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Prey electivity and optimal diet in visually oriented anurans

Grant number: 12/21051-0
Support Opportunities:Scholarships in Brazil - Scientific Initiation
Effective date (Start): December 01, 2012
Effective date (End): November 30, 2013
Field of knowledge:Biological Sciences - Zoology - Animal Behavior
Principal Investigator:Luis Felipe de Toledo Ramos Pereira
Grantee:Rafael Pereira da Ponte
Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Bufonidae can be considered "ant-specialist" (i.e., specialized ant predator). On the other hand, some authors classify them as generalists. Ranidae, however, are considered to be generalist predators. The difference between these two classifications is relative to the ability to choose prey types. According to the optimal foraging hypothesis, prey can be ranked in terms of energy/handling time ratio. This theory predicts that the predator tends to maximize their rate of energy intake consuming preferably prey of the top of this ranking, those that offer the most energy at the lowest hunting cost. In order to test this theory for anurans, we will use 3 anuran species as models: Rhinella icterica, Rhinella schneideri (Bufonidae) and Lithobates catesbeianus (Ranidae). We collected 3 R. icterica and 8 R. schneideri males nearby Unicamp, Campinas, and 30 L. catesbeianus juvenile acquired from a frog farm. For each individual it was offered different prey categories, in pairs, performing the following combinations: 1) small prey, 2) large prey, 3) small prey + large prey. The chosen prey species were: (1) workers of Atta sexdens, (2) soldiers of A. sexdens, (3) Nauphoeta cinerea and (4) Blaberus sp. The experiments were recorded enabling us to obtain information such as the prey choosed by the anuran, the most active and the bigger prey available. The results show that visualy oriented anurans have the hability to choose prey according to a scale, beign movement the first filter (choosing prey that are moving) and size the second filter (preferring the bigger prey) and that this selectivity is inate, at least in L. catesbeianus. The movement must affect prey visualization. Given that size and not prey type (roach or ant) was the only variable subjected to choice, we sugest that Bufonidae from Rhinella genera are not ant-specialist, as reported. Lithobates catesbeianus didn't show preference for any prey type, wich corroborates it's classification as generalist. (AU)

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