Masturbation is also a 'Darwinian puzzle', a trait that at first glance seems to present a fitness disadvantage, e.g. wasting time, energy, other resources, and opportunities. We find links with mating system that suggest ways that masturbation may have evolved.
www.theguardian.com/science/2026...
Study finds activity is not harmful or caused by stress of captivity – and is in fact more common in wild birds
