Black-tailed Prairie Dog, Cynomys ludovicianus
The black-tailed prairie dog (Cynomys ludovicianus) is native to the United States, occurring in the Great Plains to both the border of Canada and Mexico. Its range includes areas in Mexico, but no longer includes Arizona. This species was one of two prairie dog species to be described by Lewis and Clark on their famous expedition. It prefers a habitat within grasslands, but their habitat choices do depend on soil type, rainfall, slope angles, and vegetation cover.
The black-tailed prairie dog can reach an average body length of 14 to 17 inches, and a weight of up to three pounds. It is typically buff or sandy in color, with a paler underbelly and a distinctive black tip at the end of the tail, which can reach a length of up to four inches. It is diurnal and does not hibernate, although it may enter short periods of dormancy and its movements above ground are limited when it is raining or snowing, and if the temperature rises over 100 degrees Fahrenheit.
The black-tailed prairie dog can live in many grass types, including mixed and short grass, desert steppe, and sagebrush steppe types. In the Great Plains, these prairie dogs are often found near riverbeds and creeks. Black-tailed prairie dogs found in the Texas Panhandle will use the slopes around playa lakes to make their homes. In Phillips County, Montana, the prairie dogs were often found near areas influenced by humans, like cattle salting grounds and reservoirs.
The prairie dogs are able to live in areas that have been disturbed for long periods. In adequate habitats, new colonies are rarely formed. Although it does often occur in over grazed areas, it does not have a preference towards them, as forming colonies in those areas becomes difficult due to bad soil. In Charles M. Russell National Wildlife Refuge and Fort Belknap Agency, Montana, 150 of 154 prairie dog colonies located were found in areas with cattle tracks and roads.
Although good soil is preferred to construct burrows, the black-tailed prairie dog does not have a range that is limited due to soil type. Its chosen habitat depends on the effects of the soil on water and vegetation. It can be found in many soil types including sandy soils, deep soils, and sometimes gravel. Soil types that are not easily collapsible are often used more than softer soils. These prairie dogs will mix soil that is deeper into the soil within the burrows in order to create a better texture, and urine, feces, and remains are often used as well. Soil type, as well as geographical barriers, group conditions, and taller vegetation affect home ranges and the number of prairie dogs in each range.
The burrows that the black-tailed prairie dog constructs are vital to protecting the animals from outside elements and predators, and also provide areas for birthing nests. These burrows are used for many generations and help to maintain the social structure with the groups. The nests inside the burrows are made of soft and dried grasses, which both males and females will gather throughout the year. A typical colony will contain between twenty and fifty-seven burrows per acre.
There are three types of entrances into these burrows, and it is thought that these features prevent flooding. They include entrances covered by vegetation, dome mounds, and rimmed crater mounds. Rimmed crater mounds appear to be cone shaped and are made of uprooted vegetation, humus, litter, and mineral soil, while dome mounds are made of loosely packed soil and bear forbs. Burrows with vegetation surrounding them that are three to five inches tall are preferred because these areas help the prairie dogs maintain communication and watch for predators. The presence of cattle near the burrows is thought to increase group numbers due to decreased predation.
The black-tailed prairie dog can live in colonies of up to thousands of individuals, but larger groups tend to be separated into two or more smaller groups, depending on the landscape in the colony’s habitat. These smaller groups are typically divided into coteries, close groups of individuals. The coteries contain territorial harem groups that are aggressive to outsiders. The size of each coterie will increase after mating season due to young being born.
Although the mating season may vary depending on the latitude and location of each colony, the typical mating season for the black-tailed prairie dog occurs between late February and April. Females are only able to breed one day throughout this period.
The average age for sexual maturity is two years, but if food and living space is abundant, yearlings may breed early. In younger colonies that have more space available, reproductive success increased. In Wind Cave National Park, a young colony produced and weaned 88 percent of its young, while an older colony only successfully reproduced 41 percent of young, although the average is 47 percent.
After a pregnancy of up to 34 days, the young prairie dogs are born underground, although the size of each litter when born is not known. Above ground, litters of three to four pups have been recorded. Although growth in pups has not been recorded in the wild, in captivity, pups are able to open their eyes at thirty days of age, but will remain in the burrow for up to seven weeks. Maturity is reached at fifteen weeks of age. Female individuals tend to remain in the natal group, while males leave between 12 to 14 months after being weaned.
According to Constantine Slobodchikoff, and others, the black-tailed prairie dog uses a system of highly advanced vocalizations to communicate. It is thought that these noises contain detailed information including the type of predator spotted, how quickly it is moving, and even how close it is to the colony. Slobodchikoff asserts that these vocalizations can be compared to grammar, and that the cognitive abilities of the prairie dogs are advanced.
Whether these advanced calls are for the good of the entire group or for the good of the prairie dog calling. Prairie dogs have shown tendencies that alert other members of the group to danger, but these alerts also result in confusion, possibly giving the alerting individual more safety than other members. Studies have shown that these calls are more frequent while close family members are present, including cousins, but decrease when kin are not present. Despite this seemingly selfless defense, predators cannot easily locate prairie dog calls, and the prairie dogs alerted to the danger did not run, instead choosing to stand on mounds to locate the predator. Aside from warning vocalizations, the most distinct call of the black-tailed prairie dog is the territorial “jump-yip” call, where one prairie dog will leap into the air and yip, and this is followed by nearby prairie dogs.
The diet of the black-tailed prairie dog is considered opportunistic. Depending upon availability, these prairie dogs will feed on many types of plants that vary in growth stage. If plant food is damaged by over grazing or herbicides, the prairie dogs will quickly search for another type of food. Grasses comprise nearly 75 percent of its diet, although forbs are consumed as well. Its diet will vary during each season. Because water is not often available in prairie habitats, most water is consumed from plants like the plains prickly pear cactus. Other food consumed includes insects and fresh or old American bison scat.
The average lifespan of the black-tailed prairie dog in the wild is unknown, but males over three years of age have a high mortality rate while females tend to live longer. According to Hoogland and other experts, females may live up to seven years while males only live up to five years. The mortality rate is so high due to many factors including habitat loss, disease, infanticide, shooting, poisoning, and trapping. The most common reasons for death are infanticide and predation. Deaths can increase when colonies or smaller coterie groups disperse.
The worst disease that the black-tailed prairie dog can contract is known as sylvatic plague, a disease caused by the bacterium Yersinia pestis. Once a colony is infected, death occurs within days and entire colonies and can be decimated. Common predators of this prairie dog include coyotes, bobcats, bald eagles, and red-tailed hawks.
The black-tailed prairie dog is considered a vital species to the environment around it, because it enhances the biotic and abiotic features of its habitat. In some areas, it is considered to be an “ecosystem engineers” because it increases the diversity of invertebrates, vegetation, vertebrates by foraging, burrowing, and because it is an important source of food for its predators.
The diversity of creatures located in the same area as the black-tailed prairie dog increased when the population densities of prairie dogs were high. There are four endangered species that are associated with this prairie dog, including the burrowing owl, swift fox, black-footed ferret, and the mountain plover. Grazing animals that prefer to reside on grasslands inhabited by these prairie dogs include the red deer and the American bison.
Although this species has a wide range, it has become fragmented, leaving only two percent of the black-tailed prairie dog’s original range available for habitation. Because of this fragmenting, the diversity of plants and animals associated with the prairie dog is decreasing. Efforts to eliminate this prairie dog as a pest have also decreased its population numbers. Although it is not known whether roads are a positive or negative factor in population numbers, they do act as a barrier to the spread of sylvatic disease, along with rivers, lakes, and streams.
Experts are divided on whether the black-tailed prairie dog is a competitor to grazing species within its range or not. In many areas, this prairie dog aided the grasses around them in growing, in turn benefiting livestock. However, in Cimarron National Grassland, located in Kansas, some differences were recorded in the growth of vegetation. In other areas, studies showed that livestock did not prefer grassland inhabited by the black-tailed prairie dog. It is also unclear whether grazing species and the prairie dogs compete for food.
It has been found that some variances that occur in plant composition that aid livestock by increasing the growth of common grazing plants like the tolerant needleleaf sedge plant and the scarlet globemallow. One study conducted on a shortgrass prairie near Fort Collins, Colorado, grasses that were grazed upon by the black-tailed prairie dog showed increased nutrition. In this area, forbs and buffalo grass also increased.
Until 2003 when the practice was outlawed, the black-tailed prairie dog was the most commonly captured wild prairie dog to be used in the pet trade. Any prairie dogs that were previously owned before the ban were allowed to remain in their homes. In 2008, this ban was lifted.
Farmers often exterminate the black-tailed prairie dog because they are considered pests to crops. Because of this and the sylvatic plague, its population numbers have considerably decreased. In 2008, all eight colonies infected by this disease perished. Studies conducted over ten states in 2004 showed that this prairie dog held 1,842,000 acres across its range, and because of this, it was removed from the Endangered Species Act Candidate Species List in August of that year. Currently, the black-tailed prairie dog appears on the IUCN Red List with a conservation status of “Least Concern”.
Image Caption: A Black-tailed Prairie Dog photographed at Wichita Mountain Wildlife Refuge. Notice that it has an ear tag. Credit: LeonardoWeiss/Wikipedia (CC BY 3.0)