THE BABIES ARE OUT! During the month of May, the adult and yearling prairie dogs were occupied with fattening up, and John and the Squad kept keen eyes on regular behaviors but especially signs of infanticide. While infanticide (the killing of babies) is less common among Gunnison's prairie dogs than it is among black-tailed prairie dogs (see our page on INFANTICIDE for more), a number of infanticide events were witnessed last year at our previous study site in Redondo Meadows. Here at the new site in the Valles Grande, the team did not witness a single infanticide in May or see any aboveground signs of an infanticide having occurred.
Now that the year's offspring are beginning to emerge (which happens 5-6 weeks after birth), they are exploring their surroundings and experimentally eating grasses and greens. We now have the opportunity to compare litter counts from our ultrasounds to litter counts upon emergence. By comparing these counts, we can determine how accurate we are on our ultrasounds, and how many juveniles failed to emerge where they were expected. Despite inevitable losses pre-emergence, once the babies start coming aboveground in early June it becomes a boom of curious, cute, but vulnerable little prairie dogs.
For the next several weeks, John and the crew will be busy trapping and tagging the new offspring in order to add them to the study population. Each new individual is given unique eartags, and biological measurements and tissue samples are taken. Juveniles are marked by litter, and each litter is marked identical or similar to the mother. For example, female RR3's babies are all marked with the same marking (Ring around the Rear 3 - RR3). On our datasheets, we label each baby as an RR3x. Female babies receive one additional marking - a cap of dye on their head or tails to differentiate them from their brothers.
To trap baby prairie dogs, we bring out our smaller single-door Tomahawk live traps (which are more sensitive to the lower weight of a juvenile) and we surround nursery burrows with traps, so that litters cannot intermingle before they are all marked. By catching and marking whole litters as quickly as possible, we can be certain that in the majority of cases we have marked each juvenile as belonging to the correct mother. Sometimes nursery burrows that are connected underground make this endeavor harder, but we watch carefully where mothers go to bed at night to make sure we are identifying their babies correctly. In the end, we will have over a hundred little prairie dogs with black dye on them, frolicking about as they play, forage, and explore their surroundings.
The occurrence of infanticides drops dramatically once juveniles have emerged in June, but infanticides may still occur for a number of reasons, especially if a baby wanders too far from his or her home burrow - in these cases, an adult or yearling male will sometimes attack the baby, and if the baby cannot get away a killing can occur. The far bigger threat, however, comes from predators both terrestrial and avian. Coyotes, badgers, weasels, and birds of prey will quickly come to notice the little prairie dogs that have emerged from underground, and attempted predations may increase during this time. Depending on the colony to sound the alarm is especially critical for the babies, as they are still learning how to be vigilant while aboveground.