Black-tailed Prairie Dog, Cynomys ludovicianus

Black-tailed Prairie Dog, Cynomys ludovicianus. “Dog” photographed within the confines of the Arizona-Sonora Desert Museum, Tucson, Arizona, February, 2022.

The Black-tailed Prairie Dog, Cynomys ludovicianus, is a member of the Sciuridae family that includes Chipmunks, Marmots, Prairie Dogs and Squirrels. The Sciuridae family is commonly referred to as the Squirrel Family has five subfamilies and has two hundred seventy-nine species that have been placed in fifty-one genera. There are five species of prairie dogs  – the Black-tailed Prairie Dog, Cynomys ludovicianus, the Gunnison’s Prairie Dog, Cynomys gunnisoni, the Mexican Prairie Dog, Cynomys mexicanus, the Utah Prairie Dog, Cynomys parvidens, and the White-tailed Prairie Dog, Cynomys leucurus. The Black-tailed Prairie Dog is known in Mexico as Perrito De Las Praderas de Cola Negra.

Black-tailed Prairie Dogs undergo two molts per year, with slightly different fur coloration in each molt. In general, they are brownish to brownish-red dorsally, with whitish fur on their ventral side. The tips of their tails are sparsely covered by black fur. They have short ears and, compared to their body size, relatively large black eyes. They measure between 35.2 cm (14 inches) and 41.5 cm (16 inches) in length. They are sexually dimorphic with males being larger and heavier than the females, weighing between 850 g (1 lb 14 oz) and 1.675 kg (3 lbs, 11 oz). Conversely, females weigh between 705 g (1 lb 9 oz) and 1.050 kg (2 lbs, 5 oz). Weight varies seasonally, with both sexes reaching their highest weights in the autumn and lowest weights in the winter. 

Black-tailed Prairie Dogs are typically polygynous, with a single male mating with multiple females in a home coterie. However, in some cases, more than one male may be resident in a single, large coterie. In such cases, females within the coterie may mate with both resident males. The first male to copulate with a female will sire more of her offspring than the second male. Additionally, males rarely remain within the same coterie for more than two breeding seasons, thus reducing the possibility that they will mate with their female offspring. Reproduction occurs once per year and the exact timing of mating varies with latitude. Almost all matings occur underground and this likely helps to reduce intermale competition for females. Black-tailed Prairie Dogs have several behaviors associated with mating including frequent entrance of a breeding male and estrus female into the same burrow, self licking of genitals in both males and females, gathering of nesting materials by males, and transport of nesting materials into a burrow. In addition, males possess a unique vocalization that is only associated with mating behaviors. Gestation time ranges from 33 to 38 days and litter sizes range from 1 to 8 young. The young are altricial, being born blind, naked, and mostly helpless. Neonates measure approximately 7.0 cm in length and weigh an average of 15 g. Fur is present by three weeks of age and eyes are open by five weeks of age. The age of weaning varies with litter size, as larger litters must nurse longer than smaller litters. Lactation lasts between 37 and 51 days and the termination of lactation occurs shortly after emergence from the natal burrow. Males are not directly involved in caring for the young, but they help to protect pups within their coterie by defending them against strange males. The bulk of parental care is provided by females, who nurse, groom, and protect their offspring. Interestingly, females in the coterie frequently nurse emergent pups other than their own offspring. By the time juvenile Black-tailed Prairie Dogs emerge from their natal burrows, sexual dimorphism is already established. At emergence, males weigh an average of 147 g and females weigh an average of 141 g. Females remain with their natal coterie for life while males disperse as yearlings to minimize inbreeding. Although most Black-tailed Prairie Dogs reach sexual maturity at two years, some reach maturity earlier or later. Adult females who mate do not always produce litters and successful female reproduction is positively related to female age. Failure to give birth can be the result of failure to conceive, resorption of embryos, and miscarriage during pregnancy. As it is true for most mammals, most black-tailed prairie dogs die young. Some may not emerge from the natal burrow while others are preyed upon by predators. Under natural conditions, females can live up to eight years while males don’t tend to live longer than five years. 

Black-tailed Prairie Dogs are very social and live in colonies, or towns, that may contain hundreds of individuals living within a very restricted area. Throughout the town, they cut down anything growing taller than 15 cm (6.0 inches), which allows them to spot predators easier. Within each town there are individual neighborhoods, or coteries, that are defended aggressively from neighbors. Each coterie is populated by a group of closely related females and one or two territorial males. When multiple males are found in a single coterie, they are often brothers. Within the coterie, all things, such as burrow systems and food supplies, are shared most of the time. The only exception to this is during rearing of young, when females are aggressive toward one another and defend their burrows and nests from other prairie dogs. The system of tunnels, nesting chambers, and mounds within a colony can be quite complex. A coterie may have as many as seventy burrow entrances and cover one-third of a hectare (3,000 square meters). Burrow entrances are typically 10 cm (3.9 inches) to 30 cm (12 inches) in diameter, although tunnels narrow a bit underground. 

Black-tailed Prairie Dogs possess various means of communication, including twelve distinct calls. These include antipredator calls and the conspicuous “jump-yip” call. During this call, an individual stretches to their full height on their hind legs, then throws their forefeet into the air as they call. The “jump-yip” call of one individual seems to excite members of the coterie, as well as members of adjacent coteries, into producing their own “jump-yip” calls.

Black-tailed Prairie Dogs primarily consume leaves, stems, roots of grasses, weeds, and forbs. Although they are primarily herbivores, they sometimes consume grasshoppers, cutworms, bugs, and beetles. They do not need to drink water, rather, their leafy foods provide them with sufficient water to survive. Most individuals forage close to their burrows when possible and only move to distant foraging areas when they are forced to by local shortages. Black-tailed Prairie Dogs are preyed upon by several species including coyotes, badgers, lynx, black-footed ferrets, rattlesnakes, and bullsnakes. In addition, their avian predators include prairie falcons, golden eagles, and a variety of hawk species. When a predator is noticed, individual prairie dogs give alarm calls that warn the others that danger is nearby and to take shelter immediately in a nearby burrow. 

Black-tailed Prairie Dogs may be confused with members of the subgenus Leucrossuromys, which include the Gunnison’s Prairie Dogs, Cynomys gunnisoni), the Utah Prairie Dogs,  Cynomys parvidens, and White-tailed Prairie Dogs, Cynomys leucurus. Members of this subgenus hibernate, have white-to-gray-tipped tails, smaller molars, and possess distinctly different territorial and antipredator vocalizations than the Black-tailed Prairie Dogs. 

From a conservation perspective, the Black-tailed Prairie Dog is currently considered to be of Least Concern with large and widespread populations. There are estimated to be millions of individuals and although populations have declined in many parts of their range, they are not declining fast enough to qualify for listing in a threatened category. Range contractions have occurred in the southwestern portion of their range in Arizona, western New Mexico, and western Texas due to the conversion of grasslands to desert shrublands. In Kansas, Nebraska, Oklahoma, South Dakota and Texas, range contractions have also occurred largely due to habitat destruction and cropland development. Current threats include exotic disease (particularly sylvatic plague), loss of habitat to agriculture and urbanization, habitat fragmentation, and control activities (such as poisoning and shooting) by the government, private organizations, and individuals.