S

pecies of ground squirrels(Spermophilus)
and prairie dogs (Cynomys) comprise a monophyletic
group of fossorial species (Black 1963; Hafner 1984;
Harrison et al. 2003; Nadler et al. 1971). Cynomysrepre-
sents a specialized form of highly social species (Armitage
1981; Michener 1983a) that probably arose in the late Plio-
cene (Black 1963) in association with an adaptive radiation
of sciurids resulting from mountain uplift and drying trends
in western North America (Hafner 1984). Ground squirrels
have long been considered by many to be pests and varmints
that compete with cattle for food, dig holes that are treach-
erous to domestic ungulates, provide shelter for poison-
ous snakes, carry plague, and create unsightly disturbances
in otherwise tidy landscapes. Such problems are primar-
ily identified by farmers, ranchers, and residents of urban
edges, and have provided a rationale for localized and /or
widespread shooting and poisoning, primarily of prairie
dogs. Others, especially some urban dwellers as well as ecol-
ogists interested in maintaining ecosystems in which bur-
rowing mammals influence a wide variety of other species,
wish to see them protected. Prairie dogs, with their high
level of sociality, larger size, and appealing visage may be es-
pecially targeted by the public for conservation. Hoogland
(chap. 40 this volume) describes problems in conservation
of prairie dogs. This chapter provides a more general over-
view of ground squirrel conservation.
My intent here is to explore the biology of these species
to better understand the underlying causes of broad popu-
lation declines. It may seem counterintuitive that a group
composed of a number of widespread and seemingly robust
species that are well adapted to habitat disturbance may yet

contain several species and subspecies at risk of near-term

extinction. I will review the conservation status of these

species and summarize characteristics of species that are of

concern. This review will largely focus on North American

species, for which the most relevant information is avail-

able. I will then explore how the combination of their body

size, fossorial habits, and largely herbivorous diets greatly

restricts the range of adaptations that can be exhibited by

this group, and allows for some commonalities in patterns

of genetic variation across the landscape and in the regula-

tion of population size. From these commonalities, I will

suggest some generalizations regarding conservation.

Distribution and Conservation Status

For a visual overview of ranges of north American ground

squirrels, I have separated species of immediate conservation

concern (small to large, fig. 39.1) from smaller (fig. 39.2)

and larger (figs. 39.3, 39.4) species of less concern, and have

shown the ranges of prairie dogs separately (fig. 39.5). Con-

servation status of these species varies (table 39.1). Of the

thirty-two species of ground squirrels and prairie dogs in

North America, one, the Utah prairie dog, is considered

by NatureServe (NatureServe 2004) to be “critically imper-

iled” and is listed by the US federal government as threat-

ened. Four species (the Idaho, Washington, and Mojave

ground squirrels, and the Mexican prairie dog are consid-

ered “imperiled” on the same basis, and the Washington

ground squirrel is a candidate for US federal listing (scien-

tific names are presented in tables 39.1 and 39.2). One (the

Chapter 39Conservation of Ground Squirrels

Beatrice Van Horne