CONICET | Buscador de Institutos y Recursos Humanos

Predators can generate physiological and behavioural responses in prey individuals. Thus, carnivore reintroductions might have profound changes in communities and ecosystems by modifying anti-predatory responses. Combining observational and experimental approaches, we compared the short- and long-term anti-predator responses of capybaras ( Hydrochoerus hydrochaeris ) between a landscape with a high density of predators (Pantanal, Brazil) and a landscape where predators became extinct in the mid-XX century but where a jaguar reintroduction project is in progress (Iberá, Argentina). Generalized linear models were used to test if the presence of natural predators affects capybara behavioural budgets, gregarious behaviour, and the associated physiological stress responses and to test if, in the short term, capybaras increase their vigilance levels after detecting the proximity of a simulated predator (aplayback of jaguar calls). In the Pantanal, capybaras did not show higher levels of vigilance, but they had a higher proportion of foraging than in Iberá. Pantanal groups were smaller and foraged closer to water. The baseline levels of stress hormones tended to be higher in Iberá. In response to simulated stimuli, both populations responded to predator sound cues by increasing vigilance, but Iberá groups also increased vigilance in response to a control sound, suggesting that they were not recognizing the predator stimulus as a greater risk than another stimulus. In areas with predators, capybaras may reduce predation risk by choosing safer areas, where they can spend more time foraging when the predator is not nearby. Vigilance may be only a reactive response to cues of the predator?s proximity. Understanding the capybara?s antipredator responses may help predict the potential effects and the success of jaguar reintroduction in a region where it has been absent for over 80 years.

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