Predation risk and the community organization of montane ground squirrels and a phylogenetic test of the association between diurnal activity and gregarious behavior in mammals.

Persistent Link:
http://hdl.handle.net/10150/185454
Title:
Predation risk and the community organization of montane ground squirrels and a phylogenetic test of the association between diurnal activity and gregarious behavior in mammals.
Author:
Smith, Rosemary Josephine.
Issue Date:
1991
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:
Predation risk strongly influences the ecology and evolution of animal behaviors. However, anti-predator responses differ among species. Tradeoffs between anti-predator abilities and foraging efficiencies across habitats can promote the coexistence of ecologically similar species. In general, larger animals may better exploit riskier habitats; smaller animals, resources at low densities. I studied two montane ground squirrels Spermophilus lateralis and Tamias minimus in Colorado. Using food trays, I determined that the smaller T. minimus foraged more efficiently near meadow edges and was competitively superior to S. lateralis there. In contrast, S. lateralis had no preference for either edge or far habitat, but was competitively superior to T. minimus farther from the edge. I predicted, correctly, the exclusion of S. lateralis from meadows with primarily edge habitat. I proposed three alternatives to explain the observed patterns of habitat use: satiation, travel cost, or perceived predation risk. In a series of manipulations of energetic costs, protective cover, and predators, I eliminated all but the predation risk hypothesis. S. lateralis perceives less risk farther from the edge of the meadow than T. minimus. Faster harvesting and running speeds might decrease perceived predation risk. S. lateralis and T. minimus both experienced diminishing returns while foraging in food trays. Due to a higher encounter rate, S. lateralis harvested seeds significantly faster than T. minimus. S. lateralis also ran faster than T. minimus (3.14 m/s and 2.13 m/s, respectively). Gregarious animals may detect predators before solitary ones. I suggest that due to differences between sensory modes, this advantage occrues only to animals using vision. Thus, I predicted that gregariousness as a predator detection strategy should evolve only in diurnal animals. To test this, I mapped diurnal activity and gregarious behavior onto a phylogeny of eutherian mammals, and than calculated their degree of association. I found strong support for my prediction. This pattern may occur in other mobile animals. The data also suggest an association between larger body size and open habitat use among diurnal, gregarious organisms, paralleling a result from Colorado ground squirrels.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic; Animal behavior; Animal ecology.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Ecology and Evolutionary Biology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Rosenzweig, Michael L.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titlePredation risk and the community organization of montane ground squirrels and a phylogenetic test of the association between diurnal activity and gregarious behavior in mammals.en_US
dc.creatorSmith, Rosemary Josephine.en_US
dc.contributor.authorSmith, Rosemary Josephine.en_US
dc.date.issued1991en_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.abstractPredation risk strongly influences the ecology and evolution of animal behaviors. However, anti-predator responses differ among species. Tradeoffs between anti-predator abilities and foraging efficiencies across habitats can promote the coexistence of ecologically similar species. In general, larger animals may better exploit riskier habitats; smaller animals, resources at low densities. I studied two montane ground squirrels Spermophilus lateralis and Tamias minimus in Colorado. Using food trays, I determined that the smaller T. minimus foraged more efficiently near meadow edges and was competitively superior to S. lateralis there. In contrast, S. lateralis had no preference for either edge or far habitat, but was competitively superior to T. minimus farther from the edge. I predicted, correctly, the exclusion of S. lateralis from meadows with primarily edge habitat. I proposed three alternatives to explain the observed patterns of habitat use: satiation, travel cost, or perceived predation risk. In a series of manipulations of energetic costs, protective cover, and predators, I eliminated all but the predation risk hypothesis. S. lateralis perceives less risk farther from the edge of the meadow than T. minimus. Faster harvesting and running speeds might decrease perceived predation risk. S. lateralis and T. minimus both experienced diminishing returns while foraging in food trays. Due to a higher encounter rate, S. lateralis harvested seeds significantly faster than T. minimus. S. lateralis also ran faster than T. minimus (3.14 m/s and 2.13 m/s, respectively). Gregarious animals may detect predators before solitary ones. I suggest that due to differences between sensory modes, this advantage occrues only to animals using vision. Thus, I predicted that gregariousness as a predator detection strategy should evolve only in diurnal animals. To test this, I mapped diurnal activity and gregarious behavior onto a phylogeny of eutherian mammals, and than calculated their degree of association. I found strong support for my prediction. This pattern may occur in other mobile animals. The data also suggest an association between larger body size and open habitat use among diurnal, gregarious organisms, paralleling a result from Colorado ground squirrels.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academicen_US
dc.subjectAnimal behavioren_US
dc.subjectAnimal ecology.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineEcology and Evolutionary Biologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRosenzweig, Michael L.en_US
dc.contributor.committeememberBronstein, Judith L.en_US
dc.contributor.committeememberVleck, Daviden_US
dc.contributor.committeememberDonoghue, Michael J.en_US
dc.identifier.proquest9124162en_US
dc.identifier.oclc710154293en_US
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