, Volume 173, Issue 1, pp 107–116 | Cite as

Spatial and temporal variation in survival of a rare reptile: a 22-year study of Sonoran desert tortoises

  • Erin R. ZylstraEmail author
  • Robert J. Steidl
  • Cristina A. Jones
  • Roy C. Averill-Murray
Population ecology - Original research


Although many species may be vulnerable to changes in climate, forecasting species-level responses can be challenging given the array of physiological, behavioral, and demographic attributes that might be affected. One strategy to improve forecasts is to evaluate how species responded to climatic variation in the past. We used 22 years of capture-recapture data for Sonoran desert tortoises (Gopherus morafkai) collected from 15 locations across their geographic range in Arizona to evaluate how environmental factors affected spatial and temporal variation in survival. Although rates of annual survival were generally high (\( \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{\Upphi } \) = 0.92), survival of adults decreased with drought severity, especially in portions of their range that were most arid and nearest to cities. In three locations where large numbers of carcasses from marked tortoises were recovered, survival of adults was markedly lower during periods of severe drought (\( \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{\Upphi } \) = 0.77–0.81) compared to all other periods (\( \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\frown}$}}{\Upphi } \) = 0.93–0.98). Assuming continued levels of dependency of humans on fossil fuels, survival of adult tortoises is predicted to decrease by an average of 3 % during 2035–2060 relative to survival during 1987–2008 in 14 of the 15 populations we studied. This decrease could reduce persistence of tortoise populations, especially in arid portions of their range. Temporal and spatial variation in drought conditions are important determinants of survival in adult desert tortoises.


Capture-recapture Climate change Demography Drought Gopherus morafkai 



This project was funded primarily by the Arizona Game and Fish Department and the Bureau of Land Management. We thank A. Owens and T. Jones, who provided logistical support at the Arizona Game and Fish Department; A. P. Woodman, who led field efforts in most years of the study and provided information regarding survey methods; and countless others for their efforts in the field and other support over the 22-year study period. S. Campbell and F. Janzen provided valuable comments on earlier drafts of the manuscript. The findings and conclusions provided in this article are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service.

Supplementary material

442_2012_2464_MOESM1_ESM.pdf (234 kb)
Supplementary material 1 (PDF 233 kb)


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Erin R. Zylstra
    • 1
    Email author
  • Robert J. Steidl
    • 1
  • Cristina A. Jones
    • 2
  • Roy C. Averill-Murray
    • 3
  1. 1.School of Natural Resources and the EnvironmentUniversity of ArizonaTucsonUSA
  2. 2.Arizona Game and Fish DepartmentNongame BranchPhoenixUSA
  3. 3.Desert Tortoise Recovery OfficeU.S. Fish and Wildlife ServiceRenoUSA

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