杏吧原创

Some species of spider monkey living in the Amazon rainforest actively choose to eat fruit infested with larval insects, as a way of introducing more protein into their diet.

鈥淪pider monkeys eat mostly fruit pulp,鈥� says of Brazil鈥檚 National Amazon Research Institute. 鈥淭his is generally pretty poor in protein.鈥�

To find out how white-cheeked (Ateles marginatus) and black-faced (Ateles chamek) spider monkeys ensure a healthy mix of nutrients, Cavalcante and his colleagues watched them eating in forest along the Amazon鈥檚 Tapaj贸s river and examined their leftovers.

鈥淪pider monkeys are really messy eaters,鈥� says Cavalcante, so much of their meal ends up dropping to the forest floor. 鈥淐omparing the proportion of larvae-containing fruits on the trees with those lying part-eaten on the ground under feeding trees, meant we could work out [if] they were choosing maggoty fruits, rejecting them as humans would or just eating whatever came their way.鈥�

Of the 23 species of tree that the team collected samples from, 20 had infested fruits. For each of these species, the team compared the prevalence of infested fruit on the tree with that in the fruit bits the monkeys dropped on the ground. In 12 of the species, the monkeys were two to three times more likely to choose infested fruit than if they were selecting at random.

This suggests the monkeys are intentionally eating fruit containing larvae, which can make up one-third of the weight of the pulp. 鈥淚t makes a lot of sense,鈥� says Cavalcante. 鈥淚n the wild, most trees with pulpy fruits will have some that are larval-insect infested, and larvae can be 30 per cent protein.鈥�

For four other species, the monkeys chose at random, while for the final four they avoided infested fruit. 鈥淭hose they avoided are known to become toxic when infested,鈥� says Cavalcante.

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