THE INFLUENCE OF CLIMATE-CHANGE ON THE BODY-MASS OF WOODRATS NEOTOMA IN AN ARID REGION OF NEW-MEXICO, USA

Earth system scientists have recently concluded that anthropogenic ind uced climate change is detectable. Because many aspects of an organism 's ecology and evolution are influenced by environmental temperature, this suggests temperature mediated changes may be already occurring in natural ecosystems. Using archived mammal trapping and meteorological data, we investigated local changes in climate over the past 8 yr at the Sevilleta National wildlife Refuge in an arid region of New Mexico to determine i) if environmental conditions had altered, ii) if mean body mass of woodrats had changed over this time period, and iii) if t he answers to i) and ii) were positive, were the results correlated? B ody mass was chosen because it is highly sensitive to temperature and many crucial ecological and evolutionary parameters are affected by it . Our results indicate that winter temperature measures (average cold and minimum), and maximum summer temperature have changed significantl y over the past 8 yr. Summer and winter temperatures have both increas ed by ca 2.5 to 3 degrees C. men compared to long-term means, all year s have had significantly warmer than average minimum temperatures. Mea n body mass of woodrat populations has also changed significantly over the past 8 yr, and the changes are negatively correlated with both wi nter and summer temperatures. We predict that additional climatic warm ing will lead to further decreases in the mean body mass of woodrats a t the Sevilleta NWR. Since many important ecological parameters are ti ghtly linked with body mass (e.g. fecundity, dietary strategy, home ra nge, extinction rates, energetic requirements. predation risk, etc.). our results suggest that further climate change may lead to profound a lterations in woodrat life history and indirectly, on the dynamics and structure of the entire community. This is in addition to any direct effect temperature may have on other plants and animals.