14 DAY TRIAL // Usually, young, sick or old animals are more vulnerable to predators. 33 years of studying prairie dogs in Utah confirmed to John Hoogland, of the University of Maryland Center for Environmental Science in Cambridge, this statement. But in 2005 this changed. Utah prairie dogs (Cynomys parvidens), once abundant, were food supply for many prairie predators, like badgers, coyotes, and golden eagles.
But disease, poisoning, and habitat destruction have swiped out the prairie dogs to the edge of extinction. Hoogland and his team have been assessing the impact of predation on prairie dog survival for 11 years. They have observed a 200-member colony in Bryce Canyon National Park, where the team spent each spring in 4-meter-high observation towers all day long.
After marking the individuals, the team tracked their status and behaviors via binoculars and person-to-person radio communication.
Predators seemed a minor menace. From 1995 through 2004, they killed only 10 adult prairie dogs in their prime. And from 1988, just 22 individuals. 2005 was different. Over the 17-day mating season, the team saw red fox and northern goshawk pick off 10 healthy, breeding males. "I didn't have a clue about this level of predation and susceptibility," says Hoogland. Four pregnant females fell pray to the foxes in the following month. Then goshawks took nine juveniles.
Hoogland believes his team's presence may have scared away the predators in previous years. "For some reason, the fox and goshawks in 2005 were oblivious to humans and therefore were more likely to target prairie dogs," Hoogland says.
Prairie dogs live in colonies and warn each other of predators by screaming, so they can dive into burrows for protection.
"The males were so obsessed with sex they couldn't watch for predators," Hoogland says.
If predators were behaving more daring with people around "What really happens when we're not there?" asks Hoogland, worried about the destiny of the endangered prairie dogs. "This is by far the best documentation and quantification of selective predation," says Jerry Wolff, a behavioral ecologist at St. Cloud State University in Minnesota.
"Documenting patterns of predations, says Hoogland, will help wildlife managers develop plans to conserve Utah prairie dogs and other endangered species."