Bird masturbation is more common among wild birds, study finds

Birds do it, certainly, and they are quite content to do it alone.

New research suggests that birds deserve a place in the sweaty club of animals that masturbate, a group that is much less exclusive than previously thought.

“Avian self-pleasure is usually a rather inelegant affair, in which a bird rubs their cloaca (a shared orifice for both excretion and reproduction) against an object, like a branch, twig or toy,” the study team writes in The Conversation.

“This is often accompanied by a lot of flapping and self-satisfied vocalisation.”

Nor is it simply a pastime for bored birds in cages, as you might expect. Wild birds apparently enjoy a solo session too, perhaps even more often than those in captivity.

The discovery does, however, prompt some questions. The benefit to the individual may be clear, but why has masturbation become so common across the animal kingdom from an evolutionary standpoint?

At the risk of sounding like a puritanical preacher, masturbation ‘wastes’ considerable time and energy, as well as sperm in males. And why seek a mate at all when you can satisfy yourself?

In theory, solo sex should therefore lower reproductive success, the foundation of natural selection. So why does evolution appear to overlook the many animals that jerk, crank, rub, tap, insert or otherwise pleasure themselves?

Looking at the self-mating habits of birds could help answer that question.

Bird masturbation in the wild and captivity

For the new study, evolutionary biologists at the Universities of Lancashire, Swansea and Oxford in the UK gathered data on 120 bird species from 22 major bird groups.

The information covered the birds’ age and sex, whether they lived in the wild or captivity, which other birds shared their environment and whether their species was monogamous or promiscuous.

The researchers found that the behaviour was widespread among birds, although its prevalence varied. Males were more likely than females to masturbate: it appeared in 55 percent of male records. Females enjoyed some time alone too, with masturbation appearing in 36 percent of female records.

A species’ breeding behaviour was also associated with its tendency to masturbate. Birds that were socially monogamous or formed long-term pair bonds were much less likely to engage in self-exploration than species with multiple mates.

Neither age nor being kept alone rather than with other birds appeared to affect whether a species masturbated.

Most unexpectedly, wild birds were more likely to pleasure themselves than captive birds, directly contradicting one of the leading hypotheses about why birds masturbate.

“Despite assumptions that masturbation among captive birds like parrots is a result of their often-solitary living, our study finds that it is natural, healthy, and widespread across diverse bird species, even in different environments,” says Chloe Heys, a biologist at the University of Lancashire.

That means pet owners need not be alarmed if they catch their bird in the act. Vets have generally advised discouraging the behaviour because it is regarded as a sign of stress or poor health. Instead, it seems the bird may simply need some privacy.

Why might bird masturbation persist?

When the researchers looked at the phylogenetic relationships between bird species that engaged in solo sex, they found the behaviour clustered on particular branches of the family tree.

This points to an evolutionary connection, rather than the behaviour being something enterprising individuals in different species worked out independently.

So why has natural selection not eliminated it? Several hypotheses could explain its persistence.

In males, masturbation might clear out old sperm, leaving more viable newcomers and improving the chances of future reproductive success.

For females hoping to have a quick encounter with a neighbour, it could help bring things to an end sooner, before their main bonded partner catches them.

The explanation might, however, be simpler still. “Our findings indicate that the proximate mechanism of masturbation may be to serve as a sexual outlet in response to a high sex drive,” the researchers write in the study.

Self-pleasure across the animal kingdom

Birds are far from alone: autoeroticism occurs throughout the animal kingdom.

Monkeys in Indonesia have been observed using rocks to pleasure themselves, while dolphins use dead fish. Elephants also indulge in self-care. Walruses masturbate with their flippers and are surprisingly flexible enough to self-fellate.

There is no shame in it: a growing body of research suggests that taking care of business alone is good for you.

The new study was published in the journal Ecology and Evolution.