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Orientation of giant tortoises, Geochelone gigantea (Schweigger) while grazing on Aldabra Atoll

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dc.contributor.author Frazier, J. en
dc.date.accessioned 2019-05-29T02:03:37Z
dc.date.available 2019-05-29T02:03:37Z
dc.date.issued 1988
dc.identifier.citation Frazier, J. 1988. "<a href="https://brill.com/abstract/journals/amre/9/1/article-p27_4.xml">Orientation of giant tortoises, Geochelone gigantea (Schweigger) while grazing on Aldabra Atoll</a>." <em>Amphibia-Reptilia</em>. 9 (1):27&ndash;31. <a href="https://doi.org/10.1163/156853888X00170">https://doi.org/10.1163/156853888X00170</a> en
dc.identifier.issn 0173-5373
dc.identifier.uri https://hdl.handle.net/10088/97782
dc.description.abstract The Aldabran giant tortoise is one of the few testudines that feeds in dense herds, and in so doing the animals frequently exhibit a conspicuous orientation away from the sun. This orientation is most marked when ambient temperature is high, and it breaks down when the tortoises are shielded from direct sunlight. It was previously hypothesized that negative heliotaxis is related to thermoregulation-to reduce heat inflow to the exposed anterior appendages and instead expose the protected posterior of the shell. There has been no test of the thermoregulatory function, and pilot experiments indicate that orientation away form the sun occurs to reduce direct glare into the tortoise&#39;s eyes. The glare of the sun seems to interfere with accurately oriented biting movements and reduce feeding efficiency. Speed and intensity of reaction to solar glare is inversely related to the animal&#39;s body size. The possibility of a thermoregulatory component to the away-from-the-sun orientation cannot be discounted, but it must be investigated directly. en
dc.relation.ispartof Amphibia-Reptilia en
dc.title Orientation of giant tortoises, Geochelone gigantea (Schweigger) while grazing on Aldabra Atoll en
dc.type Journal Article en
dc.identifier.srbnumber 151269
dc.identifier.doi 10.1163/156853888X00170
rft.jtitle Amphibia-Reptilia
rft.volume 9
rft.issue 1
rft.spage 27
rft.epage 31
dc.description.SIUnit NH-Vertebrate Zoology en
dc.description.SIUnit NMNH en
dc.description.SIUnit Peer-reviewed en
dc.citation.spage 27
dc.citation.epage 31
dc.relation.url https://brill.com/abstract/journals/amre/9/1/article-p27_4.xml


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