Dean Christopher in Discover Magazine:
4 Although famously monogamous, female Adélie penguins slip away from their mates occasionally to couple with unattached males. They exact a fee (pdf) for such a dalliance—stones to bolster their nests—not unlike certain people.
5 Some talented penguin teasers can get a gift even without putting out. Again, not unlike certain people.
6 Barbary macaques have a distinctive way to get their mates to make a sperm donation: yelling. If the female does not shout, the male almost never climaxes.
7 How do we know this? German primatologist Dana Pfefferle watched a group of macaques, counting the females’ yells and the males’ pelvic thrusts. She says this work is “quite weird, but it’s science.”
8 Here in the US of A, that kind of stuff ends up on YouTube.