A new UC Davis study details for the first time the nesting needs of northern flying squirrels in the Sierra Nevada, supplying important information for managers of old-growth forests there.

One particularly important discovery suggests that the 30-yard to 100-yard creekside buffer typically recommended for logged areas may be too small.

Recent work by a UC Davis graduate student indicates that northern flying squirrels may be a keystone species in the forest web of life. The squirrels eat and store truffles (a sort of underground mushroom) and in the process help spread their spores throughout the forest. Truffles are central to forest health because they are mycorrhizae -- fungi that integrate with tree roots in a mutually beneficial (symbiotic) relationship that helps both truffle and tree get nutrients from the environment.

Additionally, the squirrels are a principal food of the California subspecies of the northern spotted owl, proposed for endangered species status.

In the study, a team of UC Davis scientists monitored 27 northern flying squirrels over the course of three nesting seasons. They found that squirrels nested most often in big fir trees -- ones that were significantly larger than any others nearby -- that were within 100 to 150 yards of year-round creeks.

"This project provides insights into the needs of a species that may be central to the ecology of Sierra Nevada forests, with important management implications," said wildlife biology professor Douglas Kelt.

The northern flying squirrel (Glaucomys sabrinus) is one of only two mammals in North America that glide on furry "wings" stretched between their forelimbs and hindlimbs. (The other glider is the southern flying squirrel; the only mammals that truly fly are bats.)

The lead researcher on the study was Marc Meyer, who was Kelt's doctoral student at the time and now is a research ecologist with the U.S. Forest Service in Davis. His co-authors were Kelt and Malcolm North, who is a research plant ecologist with the U.S. Department of Agriculture's Sierra Nevada Research Center, located in Davis, and a research associate with the UC Davis Department of Plant Sciences.

The study was published in the April 2005 issue of the Journal of Mammology. It was supported by funding from the U.S. Forest Service, a unit of the USDA.