prairie dogs have not evolved a good defense against plague,
and consequently remain highly susceptible — so that mor-
tality within an infected colony usually is 95% (Barnes
1993; Cully et al. 2006).
Over the last 20 years or so, plague has been especially
problematic for prairie dogs (Cully et al. 2005). For un-
known reasons, plague currently is absent throughout most
of the eastern one-third of the prairie dog’s geographic range
(i.e., North and South Dakota, Nebraska, Kansas, Okla-
homa, and Texas; Cully et al. 2006). In Montana, for ex-
ample, plague has been primarily responsible for reducing
the cumulative area inhabited by prairie dogs by 50% since
1986 (Luce et al. 2006). Because of the combination of cata-
strophic mortality with unpredictability regarding the place
and timing of epidemics, plague poses a formidable obstacle
for the long-term survival of prairie dogs (Cully and Wil-
liams 2001; see the following, also).
The Prairie Dog as a Keystone Species
An organism that dramatically and uniquely affects the
composition and functioning of an ecosystem is called akey-
stone species(Paine 1969; Power et al 1996; Kotliar 2000).
As summarized in the following, the prairie dog qualifies as
a keystone species because (1) so many other organisms as-
sociate with it, and (2) its grazing and burrowing radically
alter the landscape and affect ecosystem processes. These
two effects frequently overlap; the altered landscape at col-
ony sites, for example, is one reason that colonies attract
certain plants and animals.
Organisms that associate with prairie dogs
Because 200 species of plants and animals frequently as-
sociate with them, prairie dog colonies increase biological
diversity and species richness (King 1955; Clark et al. 1982;
Miller et al. 1994, 2000; Kotliar et al. 1999, 2006). Prairie
dogs are prey, for example, not only for mammalian pred-
ators such as American badgers (Taxidea taxus), bobcats
(Lynx rufus), coyotes (Canis latrans), and red foxes (Vulpes
vulpes), but also for avian predators such as golden eagles
(Aquila chrysaetos), prairie falcons (Falco mexicanus), Coo-
per’s hawks (Accipiter cooperi), ferruginous hawks (Buteo
regalis), and red-tailed hawks (B. jamaicensis). Prairie dog
burrows provide shelter and nesting sites for many kinds
of animals, including amphibians (e.g., tiger salamanders;
Ambystoma tigrinum), reptiles (e.g., prairie rattlesnakes;
Crotalus viridis), birds (e.g., burrowing owls; Athene cu-
nicularia), and myriad insects (Agnew et al. 1986; Butts and
Lewis 1982; Desmond et al. 2000). Grazing and clipping of
vegetation by prairie dogs create open habitats preferred by
animals such as horned larks (Eremophila alpestris), moun-
tain plovers (Charadrius montanus), American bison (Bison
bison), and pronghorn (Antilocapra americana;Knowles
et al. 1982; Olson 1985; Kotliar et al. 1999).
At one extreme, many of the species that associate with
prairie dogs also occur in grassland habitats with no prairie
dogs (Kotliar et al. 1999). Examples that show such casual
association with prairie dogs include American robins (Tur-
dus migratorius), slate-colored juncos (Junco hyemalis),
eastern cottontails (Sylvilagus floridanus), and northern
pocket gophers (Thomomys talpoides). At the other ex-
treme, many plants and animals depend heavily on prairie
dogs. At least four species of plants, for example, survive
and reproduce better at colony sites: black nightshade
(Solanum nigrum), pigweed (Amaranthus retroflexus), scar-
let globemallow (Sphaeralcea coccinea), and fetid marigold
(Dyssodia papposa;King 1955; Detling 2006). The species
most dependent on prairie dogs is probably the black-
footed ferret (Mustela nigripes). Prairie dogs comprise about
90% of the ferret’s diet, and their burrows provide shelter
and nesting chambers for ferrets (Clark 1989; Seal et al.
1989; Miller et al. 1996). The drastic decline of prairie dogs
over the last 200 years has been calamitous for the ferret,
which is on FLETWP and is at the brink of extinction. No
known natural populations of ferrets exist, and survival
of the species will depend on the success of reintroducing
laboratory-reared ferrets into the wild (Chadwick 1993;
Miller et al. 1996; Vargas et al. 1998; Dobson and Lyles
2000; Kotliar et al. 2006).Altered landscape and ecosystem processes
Like some other ground-dwelling squirrels (e.g., Yensen
and Sherman 1997, 2003), prairie dogs markedly alter
thegrassland ecosystems they inhabit (Kotliar et al. 1999,
2006). Their excavations promote mixing of topsoil and
subsoil, for example. They consume grasses, forbs, and
other herbaceous plants (Detling 2006). In addition, prairie
dogs sometimes clip tall vegetation but do not consume it —
presumably to enhance detection of predators (King 1955;
Hoogland 1995). The combination of consumption and
clipping decreases the height of vegetation, and also alters
floral species composition (King 1955; Koford 1958; Uresk
and Bjugstad 1983).
Even though prairie dogs reduce vegetational biomass
by their clipping and foraging, the quality of grasses and
forbs at colony sites is sometimes better (i.e., has a higher
concentration of proteins) because of (1) fertilization of
the topsoil via the feces and urine of prairie dogs, (2) redis-
tribution of minerals and nutrients in soil via burrowing,
and (3) better penetration and retention of water within soil
via burrows (Munn 1993; Detling 2006). Enhanced quality474 Chapter Forty