{"pk":5384,"title":"An Unparalleled Sexual Dimorphism of Sperm Whale Encephalization","subtitle":null,"abstract":"The sperm whale \nPhyseter macrocephalus\n (Linnaeus, 1758) is the largest toothed whales and possesses the highest absolute values for brain weight on the planet (together with the killer whale \nOrcinus orca\n). Former calculations of the encephalization quotient (EQ), which is used to compare brain size of different mammalian species, showed that the sperm whale brain is smaller than expected for its body mass. However, the data reported in the literature and formerly used to calculate the sperm whale EQ suffered from a potential bias due to the tendency to measure mostly larger males of this extreme sexually dimorphic species. Accordingly, we found that the brains of female sperm whales are close to the absolute weight range of the males, but, given the much lower body mass of females, their EQ results more than double of what reported before for the whole species, and is thus nearly into the primate range (female EQ = 1.28, male EQ = 0.56). This sexual dimorphism is unique among mammals. Female sperm whales live in large families in which social interactions and inter-individual communication are essential, while adult males live solitarily. Thus the particular sex-specific behavior of SWs may have led to a maternally-driven social evolution, and eventually contributed to achieve female EQ values (but not male EQs) among the highest ever calculated for mammals with respect to their large body mass.","language":"en","license":{"name":"Creative Commons Attribution 4.0","short_name":"CC BY 4.0","text":"Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.\r\n\r\nNo additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.","url":"https://creativecommons.org/licenses/by/4.0"},"keywords":[{"word":"Encephalization Quotient"},{"word":"sperm whale"},{"word":"brain size"},{"word":"sexual dimorphism in the brain"},{"word":"social evolution"}],"section":"Research Article","is_remote":true,"remote_url":"https://escholarship.org/uc/item/4jv59569","frozenauthors":[{"first_name":"Bruno","middle_name":"","last_name":"Cozzi","name_suffix":"","institution":"Department of Comparative Biomedicine and Food Science, University of Padova","department":"None"},{"first_name":"Sandro","middle_name":"","last_name":"Mazzariol","name_suffix":"","institution":"Department of Comparative Biomedicine and Food Science, University of Padova","department":"None"},{"first_name":"Michela","middle_name":"","last_name":"Podestà","name_suffix":"","institution":"Museum of Natural History of Milan","department":"None"},{"first_name":"Alessandro","middle_name":"","last_name":"Zotti","name_suffix":"","institution":"Department of Animal Medicine, Production and Health, University of Padova","department":"None"},{"first_name":"Stefan","middle_name":"","last_name":"Huggenberger","name_suffix":"","institution":", Department II of Anatomy (Neuroanatomy), University of Cologne","department":"None"}],"date_submitted":"2016-06-27T09:49:33Z","date_accepted":"2016-06-27T09:49:33Z","date_published":"2016-12-16T08:00:00Z","render_galley":null,"galleys":[{"label":"","type":"","path":"https://journalpub.escholarship.org/uclapsych_ijcp/article/5384/galley/3238/download/"}]}