WTPD Conservation Assessment - Endangered Species & Wetlands ...

Population Analysis
Limited current data and lack of consistent past survey information for white-tailed
prairie dog complexes in Wyoming makes long-term trend analysis biologically and statistically
unsupportable for most individual complexes and at the Statewide level. However trends can be
inferred from a few areas that have comparable survey efforts.
Declines in the white-tailed prairie dog estimate at the Meeteetse complex have been
documented and reported by Biggins (2003b). Biggins (2003b) reported an estimated
25,494 white-tailed prairie dogs within the Meeteetse complex in 1988, but by 1989, the reported
white-tailed prairie dog estimate decreased to 17,692, and then dropped to a low of 1,299 in
1993. These declines followed, and were probably the result of, the sylvatic plague epizootic of
the mid-1980s. By 1997, the white-tailed prairie dog estimate for Meeteetse had increased to
7,095 (Table 18).
Sample transects in 10 of the 11 white-tailed prairie dog colonies (Colonies # 2-11)
mapped by Luce in 2000 (Luce 2000a) did not reveal any transects with greater than 8 total
burrows, therefore sampling using Biggins et al. (1989,1993) was not conducted. Small areas of
high white-tailed prairie dog densities and/or large areas of low white-tailed prairie dog densities
both tended to fall out of the Biggins et al. (1993) model. Colony #1, with a mapped area of
35 ha (87 ac), was transected, however, only three transects had greater than 8 total burrows, and
no transect had greater than 25 active burrows. All data combined indicate very low densities,
and the colonies surveyed in 2000 combined for only 14% (1,066) of the total white-tailed prairie
dog estimate reported in 1997 by Biggins (2003b) for the same area. Data are not available to
estimate population trends for the entire Meeteetse complex after 1997 however Biggins (2003b)
suggests that white-tailed prairie dogs remained scattered throughout the larger area.
Sylvatic plague was first documented in Shirley Basin in 1987 (Orabona-Cerovski 1991)
and impacted colonies to at least some extent through 1995. The WGFD conducted surveys of
selected prairie dog colonies between 1992 and 2001 in Shirley Basin PMZ1. Results indicated
that white-tailed prairie dog abundance appeared to have decreased, as a result of sylvatic plague
and at least in one year, flooding. However, Grenier et al. (2003) indicated a different trend.
White-tailed prairie dog abundance appeared to be increasing in PMZ1 and adjacent areas, in
part due to increases in occupied hectares both in areas previously mapped, and in new areas.
This trend is difficult to document from the transecting data (Luce 2000b, Grenier et al. 2003).
Large annual fluctuations of white-tailed prairie dog estimates within colonies were reported in
Shirley Basin (Luce 2000b). Consistent comparative data are available for four colonies (#165,
#166, #167 and #168). These colonies were surveyed during each year from 1991 to 2000,
including in 1994 when only 6% of PMZ1 was transected (Figure 15). For example, Colony
#166 decreased from an estimated high of 7,321 prairie dogs in 1991 to low of 0 in 1995, then
rebounded to 5,480 in 1996 and decreased again to 0 in 1999 and 2000. Colony #168 decreased
from an estimated 4,066 prairie dogs in 1992 to 404 in 1995, then increased to 2,433 in 1997,
dropped to 0 in 1999 and increased again to 638 in 2000 (Figure 15). Despite those fluctuations,
the changes in distribution of white-tailed prairie dogs within the Shirley Basin complex,
especially pioneering of new colonies, reported in Grenier et al. (2002), have increased the
white-tailed prairie dog occupied area. Ocular estimates of white-tailed prairie dog populations
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