SNOWBIRD, UTAH--Trying to cope with a changing world is unsettling--it's enough to drive even animals back to bed. A new study shows that chipmunks and ground squirrels in the Rocky Mountains of Colorado are hibernating much longer than they did a quarter-century ago. Researchers think their long snooze may reflect a changing climate.
The finding, based on data from the Rocky Mountain Biological Laboratory in Gothic, Colorado, seems at odds with another study by the same researchers. In February in the Proceedings of the National Academy of Sciences, University of Maryland, College Park, ecologist David Inouye and his colleagues concluded that yellow-bellied marmots (Marmota flaviventris) in the Rockies are emerging from hibernation 38 days earlier than they were 23 years ago. The team attributed this change to a 1.4-degree-Celsius increase in April's average minimum temperature recorded over the same period.
But that's apparently not true for all Rocky Mountain rodents. On 8 August at the annual meeting of the Ecological Society of America, Inouye showed that golden-mantled ground squirrels (Spermophilus lateralis) and least chipmunks (Eutamias minimus) get up 26 and 11 days later, respectively, than 25 years ago. Sleeping late may cause problems for the chipmunks and squirrels, Inouye says; these animals store food in their burrows so they can occasionally wake up and snack during winter. "If they don't have enough stored, they have the potential to starve," Inouye says.
Although he can't prove it, Inouye suspects that the species are taking their cues from different sources. The marmots likely react to air temperature, he says, whereas the other two rodents may monitor the snow pack over their burrows--which has on average thickened over the past decades, because winter snowfall has increased.
"I'm fascinated by the differences in the extension or reduction of the time spent in hibernation," says O. J. Reichman, a mammalogist at the University of California, Santa Barbara. "It shows that global warming might cause organisms to become disconnected in some way from their resources--the plants come out on their own schedule, and the animals come out on a different schedule."