Factors affecting the thermal environment of Agassiz’s Desert Tortoise (Gopherus agassizii) cover sites in the Central Mojave Desert during periods of temperature extremes

Journal of Herpetology
By: , and 

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Abstract

Agassiz's Desert Tortoises (Gopherus agassizii) spend >95% of their lives underground in cover sites that serve as thermal buffers from temperatures, which can fluctuate >40°C on a daily and seasonal basis. We monitored temperatures at 30 active tortoise cover sites within the Soda Mountains, San Bernardino County, California, from February 2004 to September 2006. Cover sites varied in type and structural characteristics, including opening height and width, soil cover depth over the opening, aspect, tunnel length, and surficial geology. We focused our analyses on periods of extreme temperature: in summer, between July 1 and September 1, and winter, between November 1 and February 15. With the use of multivariate regression tree analyses, we found cover-site temperatures were influenced largely by tunnel length and subsequently opening width and soil cover. Linear regression models further showed that increasing tunnel length increased temperature stability and dampened seasonal temperature extremes. Climate change models predict increased warming for southwestern North America. Cover sites that buffer temperature extremes and fluctuations will become increasingly important for survival of tortoises. In planning future translocation projects and conservation efforts, decision makers should consider habitats with terrain and underlying substrate that sustain cover sites with long tunnels and expanded openings for tortoises living under temperature extremes similar to those described here or as projected in the future.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Factors affecting the thermal environment of Agassiz’s Desert Tortoise (Gopherus agassizii) cover sites in the Central Mojave Desert during periods of temperature extremes
Series title Journal of Herpetology
DOI 10.1670/13-080
Volume 49
Issue 3
Year Published 2015
Language English
Publisher The Society for the Study of Amphibians and Reptiles
Contributing office(s) Western Ecological Research Center
Description 10 p.
First page 405
Last page 414
Country United States
State California
Other Geospatial Central Mojave desert
Online Only (Y/N) N
Additional Online Files (Y/N) N