Cynomys gunnisoniGunnison's prairie dog

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Geographic Range

This species is limited to the high mountain valleys and plateaus in the southern Rocky Mountains, and it is found at elevations of 1,830 to 3,660 m (Pizzimenti and Hoffmann 1973). Its distribution centers around the Four Corners region where the states of Utah, Colorado, New Mexico, and Arizona meet (Pizzimenti and Hoffmann 1973). The northernmost population of C. gunnisoni is found in South Park, CO, while the southernmost population resides near the Mogollon Mountains in southwestern New Mexico (Pizzimenti and Hoffmann 1973).

Habitat

Compared to the habitats of other prairie dog species, the habitat of C. gunnisoni varies greatly with respect to topography and vegetation (Pizzimenti and Hoffmann 1973). In addition, the burrow systems of C. gunnisoni are more similar to those of ground squirrels than they are to other species of prairie dogs (Pizzimenti and Hoffmann 1973). Entrances are usually located on slopes or small hummocks rather than in depressions, which protects the burrows from flooding (Pizzimenti and Hoffmann 1973). The older burrow systems are deeper, have more entrances at the surface, and more bifurcations below (Pizzimenti and Hoffmann 1973). Usually, each burrow contains a single nest composed of dried vegetation, and there is no evidence that C. gunnisoni uses its burrow for food storage (Pizzimenti and Hoffmann 1973).

Physical Description

Gunnison's prairie dog is a stout-bodied creature whose total length varies from 309 to 373 mm (Pizzimenti and Hoffmann 1973). Males are larger than females on average, and subspecies differ slightly in color and size (Pizzimenti and Hoffmann 1973). The dorsal pelage of these animals is yellowish buff intermixed with blackish hairs, while the top of the head, sides of the cheeks, and eyebrows are noticeably darker than the other portions of the pelage (Pizzimenti and Hoffmann 1973). Two annual molts occur in these animals-- one in the spring and another in the fall (Pizzimenti and Hoffmann 1973). The spring molt begins anteriorly and proceeds posteriorly until the tail hair is renewed (Pizzimenti and Hoffmann 1973). In contrast, the winter coat renewal, which is usually complete by mid-September, begins in the posterior region of the body and progresses anteriorly (Pizzimenti and Hoffmann 1973). Cynomys gunnisoni has a much shorter tail - 39 to 68 mm - than other prairie dogs, and it is uniquely colored (Pizzimenti and Hoffmann 1973). The proximal half of the tail is the same color as the dorsal pelage; however, the distal half is grayish with grayish-white hairs appearing at the terminus (Pizzimenti and Hoffmann 1973). This character is very useful in differentiating C. gunnisoni from other white-tailed species, which possess pure white hairs on the distal half of their tails (Pizzimenti and Hoffmann 1973).

It should be noted that one of the most interesting physical characteristics of these animals is the placement of their eyes (Pizzimenti and Hoffmann 1973). Their eyes, positioned on the sides of the head, appear to be adapted for detecting movement over a wide arc, and this allows these prairie dogs to detect predators with greater success (Pizzimenti and Hoffmann 1973).

  • Average mass
    900 g
    31.72 oz
    AnAge

Reproduction

The onset of reproduction is somewhat variable and dependent on latitiude, elevation, and seasonal variation (Pizzimenti and Hoffmann 1973). Females are capable of reproducing at 1 year of age and bear a single litter per year (average size is 4.78 young) after a 30 day gestation period (Pizzimenti and Hoffmann 1973). Previous studies have shown that parturition occurs between the months of April and early May (Pizzimenti and Hoffmann 1973). Young remain underground for about a month after birth (Pizzimenti and Hoffmann 1973). Consequently, little is known about growth and development during this period (Pizzimenti and Hoffmann 1973). During the lactation period newborns nurse from one of five pairs of mammae-- two pectoral and three inguinal (Pizzimenti and Hoffmann 1973). After the young begin emerging from the nesting burrow, nursing soon ends, and the offspring must become independent and feed on surrounding vegetation (Pizzimenti and Hoffmann 1973). After all the offspring are weaned, the mother leaves them in the nesting burrow and establishes herself in another burrow (Pizzimenti and Hoffmann 1973). Soon thereafter, the young leave the nesting burrow and disperse to other unoccupied burrows (Pizzimenti and Hoffmann 1973). Males of this species have a baculum which resembles that of ground squirrels (genus Spermophilus), and therefore, males are often described as spermophile-like (Pizzimenti and Hoffmann 1973).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    4.4
    AnAge
  • Average gestation period
    30 days
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    365 days
    AnAge

Behavior

Cynomys gunnisoni is often found in semi-social aggregations; yet, colonies of these mammals are generally smaller than those of other species of prairie dogs and usually consist of fewer than 50 to 100 individuals (Pizzimenti and Hoffmann 1973). Interestingly, in open habitats where Gunnison's prairie dogs have been afforded protection, the colonies become quite extensive and densely populated (Pizzimenti and Hoffmann 1973). Overall, the social organization of these creatures is loosely knit and more closely resembles that of ground squirrel aggregations than it does more highly structured organizations of other prairie dogs (Pizzimenti and Hoffmann 1973, Rayor 1988). Social structure consists mainly of mother-offspring relationships, while adult males live somewhat apart from females and offspring during the post-natal period (Pizzimenti and Hoffmann 1973 and Rayor 1991). Territoriality is rarely exhibited by a male C. gunnisoni; older males may defend a small area near their burrows, but they often feed alongside other members of the colony without conflict (Pizzimenti and Hoffmann 1973). In contrast, a female C. gunnisoni is highly territorial and aggressive during the post-natal period (Pizzimenti and Hoffmann 1973). However, as soon as her pups emerge above ground, the aggressive behavior subsides (Pizzimenti and Hoffmann 1973). Gunnison's prairie dogs are strictly diurnal, and their greatest periods of activity occur in the early morning and late afternoon (Pizzimenti and Hoffmann 1973). Above ground activities mostly include feeding, playing, and grooming; however, these animals are constantly on the lookout for possible danger while venturing out of their burrows (Pizzimenti and Hoffmann 1973 and Rayor 1991). Cynomys gunnisoni will sit up on its hind feet to survey its surroundings from the tops of the dirt mounds that form at burrow entrances (Pizzimenti and Hoffmann 1973).

Although several physical attributes can be used to distinguish C. gunnisoni from other species of prairie dogs, vocalizations - particularly alarm barks - are species specific and permit identification (Pizzimenti and Hoffmann 1973). Besides the alarm call, which consists of a series of repetitive barks, C. gunnisoni is capable of generating four other calls: raspy chatter,a contact call given under peaceful surroundings; a snarl or rasp, an aggressive call; a growl, another aggressive call; and a scream, an injury or escape call (Slobodchikoff and Coast 1980). A study of the alarm calls of adult C. gunnisoni from three separate Arizona towns during April-September 1977 uncovered some very interesting facts (Slobodchikoff and Coast 1980). First, the alarm calls of Gunnison's prairie dog have diverged into local dialects and therefore differ between the three studied locations (Conner 1982 and Slobodchikoff and Coast 1980). Second, within a particular C. gunnisoni colony there were significant differences in the calls announcing the presence of different predators -- the different predators used in the study were humans, dogs, coyotes, and hawks (Slobodchikoff et al. 1991). In addition, a significant difference in calls existed when the same predator was announced in different colonies (Slobodchikoff and Coast 1980). Third, the number of syllables and the total call length were strongly correlated with the complexity of the habitat-- the more complex the habitat was in terms of vegetation, rocks, and tree stumps, the longer the call became and the more syllables it contained (Slobodchikoff and Coast 1980). This phenomenon may be explained by the fact that sound attenuates faster in a more complex habitat, and a longer call with a larger number of syllables may be needed in a more complex habitat to maintain the same alarm function as a shorter call in a less complex habitat (Slobodchikoff and Coast 1980).

Above ground activity of C. gunnisoni occurs between late March and October, and the winter months comprise a period of inactivity for C. gunnisoni in most locations (Pizzimenti and Hoffmann 1973). Snowfall forces many of these creatures to remain underground and to survive off the fat stores they developed over the summer months (Pizzimenti and Hoffmann 1973). There is little evidence regarding hibernation in these animals, but periods of inactivity, which may last several months, support the contention that Gunnison's prairie dogs hibernate, at least in the colder parts of their range (Pizzimenti and Hoffmann 1973). Additional evidence supporting this claim comes from a laboratory colony observed during the winter months, in which members entered short periods of deep sleep with low food intake (Pizzimenti and Hoffmann 1973). No information regarding the body temperature of prairie dogs in the wild during the winter months is currently available, however (Pizzimenti and Hoffmann 1973).

Communication and Perception

Food Habits

The masticatory muscles among members of the genus Cynomys are, proportionally, the stoutest and most highly developed among the Nearctic Sciuridae, and the crown height of their cheekteeth equals or exceeds that of all other Nearctic Sciuridae (Pizzimenti and Hoffmann 1973). These characteristics reflect the adaptation of Gunnison's prairie dogs to an almost exclusively graminivorous diet (Pizzimenti and Hoffmann 1973). In addition, analyses of the stomach contents of Gunnison's prairie dogs have shown that these creatures also eat forbs, sedges, and shrubs (Pizzimenti and Hoffmann 1973).

Economic Importance for Humans: Positive

Although C. gunnisoni is primarily a graminivorous species, it has been known to consume small quantities of insects such as grasshoppers and beetles (Pizzimenti and Hoffmann 1973). Therefore, it may play a role in the maintenance of insect populations in certain farming communities and help reduce insect-related crop damage.

Economic Importance for Humans: Negative

Cynomys gunnisoni is considered an agricultural pest and economically deleterious because of its tendency to burrow in lands used for farming (Pizzimenti and Hoffmann 1973).

Conservation Status

Most deaths of Gunnison's prairie dogs can be attributed to predators, disease, and disturbance by man (Pizzimenti and Hoffmann 1973). Predators include such animals as badgers, coyotes, weasels, and several species of raptors, and an occasional pup may be lost to the rattlesnakes that often inhabit the burrow systems of C. gunnisoni (Cully 1991 and Pizzimenti and Hoffmann 1973). Concerning disease, C. gunnisoni carries several types of ectoparasites such as fleas and ticks, and these fleas can carry Yersinia pestis - the causative agent of plague - to which both men and Gunnison's prairie dogs are susceptible (Cully 1991 and Pizzimenti and Hoffmann 1973). Disturbance by man is without a doubt the greatest danger to C. gunnisoni (Pizzimenti and Hoffmann 1973). Extermination programs implemented at the turn of the century have greatly reduced the numbers and the range of Gunnison's prairie dog via such methods as drowning or treatments with carbon bisulfide, strychnine, or fluoride compound 1080 (Pizzimenti and Hoffmann 1973). Fortunately, however, these animals have been given protection in some areas such as the Blue River Reservoir in Gunnison County, CO (Pizzimenti and Hoffmann 1973).

Other Comments

Gunnison's prairie dog has a diploid number of 40 chromosomes, which is strikingly different from all other species of prairie dogs, who have a diploid number of 50 chromosomes (Pizzimenti and Hoffmann 1973).

Contributors

Nathan Landesman (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Conner, D. A. 1982. Dialects Versus Geographic Variation in Mammalian Vocalizations. Anim. Behav. 30:297-298.

Cully, J. F. Jr. 1991. Response of Raptors to Reduction of a Gunnison's Prairie Dog Population by Plague. Am. Midl. Nat. 125:140-149.

Pizzimenti, J. J. and R. S. Hoffmann. 1973. Mammalian Species: Cynomys gunnisoni. Volume One. The American Society of Mammalogists, New York City.

Rayor, L. S. 1988. Social Organization and Space-Use in Gunnison's Prairie Dog. Behav. Ecol. Sociobiol. 22:69-78.

Rayor, L. S. and K. B. Armitage. 1991. Social Behavior and Space-Use of Young of Ground Dwelling Squirrel Species with Different Levels of Sociality. Ethol. Ecol. & Evol. 3:185-205.

Slobodchikoff, C. N. and R. Coast. 1980. Dialects in the Alarm Calls of Prairie Dogs. Behav. Ecol. and Sociobiol. 1:49-53.

Slobodchikoff, C. N., J. Kiriazis, C. Fischer, and E. Creef. 1991. Semantic Information Distinguishing Individual Predators in the Alarm Calls of Gunnison's Prairie Dogs. Anim. Behav. 42:713-719.