WTPD Conservation Assessment - Endangered Species & Wetlands ...

disappeared after the 1994 surveys. Because of this, the area was dropped from consideration as
a reintroduction site and surveys were discontinued until populations could recover to their
pre-plague levels.
In 1999, occupied habitat in sub-complexes A1 and A3 was remapped and transected to
evaluate recovery rates and black-footed ferret habitat potential (Squires 1999). This remapping
resulted in identification of 41 colonies covering 735 ha (1,816 ac); a decline of 92% in occupied
habitat from 1990 when sub-complexes A1 and A3 contained 64 colonies on 9,272 ha
(20,827 ac) (Figure 4). Area of good black-footed ferret habitat in 1999 was 465 ha (1,148 ac)
with an estimated white-tailed prairie dog population of 5,064 (10.3-11.6 white-tailed prairie
dogs per ha [4.2-4.69 per ac]). Most of the burrows outside of the areas mapped as active
revealed signs of collapse indicating that they had not been occupied since the 1994 population
decline.
In 2002, the active colonies in sub-complexes A1 and A3 were remapped and
white-tailed prairie dog activity in other sub-complexes was informally assessed. From this
effort there appeared to be little change from the 1999 survey and what changes did occur were
largely negative (Renner 2002). In 2003, white-tailed prairie dog colonies in sub-complexes A2
and A4 were remapped and other areas informally assessed (Renner 2003). The 2003 survey
showed modest improvement over the 2002 surveys however, there was concern that this
observed recovery may not continue due to the continued drought conditions causing significant
amounts of sagebrush and saltbush to become dormant or die over large portions of the area
(Renner 2003). The areas surveyed had virtually no forb or grass cover forcing prairie dogs to
subsist on underground roots. This lack of plant growth may ultimately decrease winter survival
and subsequent reproductive rates.
Current Occupancy
In 2002, the CDOW embarked on a Statewide effort to document occupied white-tailed
prairie dog habitat by interviewing field personnel from CDOW, the USFWS and the BLM
(CDOW 2003). White-tailed prairie dog colonies were mapped on 1:50,000 USGS county
sheets and were designated as active (known to have white-tailed prairie dogs inhabiting the
colony within the last 3 years) or as unknown (white-tailed prairie dogs were known to occur
historically, but current status was unknown). From this mapping, a total of 77,648 ha
(191,866 ac) of active and 19,021 ha (47,001 ac) of unknown white-tailed prairie dog colonies
were documented. These data are preliminary and represent only those colonies and areas
identified by agency personnel. Field verification of identified colonies is planned and budgeted
for spring 2005.
Predicted Range Model
Twenty-one percent of the white-tailed prairie dog gross range and 11% of the
white-tailed prairie dog predicted range occurs in Colorado (Table 1, Figure 5). The gross range
boundary overestimates percent of habitat in Colorado as it includes large areas within it that are
not, nor have ever been suitable habitat for white-tailed prairie dogs. Six percent of the
white-tailed prairie dog gross range in Colorado is located on agricultural lands and 0.2% it is
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