There might be fewer bonobos left in the wild than we thought. For the last 40 years, scientists have estimated the abundance of endangered bonobos by counting the numbers of sleeping nests left by the apes in forests of the Congo Basin. Now, researchers from the Max Planck Institute of Animal Behavior report that the rate of sleeping nest 'decay' has lengthened by 17 days over the last 15 years as a result of declining rainfall in the Congo Basin. The study warns that longer nest decay times have serious implications for ape conservation: failure to account for these changes would lead to overestimating population density by up to 60 percent, subsequently jeopardizing conservation of these endangered great apes in the wild.