title: Using motion-sensor camera technology to infer seasonal activity and thermal niche of the desert tortoise (Gopherus agassizii).
abstract: 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.
authors.affiliation: Department of Forestry, University of Kentucky, Lexington, KY 40546, USA. Electronic address: mickey.agha@uky.edu.
authors.forename: Mickey
authors.initials: M
authors.lastname: Agha
authors.affiliation: Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address: ben.augustine@uky.edu.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Augustine
authors.affiliation: US Geological Survey, Southwest Biological Science Center, MS-9394, Flagstaff, AZ 86001, USA. Electronic address: jeffrey_lovich@usgs.gov.
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Lovich
authors.affiliation: US Army Construction Engineering Research Laboratory, P.O. Box 9005, Champaign, IL 61826-9005, USA. Electronic address: David.Delaney@usace.army.mil.
authors.forename: David
authors.initials: D
authors.lastname: Delaney
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA. Electronic address: lizardrps@gmail.com.
authors.forename: Barry
authors.initials: B
authors.lastname: Sinervo
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY 40546, USA. Electronic address: mason.murphy@uky.edu.
authors.forename: Mason O
authors.initials: MO
authors.lastname: Murphy
authors.affiliation: Tennessee Aquarium Conservation Institute, 201 Chestnut Street, Chattanooga, TN 37402, USA. Electronic address: jre@tnaqua.org.
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Ennen
authors.affiliation: Warner College of Natural Resources, Colorado State University, Fort Collins, CO 80523, USA. Electronic address: jessiebriggs13@gmail.com.
authors.forename: Jessica R
authors.initials: JR
authors.lastname: Briggs
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA. Electronic address: rdcooper408@gmail.com.
authors.forename: Robert
authors.initials: R
authors.lastname: Cooper
authors.affiliation: Department of Forestry, University of Kentucky, Lexington, KY 40546, USA. Electronic address: steven.price@uky.edu.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Price
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D003889:Desert Climate; D005260:Female; D008297:Male; D009043:Motor Activity; D012621:Seasons; D013696:Temperature; D014426:Turtles / Q000502:physiology*
keywords: Climate change; Desert southwest; Normal mixture models; Resource Selection Functions; Wildlife management