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

16 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

Publisher Copyright:
© 2015 Elsevier Ltd.


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

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • General Agricultural and Biological Sciences
  • Developmental Biology


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