Animal Sexual Behavior

INTRODUCTION
Talking about human sexuality last year, I was asked whether the different sexual orientations could be found in animals other than humans. Well, the answer was “yes”. But sexual orientation is just a bit of the big whole called sexual behavior. That is why in this occasion I am going to talk about animal sexual behavior.
To put you in context, the study of animal sexuality is a rapidly developing field. It used to be believed that only humans and a handful of other species performed sexual acts other than for procreation, and that animals' sexuality was instinctive. Current understanding is that a wide range of species appear both to masturbate and to use objects as tools to help them do so; in many species animals try to give and get sexual stimulation with others where procreation is not the aim; and homosexual behavior has now been observed among 1,500 species.

SEX FOR PLEASURE
Do animals get pleasure from sex?
Science cannot say for sure what animals do or do not find "pleasurable". However, current understanding suggests that anything an animal does that furthers its own survival is pleasurable; in order to make sure the animal keeps doing it. That includes sexual intercourse. They say it is nature's way of ensuring the continuation of the species. Remember that the only purpose of the clitoris is to give pleasure, and nearly all female mammals have a clitoris. Nevertheless, very few animals have sex purely for pleasure, rather than for procreation. That is to say that, though most of animals do get pleasure from sex, not all of them will have sex just for the sake of it.

TYPES OF ACTIVITIES 1. AUTOESTIMULATION OR MASTURBATION
Petter Bockman of the Natural History Museum at the University of Oslo commented that: “Masturbation is common in the animal kingdom... There are plenty of animals who will masturbate when they have nothing better to do. Masturbation has been observed among primates, deer, killer whales and penguins, and we're talking about both males and females. They rub themselves against stones and roots. Orangutans are especially inventive. They make dildos of wood and bark.”

2. ORAL SEX
Auto-fellating or licking, sucking and/or nuzzling by a male of his own penis in animals is documented in goats, primates, hyenas, bats and sheep, among others.

3. CROSS SPECIES SEX
Many animals are sexual opportunists, partaking in sexual relations with individuals of visibly distinct species. This is more visible in domesticated species and animals in captivity, because in the wild, the two species would normally not share enough common territory to provide adequate opportunity for much cross-species sexual activity. Hybrid offspring can result from two organisms of distinct but closely related parent species, although the resulting offspring is not always fertile. This is the case of the mule (jack/mare cross), the hinny (horse/jenny cross), the tiglon (tiger/lioness cross) and the liger (lion/tigress cross).

4. PROSTITUTION
In some penguin species, the females, even when in a committed relationship, will exchange sexual favors with strange males for the pebbles they need to build their nests. Prostitution was also observed among chimpanzees, which trade food for sex.

5. SEXUAL IMAGINARY VIEWING
Problems with encouraging pandas to mate in captivity have been very common. However, showing young male pandas "panda pornography" is widely credited with a recent population boom among pandas in zoos. It shows that pandas, as well as most of primates, really value the images and are able to put sexual meaning on them.

6. NECROPHILIA
Necrophilia in animals is where a living animal engages in a sexual act with a dead animal. It has been reported in cane toads and ducks.

7. HOMOSEXUAL BEHAVIOR
No species has been found in which homosexual behavior has not been shown to exist, with the exception of species that never have sex at all. Homosexual behavior in animals refers to the documented evidence of homosexual and bisexual behavior in animals other than humans.

Birds:
Black swans: An estimated one-quarter of all black swans pairings are homosexual and they steal nests, or form temporary threesomes with females to obtain eggs, driving away the female after she lays the eggs. More of their cygnets survive to adulthood than those of different-sex pairs, possibly due to their superior ability to defend large portions of land. The same reasoning has been applied to male flamingo pairs raising chicks.
Gulls: 10 to 15 percent of female western gulls in some populations in the wild exhibit homosexual behavior.
Mallards: form male-female pairs only until the female lays eggs, at which time the male leaves the female. Mallards have rates of male-male sexual activity that are unusually high for birds, in some cases, as high as 19% of all pairs in a population.
Penguins: Male penguin couples have been documented to mate for life, build nests together, and to use a stone as a surrogate egg in nesting and brooding.
Vultures, ibises and pigeons.

Mammals
Amazon Dolphin: The Amazon River dolphin or boto has been reported to form up in bands of 3–5 individuals enjoying group sex. The groups usually comprise young males and sometimes one or two females. Sex is often performed in non-reproductive ways, using snout, flippers and genital rubbing, without regards to gender. In captivity, they have been observed to sometimes perform homosexual and heterosexual penetration of the blowhole, a hole homologous with the nostril of other mammals, making this the only known example of nasal sex in the animal kingdom.
American Bison: Courtship, mounting, and full anal penetration between bulls has been noted to occur among American Bison. Also, mounting of one female by another is common among cattle.
Bonobo: The Bonobo, which has a matriarchal society, unusual amongst apes, is a fully bisexual species—both males and females engage in heterosexual and homosexual behavior, being noted for female-female homosexuality in particular. About 60% of all sexual activity in this species is between two or more females. Bonobos use sex to divert attention and to defuse tension.
Elephants: African and Asian males will engage in same-sex bonding and mounting. Such encounters are often associated with affectionate interactions, such as kissing, trunk intertwining, and placing trunks in each other's mouths. Unlike heterosexual relations, which are always of a fleeting nature, the relationships between males may last for years. Asiatic elephants in captivity devote roughly 45% of sexual encounters to same-sex activity
Giraffes: Mounting between male giraffes males have been found to be more frequent than heterosexual coupling: up to 94% of mounting incidents take place between two males.
Japanese macaque: With the Japanese macaque same-sex relations are frequent, though rates vary between troops. Females will form "consortships" characterized by affectionate social and sexual activities.
Sheep: homosexuality in male sheep (found in 8% of rams) is associated with a region in the rams' brains which is half the size of the corresponding region in heterosexual male sheep.
Spotted hyenas, bottlenose dolphins, whales, deer, polecats and lions.

Others:
Dragonflies: Male homosexuality has been inferred in several species of dragonflies. About 80 % of sexual coupling occurs between males.

Sources:
Bagemihl, B. 1999. Biological Exuberance: Animal Homosexuality and Natural Diversity. St. Martin's Press. 752 pp.

de Waal, F. M. B. & R. Ren (1988): Peacemaking among Primates. Harvard University Press, Cambridge (Massachusetts).

Roughgarden, J. 2004. Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press. Berkeley CA. 474 pp

Sommer, V & P. L Vasey (2006): Homosexual Behaviour in Animals, An Evolutionary Perspective. Cambridge University Press, Cambridge.