WTPD Conservation Assessment - Endangered Species & Wetlands ...

To quantify gross spatial changes that have occurred in occupied habitat within the range
of the white-tailed prairie dog, 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 more recent mapping efforts. Direct comparison in
the estimation of occupied hectares of prairie dog colonies is problematic and needs to be
evaluated with caution. White-tailed prairie dogs exhibit a mosaic pattern of distribution making
accurate mapping of colony boundaries difficult. Distribution, burrow density and activity levels
are also extremely variable throughout a complex or colony. Much of the mapping of colonies
therefore relies upon use of topographic features, substrate variations or the best estimate of the
investigator, making many mapping efforts a reflection of suitable rather than occupied habitat.
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 however, 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 the Conservation Assessment show that white-tailed prairie
dog populations can fluctuate year-to-year with calculated coefficient of variations ranging from 14 to
91% in areas surveyed in Utah and Colorado. Large annual fluctuations of white-tailed prairie dog
estimates within colonies 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 show that white-tailed prairie dog distribution is dynamic, with
white-tailed prairie dog occupation shifting on a landscape scale. No clear pattern emerged to account
for increases or decreases in occupied habitat, though 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); for 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 range-wide assessment of the status and distribution of this
species. Colonies must remain arrayed across the range in both viable, isolated colonies and
complexes that allow repopulation of depleted colonies and complexes, yet do not encourage 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
increased from a low of 3,670 white-tailed prairie dogs (3.07 prairie dogs per ha) in 2001 to
10,282 white-tailed prairie dogs (8.60 prairie dogs per ha) in 2002). Why there is a difference between
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