WTPD Conservation Assessment - Endangered Species & Wetlands ...

crucial to the maintenance of white-tailed prairie dog populations because without it, they can
not remain active long enough to put on sufficient weight to guarantee winter survival (Beck
1994).
Population Dynamics
White-tailed prairie dog populations are reported to fluctuate by more than 50% between
consecutive years (Menkens 1987, Menkens and Anderson 1989). In most cases adult variation
in density (27-167%) was less than that reported for juveniles (124-348%) (Menkens 1987).
Variation in densities between years and also among habitats is likely driven partly by local
ecology such as site-specific topography, soil type, climate and vegetation quantity and quality.
Hyper-productive environments have been found to correlate with higher densities of prairie
dogs. For example, a comparison study examining the life history traits of the Utah prairie dog
at three different locations found prairie dog densities to range from 2.3 prairie dogs per ha
(0.9 per ac) at a high elevation site, 16 prairie dogs per ha (6.5 per ac) at a low elevation site and
36 prairie dogs per ha (14.6 per ac) at a low elevation site associated with an alfalfa field
(Crocker-Bedford 1976). The difference in densities was attributed to quantity and quality of
available vegetation. Turner (2001) found that after a plague epizootic severely reduced a
population of Utah prairie dogs in Bryce Canyon, survival of juveniles, juvenile mass and the
number of females successfully weaning young increased. These factors were thought to
contribute to the rapid recovery of the population. The mechanism driving the increase in these
three factors was unclear, but was thought to be due to the increase in resource availability after a
population decline. Cooke (1993) found both yearling and adult females were more successful at
weaning litters on sites with high quality food resources than those on poorer sites. In addition,
female juveniles remained resident on their natal home ranges on higher quality sites.
Disease, especially the introduced pathogen Yersinia pestis responsible for sylvatic
plague, may play a role in amplifying population fluctuations. Historically, white-tailed prairie
dog populations were probably not static, but with the evolution of an obligate predator such as
the black-footed ferret that relies on prairie dogs as their main food source, it is unlikely that
populations fluctuated as dramatically as they do today. A plague free black-tailed prairie dog
colony in the Wind Cave National Park, South Dakota provides an example (Hoogland 1995).
Plague has never been detected within this colony and yearly population levels are relatively
stable. This differs from a population at the Rocky Mountain Arsenal National Wildlife Refuge
near Denver, Colorado where epizootics of plague are frequent and extreme population
fluctuations are common (Biggins and Kosoy 2001b).
Reports on burrow densities vary greatly from location-to-location ranging from 0.8 to
291 per ha, (0.3-118 per ac) with a mean of 2.1 to 41.7 per ha (0.8-16.8 per ac) (Tileston and
Lechleitner 1966, Clark et al. 1986, Menkens 1987, Orabona-Cerovski 1991). Collins and
Lichvar (1986) found that burrows were widely distributed and equidistant from one another in
white-tailed prairie dog colonies located in contiguous homogeneous suitable habitat. However,
if colonies occurred within a mosaic of habitat types with not all areas suitable for prairie dogs,
burrows were are ranged in a clumped pattern.
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