Female Agassizs Desert Tortoise Activity at a Wind Energy Facility in Southern California: The Influence of an El Nino Event

Journal Article

Title: Female Agassizs Desert Tortoise Activity at a Wind Energy Facility in Southern California: The Influence of an El Nino Event
Publication Date:
January 13, 2012
Journal: Natural Science
Volume: 4
Issue: 1
Pages: 30-37
Publisher: SciRes.
Stressor:

Document Access

Website: External Link
Attachment: Access File
(177 KB)

Citation

Ennen, J.; Meyer, K.; Lovich, J. (2012). Female Agassizs Desert Tortoise Activity at a Wind Energy Facility in Southern California: The Influence of an El Nino Event. Natural Science, 4(1), 30-37.
Abstract: 

We compared spring-summer activity of adult female Agassiz’s Desert Tortoises (Gopherus agassizii) 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 (October-March = 114 mm) for this area in water years (WY) 1997, 1998, and 1999, respectively. The substantial precipitation caused by an El Niño Southern Oscillation (ENSO) event in WY 1998 produced a generous annual food plant supply (138.2 g dry biomass/m2 ) in the spring. Primary production of winter annuals during below average 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 indices (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 different from ENSO using activity area, minimum number of burrows used, and percentage of nonmovements. Our data suggest that female G. agassizii activity can be influenced by environmental conditions in previous years.

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