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Encephalization quotients and life-history traits in the Sirenia

January 1, 1990

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.

Publication Year 1990
Title Encephalization quotients and life-history traits in the Sirenia
DOI 10.2307/1381792
Authors T. J. O'Shea, R.L. Reep
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Mammalogy
Index ID 1008564
Record Source USGS Publications Warehouse
USGS Organization Florida Integrated Science Center