Animal sexual behaviour
Sexual behaviour may be tied more strongly to the establishment and maintenance of complex social bonds across a population which support its success in non-reproductive ways.
Both reproductive and non-reproductive behaviours can be related to expressions of dominance over another animal or survival within a stressful situation (such as sex due to duress or coercion).
Many animals that form pairs to mate and raise offspring regularly engage in sexual activities with extra-pair partners.
Genetic tests frequently show that some of the offspring raised by a monogamous pair come from the female mating with an extra-pair male partner.
"[20] Tournament behaviour often correlates with high levels of sexual dimorphism, examples of species including chimpanzees and baboons.
[21] The new male may achieve this in many different ways, including: Von Haartman specifically described the mating behaviour of the European pied flycatcher as successive polygyny.
[25] As polygyny is the most common form of polygamy among vertebrates (including humans), it has been studied far more extensively than polyandry or polygynandry.
[31] Post mating, banana slugs will some times gnaw off their partners penis as an act of sperm competition called apophallation.
[37][38] For many amphibians, an annual breeding cycle applies, typically regulated by ambient temperature, precipitation, availability of surface water and food supply.
Then, in the 1990s, research with prairie voles found that giving them a dose of oxytocin resulted in the formation of a bond with their future mate (Azar, 40)."
[citation needed] Some species of birds have been observed combining sexual intercourse with apparent violent assault; these include ducks,[81][82] and geese.
Lizards that perform the courtship ritual have greater fecundity than those kept in isolation due to an increase in hormones triggered by the sexual behaviours.
These include: Seahorses, once considered to be monogamous species with pairs mating for life, were described in a 2007 study as "promiscuous, flighty, and more than a little bit gay".
Bisexual behaviour was widespread and considered "both a great surprise and a shock", with big-bellied seahorses of both sexes not showing partner preference.
[129] In comparison to socio-sexual behaviours such as dominance displays, homosexual mounts last longer, happen in series, and usually involve pelvic thrusting.
[130] Male bottlenose dolphins have been observed working in pairs to follow or restrict the movement of a female for weeks at a time, waiting for her to become sexually receptive.
Janet Mann, a professor of biology and psychology at Georgetown University, argues[131] that the common same-sex behaviour among male dolphin calves is about bond formation and benefits the species evolutionarily.
Studies have shown the dolphins later in life are bisexual and the male bonds forged from homosexuality work for protection as well as locating females with which to reproduce.
[132] The female spotted hyena has a unique urinary-genital system, closely resembling the penis of the male, called a pseudo-penis.
[135] The female may exhibit lordosis in which she arches her back ventrally to facilitate entry of the penis, which is particularly present in elephants, felids, and rodents.
Amongst the land mammals, other than humans, only bonobos mate in a face-to-face position,[136][better source needed] as the females' anatomy seems to reflect,[117] although ventro-ventral copulation has also been observed in Rhabdomys.
[145][146] During mating, a "copulatory tie" occurs in mammals such as fossas,[147] canids with the exception of African wild dogs,[148] and Japanese martens.
The two snails circle around each other for up to six hours, touching with their tentacles, and biting lips and the area of the genital pore, which shows some preliminary signs of the eversion of the penis.
As the snails approach mating, hydraulic pressure builds up in the blood sinus surrounding an organ housing a sharpened dart.
On ten of these occasions the male's pedipalps then seemed to get stuck while he was transferring the sperm (which is rarely the case in other species of spider), and he had great difficulty freeing himself.
[160] In the orb-weaving spider species Zygiella x-notata, individuals engage in a variety of sexual behaviors including male choosiness, mate guarding, and vibrational signaling in courtship.
[164] A 2012 study questioned this explanation, concluding that "there is no strong reason to involve complicated factors in explaining the autosomal data".
[168] In the house mouse, the major urinary protein (MUP) gene cluster provides a highly polymorphic scent signal of genetic identity that appears to underlie kin recognition and inbreeding avoidance.
Inbreeding depression was evident for a variety of traits: pup mass at emergence from the natal burrow, hind-foot length, growth until independence and juvenile survival.
In natural populations of the bird Parus major (great tit), inbreeding is likely avoided by dispersal of individuals from their birthplace, which reduces the chance of mating with a close relative.
