Raiding parties of rampaging chimpanzees are changing farming practices in Africa, research has shown.
Hundreds of thousands of subsistence farmers and their families are losing edible crops to the apes each year, say scientists.
Many farmers have admitted defeat and reduced cultivation of staples such as maize and beans which are highly prized by humans and chimps.
In addition, being forced to guard their crops at night is leaving farm workers more exposed to insects that spread disease, such as malaria-carrying mosquitoes.
The conflict is said to be harming the nutrition of communities living near the edge of tropical forests.
Shane McGuinness, from Trinity College Dublin in the Irish Republic, who led the interview-based study in western Rwanda, said: "Unsurprisingly, non-human primates are quite fond of the food crops we grow. The chimps are basically imposing a 'natural tax' on farmers growing crops near the nutrient-rich soils of the forest."
A marauding band of 19 chimps living in Rwanda's Gishwati Forest had been identified as one group of raiders, but there were likely to be more.
Chimpanzees are an internationally protected species.
Action to reduce their impact must be carefully balanced with conservation of their habitat while protecting the livelihoods of local people, said the scientists.
"Using local knowledge and appropriate scientific know-how to solve these human-wildlife conflicts is imperative to implementing lasting and robust conflict mitigation," said McGuinness.
The research is published in the journal Human Dimensions of Wildlife.