"Deer mice just kind of eat everything, they live everywhere and they don't operate with the same complexity in an ecosystem that these other animals take as their roles," said Hadly. She said deer mice are considered a "weedy" species and, like the plants, don't have a strong habitat preference they are generalists that will move in wherever there is an opening. When they replace other small-mammal species, the effects ripple through the ecosystem.
Deer mice don't dig the elaborate deep burrows that gophers do, so the mice don't aerate soils as effectively. They also don't disperse seeds the same way as tree squirrels, the consummate hoarders and forgetters of seeds; each forgotten cache is another colonization opportunity for the trees.
Nor do the nocturnal mice feed predators the same way as ground squirrels or chipmunks, which are active in the daytime. If those species are supplanted by deer mice, the change can affect the food supply of hawks and other creatures that feed in the daytime.
"Even though all of the species survived, small-mammal communities as a whole lost a substantial amount of diversity, which may make them less resilient to future change," Blois said.
And according to Hadly, an extraordinarily rapid change is looming.
"The temperature change over the next hundred years is expected to be greater than the temperature that most of the mammals that are on the landscape have yet witnessed as a species," she said. "The small-mammal community that we have is really resilient, but it is headed toward a perturbation that is bigger than anything it has seen in the last million years."
|Contact: Louis Bergeron|