Progress 07/01/04 to 06/30/08

Outputs
OUTPUTS: Pygmy rabbits (Brachylagus idahoensis) are extreme habitat specialists restricted to the sagebrush communities of Montana, Idaho, Utah, Nevada, Oregon, California, and Washington. They require dense big sagebrush vegetation, which has been impacted heavily by urbanization, agriculture, improper livestock grazing, and wildfires. Due to declines in populations in Oregon and Washington and a lack of solid information about its status elsewhere, the species has been proposed for listing under the US Endangered Species Act. We surveyed the historic range of pygmy rabbits in Nevada and eastern California using infrared-triggered cameras to determine the species' current distribution and habitat selection. We also noted the extent and likely cause of degradation to pygmy rabbit habitat at these sites. Pygmy rabbits were present at 36% of the surveyed historic sites. Historic sites showed signs of pinyon-juniper woodland encroachment (14%), fires (16%), urbanization (13%), and agricultural conversion (6%). There was more extirpation at lower elevation sites. Additionally we surveyed 1,394 other sites across the species' historic range and found current pygmy rabbit activity at 258 of these sites. We modeled pygmy rabbit habitat, and the top-ranked model (79% accuracy rate) suggested that likelihood of pygmy rabbit occupancy at a site increased with increasing sagebrush cover, decreasing understory stem density, absence of cottontails, absence of cheatgrass, and absence of rodent burrows. We also looked at the genetic relatedness of pygmy rabbit populations using microsatellite loci and found three minor genetic subdivisions among extant populations within the sample area: central Nevada, eastern Nevada, and the Mono Basin in California. These data will enhance our ability to manage for the species without the necessity of a listing under the Endangered Species Act. PARTICIPANTS: Eveline Larrucea Mary Peacock Peter Brussard Larrucea learned how to do microsatellite analyses. TARGET AUDIENCES: Our findings on the pygmy rabbit should be very useful to management agencies (US Bureau of Land Management and US Fish and Wildlife Service) when managing for this species and when determining whether or not the species should be listed under the Endangered Species Act. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Pygmy rabbits (Brachylagus idahoensis) are extreme habitat specialists restricted to the sagebrush communities of the intermountain west. They require dense big sagebrush vegetation, which has been impacted heavily by urbanization, agriculture, improper livestock grazing, and wildfires. Due to declines in populations in Oregon and Washington and a lack of solid information about its status elsewhere, a petition was filed to list the species under the US Endangered Species Act. We surveyed the historic range of pygmy rabbits in Nevada and eastern California using infrared-triggered cameras to determine the species' current distribution and habitat selection. We also noted the extent and likely cause of degradation to pygmy rabbit habitat at these sites. Each location was assessed for signs of agricultural use, fire, livestock grazing, human occupation (urbanization), and the presence of encroaching pinyon-juniper. Pygmy rabbits were present at 36% of the surveyed historic sites. Fourteen percent of historic sites showed signs of pinyon-juniper woodland encroachment with only one of these sites still harboring pygmy rabbits. Historic sites also showed current evidence of fires (16%), urbanization (13%), and agricultural conversion (6%). There was more extirpation at lower elevation sites, and the mean elevation of extant sites was 121 m higher than the mean elevation of extirpated sites, closely corresponding to the predicted elevation increase with the rise in average global temperature seen over the last century. Additionally we surveyed 1,394 other sites across the species' historic range and found current pygmy rabbit activity at 258 of these sites. We measured sagebrush cover, sagebrush height, understory stem density, and presence / absence of cottontail rabbits, jackrabbits, cheatgrass, and rodent burrows at 454 of the total sites. We used 80% of the data to create a logistic regression model. The top-ranked AIC selected model suggested that likelihood of pygmy rabbit occupancy at a site increased with increasing sagebrush cover, decreasing understory stem density, absence of cottontails, absence of cheatgrass, and absence of rodent burrows. This model showed a 79% accuracy rate in predicting occupancy within the remaining 20% of the data. We also looked at the genetic relatedness of pygmy rabbit populations by analyzing DNA samples collected from throughout the study area. We obtained tissue samples from museum specimens (mostly collected prior to 1950) and fecal and tissue samples from extant populations, and we resolved nine microsatellite loci. The resulting data, representing 26 total sites across Nevada and California, show historic connectedness among all pygmy rabbit populations in this area but some isolation among extant populations. Contemporary samples show three minor genetic subdivisions: central Nevada, eastern Nevada, and the Mono Basin in California. The genetic data complement information being compiled in adjacent states and will enhance our ability to manage for the species.

Publications

• Larrucea, E.S. and P.F. Brussard. 2008. Shift in location of pygmy rabbit habitat in response to changing environments. Journal of Arid Environments. 59:271-297.
• Larrucea, E. S. and P. F. Brussard. 2008. Efficiency of various methods used to detect presence of pygmy rabbits in summer. Western North American Naturalist 68:303-310.

Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: All of our findings on the pygmy rabbit have been sent to the US Fish and Wildlife Service's Washington D.C. office. They are re-evaluating a petition to list the species under the US Endangered Species Act, and our data will be critical to their evaluation. These data also have been sent to the Nevada State Bureau of Land Management Office. PARTICIPANTS: Peter F. Brussard, Ph.D.was the P.I. Eveline Sequin Larrucea received her Ph.D.working on this project. TARGET AUDIENCES: The results of this project will be of interest to the US Fish and Wildlife Service and the US Bureau of Land Management, the Nevada Division of Wildlife, and to ranchers who have pygmy rabbit habitat on their land or grazing allotments.

Impacts
Pygmy rabbits (Brachylagus idahoensis) are extreme habitat specialists restricted to the sagebrush communities of Montana, Idaho, Utah, Nevada, Oregon, California, and Washington. They require dense big sagebrush vegetation, which has been impacted heavily by urbanization, agriculture, improper livestock grazing, and wildfires. Due to declines in populations in Oregon and Washington and a lack of solid information about its status elsewhere, a petition was filed to list the species under the US Endangered Species Act as threatened or endangered throughout the entire Great Basin. We surveyed the historic range of pygmy rabbits in Nevada and eastern California using infrared-triggered cameras to determine the species' current distribution and habitat selection. We also noted the extent and likely cause of degradation to pygmy rabbit habitat at these sites. Each location was assessed for signs of agricultural use, fire, livestock grazing, human occupation (urbanization), and the presence of encroaching pinyon-juniper. Pygmy rabbits were present at 36% of the surveyed historic sites. Fourteen percent of historic sites showed signs of pinyon-juniper woodland encroachment with only one of these sites still harboring pygmy rabbits. Historic sites also showed current evidence of fires (16%), urbanization (13%), and agricultural conversion (6%). There was more extirpation at lower elevation sites, and the mean elevation of extant sites was 121 m higher than the mean elevation of extirpated sites, closely corresponding to the predicted elevation increase with the rise in average global temperature seen over the last century. Additionally we surveyed 1,394 other sites across the species' historic range and found current pygmy rabbit activity at 258 of these sites. We measured sagebrush cover, sagebrush height, understory stem density, and presence / absence of cottontail rabbits, jackrabbits, red soils, cheatgrass, and rodent burrows at 454 of the total sites. We used 80% of the data to create a logistic regression model. The top-ranked AIC selected model suggested that likelihood of pygmy rabbit occupancy at a site increased with increasing sagebrush cover, decreasing understory stem density, absence of cottontails, absence of reddish soils, absence of cheatgrass, and absence of rodent burrows. This model showed a 79% accuracy rate in predicting occupancy within the remaining data.We are now looking at the genetic relatedness of pygmy rabbit populations by collecting and analyzing DNA samples from active populations throughout the state to determine whether populations in Nevada function as one homogeneous population or as many separate populations. We have resolved 12 microsatellite loci from fecal samples collected from 16 populations. Preliminary data suggest that there are three major genetic subdivisions within the sample area: central Nevada, northwestern Nevada, and the Mono Basin in California. These data will complement information being compiled in adjacent states and enhance our ability to manage for the species.

Publications

• Larrucea, E.S. and P.F. Brussard. 2007. A method for capturing pygmy rabbits (Brachylagus idahoensis) in summer. Journal of Wildlife Management 71(3):1016-1018.
• Larrucea, E.S. and P.F. Brussard. Habitat selection and current distribution of the pygmy rabbit in Nevada and California, USA. Journal of Mammalogy. In press (June 2008)

Progress 01/01/06 to 12/31/06

Outputs
This study is examining the current status and behavior of the pygmy rabbit (Brachylagus idahoensis) in Nevada and California. Pellet, burrow, visual, and infrared-triggered camera surveys were compared to determine an efficient method for establishing current pygmy rabbit activity at a site. Camera surveys had 95% detection efficiency, and this method was used to survey the historic range. We revisited 105 historic pygmy rabbit sites and determined current presence at 36% of the sites. The greatest predictors of loss of pygmy rabbits from a historic site were fire, elevation, pinyon-juniper encroachment, and agricultural conversion. The mean elevation of extant sites was higher than historic sites by 121 m, closely corresponding to the predicted elevation increase with the 0.7 C rise in global temperature seen over the last century. An additional 1,292 new sites were surveyed, of which 258 were positive. Pygmy rabbits were more likely to be found in islands of taller sagebrush. Mean sagebrush cover and height at occupied sites was 44.7% and 98.4 cm respectively. Soils had a mean sand and clay content of 39.1% and 20.4%. Akaike's information criterion model-selection technique showed that pygmy rabbits were more likely to occupy sites with loamy, non-reddish soils, dense big sagebrush, and low amounts of understory. They were negatively associated with cottontail rabbits, rodent burrows, and cheatgrass. In contrast to other studies, sagebrush height per se was not correlated with pygmy rabbit presence at a site. Current pygmy rabbit populations were found throughout most of the historic range in Nevada and California. Activity patterns in five populations were determined using the number of photographs obtained per hour as a relative level of activity. All populations showed a bi-modal daily activity pattern during all seasons with greatest activity occurring at dawn and at dusk. All but one population showed similar levels of activity. Seasonal differences in spatial use were observed with pygmy rabbits using burrows less often during summer months and occupying certain sites only intermittently. All this information has been combined into a conservation blueprint to make recommendations for the management of pygmy rabbit habitat.

Impacts
These data are critically important for keeping the pygmy rabbit from being listed under the US Endangered Species Act. Although a petition to list the species has been rejected by the US Fish and Wildlife Service, the perception in the environmental community is that the pygmy rabbit is in deep trouble, so another petition is likely to follow. Such a listing could have substantial negative impacts on rural economies in the intermountain West.

Publications

• Larrucea, E.S., and P.F. Brussard. 2007, A method for capturing pygmy rabbits (Brachylagus idahoensis) in summer. Journal of Wildlife Management in press.

Progress 01/01/05 to 12/31/05

Outputs
We obtained 93 historic records of pygmy rabbits in Nevada from the published literature, museum collections, and agency files. As of January 2006, we have visited 86 of the 93 sites, and using camera surveys found current pygmy rabbit activity at 40 (47%) of them. Camera surveys were shown to be more effective in documenting pygmy rabbit activity at sites than burrow, pellet, or observational surveys. Additionally, we surveyed 818 new locations and documented pygmy rabbit activity at 222 of the sites. We have located active sites ranging from 4890 - 8416 ft in elevation. While the overall elevation of current sites seems to have increased compared to historic records, on a more local scale sites have moved down slope. Many historic locations were located on hillsides that are now covered in juniper trees, while newly documented locations are mostly located in valley bottoms. Historic locations in the lowest elevation valleys seem to have been extirpated. In general, active locations seem to fluctuate frequently. Certain sites that showed no activity last year had high levels of activity this year. Conversely, certain locations that were active only last year had no sign of activity this year. Some of these sites had flooded due to high spring run-off in Spring 2005. To test for microhabitat preferences of pygmy rabbits, GIS was used to select 50 random points in loamy 8"-10" Wyoming big sagebrush ecological sites. Fifty additional sites with prominent sagebrush clusters within this ecological site also were chosen non-randomly in the field. As of January 2006, 48 of these paired-sites have been surveyed. Of the selected sites 68% had pygmy rabbits, while only 10% of the random sites were positive. Pygmy rabbit burrows have been found in vegetation ranging in average height from 32 cm - 184 cm, and rabbit activity was found in areas containing 100% big sagebrush cover to areas with up to 73% rabbitbrush (Chrysothamnus spp.) cover. Early indications from soil samples are that areas with greater clay content only may be used seasonally, while loamy and sandy loam sites are used year round. Increased levels of cheatgrass (Bromus tectorum) may be associated with decreased probability of pygmy rabbit presence while increased ground litter and a lower understory were found to correlate with increased probability of pygmy rabbit presence. Pygmy rabbit population density estimates depended heavily on the size of the area sampled. Small areas included a greater percentage of appropriate habitat and produced estimates as high as 40 rabbits / ha. Larger areas included regions with less- or non-suitable habitat, and population densities ranged from 0.4 - 1.2 rabbits / ha. In general pygmy rabbits were found to be more abundant than originally thought. The pygmy rabbit is still found in appropriate habitat in most of the higher intermountain regions in the Great Basin Desert of Nevada. To date we have completed the majority of the field work for this project and are now working on entering and analyzing data. We plan on completing data analysis and write up our results by the end of next year.

Impacts
These data are critically important for keeping the pygmy rabbit from being listed under the US Endangered Species Act. Although a petition to list the species has been rejected by the US Fish and Wildlife Service, the perception in the environmental community is that the pygmy rabbit is in deep trouble, so another petition is likely to follow. Such a listing could have substantial negative impacts on rural economies in the intermountain West.

Publications

• No publications reported this period

Progress 07/01/04 to 12/31/04

Outputs
This project has the following objectives: (1) determine the number of historic pygmy rabbit sites that are still occupied, (2) discover additional new occupied sites, (3) describe the soil, vegetation, and landscape characteristics of occupied sites and determine any differences between sites with and without rabbits, (4) contrast survey methods to determine the most effective one, (5) to determine if there are any daily, seasonal, or latitudinal variations in activity patterns, (6) to make population estimates and to (7) produce an accurate GIS map of the status of the pygmy rabbit and an envirogram describing the critical factors influencing its distribution and abundance. 1. Historical sites: Ninety-three historical pygmy rabbit records from Nevada were obtained from the published literature, museum collections, and agency files. To date 64 of these sites have been visited and assessed, and 48% (31/46) of sites currently still have pygmy rabbits. 2. New sites: To date we have found 139 new occupied sites in Nevada, and we have now been able to locate pygmy rabbits in every county that historically had them. This information is beginning to provide an up-to-date survey of historic and new locations and is greatly enhancing our understanding of the status of pygmy rabbits in Nevada. 3. Site characteristics: To test the hypothesis that pygmy rabbits prefer islands of taller sagebrush within Wyoming big sagebrush stands as habitat, GIS was used to select 50 random points in loamy Wyoming big sagebrush ecological sites that receive 8 to 10 inches of precipitation annually. Fifty additional sites with prominent sagebrush clusters higher than surrounding sagebrush within this ecological site also were chosen non-randomly in the field. As of December 2004, 46 sites have been surveyed and measured. Of the selected sites 65% have had pygmy rabbits, while only 13% of the random sites have been positive for the species. 4. Survey methods: Juvenile cottontails and black-tailed jackrabbits can be mistaken rather easily for pygmy rabbits, so false positives are often a serious problem in pygmy rabbit surveys. Comparison of camera techniques with more traditional burrow, visual, and pellet surveys has shown that camera traps were the most effective and efficient method for detecting current pygmy rabbits at a site. 5. Activity patterns: Pygmy rabbits are largely crepuscular, with major activity periods just after and just before sunset. There do not seem to be geographic differences in this pattern. 6. Population estimates: Individual pygmy rabbits are usually indistinguishable in photographs, so we will have to capture and mark individuals to make such estimates. This is planned for next year. 7. GIS map and envirogram. Both a preliminary map and envirogram have been prepared; however the final versions will not be completed until the end of the study.

Impacts
Because the pygmy rabbit has been petitioned for listing under the U.S. Endangered Species Act and because such a listing would have substantial impacts on ranching and other activities in Nevada, it is critically important to obtain accurate information on the distribution, abundance, and biology of this species. We have found it at 170 sites, and much of its historical range still appears to be occupied. These data do not support a listing of the species. This is important because the US Fish and Wildlife Service has to issue a preliminary finding soon.

Publications

• No publications reported this period