Evaluating Monitoring Strategies and Habitat for Tortoises in the Sonoran Desert

Persistent Link:
http://hdl.handle.net/10150/193429
Title:
Evaluating Monitoring Strategies and Habitat for Tortoises in the Sonoran Desert
Author:
Zylstra, Erin R.
Issue Date:
2008
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Effective conservation requires efficient population monitoring, which can be challenging for rare species like the desert tortoise (Gopherus agassizii). We compared two alternative survey methods that can be used to monitor tortoise populations: distance sampling and site occupancy estimation. In 2005 and 2006 combined, we surveyed 120 1-km transects to estimate density and 40 3-ha plots with five presence-“absence” surveys to estimate occupancy of Sonoran desert tortoises in two mountain ranges in southern Arizona. We found that monitoring programs based on an occupancy framework were more efficient and had greater power to detect linear trends. We also found that habitat use by Sonoran desert tortoises was influenced most by slope and aspect, contrasting with patterns observed in the Mojave Desert. Given its efficiency, power, and ability to gauge changes in distribution while accounting for variation in detectability, occupancy offers a promising alternative for long-term monitoring of Sonoran desert tortoise populations.
Type:
text; Electronic Thesis
Keywords:
desert tortoise; detection probability; Gopherus agassizii; habitat; monitoring; site occupancy
Degree Name:
M.S.
Degree Level:
masters
Degree Program:
Natural Resources; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Steidl, Robert J.
Committee Chair:
Steidl, Robert J.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleEvaluating Monitoring Strategies and Habitat for Tortoises in the Sonoran Deserten_US
dc.creatorZylstra, Erin R.en_US
dc.contributor.authorZylstra, Erin R.en_US
dc.date.issued2008en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractEffective conservation requires efficient population monitoring, which can be challenging for rare species like the desert tortoise (Gopherus agassizii). We compared two alternative survey methods that can be used to monitor tortoise populations: distance sampling and site occupancy estimation. In 2005 and 2006 combined, we surveyed 120 1-km transects to estimate density and 40 3-ha plots with five presence-“absence” surveys to estimate occupancy of Sonoran desert tortoises in two mountain ranges in southern Arizona. We found that monitoring programs based on an occupancy framework were more efficient and had greater power to detect linear trends. We also found that habitat use by Sonoran desert tortoises was influenced most by slope and aspect, contrasting with patterns observed in the Mojave Desert. Given its efficiency, power, and ability to gauge changes in distribution while accounting for variation in detectability, occupancy offers a promising alternative for long-term monitoring of Sonoran desert tortoise populations.en_US
dc.typetexten_US
dc.typeElectronic Thesisen_US
dc.subjectdesert tortoiseen_US
dc.subjectdetection probabilityen_US
dc.subjectGopherus agassiziien_US
dc.subjecthabitaten_US
dc.subjectmonitoringen_US
dc.subjectsite occupancyen_US
thesis.degree.nameM.S.en_US
thesis.degree.levelmastersen_US
thesis.degree.disciplineNatural Resourcesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorSteidl, Robert J.en_US
dc.contributor.chairSteidl, Robert J.en_US
dc.contributor.committeememberSchwalbe, Cecil R.en_US
dc.contributor.committeememberShaw, Williamen_US
dc.identifier.proquest10034en_US
dc.identifier.oclc659749979en_US
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