Prairie dogs exhibit no paternal care, and the rearing of offspring falls entirely on the mother. With no time to waste in the spring, impregnated prairie dogs begin to exhibit maternal behavior within days after mating. It's important that they choose and maintain a nursery burrow for their upcoming litters, who will be born after four weeks of gestation. Once they have mated, mothers begin gathering nesting material (mostly dry grass) to bring into their burrows, and will increase their gathering behavior markedly for the period of their pregnancy.
Prairie dog gestation varies slightly among the species but is approximately 26-30 days long, at which time the altricial offspring are born underground, where they will remain for 5-6 weeks feeding on mother's milk. In contrast to precocial offspring, altricial babies are generally hairless, are unable to walk, and are entirely helpless. Anywhere between 1 and 7 babies (with an average around 4-5) are born per litter. The weaning period is a dangerous time for these juveniles, and is when most infanticides will occur. The mother, therefore, is extremely protective of her nursery burrow, and will often be standoffish toward other prairie dogs approaching. She will continue to bring nesting material (NM) on a semi-regular basis, and toward the end of the weaning period she may include fresh grass in her NM, likely for the juveniles to begin testing it.
During gestation and the nursery preparation phase, female prairie dogs become hostile toward each other, engaging in territorial disputes over potential nursery burrows, and sometimes even contact fighting. The defensiveness also serves as protection against infanticidal females, who make up the majority of juvenile killers.
At approximately 5 1/2 weeks after birth, prairie dog juveniles are finally ready to emerge from their nursery burrows. Synchronization among females means offspring emerge at approximately the same time in the summer: late May to early June. Juveniles are timid when they first emerge, but as they become more aware of their surroundings over a few days, they begin to venture farther from their nursery burrow, interacting with other litters, exploring their surroundings, and watching and learning from yearlings and adults around them.
Juveniles are not yet fully weaned upon first emergence but are ready to forage on grass and greens on their own. Occasionally the growing juveniles will continue to nurse, though mothers will spend the majority of their days foraging away from the home burrow; now that their babies are old enough to put up a fight, the threat to them from infanticidal conspecifics is greatly diminished. This does not mean mothers no longer protect their offspring, however, as they are never too far away and will come home throughout the day to check on their babies.
Hostilities among lactating females generally comes to an end when litters begin to emerge, as the risk of infanticide drops considerably now the juveniles are large enough to defend themselves. Occasionally, though, disagreements still arise between females, especially those who appear to show more protectiveness over their nursery burrow and offspring. These disagreements are usually brief, however.
Sometimes a nursery burrow becomes compromised, and the mother may feel it is no longer safe or ideal to keep her offspring there. Perhaps an infanticidal event has occurred nearby, or a predator has threatened her burrow, or there has been human disturbance. At any time after birth, and even after juveniles have emerged, a mother may feel the need to transfer her offspring to a new burrow. The first step she takes is usually preparing the new burrow by bringing nesting material into it, either newly collected or grabbed from the compromised nursery. When she is satisfied, she will begin the transfer. If the babies are very small, they will be carried one-by-one in their mother's mouth; if the babies are too large to carry or otherwise old enough to run, the mother will give them a unique (and quiet) vocal signal, often accompanied by kisses, and will lead her offspring to follow her to the new burrow - sometimes one-at-a-time and sometimes multiple in a line. Whether leading or carrying, it may take anywhere from several minutes to half a day for a mother to complete a transfer, as she is often interrupted by the impulse to forage.
We don't know if prairie dogs are capable of counting but it does not appear that they count their offspring during transfers. Rather, to assure no one has been left behind, the mother will frequently come back to the compromised burrow to check underground and around the entrance for any offspring that may remain. She will do this until she is satisfied she has left no one behind.
Communal nursing has been observed in the black-tailed, Utah, and more rarely in Gunnison’s prairie dog species. Upon first emergence, because juveniles are not fully weaned they are still supplementing with milk. Emergent juveniles will sometimes nurse from their mothers aboveground, and we will sometimes even see lactating mothers suckling nondescendant juveniles – that is, allowing babies who are not their offspring to nurse from them. This phenomenon has been observed across many taxa of colonial animals, and is called communal nursing.
Foster Mothers and Offspring
The proximate (immediate) and ultimate (evolutionary) reasons for communal nursing are especially apparent among prairie dogs. After the juveniles have emerged and begin to explore their surroundings and intermingle with nearby litters, it becomes more difficult for mothers to immediately differentiate between their own offspring and the offspring of other mothers in their coterie or clan. By this period, juveniles are demanding less milk from their mothers, and have expanded their diets, so the cost to the mother of nursing babies that are not her own is not arduous. Furthermore, as litters intermingle, groupings of babies become larger, and the larger a group of babies, the more protection each baby has against predators – this benefit far outweighs any cost to a mother who, while suckling her own offspring, might offer milk to a nondescendant baby who is mingling with her own. In essence, this mother is fostering care to this baby, and we call them foster offspring and foster mother.
Being both philopatric and matrilocal (see COLONIALITY), prairie dogs live in coteries or clans of genetically related females. Juveniles intermingling after emergence are genetically related, as their mothers are sisters, cousins, aunts, and daughters to each other. And so when a foster mother suckles a foster offspring, she is furthering the survival of genetically related kin. Ultimately speaking, this is a benefit to the bloodline and the colony as a whole. Communal nursing does not occur outside of clans – that is, lactating mothers will only nurse offspring in their family group. Because these emergent juveniles are not demanding large amounts of milk by this stage, the benefit of nursing a nondescendant (but still blood related) baby is clearly advantageous to the colony's survival as a whole.
Juveniles require and utilize large amounts of energy as they develop physiologically, mentally, and socially. When they first emerge from their burrows, they are shaky on their feet, easily startled, and naive to many social parameters. The first order of business is foraging independently, testing grasses and forbs, clumps of dirt, rocks, flowers, and even burrow markers for edibility. Sometimes a juvenile will even attempt to snatch a food item from a sibling out of curiosity.
While they forage, juveniles will spend a lot of time watching for dangers, gradually becoming more bold but remaining quite vigilant throughout their first summer. As they become more familiar with clan members and prairie dogs around them, they will begin to practice communicating - kissing, touching, and sometimes attempting vocalizations.
As extremely social animals, prairie dogs learn a lot from each other, and juveniles are often observed watching their mothers and older prairie dogs going about their daily business, foraging, working their mounds, digging, and interacting with one another. As they grow, juveniles wander farther and farther from their nursery burrows, offering play that was earlier reserved for siblings to newly met offspring across the clan territory.
Play is critical for juveniles across taxa, and prairie dogs are no exception. Play behavior typically involves chasing, somersaulting, wrestling, and mounting - all of which will play important roles in their interactions as adults, both friendly and hostile. A juvenile's role is to grow and learn, which at face value may seem lighthearted and carefree as they play, stumble, and explore their surroundings, but effectually serves the sole purpose of honing the tools they will need to survive and socialize as a colonial animal, a prey animal - an animal in the wild.