Climate Change and the North American Red Squirrel

The American red squirrel, also known as the pine squirrel and the chickaree, is a medium-sized tree squirrel that inhabits much of the northern and eastern regions of North America, including most of Canada and the northeastern United States. Its diet consists largely of the seeds of conifer cones, although they also enjoy many other foods including conifer buds and needles, mushrooms, flowers, berries, and sometimes birds' eggs. Unlike the scatter-hoarding gray squirrel, the red squirrel stores food, primarily conifer cones, in a central location to provide food for the winter. The accumulated uneaten scraps from these food stores left behind by a red squirrel create a "midden" or trash pile that can measure as much as a meter in diameter.

Compared to the eastern gray squirrel, the American red squirrel is smaller but more aggressive in defending its territory. It is less likely to be seen in suburban yards and city parks, preferring wilderness areas more isolated from human activity. Also in contrast to the gray squirrel, the red squirrel will sometimes nest underground during the winter, although like other tree squirrels the red squirrel does not hibernate.

A recent study has examined the effects of global climate change on the feeding and mating habits of red squirrels over a period of several generations.

The authors of the study tagged and monitored the females of a population of approximately 325 red squirrels in the Yukon territory of Canada, from 1989-2001. During that period, the researchers kept track of the weather in the area, and monitored the feeding and reproductive habits of the squirrels. During the time of the study the mean spring temperature increased by 2 degrees Celsius. The production of the spruce cones that provide the squirrels' most important food source increased by 35 percent during the same period. And at the same time, the squirrels' breeding took place 18 days earlier by the end of the study period, advancing by about 6 days each generation.

The findings of this study seem on the surface to suggest that global warming has been beneficial to this population of squirrels. However, it is impossible to know what the long-term effects could be, both to the red squirrels and to other plant and animal species, and to the ecosystem as a whole. What seems to me most important about this research is the demonstration that climate change is having very real and demonstrable effects on the environment that has repercussions for the behavior of species. Much more long-term research is needed in this area.