Cully 2001). More recently, Hoogland (2007b) reviewed the conservation of prairie dogs. Strategies and techniques for management of plague by vaccinating prairie dogs are under active research (Rocke et al. 2008). Despite concern by preservationists, prairie dogs are considered small game in Colorado, and there is an open season on all species of Cynomys from June 15 through February (Colorado Division of Wildlife 2009f). There is no bag or possession limit. Estimated harvest in some recent years is shown in Table 4-3, indicating that prairie dogs are by far the most harvested small game, with more than 300,000 individuals killed most years by upwards of 5,000 hunters. Cynomys gunnisoni GUNNISON'S PRAIRIE DOG Description Gunnison's prairie dog is the smallest of Colorado's prairie dogs. Dorsal color is yellowish buff to cinnamon with numerous interspersed black hairs. The ventral color is slightly paler. The top of the head, cheeks, and superciliary line above the eyes are darker than the rest of the body, albeit less strikingly so than in the white-tailed prairie dog. The terminal third of the tail is gray to dirty white in color. Measurements are: total length 300-390 mm; length oftail40-64 mm; length ofhindfoot 53-61 mm; weight 450-1,350 g. Males are heavier than females by as much as 30 percent early in the breeding season (Hoogland 2003a). D1git1zed by Goog le
PHOTOGRAPH 8-13. Gunnison's prairie dog (Cynomys gunnisoni). Photograph by J. Perley Fitzgerald. Overall, the animals are darker and less strikingly patterned than the whitetailed prairie dog. Because of its dark color and relatively small size, Gunnison's prairie dog is sometimes mistaken for the Wyoming ground squirrel, from which it is distinguished by its larger size, relatively shorter tail, stockier build, and distinctive vocalizations. The skull of Gunnison's prairie dog differs from that of the white-tailed prairie dog in having a more broadly spreading zygomatic process of the maxillary, smaller and more oblique mastoids, and smaller auditory bullae. Females have 10 mammae. D1git1zed by Goog le
D~scriptien Gunnison's prairie dogs are restricted to southwestern and south-central Colorado. They range in elevation from 1,830 to 3,660 m (6,000-12,000 feet). Plague and poisoning have had major impacts on the distribution of this species in Colorado (Ecke and Johnson 1952; Lechleitner et al. 1962, 1968; J. Fitzgerald 1970, 1993a; Pizzimenti 1981; Raynor 1985a) and adjacent states (Cully et al. 1997). An epizootic in the 1940s greatly reduced numbers of prairie dog in South Park (Ecke and Johnson 1952), and J. Fitzgerald (1970) reported that most colonies were gone from the area, having been replaced by Wyoming ground squirrels. Pizzimenti and Hoffmann (1973) reviewed general literature on the species. Cynomys gunnisoni gunnisoni occurs in the Gunnison River drainage, the upper Arkansas and South Platte drainages, and the San Luis Valley. This subspecies has been extirpated over much of its former range, although in 1991, R. B. Finley (personal communication) found small colonies in several areas of south-central Colorado. C. g. zuniensis occurs at lower elevations in southwestern Colorado in Montezuma, La Plata, Dolores, San Miguel, and Montrose counties. D1git1zed by Goog le
0!00 10011 M~ & I!:ilo 1,~I tsll(to'l\l!lt~ " 10 MAP 8-26. Distribution of Gunnison's prairie dog (Cynomys gunnisoni) in North America. D1git1zed by Goog le
-- Moros MAP 8-27. Distribution of Gunnison's prairie dog (Cynomys gunnisoni) in Colorado. aescritttien Gunnison's prairie dogs frequently are called "keystone species" (or "keystone engineers"; Bangert and Slobodchikoff 2000) in shrub-steppe communities within their range. Restoration of C. gunnisoni on the Sevilleta National Wildlife Refuge in west-central New Mexico had only minor impact on species richness of small mammals and plants during the first year, although bannertailed kangaroo rats were more abundant on restoration sites than off (Davidson o1git1zed by Goog le
et al. 1999). Impacts of prairie dogs on biotic communities may be as subtle as improving locomotor efficiency for beetles (Bangert and Slobodchikoff 2004 ). Studies in northern Arizona (Gallie and Drickamer 2008) indicated potential competition between two "ecosystem engineers," C. gunnisoni and valley pocket gophers (Thomomys bottae). Specifically, presence of prairie dogs seemed to have a negative influence on presence of pocket gophers, and density of prairie dog burrows was twice as high when pocket gophers were present. The authors speculated that pocket gopher mounds may favor the broad-leafed plants preferred by prairie dogs. Where Gunnison's prairie dogs were killed by plague in northern New Mexico, declines were noted in some raptors, especially ferruginous hawks (Buteo regalis) (Cully 1991). Gunnison's prairie dogs inhabit grasslands and semi-desert and montane shrublands. Their diet consists mostly of grasses and sedges. In Costilla County, grasses constituted 81 percent of the diet (Longhurst 1944); other foods included borages, goosefoot, pigweed, lupine, dandelions, and mustards. In South Park, fescues, June grass, muhley, sedges, rushes, Indian paintbrush, Senecio, chiming bells, prairie sage, big sage, and rabbitbrush were commonly used (J. Fitzgerald and Lechleitner 1974). Flowers and other succulent parts of forbs and shrubs are also consumed but the animals do little digging for roots and tubers. About 60 percent of the time aboveground is spent foraging and feeding (Tileston and Lechleitner 1966). Clipping of nonfood vegetation, so characteristic of black-tailed prairie dogs, has not been documented. As with all species of prairie dogs and most ground squirrels, Gunnison's prairie dogs gather grasses and forbs for nesting materials, especially in late summer. Free water is not required. Reproduction occurs shortly after emergence from hibernation. Mating was observed in South Park in late April and May. Most copulation occurs belowground (Hoogland 1998). In an Arizona study of microsatellite DNA, 77 percent of litters had multiple sires (Haynie et al. 2003 ). Length of gestation is estimated at about 29 days (Hoogland 1997). Pups remain belowground for 4 to 5 weeks after birth, suggesting the duration of lactation (Hoogland 1997). Lactating females were noted in South Park in May and June, with first D1git1zed by Goog le
appearance of pups in the first week of July. Females have 1 litter per year. In northeastern Arizona, average litter size was 3.77 young (range, 2 to 7; Hoogland 2001). Sex ratios favor males at birth, with adult populations slightly favoring females. Such unequal sex ratios have been reported in black-tailed prairie dogs and are attributed to increased chance for mortality in young males. Cully (1997) reported that following a severe outbreak of plague (more than 99% decline in population) in northern New Mexico, populations showed greater survival to weaning, greater interyear survival, and breeding by yearling females, with populations tripling annually. Gunnison's prairie dogs hibernate. In central Colorado at elevations around 3,500 m (10,000 ft.) individuals entered burrows by October and emerged in mid-april. Hibernation periods at lower elevations are shorter and some individuals may even appear aboveground during the winter months (Raynor et al. 1987). The animals are diurnal, with bimodal peaks of activity typical during warmer times of the year. Although brief showers do not interrupt activity, periods of prolonged rain or snow cause the animals to retreat to their burrows. Prairie dogs are considerably more cautious in their behaviors on cloudy, overcast days than on days with bright sunshine. Alarm calls are used in response to predators, and all individuals within hearing range probably benefit. Interestingly, their alarm calls appear to have semantic properties; in an experimental situation, Gunnison's prairie dogs appeared to distinguish between (and announce information about) individual "predators" (in this case, researchers clothed in different ways) (Slobodchikoff, Kiriazis, et al. 1991), and their alarm calls show regional differences ("dialects"; Slobodchikoff, Ackers et al. 1998) in the Southwest. Gunnison's prairie dogs are considerably less social than black-tailed prairie dogs, so colony organization is more similar to that of the less social ground squirrels (Scheffer 1947). aggregate in "clans" similar to those of white-tailed prairie dogs. Clans include 1 to 19 (mean, 5.3) individuals (Hoogland 1999). Females and young are tied more closely to particular locations within the colony than are males. Most agonistic behavior is between clans, related to D1git1zed by Goog le
disputes over feeding areas or specific burrow clusters rather than discrete territorial boundaries such as those of the coterie boundaries observed in blacktailed prairie dogs. Densities of Gunnison's prairie dogs range from 5 or 6 to more than 57 animals per hectare in especially favorable habitat (Burnett and McCampbell 1926; Lechleitner et al. 1962; J. Fitzgerald and Lechleitner 1974; Raynor 1985b ). Burrow systems and mound construction are less well developed than within black-tailed prairie dogs. In South Park only 13 percent of burrows had well-developed mounds, and 77 percent showed little or no excavated soil. Predators include badgers, golden eagles, coyotes, bobcats, and red-tailed hawks. Infanticide is rare or absent (Hoogland 1999). Like all Coloradan prairie dogs, C. gunnisoni is listed as a small game animal (Table 4-1 ). Seasons are set annually and in recent years hunting has been more restricted on public land than on private land. There is no bag limit, but the season is closed from March through mid-june (Colorado Division of Wildlife 2009f) to reduce the chance of killing lactating females with dependent young in the den. For comments on harvest by humans, see the generic account of Cynomys above. C. Knowles (2002) reviewed the conservation status of C. gunnisoni across its range. The literature on Gunnison's prairie dog was reviewed by Hoogland (2003b ). The extensive work on Gunnison's prairie dog by Conrad Slobodchikoff and colleagues in northeastern Arizona probably is generally pertinent to the species in southwestern Colorado, including research on diet (Shalaway and Slobodchikoff 1988), habitat (Slobodchikoff, Robinson, and Schaack 1988), vocalizations (Slobodchikoff, Kiriazis, et al. 1991; S. Travis et al. 1996; Slobodchikoff, Ackers, and Van Ert 1998; Ackers and Slobodchikoff 1999; Placer and Slobodchikoff 2000; Perla and Slobodchikoff 2002; Slobodchikoff 2002; Frederiksen and Slobodchikoff 2007; Kiriazis et al. 2006; Slobodchikoff and Placer 2006), social systems (S. Travis and Slobodchikoff 1993; S. Travis et al. 1995, 1996), genetics (S. Travis et al. 1997), and community ecology (Slobodchikoff, Vaughan, and Warner, 1987; Bangert and Slobodchikoff2000, 2004, 2006; Verdolin and Slobodchikoff2002). D1git1zed by Goog le