Literaturdatenbank
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Mann, G. K. H., O'Riain, M. J., & Hofmeyr, M. D. (2006). Shaping up to fight: sexual selection influences body shape and size in the fighting tortoise (chersina angulata). Journal of zoology, 269, 373–379.
Added by: Admin (14 Aug 2008 20:31:53 UTC) |
| Resource type: Journal Article BibTeX citation key: Mann2006 View all bibliographic details  |
Categories: General Keywords: Chersina, Chersina angulata, Schildkröten = turtles + tortoises, Systematik = taxonomy, Testudinidae, Verhalten = ethology Creators: Hofmeyr, Mann, O'Riain Collection: Journal of zoology |
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| Abstract |
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Testudinidae The angulate tortoise Chersina angulata is unique among South African tortoises in having a single unpaired gular (extension of the ventral plastron) that is used to ram and overturn rival conspecifics. This behaviour has earned it the reputation of a 'fighting tortoise', and in this paper we test the hypothesis that the morphology of this tortoise is a result of intrasexual selection. Research was carried out on the tortoise population of Dassen Island in September 2004. Tortoises were captured and processed (body mass and five morphological measurements) in situ in the field. A total of 144 males and 99 females were sampled. Males were significantly larger than females for all body parameters measured. Males had significantly longer gulars (F=17.783, P<0.005, n=242) and greater posterior carapace width (F=143.664, P<0.005, n=242) relative to body size than females. A total of 66 male–male interactions was observed in the field. Males that won fights were significantly longer than males that lost fights (t=2.238, P<0.034, n=28) and had significantly greater rear carapace width relative to middle carapace width (F=5.591, P=0.026, n=28). Gular length was found to be irrelevant to fighting success. Tortoises of both sexes were placed upside down to compare righting ability. Males were significantly more successful at righting themselves than females (χ2=5.347, P=0.0208, n=70). It was concluded that posterior carapace width is a more important variable than gular length in determining male fighting success, and it is suggested that, in addition to righting ability, posterior carapace width may well be a trait under sexual selection in male angulate tortoises.
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