Relationships are equally diverse, including long term pair bonds, in both between-sex and same-sex couples, one-off copulation, strictly monogamous and non-monogamous relationships, polygamy, polyandry and group orgies.
Families and child rearing are diverse. There’s male and female pederasty, incest, and likewise butch/femme female relationships. There are single parents, between- sex parent couples, and same-sex parent couples, who may acquire kids by finding sperm donors (if female), surrogate mothers (if male), or by adoption. (In some species, male couples turn out to be more successful parents than between-sex parents, just like research suggests for humans).
As in humans, there are a range of “purposes” of sex, from the obvious one of simple pleasure, to asserting domination and status, to procreation. Bonobos even use it as a form of social peacekeeping. There’s also a negative side: rape and sexual violence also occur. I confess I’ve not yet come across the wildlife equivalent of consensual S/M, but I wouldn’t be surprised if I did. Just about everything else is there, including transgender (routine in some species), transvestism, and the use of sex toys.
The use and manufacture of tools by primates is considered an important example of cultural behaviour in animals, and a forerunner of the activities that are so widespread among human beings.although many different forms and functions are evident in animal tool use, these examples show that nonreproductive sexual activities are part of the overall behavioral pattern: the primate capacity for object manipulation extends seamlessly into the sexual sphere.
Similar types of activities occur among people too, of course, and sexual implements of various sorts have a long and distinguished history in human culture. …Examples have been found from as far back as the Palaeolithic through to medieval times – including some Biblical references – as well as in the ongoing traditions of many indigenous peoples throughout the world.
At Seed Magazine:
Roughgarden, Joan: Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People
Sommer, Volker and Vasey, Paul: Homosexual Behaviour in Animals: An Evolutionary Perspective