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RELATIVE BRAIN SIZE AND FEEDING STRATEGIES IN THE CHIROPTERA
Author(s) -
Eisenberg John F.,
Wilson Don E.
Publication year - 1978
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1978.tb04627.x
Subject(s) - national museum of natural history , national park , wildlife , natural history , fish <actinopterygii> , biology , institution , national museum , national laboratory , environmental ethics , library science , archaeology , zoology , history , ecology , fishery , political science , law , engineering , philosophy , engineering physics , computer science
Pirlot and Stephan (1970) demonstrated that the relative brain size varied greatly when nine families of Chiroptera were compared. Some 51 species were studied and an average index of encephalization for each family was calculated. They pointed out that the Pteropidae, Desmodontinae, and Noctilionidae had the highest indices of encephalization for their sample. Stephan and Pirlot (1970) expanded the above observations by comparing the relative volumes of 11 brain structures for 18 species drawn from eight families. These volumes were then compared with equivalent volumes derived for a series of "basal" insectivores (Suncus, Sorex, Tenrec, Hemicentetes). Although specific brain structures evolve at different rates within each family with some structures declining in relative size and others increasing, a generalized correlation of brain size with feeding habits could be made. The relative size of the neocortex showed a strong positive correlation with the degree of encephalization. This correlation in turn could be related to dietary specializations. They proposed that the Noctilionidae, Desmodontinae, and Pteropidae showed the highest development of the neocortex, but were broadly overlapped by certain species of the Phyllostomatidae. The order Chiroptera includes two distinct lineages which have been separated since the Eocene: the Pteropidae or Megachiroptera and the Microchiroptera. The ancestral Pteropidae may have attained the capacity for flight after diverging from a flightless common ancestor which in turn gave rise to the ancestral microchiropteran. The species of the microchiropteran family Phyllostomatidae are rather unified morphologically, but their origins are somewhat obscure (Smith, 1976). No doubt they separated from ancestral microchiropterans before the Oligocene and radiated in the Neotropics without competition from the Megachiroptera. In their exploitation of feeding niches in the Neotropics through adaptive radiation, the phyllostomatid bats exhibit the principle of complementarity (Darlington, 1957) in that they parallel the niche subdivision seen in the radiation of the Megachiroptera in the Palaeotropics. We measured the cranial capacities of 225 species of bats from 14 families including all families and genera previously studied by Stephan and Pirlot (1970). We wished to confirm their conclusions about encephalization and refine their first order correlation with dietary specializations. We did not use actual brain weights but estimated brain volume from a measurement of cranial capacity, using lead shot and volumetric correction constants.