FEEDING BEHAVIOUR

Capuchins like junk food but remain cautious about it

In the Parque Nacional de Brasilia capuchins became smart-aleck. They learned that tourists could give them delicacies. It is much more easier than looking for food in the forest, especially during the dry season when fruit is scarce. But how does the human presence affect capuchins’ diet and behavior toward novel food? Well, thanks to the visitors they taste foods they would have never eaten in the forest, but they still remain cautious.

In the Parque Nacional de Brasilia there are some groups of wild capuchins, that are used to visitors’ presence. Capuchin monkeys habitually eat the the food that visitors give them, take food from the garbage or steal it from the visitors. In collaboration with the Parque and the Brasilia University, we investigated the interactions between capuchin monkeys and visitors in the Park, by means of interviews to the visitors and direct observations of the behaviour of capuchins and visitors. We also examined whether seasonal differences in the availability of wild food (that monkeys find in the forest), and whether the presence and abundance of human food (brought by visitors to the Park) affected capuchins’ activity budgets and diet.

In general, we found that capuchins living in the Park, spent less time foraging for wild foods than other groups living in similar habitats. Moreover, the capuchins living in the Park relied more on human food during the dry season, when pulpy fruits were less available, than in the wet season. Nearly 80% of the interactions observed involved the presence of food. There were some differences emerged between what the visitors reported in the interviews and what we observed. In the interviews most respondents (76.1%) reported that interactions were started by monkeys, while the analysis of direct interactions showed that 47.3% were initiated by visitors and only 39.6% by capuchins. Moreover, 83.9% of the visitors affirmed they didn’t feed capuchins, while 70.2% of them reported having seen other visitors feeding them.

These findings confirm other studies conducted on different monkey species, that demonstrate that access to human food decreases in relation to the time spent foraging for wild food and to the home range size. Moreover these findings demonstrate that capuchins are able to modify their diet, to exploit alternative food sources and to change their activity budget, in response to new food opportunities and to seasonal food availability. On the basis of the results listed above, it would be useful to establish an educational program that provides information regarding capuchins' behavior; underlining the consequences that feeding them could have on their ways of behaving and their interaction with visitors.

Video. In the National Park of Brasilia (Agua Mineral), monkeys usually eat human food from garbage cans. Despite that giving food to animals is forbidden, visitors of the park interact with monkeys giving them food. Video by Gloria Sabbatini.

In another study, we investigated the response of capuchins living in the Parque toward novel food. In fact given their daily exposure to human foods, we expected them to be more explorative toward novel food compared with capuchins that are not habituated used to visitors. However, since the safety and palatability of potential foods is to be learnt we expected capuchins to remain cautious about eating novel food, as it was reported for wild and captive populations. We gave capuchins familiar and novel foods on a platform, observing their behavior. Latency to contact the platform, and ingest food did not differ between novel and familiar stimuli. However, capuchins were less interested in manipulating the novel food than the familiar one, and consequently they ate only small pieces of the former while and they ingested big quantities of the latter. These results show that, despite capuchins used to humans’ presence become more explorative towards novelty, they still remain cautious about unfamiliar food, thus demonstrating that neophilia and neophobia are motivationally independent responses.

Wild capuchins use complex processing techniques to avoid caustic chemicals

Complex and flexible food processing enlarges the range of exploitable foods. Only a few primate species crack open encased food by using percussive tools and/or avoid physical contact with irritant compounds by removing the structures containing them.

Sirianni and Visalberghi discovered that the population of bearded capuchin monkeys (Sapajus libidinosus) living in Fazenda Boa Vista (www.ethocebus.net) accesses the nutritious kernel of cashew fruit (Anacardium spp.) avoiding the caustic chemical protecting it (present in the green mesocarp) (a, in the figure), or in the brown mesocarp when the fruit is dry.

feeding

Figure. The kidney-shaped fresh cashew nut is hanging below the bell-shaped pseudofruit (a). An adult male rubbing a fresh cashew nut (b). An adult female extracting the kernel with the index finger (c). Fresh nut with the hole (produced by rubbing) from which the kernel has been extracted; the caustic chemicals are contained inside the green mesocarp (d).

To access the very nutritious kernel capuchins use different processing strategies. When the fruit is not dry they rub it on a surface (b, in the figure) until a hole is produced and then use their index finger to extract the seed (c, in the figure). Later, when the fruit is dry they crack the shell with a tool and then extract the seed.

At both levels of ripeness, capuchins can easily break the fruit with their teeth. But in order to avoid the caustic liquid (when the nut is fresh) or the caustic resin (when the nut is dry) capuchins do not do use teeth. Infants and juveniles are by far less skilled than adults. This same set of processing strategies appears to be absent in other capuchin populations, making cashew nuts processing an excellent candidate for social transmission.