Habitat Impoverishment and Egg Predation by Alouatta caraya
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Species response to habitat loss, fragmentation, or alteration ranges from intolerance and extinction to tolerance and population growth. An ability to increase trophic niche breadth is likely to play a key role in promoting tolerance to habitat change in many species. Howlers (Alouatta spp.) are good examples of these tolerant species. Researchers have related their capacity to thrive well in disturbed habitats to their ability to exploit an eclectic vegetarian diet. Despite >50,000 h of observation of habituated free-ranging groups throughout the distribution of Alouatta, no case of intentional ingestion of animal matter has ever been observed. Here, we report an unexpected trophic niche broadening for free-ranging groups of black-and-gold howlers (Alouatta caraya) living in small (≤2 ha) impoverished habitat islands in the State of Rio Grande do Sul, Brazil. We studied 3 isolated social groups (15–17, 12–14, and 5 individuals) and observed 1 of them preying on birds’ nests. We recorded 19 events of egg-eating during 2274 h of observation in 1 group and 2 suspected cases in another. Our findings highlight the dietary flexibility that characterize howlers and contrast with the widely held view that they observe a strictly vegetarian diet.
KeywordsAlouatta caraya habitat deterioration herbivory to omnivory increase in trophic niche breadth nest predation
We thank the owners of the study sites for permission and logistical support (ECB, Osório family; ENSC, Mr. Mauro Estácio Azambuja da Silva; BX, Mr. Sérgio Kneuhaus), the Brazilian National Research Council (CNPq, Proc. no. 306090/2006-6), and the World Wildlife Fund (WWF-US) for financial support; our colleagues T. Grant, E. A. Jeckel Neto, V. M. Silva, and M. R. Bogo for help in different steps of this study; and 2 anonymous reviewers for critical comments.
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