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USGS · 1008564

Encephalization quotients and life-history traits in the Sirenia

T. J. O'Shea·R.L. Reep
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Abstract

Relative brain size in the Sirenia is unusually small. Encephalization quotients are 0.27 for Florida manatees ( Trichechus manatus ) and 0.38 for dugongs ( Dugong dugon ). Estimates for Steller's sea cow ( Hydrodamalis gigas ) range from 0.12 to 0.19. These values are among the lowest known for Recent mammals, and seemingly have changed little since the Eocene. A body plan specialized for the aquatic environment does not account for low encephalization quotients; values are substantially less than predicted based on cetacean or pinniped allometry. Life-history, ecological, and behavioral traits of the Sirenia are typical of relatively large-brained species. Low quality food and a low metabolic rate, however, are characteristic of the Sirenia and other small-brained mammals. Acting through prolonged postnatal growth, selection also likely favored large body size in the Sirenia without a correlated increase in brain size.

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BibTeXRIS

T. J. O'Shea, R.L. Reep. 1990. Encephalization quotients and life-history traits in the Sirenia. https://doi.org/10.2307/1381792

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