White-Tailed Prairie Dog Conservation Assessment

WHITE-TAILED PRAIRIE DOG CONSERVATION ASSESSMENT Amy E. Seglund, Andrea E. Ernst, Martin Grenier, Bob Luce, Allison Puchniak, and Pam Schnurr White-tailed Prairie Dog photo by Ron Stewart Western Association of Fish and Wildlife Agencies January 2006 RECOMMENDED CITATION Seglund, A.E., A.E. Ernst, M. Grenier, B. Luce, A. Puchniak, and P. Schnurr. 2006. White-tailed prairie dog conservation assessment. Western Association of Fish and Wildlife Agencies. Laramie, Wyoming. Unpublished Report. 137 pp. ACKNOWLEDGMENTS We received significant input from a number of sources or their publications. We especially wish to acknowledge the following people and organizations: Dean Biggins, U.S. Geological Survey; Brent Bibles, Utah State University Extension in Vernal, Utah; Bart Zwetzig, Ed Hollowed, Steve Madsen, Robin Sell, Dave Roberts, Mike Albee, and Jay Parks, U.S. Bureau of Land Management; Erin Robertson, Center for Native Ecosystems; Lonnie Renner, contractor for the Colorado Division of Wildlife; Larry Nelson, Colorado Division of Wildlife; Heidi Youmans, Montana Department of Fish, Wildlife, and Parks; Brian Maxfield and Craig McLaughlin, Utah Division of Wildlife Resources; Bob Oakleaf, Wyoming Game and Fish Department; Craig Knowles, Fauna West Consulting; Bob Leachman, Laura Romin, and Renee Chi, U.S. Fish and Wildlife Service; and Sterling Miller, National Wildlife Federation. Deb O’Neill, Shortgrass Prairie Interstate Coordinator, and Terry B. Johnson, Chair of WAFWA’s Nongame and Endangered Species Committee, helped edit the final drafts of this report. Western Association of Fish and Wildlife Agencies January 2006 White-tailed Prairie Dog Conservation Assessment – Final Page ii of 137 EXECUTIVE SUMMARY On 11 July 2002, the U.S. Fish and Wildlife Service was petitioned by the Center for Native Ecosystems, Biodiversity Conservation Alliance, Southern Utah Wilderness Alliance, America Lands Alliance, Forest Guardians, Terry Tempest Williams, Ecology Center and Sinapu to list the white-tailed prairie dog under the federal Endangered Species Act. After the petition was received, the White-tailed Prairie Dog Working Group of the 12-state Prairie Dog Conservation Team began development of a Conservation Assessment for the white-tailed prairie dog to assess the current status of the species rangewide and address possible threats limiting conservation. Data integrated into the Conservation Assessment came from an assemblage of sources including published literature, Environmental Impact Statement reports for energy clearances on potential black-footed ferret habitat, and state and federal grey literature. These sources provided information used to index temporal population changes, evaluate gross changes in occupied habitat, and examine current management of white-tailed prairie dogs within each state. A risk assessment for the species based upon the five listing criteria used by the U.S. Fish and Wildlife Service when evaluating a species’ potential for listing under the Endangered Species Act was also completed. To provide the most scientifically accurate assessment regarding the current status of the white- tailed prairie dog, two types of data were analyzed. The first data set indexed population changes at Black-footed Ferret Management Areas. The second data set evaluated gross changes in occupied habitat at mapped locations in individual states. Both data sets had weaknesses and limitations as described in the text, but were the best and only data available for this assessment. The incorporation of both data sources provided a more complete assessment of the rangewide status of the white-tailed prairie dog by describing changes not only with regard to numbers of animals, but also examining the distribution of occupied habitat across the range. In addition to the population and occupied habitat data analysis, a Geographic Information Systems spatially detailed, Predicted Range Model for the white-tailed prairie dog was produced. This model provided information on the number of hectares in the gross and predicted ranges of the species and the amount of its range being impacted by anthropogenic disturbances. In 1981, with the discovery of black-footed ferrets at Meeteetse, Wyoming, states within the historic range of this species initiated programs to identify complexes of white-tailed prairie dogs as potential reintroduction sites for black-footed ferrets. Because white-tailed prairie dogs and black-footed ferrets occur sympatrically, evaluation of suitable black-footed ferret habitat was dependent upon mapping prairie dog colonies and determining densities of animals within these colonies. To determine densities, a technique was developed that involved counting active burrows within 1 km x 3 m transects distributed over colonies. The active burrow data were converted to prairie dog counts and finally to an estimate of density. Although burrow counts are inaccurate at producing precise population estimates of white-tailed prairie dogs, they are useful for indexing abundance over large scales of time and space. Since no long-term monitoring data were available from sites where black-footed ferret reintroduction was not a consideration, the evaluation of temporal population changes of white-tailed prairie dog populations was based solely on surveys at black-footed ferrets reintroduction sites. Western Association of Fish and Wildlife Agencies January 2006 White-tailed Prairie Dog Conservation Assessment – Final Page iii of 137 To quantify gross spatial changes that have occurred in occupied habitat within white-tailed prairie dog range, colonies and complexes that were mapped in response to specific energy project clearances as well as those mapped in the identification of potential black-footed ferret reintroduction sites were compared to recent mapping efforts. Direct comparison in the estimation of occupied hectares of prairie dog colonies was problematic and needed to be evaluated with caution. White-tailed prairie dog colony boundaries are difficult to discern and their distribution and activity levels within these boundaries are extremely variable. This results in the investigator relying on their best estimate by using topographic features or breaks in habitats to delineate boundaries. Until variation between mapping efforts can be described and compensated for, mapping can only provide a gross approximation of white-tailed prairie dog occupied hectares. These gross approximations are meaningful in areas that have experienced significant declines or increases. In areas where changes have been less extreme, mapping cannot produce comparable results. Population information analyzed in this Conservation Assessment showed that white-tailed prairie dog populations can fluctuate year-to-year with calculated coefficients of variation ranging from 14% to 91% in areas surveyed in Utah and Colorado. Large annual fluctuations of white-tailed prairie dog estimates within colonies also were reported in Shirley Basin, Wyoming. Continued population monitoring is needed to assess the level of observed fluctuations and resultant long-term projections of population viability. The data available are not sufficient to evaluate whether white-tailed prairie dogs currently exist at lower densities and experience more extreme fluctuations in numbers than they did historically. Changes in occupied habitat showed that white-tailed prairie dog distribution is dynamic, with occupation shifting on a landscape scale. No clear pattern emerged to account for increases or decreases in occupied habitat; information such as plague monitoring and periodic habitat evaluations were not available for most sites. Significant declines and increases in occupied habitat that could not be attributed to mapping error were apparent in the Little Snake Black- footed Ferret Management Area, Colorado (92% decline from 1994-1999); Cisco complex, Utah (84% decline from 1985-2002); all colonies in Montana (83% decline from 1975-2003); and portions of Shirley Basin, Wyoming (50% increase from 1990-2004). This evaluation of occupied habitat underscores the importance of evaluating white-tailed prairie dog populations on a landscape scale in order to provide an accurate rangewide assessment of the status and distribution of this species. Colonies and complexes must remain arrayed across the range as both viable and isolated to allow repopulation of depleted colonies and complexes, yet not to encourage the spread of plague between complexes. Concern over the long-term viability of white-tailed prairie dog populations is warranted. It appears that some individual colonies and complexes are prone to significant declines without recovery to previous occupied habitat or population levels (e.g. Little Snake, Colorado). Other areas however, appear able to recover rapidly after significant population declines (e.g. Kennedy Wash, Utah). Why there is a difference between recoveries at sites is unknown. It may be due to the continued infection of areas by plague and lack of immigration into areas after infection. Plague may be the reason that colonies and complexes show such dramatic oscillations in densities and shifts in occupied habitat. Prior to the introduction of the disease, populations likely Western Association of Fish and Wildlife Agencies January 2006 White-tailed Prairie Dog Conservation Assessment – Final Page iv of 137 were more stable, providing a reliable prey source for such species as ferruginous hawks and development of a specialized predator like the black-footed

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