North Dakota Nature Notes
Prairie dogs are active all winter but their activity intensifies in March
March is a busy month for prairie dogs. North Dakota’s prairie dogs are active all winter, and in March that activity increases.
Black-tailed prairie dogs, the kind found in the Dakotas, do not hibernate. They continue their usual activities during the winter but are above ground for less time than in the summer, generally emerging from their burrows not until 10 AM and retiring by 3 PM. During very cold weather, prairie dogs may not come up at all and remain below ground for several days. Their burrows stay warmer than the cold prairie above, averaging 41 to 50 degrees Fahrenheit throughout the season.
Black-tailed prairie dogs are able to remain active during the winter because they are very efficient at metabolizing stored body fat, an energy source that helps sustain them through the cold season. Prairie dogs accumulate fat reserves during summer months when they can eat grasses, forbs and even insects. In the winter, fewer foods are available, forcing prairie dogs to eat less nutritious plant roots, thistles and prickly pear cactus pads.
Come March (earlier, in some locations), longer days trigger the start of the prairie dogs’ mating season. Prairie dogs chase off other dogs that trespass onto their family’s territory (or coterie), and during the mating season they become very aggressive toward intruders. Fights between competing males are not uncommon. The dominant male dog seeks to prevent any others from mating with the three or four females that are in heat in his coterie. Males call to females by making a “chirk” call similar, but slower, to the predator warning call familiar to prairie dog watchers.
Males also help females build their underground nests and dog watchers can see paired animals gathering nesting material and carrying it into their burrows. Mating takes place underground and is rarely seen.
Females are pregnant for about 35 days and give birth to three to five young (sometimes as many as eight) that are born naked with their eyes shut. Newborn prairie dogs are tiny, only two to three inches long, but they grow quickly, nearly doubling in size by their second week. Their eyes open at five weeks and a week later the new dogs are ready to emerge from the burrow. They are weaned soon afterward.
Not all newborn prairie dogs make it to above ground. Up to 39 percent of all prairie dog litters may be killed by other prairie dogs – not by their parents but by related dogs within the same coterie. Both males and females kill and cannibalize these newborns. Why this infanticide occurs is unknown; it could be a result of nutritional needs of the killers or a response to population pressures. For this reason, prairie dog nursery chambers have only one entrance from the underground network of tunnels, making it easier for the parents within to defend their young against intruders.
Those young prairie dogs that do survive their first year typically live for another two to four years. They mature and are able to breed in their second year but only the females remain in the coterie – young males are chased away by older males unwilling to share their mates. A good place to watch black-tailed prairie dogs year ‘round in North Dakota is Theodore Roosevelt National Park.