Using motion-sensor camera technology to infer seasonal activity and thermal niche of the desert tortoise (Gopherus agassizii)

Mickey Agha, Benjamin Augustine, Jeffrey E. Lovich, David Delaney, Barry Sinervo, Mason O. Murphy, Joshua R. Ennen, Jessica R. Briggs, Robert Cooper, Steven J. Price

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Understanding the relationships between environmental variables and wildlife activity is an important part of effective management. The desert tortoise (Gopherus agassizii), an imperiled species of arid environments in the southwest US, may have increasingly restricted windows for activity due to current warming trends. In summer 2013, we deployed 48 motion sensor cameras at the entrances of tortoise burrows to investigate the effects of temperature, sex, and day of the year on the activity of desert tortoises. Using generalized estimating equations, we found that the relative probability of activity was associated with temperature (linear and quadratic), sex, and day of the year. Sex effects showed that male tortoises are generally more active than female tortoises. Temperature had a quadratic effect, indicating that tortoise activity was heightened at a range of temperatures. In addition, we found significant support for interactions between sex and day of the year, and sex and temperature as predictors of the probability of activity. Using our models, we were able to estimate air temperatures and times (days and hours) that were associated with maximum activity during the study. Because tortoise activity is constrained by environmental conditions such as temperature, it is increasingly vital to conduct studies on how tortoises vary their activity throughout the Sonoran Desert to better understand the effects of a changing climate.

Original languageEnglish
Pages (from-to)119-126
Number of pages8
JournalJournal of Thermal Biology
StatePublished - Apr 1 2015

Bibliographical note

Funding Information:
Our research at the site has been supported at various times by the California Energy Commission-Public Interest Energy Research Program (Contract # 500-09-020 ), the Bureau of Land Management , the University of Kentucky – Department of Forestry , the California Desert Managers Group , and the Desert Legacy Fund of the California Desert Research Program . Research was conducted under permits from the United States Fish and Wildlife Service, California Department of Fish and Wildlife, and the Bureau of Land Management. We acknowledge B. Todd of the University of California, Davis, R. Huey of the University of Washington, and anonymous peer reviewers for valuable comments and critical reading of earlier versions of the manuscript. Special thanks are given to A. Muth of the Boyd Deep Canyon Desert Research Center of the University of California, Riverside, for providing accommodations during our research. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Publisher Copyright:
© 2015 Elsevier Ltd.


  • Climate change
  • Desert southwest
  • Normal mixture models
  • Resource Selection Functions
  • Wildlife management

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Agricultural and Biological Sciences (all)
  • Developmental Biology


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