler microsites. The same pattern was igate the relatively warm and lower-elevation reflected in the minimum July temperatures. environment. The Painted Point Range had Regardless of whether occupied sites trend the third highest median precipitation in the warmer or cooler than relict sites, differences study area. in median temperature (both July minimum Classification Tree Analysis and maximum) between occupied and relict sites is <1 °C in almost all cases (with mini- The classification tree shows a series of mum July temperature in the Hays Canyon “checks and balances,” with environmental Range being the exception). Our results and climatic variables mitigating potentially could be due to an inability of the large harsh overarching conditions (e.g., a site with 800-m PRISM cell size to accurately reflect low precipitation will have a higher chance of conditions in small patches, or it could sug- remaining occupied if temperatures are cool). gest that minor yet persistent temperature Variable “importance,” a measure of predictive differences are important in site suitability power of each variable, was ranked in the for pikas. In the 2 ranges (Home Camp and following order: water year precipitation, fol- Painted Point) that had the lowest median lowed closely by minimum July temperature, elevation and that were the hottest ranges in maximum July temperature, binned aspect our study region, occupied sites were more categories, and solar radiation (Fig. 11). The likely to be found at the lower and hotter occupied sites were characterized by wet parts of the range. However, the pika popula- (water year precipitation over 292 mm) and tion on Painted Point covers Massacre Rim, a cold (minimum July temperature under 8.8 °C) large area that we suspect was occupied over climates and were mostly located on aspects a greater extent than where we surveyed. not southerly or easterly. 264 WESTERN NORTH AMERICAN NATURALIST [Volume 77

ISCUSSION associations, pikas in the Home Camp Range appeared to be the most connected and largest Survey results presented here make evident population documented in our survey area. that pika range and distribution in northwest- Pikas are hypothesized to be affected in ern Nevada have changed dramatically in the many ways by decreased precipitation input 20th and into the early 21st centuries, with and loss of snowpack, including reduced <30% of survey sites showing signs of current available forage due to lowered vegetation pika persistence. Localized extirpations are productivity, increased spread of disease, loss evident on the western side of the range at of insulating cover, and exposure to more high-elevation sites such as Little Hat Moun- extreme cold temperatures (Wilkening et al. tain and Forty-Niner Mountain and on the 2011). Our study did not measure precipita- eastern side of the range throughout the high- tion changes over time in relation to changing elevation Black Rock Range. To the north, occupancy over time. We report here only the many sites in the Crooks Lake Hills and Mos- differences in water year precipitation amounts quito Mountains appear extirpated, and the across sites overall and across sites within a Barrel Springs area (previously described as range. Thus, we cannot comment on how extirpated by Beever et al. 2003, 2008, Wilken- precipitation changes have driven changes in ing et al. 2011, Millar et al. 2014) remains occupancy, especially since we do not know extirpated. espite these range retractions and exactly when sites became extirpated. How- calls for more spatially extensive fieldwork ever, we do note that in 2 mountain ranges (Beever et al. 2008), we note several previously where pikas are persisting at lower elevations undocumented extant populations in a region (Painted Point and Home Camp), precipitation formerly described as containing only extir- input over the survey areas within the ranges pated sites outside of the extant Massacre Rim, is among the highest in our study, suggesting Sheldon NWR, and Boulder Canyon (Hays that there could be some ameliorating influ- Canyon Range) populations (Beever et al. 2003, ence of precipitation and the corresponding 2008, Wilkening et al. 2011). vegetation response in warmer areas. Places Similar to recent pika inventories on the that received the highest amounts of precipita- Sheldon National Wildlife Refuge (Collins and tion (e.g., Black Rock Range, upper elevations Bauman 2012), all of our currently occupied of Home Camp Range, and Hays Canyon and most (all but 2) of our relict sites were Range) appear extirpated, and because of this below the 2500-m “threshold” considered trend, the classification tree does place occu- typical for pikas in the western Great Basin pied sites below a maximum precipitation (Smith 1974, Smith and Weston 1990, Millar threshold. The degree to which this threshold et al. 2013), although we note that our sites are is actually representative of a true limitation near the northern portion of the region and for pikas is unclear, particularly because we some latitudinal depression would be expected. suspect that some type of stochastic event, such When landform is considered, pikas in our as fire or a disease outbreak (likely common in study are generally occupying more moderate pika populations; Wilkening et al. 2011), and areas, perhaps indicative of the “goldilocks resulting fragmentation, prompted the loss of effect” (not too hot, not too cold) where envi- pikas in these areas. ronmental position (i.e., aspect, slope, and The inconsistency of modeled climate fac- elevation) and local climate (i.e., precipitation tors in explaining occupied versus relict sites and temperature) create a more hospitable in our analyses might relate to the unique and less variable environment. Unlike the conditions of pikas’ talus habitat and the scale more typical patterns in places such as Crooks at which variables were examined. For example, Lake Hills, Mosquito Mountain, and Nut whereas weather station and modeled data Mountain, many other areas in northwestern such as PRISM provide information about Nevada do not fit the traditional pattern surface free-air conditions, talus and related where elevation is lower and heat stress is broken-rock landforms are widely known to higher at relict sites than at occupied sites. In have thermal regimes that are decoupled from ranges such as Hays Canyon, Home Camp, external surface air (Harris and Pederson and Massacre, occupied sites trend lower and 1998, Sawada et al. 2003, Gude et al. 2003, hotter than relict sites. espite these atypical elaloye and Lambiel 2005, Zacharda et al. 2017] RECENTLY ISCOVERE GREAT BASIN PIKA SITES 265

2007, Millar et al. 2014). ecoupling of talus extirpations. Although the cause(s) may never from free-air circulation offers potential clues be known, potential reasons for extirpation in to the ability of pikas to persist under synoptic some of these areas include loss of connectivity, and regional climates that would appear unsuit- small patch size (Stewart and Wright 2012), or able for them (Millar et al. 2016). Lava flows impacts of stochastic events (e.g., disease). In and other volcanic taluses, such as those found other cases, it seems local climates may have in our study area, are known to have particu- become unsuitable either over space (at rela- larly cold matrices with highly attenuated tively lower elevations within or at the far diurnal temperatures and often sustain persis- edge of a local distribution) or over time. For tent embedded ice that may provide beneficial example, some of the sites we found appeared daily and seasonal refuges for pikas (Millar et to have been recently extirpated, such as in al. 2016, Ray et al. 2016, Smith et al. 2016). the Upper High Rock Canyon and the Hang- ecoupling processes may be responsible for ing Rock Canyon in the High Rock Range. In our solar radiation finding, where mean solar other areas (e.g., Nellie Springs Mountain), radiation is higher at occupied than at relict the few extant sites we found may be vestiges sites. Higher solar radiation may indicate of more abundant and widespread populations. increased potential for vegetation growth at Outside of these peripheral areas, we find mid- and upper-elevation sites where pikas currently occupied sites in spatially clustered are found, while the ameliorating influence areas where climate and connectivity appear of the belowground structure allows pikas to conducive to maintaining pika populations in remain in these sites. Vegetation growth the long-term. Although Massacre Rim in the within and around the talus may also moder- Painted Point Range was not thoroughly sur- ate surface temperatures, and solar radiation veyed, we suspect pikas are dense and abun- may interact with temperature, precipitation, dant across the entirety of the almost 7-km subsurface structures, and vegetation at each face, which possibly serves as a “mainland site to create beneficial conditions such as habitat” in the region. Techniques such as increased herbaceous vegetation and increased radiocarbon dating of scat samples from relict access to food through more frequent and sites (as done in Millar et al. 2014) could pro- earlier snowmelt. Unfortunately, our study has vide insight regarding the pattern and causes no data regarding the temperatures within the of extirpations. For instance, considering that talus matrices, as might be collected with the Black Rock Range has burned in the last data-logging sensors, but future work in the century, relating relict site ages as obtained area would benefit from these and other from radiocarbon dating to fire history could microsite data. help us better understand the influence of fire A myriad of factors govern patch occupancy on pikas in more xeric, low-elevation sites. dynamics, including connectivity to source Radiocarbon dating might also indicate the patches, the amount of suitable habitat in an direction of local range retractions, which area, macro- and microclimate and the link could consequently be used to predict high- between the two as mediated by the above- priority conservation areas and areas of possible and belowground talus structure, vegetation future retractions or (re)colonizations. surrounding the patch, landscape variables In our surveys, we found relict sites that we that influence connectivity, source-sink dynam- expected to be occupied (e.g., Black Rock ics, competition, predation, and disease, as Range and the upper elevations of the Hays well as the lag effects of many of these factors. Canyon Range) and occupied sites where we As pikas are a classic example for metapopula- did not expect pikas to currently exist (e.g., tion biology and source-sink dynamics (Kreuzer Home Camp Range and the lower elevations and Huntly 2003), it is possible that some site of the Hays Canyon Range) based on typical “extirpations” may only be temporary and niche descriptions. In our study area, no sin- sites might be recolonized after some time. gle variable distinguished currently occupied However, we suspect that numerous relict sites from relict sites in the same manner sites documented across entire ranges (e.g., across the mountain ranges, and the concept Black Rock Range) or areas within large por- that current and historic pika distributions are tions of each range (e.g., Hays Canyon Range contingent on particular combinations of local and northern High Rock Range) are true site characteristics, regional climate regimes, 266 WESTERN NORTH AMERICAN NATURALIST [Volume 77 historical context, and connectivity (“idiosyn- might have concluded that the area was crasies of place”; Jeffress et al. 2013) is repeated recently extirpated when nearby patches were in our work. Our results provide further evi- actually currently occupied. dence of the seemingly weak predictive power Understanding pika population stressors of thermal indices alone in many of these may be particularly important to Bureau of low-elevation and warm mountain ranges of Land Management managers in northwestern northwestern Nevada. For example, the classi- Nevada, where some districts include the fication tree describes unique environmental American pika on sensitive species lists that are settings that appear to foster persistence or considered in decisions regarding land man- extirpation. In the tree, the probability of a agement activities and others do not (possibly site being occupied ranged from 54% to 67% because they were not even aware the species but the probability of a site being relict occurred in their district until now!). Beever ranged from 55% to 95%, indicating (1) a much et al. (2003) reported a higher probability of higher predictive power with the variables pika presence in places without livestock used in pinpointing relict sites on the land- activity and in wilderness areas, and Millar scape, (2) significant overlap in environmental (2011) discussed how grazing might be a factor settings conducive to co-occurrence of both influencing population conditions and status occupied and relict sites, and (3) the lack of of pikas in the eastern Sierra Nevada and additional predictive variables needed to dis- Great Basin. Many of our sites in the Crooks criminate occupied and relict sites in this Lake Hills, Carter Reservoir, Mountain View study. When linked to environmental and cli- drainage to the west of Boulder Canyon, and mate variables, new analysis techniques, such Grassy Canyon had active livestock grazing as measuring stress hormones in individuals as well as a presence but, due to (Wilkening and Ray 2016), might provide difficulty in quantifying, we were unable to additional insight into pika survival and factors include these variables and others, such as the influencing pika persistence. Furthermore, pika presence of invasive plants (e.g., cheatgrass), presence at a site does not necessarily mean in our current analysis. In spite of this, our the site has suitable habitat conditions that study and future studies can help inform land will allow for long-term pika persistence management decisions and may guide proac- (Kreuzer and Huntly 2003). To more fully tive management opportunities to potentially untangle why and how some populations improve connectivity, such as providing artifi- persist and others do not, a more comprehen- cial talus corridors or considering assisted sive approach beyond occupancy surveys alone migration (Hobbs et al. 2010, Morueta-Holme will be needed. et al. 2010, Wilkening et al. 2015). Similar to Millar et al. (2013), we noted that Our surveys reveal new populations across previous studies often do not examine multiple northwest Nevada in several hotter and drier scales of pika occupancy, which we attempted places than have been described for the Ameri- to address. elineation of possible demes in our can pika. Because of their isolated nature and survey area provided insight into the potential relatively harsh conditions, these sites merit a for connectivity and allowed a better under- long-term and robust monitoring program to standing of the importance of a “patch”-sized address both population loss at currently scale in determining area occupancy. We occup ied sites and possible recolonization of acknowledge that because we were unable to seemingly extirpated sites. Regional patterns survey all potential habitat in every area, not in pika persistence and several seemingly every currently occupied and relict site was imperiled populations underscore the need detected in our survey effort, and this lack of for more thorough inventory and monitoring data may artificially cause some demes to programs that examine not just occupancy at a appear disjunct. However, our approach was a single site but also incorporate a more com- significant improvement on previous studies prehensive regional understanding of connec- that relied on a survey of only one site or one tivity and population dynamics at larger scales. habitat patch. For example, if we relied on The need for such work is urgent, given that survey results from only our first 1 or 2 sites, we found twice as many relict sites as occu- our understanding of the occupancy of the pied sites in this region, with that ratio exag- area would have been very different, and we gerated in places like the Crooks Lake Hills. 2017] RECENTLY ISCOVERE GREAT BASIN PIKA SITES 267

Many questions remain, most urgently ones ALY, C., M. HALBLEIB, J.I. SMITH, W.P. GIBSON, M.K. surrounding connectivity, habitat patch size OGGETT, G.H. TAYLOR, J. CURTIS, AN P.P. PASTERIS. 2008. Physiographically sensitive mapping of clima- relative to connectivity, population trends, and tological temperature and precipitation across the protection and conservation measures for conterminous United States. International Journal of extant pika populations, such as those that Climatology 28:2031–2064. exist in Home Camp Range, Painted Point E’ATH, G., AN K.E. FABRICIUS. 2000. Classification and regression trees: a powerful yet simple technique for Range, Nut Mountain, and Crooks Lake Hills. ecological data analysis. 81:3178–3192. Consequently, we hope that this study is the ELALOYE, R., AN C. LAMBIEL. 2005. Evidence of winter first of many in the region. ascending air circulation throughout talus slopes and rock glaciers situated in the lower belt of alpine discontinuous permafrost (Swiss Alps). Norsk ACKNOWLE GMENTS Geografisk Tidsskrift – Norwegian Journal of Geog- raphy 59:194–203. We especially thank Mark Enders, Rory ERB, L.P., C. RAY, AN R. GURALNICK. 2011. On the gener- Lamp, and Christy Klinger from the Nevada ality of a climate-mediated shift in the distribution of the American pika (Ochotona princeps). Ecology epartment of Wildlife (N OW) for their 92:1730–1735. help with surveys across the study region. We FU, P., AN P.M. RICH. 1999. esign and implementation thank Kenny Pirkle, Brad Bauman, and Cody of the Solar Analyst: an ArcView extension for mod- Byrne from N OW and Erik Beever with the eling solar radiation at landscape scales. Proceedings U.S. Geological Survey for their knowledge of the Nineteenth Annual ESRI User Conference. FU, P., AN P.M. RICH. 2002. A geometric solar radiation and recommendations regarding survey areas. model and its applications in agriculture and Gail Collins shared shapefiles for the Sheldon forestry. Proceedings of the Second International NWR, and Tom ilts helped with the PRISM Conference on Geospatial Information in Agricul- data compilation and derivation. We thank ture and Forestry I-357-364. GU E, M., S. IETRICH, R. MÄUSBACHER, C. HAUCK, R. Elias Flores and staff at the Applegate Bureau MOLEN A, V. RUZICKA, AN M. ZACHAR A. 2003. Prob- of Land Management field office for insight able occurrence of sporadic permafrost in non-alpine and assistance with surveys on Massacre Rim. scree slopes in central . Proceedings of the 8th International Conference on Permafrost, Zurich The N OW provided the majority of the sup- 2003:331–336. port for biologist field time and equipment, HAFNER, .J., AN A.T. SMITH. 2010. 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Thermal regime of three low elevation scree slopes in central regime of sporadic permafrost in a block slope on Europe. Permafrost and Periglacial Processes 18: Mt. Nishi-Nupukaushinupuri, Hokkaido Island, 301–308. North ern Japan. Geomorphology 52:121–130. SCHWALM, ., C.W. EPPS, T.J. RO HOUSE, W.B. MONAHAN, Received 8 July 2016 J.A. CASTILLO, AN M.R. JEFFRESS. 2016. Habitat Accepted 23 March 2017 availability and gene flow influence diverging local Published online 19 July 2017