Anup Shah / Eastern chimpanzee (Pan troglodytes schweinfurtheii) female 'Eliza' aged 21 years swollen sexual skin. Gombe National Park, Tanzania. October 2012.

Nick Upton / Close up of female captive bred Water vole (Arvicola amphibius) being sexed before release into wild during reintroduction project, Derek Gow Consultancy, near Lifton, Devon, UK, March. Model release...

Yukihiro Fukuda / Japanese squirrel (Sciurus lis) oestrous female grooming, Mount Yatsugatake, Nagano Prefecture, Japan, February. Endemic species.

Jane Burton / Border Collies, pre-mating behaviour, male licking female's vulva

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) Gongzhu licking her vulva and eating afterbirth after giving birth, common postpartum behavior, China Conservation and Research Center for the Giant Panda, Wolong...

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) Gongzhu licking her vulva and eating afterbirth after giving birth, common postpartum behavior, China Conservation and Research Center for the Giant Panda, Wolong...

Katherine Feng / Giant Panda (Ailuropoda melanoleuca) Gongzhu licking her vulva and eating afterbirth after giving birth, common postpartum behavior, China Conservation and Research Center for the Giant Panda, Wolong...