Document: DAV-3-66-28

Implications of changes in hibernation behavior by three high-altitude mammal species, and correlations with climate change.

ARMITAGE, K.B.* ^1,2, D.W.INOUYE ^2,3 and B.BARR ²

Univ. Kansas, Lawrence, KS 66045 ¹
Rocky Mtn. Biological Laboratory, Crested Butte, CO 81224 ²
Univ. of Maryland, College Park, MD 20742 ³

Abstract:
Climate change has had measurable effects on a variety of plants and animals, including changes in the timing of initiation of the growing season and migration, and even species' distributions. The first evidence of an effect on hibernation behavior of a mammal (yellow-bellied marmot, Marmota flaviventris) was recently published; marmots are emerging 38 days earlier than they did 23 years ago, perhaps in response to warmer nocturnal air temperatures in April. We present evidence of changes in hibernation since 1974 by two other mammals, golden-mantled ground squirrel (Spermophilus lateralis) and least chipmunk (Eutamius minimus). Data on the first spring sighting since 1974 at the Rocky Mountain Biological Laboratory (2,800 m) indicate that, in contrast to earlier emergence by marmots, these two smaller species are emerging later. Spermophilus on average emerge 27 days later than they did in 1974, and Eutamius 12 days later. For Spermophilus, snowpack depth on 30 April is a statistically significant predictor of the date of first sighting (r² = 0.301, p = 0.005), as is the mean daily maximum temperature in April. For Eutamius these same variables are also significant, but not as good predictors; for snowpack depth on 22 April r² = 0.195, p = 0.03, and for mean daily maximum temperature (MDMT) in April r² = 0.195, p = 0.04. For both species, mean daily minimum temperatures in April are not significant predictors, leading to the hypothesis that both species are emerging through the snowpack in late April, and using mid-day air temperature as a cue for whether to return to hibernation or remain above ground. Although there is too much scatter for a statistically significant correlation, MDMT in April has tended to decrease (by 1.9 C, 1974-79). This decline has been extraordinary since 1987 (r² = 0.660, p = 0.001); over this shorter time period MDMT (at the Crested Butte NOAA weather station) has declined 5.7 C. During the study period plant phenology has not changed significantly, so that the interval between first sighting and the availability of food resources such as leaves, flowers and seeds has become shorter for ground squirrels and chipmunks (in contrast to marmots, for which it is increasing). If the date on which they enter hibernation does not change, these species face longer and longer periods of hibernation (already about 8 months).

Keywords: climate change; hibernation; Spermophilus; Eutamius; Marmota; ground squirrel; chipmunk; marmot; RMBL

This abstract is being presented at: 11:30 AM in session:
Oral Session #43: Plant Community Responses to Climate Change.