black-tailed prairie dog) is “vulnerable.” Merriam’s and
Townsend’s ground squirrels are “apparently secure,” that
is, uncommon but not rare, but with possible cause for long-
term concern. The remaining eighteen species are consid-
ered “secure,” that is, common, widespread, and abundant,
although Franklin’s ground squirrel has been declining
rapidly because of loss of its tall grass habitat resulting
from agricultural and urban expansion (Johnson and
Choromanski-Norris 1992), and is considered “vulner-
able” by the IUCN.
In Europe and Asia there is uneven knowledge about the
status of the thirteen Spermophilusspecies. The European
ground squirrel has declined in Europe because of habitat
destruction by modern agricultural techniques and urban-
ization (Smit and Van Wijngaarden 1981). The European
and speckled ground squirrels are considered “vulnerable”
by the IUCN (World Conservation Union: IUCN 2003),
while the Russet ground squirrel is “near threatened.”
The causes of imperiled status are varied. Control pro-
grams (Pizzimenti and Collier 1975), along with a restricted
range following the last major episode of climate change
(see Goodwin 1995), may account for the status of the Utah
prairie dog (fig. 39.5). Remaining imperiled Idaho ground
squirrels consist of two subpopulations, each having dif-
ferent factors that have led to habitat loss. Northern
Idaho ground squirrels are threatened by thick growth
of young trees into their preferred open stands of conifers
with herbaceous understory, a condition attributable to fire464 Chapter Thirty-Nine
Figure 39.1 Ranges of ground squirrel species of conservation concern (Pat-
terson et al. 2003). These include species designated “critically imperiled” or
“imperiled” by NatureServe. Range sizes are distorted by map projections.
Figure 39.2 Ranges of “smaller” ground squirrels (average body length 13.9 –21.9 cm; Patterson et al. 2003) Range sizes are distorted by map projections.