It's not possible to grow cacao without insects -- that's logical. After all, they ensure that the flowers are pollinated and that the valuable cacao fruits, a sought-after material for the food industry, develop. Studies in Indonesia had shown in the past that birds and bats also contribute to increasing crop yields. However, a new study published in the journal Proceedings of the Royal Society B shows now how large this contribution is. The study is the result of new findings from scientists from the universities of Würzburg, Göttingen and Vienna and the Alliance of Bioversity International and CIAT. The biologists responsible for the study are Justine Vansynghel, researcher at the Department of Animal Ecology and Tropical Biology at the Julius-Maximilians-Universität Würzburg (JMU), and Carolina Ocampo-Ariza, researcher at the Agroecology Department at the University of Göttingen. Sometimes pest, sometimes pest controller Animals such as birds, bats and insects, but also rodents, are important for cacao agro forestry," Justine Vansynghel explains. On the one hand, they can increase yields, for example by pollinating the plants or acting as "biological pest control agents." On the other hand, they can reduce yields, for example when squirrels steal the valuable seeds and prefer to eat them themselves. It was known that various animal species affect cacao cultivation and crop yield. "Until now, however, it was not clear how the individual contributions of all these animals interact and how other factors, such as the proximity of the cultivated area to a forest or its level of shading, can influence these contributions," Carolina Ocampo-Ariza says. As part of their study, which has now been published, the two researchers therefore quantified the animals' combined contributions to crop yield and explored how distance to the forest and shading affect productivity.