Do Male Apes Suffer From Mid-Life Crises?

A large study involving male Common chimpanzees and Orang-utans in zoos suggests that their keepers rate these apes as showing a 'U'-shaped function in their 'happiness' or well-being, generally being most content when young and old (http://www.dailymail.co.uk/sciencetech/article-2235329/Chimpanzees-orang-utans-suffer-mid-life-crises-New-research-claims-ape-cousins-happiness-dips-middle-age.html?ito=feeds-newsxml). It is a bit difficult to work out why these animals would show the human equivalent of the mid-life crisis (chasing young women and buying a sport's car?) but it could simply reflect the fact that more male apes reach mid and old age in zoos than is the case in the wild. I suspect that the age profile of these animals in nature and in zoos is very different. Breeding is often very restricted. Another difference, is that it is impossible for zoo-based animals to leave their group even for limited periods.