Female Agassiz’s desert tortoise activity at a wind energy facility in southern California: The influence

We compared spring-summer activity of adult female Agassiz’s Desert Tortoises (Gopherus aga-ssizii) among three consecutive years (1997, 1998, and 1999) that differed dramatically in winter rainfall and annual plant production at a wind energy facility in the Sonoran Desert of southern California. Winter rainfall was approximately 71%, 190%, and 17 % of the long-term average (Octo-ber-March = 114 mm) for this area in water years (WY) 1997, 1998, and 1999, respectively. The sub-stantial precipitation caused by an El Niño Sou-thern Oscillation (ENSO) event in WY 1998 pro-duced a generous annual food plant supply (138.2 g dry biomass/m2) in the spring. Primary production of winter annuals during below aver-age rainfall years (WY 1997 and WY 1999) was reduced to 98.3 and 0.2 g/m2, respectively. Mean rates of movement and mean body condition in-dices (mass/length) did not differ significantly among the years. The drought year following ENSO (WY 1999) was statistically similar to ENSO in every other measured value, while WY 1997 (end of a two year drought) was statistically dif-ferent from ENSO using activity area, minimum number of burrows used, and percentage of non-movements. Our data suggest that female G. agassizii activity can be influenced by environ-mental conditions in previous years