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".
Prairie dogs are chiefly herbivorous, though they eat some 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, and buds. Grasses of various species are eaten. 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 Edit
Prairie dogs live mainly at altitudes ranging from 2,000 to 10,000 ft above sea level. The areas where they live can get as warm as 38 °C (100 °F) in the summer and as cold as −37 °C (−35 °F) 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 (Thermoregulation) as they are 5–10 °C during the winter and 15–25 °C 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 5–10 m (16–33 ft) long and 2–3 m (6.6–9.8 ft) below the ground. The entrance holes are generally 10–30 cm (3.9–11.8 in) 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 0.2–0.3 m (7.9–11.8 in) high. Other mounds, known as rim craters, can be as high as 1 m. 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 a meter below the surface. Nursery chambers tend to be deeper, being two to three meters below the surface.
Social organization and spacing Edit
Highly social, prairie dogs live in large colonies or "towns", and collections of prairie dog families that 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" are used to describe 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. There may also be 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 to three adult females and one to two male offspring and one to two female offspring. Females remain in their natal groups for life and are thus 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 to not be related. Two to three groups of females may be controlled by one male. However, among these female groups, there are no friendly relations.
The average prairie dog territory takes up 0.05–1.01 hectares. Territories have well-established borders that coincide with physical barriers such as rocks and trees. The resident male of a territory defends it and agonistic behavior will occur 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 will start staring, make bluff charges, flare their tails, chatter their teeth, and sniff each other's perianal scent glands. When fighting, prairie dogs will bite, kick and ram each other. If their competitor is around their size or smaller, the females will participate in fighting. Otherwise, if a competitor is sighted, the females signal for the resident male.
Reproduction and parenting Edit
Prairie dog copulation occurs in the burrows, and this 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 a set of 2 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 it seems young will sleep in 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 which 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.
Antipredator calls Edit
The prairie dog is well adapted to predators. Using its dichromatic color vision, it can detect predators from a great distance; it then alerts other prairie dogs of the danger with a special, high-pitched call. Constantine Slobodchikoff and others assert that prairie dogs use a sophisticated system of vocal communication to describe specific predators. According to them, prairie dog calls contain specific information as to what the predator is, how big it is and how fast it is approaching. These have been described as a form of grammar. According to Slobodchikoff, these calls, with their individuality in response to a specific predator, imply that prairie dogs have highly developed cognitive abilities. He also writes that prairie dogs have calls for things that are not predators to them. This is cited as evidence that the animals have a very descriptive language and have calls for any potential threat.
Alarm response behavior varies according to the type of predator announced. If the alarm indicates a hawk diving toward the colony, all the prairie dogs in its flight path dive into their holes, while those outside the flight path stand and watch. If the alarm is for a human, all members of the colony immediately rush inside the burrows. For coyotes, the prairie dogs move to the entrance of a burrow and stand outside the entrance, observing the coyote, while those prairie dogs that were inside the burrows will come out to stand and watch as well. For domestic dogs, the response is to observe, standing in place where they were when the alarm was sounded, again with the underground prairie dogs emerging to watch.
There is debate over whether the alarm calling of prairie dogs is selfish or altruistic. It is possible that prairie dogs alert others to the presence of a predator so they can protect themselves. However, it is also possible that the calls are meant to cause confusion and panic in the groups and cause the others to be more conspicuous to the predator than the caller. Studies of black-tailed prairie dogs suggest that alarm-calling is a form of kin selection, as a prairie dog’s call alerts both offspring and nondescended kin, such as cousins, nephews and nieces. Prairie dogs with kin close by called more often than those that did not have kin nearby. In addition, the caller may be trying to make itself more noticeable to the predator. Predators, though, seem to have difficulty determining which prairie dog is making the call due to its "ventriloquistic" nature.
Perhaps the most striking of prairie dog communications is the territorial call or "jump-yip" display of the black-tailed prairie dog. A black-tailed prairie dog will stretch the length of its body vertically and throw its forefeet into the air while making a call. A jump-yip from one prairie dog causes others nearby to do the same.