Prairie dog


Prairie dogs are herbivorous burrowing ground squirrels native to the grasslands of North America. There are five recognized species of prairie dog: black-tailed, white-tailed, Gunnison's, Utah, and Mexican prairie dogs. In Mexico, prairie dogs are found primarily in the northern states, which lie at the southern end of the Great Plains: northeastern Sonora, north and northeastern Chihuahua, northern Coahuila, northern Nuevo León, and northern Tamaulipas. In the United States, they range primarily to the west of the Mississippi River, though they have also been introduced in a few eastern locales. They are also found in the Canadian Prairies. Despite the name, they are not actually canines; prairie dogs, along with the marmots, chipmunks, and several other basal genera belong to the ground squirrels, part of the larger squirrel family.
Prairie dogs are considered a keystone species, with their mounds often being used by other species. Their mound-building encourages grass development and renewal of topsoil, with rich mineral and nutrient renewal in the soil, which can be crucial for soil quality and agriculture. They are extremely important in the food chain, being important to diets of many animals such as the black-footed ferret, swift fox, golden eagle, red tailed hawk, American badger, and coyote. Other species, such as the golden-mantled ground squirrel, mountain plover, and the burrowing owl, also rely on prairie dog burrows for nesting areas. Grazing species, such as plains bison, pronghorn, and mule deer, have shown a proclivity for grazing on the same land used by prairie dogs, with their regeneration of topsoil being important for maintaining healthy humus. Prairie dogs have some of the most complex systems of communication and social structures in the animal kingdom.
The prairie dog habitat has been affected by direct removal by farmers, and the more obvious encroachment of urban development, which has greatly reduced their populations. The removal of prairie dogs "causes undesirable spread of brush", the costs of which to livestock range and soil quality often outweighs the benefits of removal. Other threats include disease. The prairie dog is protected in many areas to maintain local populations and ensure natural ecosystems.

Etymology

Prairie dogs are named for their habitat and warning call, which sounds similar to a dog's bark. The name was in use at least as early as 1774. The 1804 journals of the Lewis and Clark Expedition note that in September 1804, they "discovered a Village of an animal the French Call the Prairie Dog". Its genus, Cynomys, derives from the Greek for "dog mouse".
The prairie dog is known by several indigenous names. The name wishtonwish was recorded by Lt. Zebulon Pike while on the Arkansas two years after Lewis and Clark's expedition. In Lakota, the word is pispíza or pìspíza.

Classification and first identification

The black-tailed prairie dog was first described by Lewis and Clark in 1804. Lewis described it in more detail in 1806, calling it the "barking squirrel".

Description

Prairie dogs are stout-bodied rodents that, on average, are long, including the short tail, and weigh between. Sexual dimorphism in body mass in the prairie dog varies 105 to 136% between the sexes. Among the species, black-tailed prairie dogs tend to be the least sexually dimorphic, and white-tailed prairie dogs tend to be the most sexually dimorphic. Sexual dimorphism peaks during weaning, when the females lose weight and the males start eating more, and is at its lowest when the females are pregnant, which is also when the males are depleted from breeding.
Despite their name, a prairie dog skull has a condylobasal length of between 5.2 and 6.4 cm shorter than the skull of a canine or actual dog which is between 11.39 and 17.96 cm in length.
The average lifespan of a prairie dog in the wild is 8 to 10 years.

Ecology and behavior

Diet

Prairie dogs are chiefly herbivorous, although they occasionally eat insects. They feed primarily on grasses and small seeds. In the fall, they eat broadleaf forbs. In the winter, lactating and pregnant females supplement their diets with snow for extra water. They also will eat roots, seeds, fruit, buds, and grasses of various species. Black-tailed prairie dogs in South Dakota eat western bluegrass, blue grama, buffalo grass, six weeks fescue, and tumblegrass, while Gunnison's prairie dogs eat rabbit brush, tumbleweeds, dandelions, saltbush, and cacti in addition to buffalo grass and blue grama. White-tailed prairie dogs have been observed to kill ground squirrels, a competing herbivore.

Habitat and burrowing

Prairie dogs live mainly at altitudes ranging from above sea level. The areas where they live can get as warm as in the summer and as cold as in the winter. As prairie dogs live in areas prone to environmental threats, including hailstorms, blizzards, and floods, as well as drought and prairie fires, burrows provide important protection. Burrows help prairie dogs control their body temperature as they are during the winter and in the summer. Prairie dog tunnel systems channel rainwater into the water table, which prevents runoff and erosion, and can also change the composition of the soil in a region by reversing soil compaction that can result from cattle grazing.
Prairie dog burrows are long and below the ground. The entrance holes are generally in diameter. Prairie dog burrows can have up to six entrances. Sometimes, the entrances are simply flat holes in the ground, while at other times, they are surrounded by mounds of soil either left as piles or hard-packed. Some mounds, known as dome craters, can be as high as. Other mounds, known as rim craters, can be as high as. Dome craters and rim craters serve as observation posts used by the animals to watch for predators. They also protect the burrows from flooding. The holes also possibly provide ventilation as the air enters through the dome crater and leaves through the rim crater, causing a breeze though the burrow. Prairie dog burrows contain chambers to provide certain functions. They have nursery chambers for their young, chambers for night, and chambers for the winter. They also contain air chambers that may function to protect the burrow from flooding and a listening post for predators. When hiding from predators, prairie dogs use less-deep chambers that are usually below the surface. Nursery chambers tend to be deeper, being below the surface.

Social organization and spacing

Prairie dogs are highly social animals. They live in large colonies or "towns", and collections of prairie dog families can span hundreds of acres. The prairie dog family groups are the most basic units of its society. Members of a family group inhabit the same territory. Family groups of black-tailed and Mexican prairie dogs are called "coteries", while "clans" describes family groups of white-tailed, Gunnison's, and Utah prairie dogs. Although these two family groups are similar, coteries tend to be more closely knit than clans. Members of a family group interact through oral contact or "kissing" and grooming one another. They do not perform these behaviors with prairie dogs from other family groups.
A prairie dog town may contain 15–26 family groups, with subgroups within a town, called "wards", which are separated by a physical barrier. Family groups exist within these wards. Most prairie dog family groups are made up of one adult breeding male, two or three adult females, and one or two male offspring and one or two female offspring. Females remain in their natal groups for life, thus are the source of stability in the groups. Males leave their natal groups when they mature to find another family group to defend and breed in. Some family groups contain more breeding females than one male can control, so have more than one breeding adult male in them. Among these multiple-male groups, some may contain males that have friendly relationships, but the majority contain males that have largely antagonistic relationships. In the former, the males tend to be related, while in the latter, they tend not to be related. Two or three groups of females may be controlled by one male. However, among these female groups, no friendly relationships exist.
The typical prairie dog territory takes up. Territories have well-established borders that coincide with physical barriers such as rocks and trees. The resident male of a territory defends it, and antagonistic behavior occurs between two males of different families to defend their territories. These interactions may happen 20 times per day and last five minutes. When two prairie dogs encounter each other at the edges of their territories, they stare, make bluff charges, flare their tails, chatter their teeth, and sniff each other's perianal scent glands. When fighting, prairie dogs bite, kick, and ram each other. If their competitor is around their size or smaller, the females participate in fighting. Otherwise, if a competitor is sighted, the females signal for the resident male.

Reproduction and parenting

Prairie dog copulation occurs in the burrows, which reduces the risk of interruption by a competing male. They are also at less risk of predation. Behaviors that signal that a female is in estrus include underground consorting, self-licking of genitals, dust-bathing, and late entrances into the burrow at night. The licking of genitals may protect against sexually transmitted diseases and genital infections, while dust-bathing may protect against fleas and other parasites. Prairie dogs also have a mating call which consists of up to 25 barks with a 3- to 15-second pause between each one. Females may try to increase their reproduction success by mating with males outside their family groups. When copulation is over, the male is no longer interested in the female sexually, but will prevent other males from mating with her by inserting copulatory plugs.
For black-tailed prairie dogs, the resident male of the family group fathers all the offspring. Multiple paternity in litters seems to be more common in Utah and Gunnison's prairie dogs. Mother prairie dogs do most of the care for the young. In addition to nursing the young, the mother also defends the nursery chamber and collects grass for the nest. Males play their part by defending the territories and maintaining the burrows. The young spend their first six weeks below the ground being nursed. They are then weaned and begin to surface from the burrow. By five months, they are fully grown. The subject of cooperative breeding in prairie dogs has been debated among biologists. Some argue prairie dogs will defend and feed young that are not theirs, and young seemingly sleep in a nursery chamber with other mothers; since most nursing occurs at night, this may be a case of communal nursing. In the case of the latter, others suggest communal nursing occurs only when mothers mistake another female's young for their own.
Infanticide is known to occur in prairie dogs. Males that take over a family group will kill the offspring of the previous male. This causes the mother to go into estrus sooner. However, most infanticide is done by close relatives. Lactating females will kill the offspring of a related female both to decrease competition for the female's offspring and for increased foraging area due to a decrease in territorial defense by the victimized mother. Supporters of the theory that prairie dogs are communal breeders state that another reason for this type of infanticide is so that the female can get a possible helper. With their own offspring gone, the victimized mother may help raise the young of other females.