Sexual orientation and the rewarding brain

When Michael Stipe of the alternative band R.E.M. wrote, ‘sexuality isn’t just black and white, or simple—it is every shade and gradation of the rainbow,’ he very well could have been writing about the animal kingdom at large. Sexual orientation is remarkably fluid—not just in humans, but in all kinds of animals [1]. Female bonobos, for instance, will lie on top of one another rubbing genitalia. Male Adelie penguins from Antarctica routinely take turns copulating with each other. Bottle-nosed dolphins are known to have sex with turtles, sharks and even eels. (Yes, eels). And more recently, female Japanese macaques were observed to ride male sika deer and sexually grind their genitals against