Masturbation, common in humans but rarely discussed in animals, has long been considered a Darwinian puzzle. It was previously thought to be caused by unnatural captive living conditions and is a damaging behavior that requires veterinary interventions, including dietary adjustments, drug and hormonal therapy, and, in some extreme cases, even surgery.
Now, a new, sweeping analysis of birds suggests that this behavior is not maladaptive but rather part of the evolutionary toolkit. Parrots and other birds do not use masturbation as a sign of stress or pathology. Often dismissed as an incidental feature of captivity or ecological deprivation, it is, in fact, a natural part of their sexual repertoire.
The study, published in Ecology and Evolution, is the first of its kind and challenges current approaches amongst vets and animal practitioners.
Chloe Heys at the University of Lancashire said, “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.”
Doing it more often could improve sperm quality, study
In the original description of the mechanisms of evolution, Charles Darwin pointed out that behaviors and even traits must ultimately contribute to survival or reproduction. But what about when a certain behavior simply wastes energy, time, and even sperm?
Shedding light on the evolutionary origins of this behavior by exploring why masturbation has evolved, the study found that it is widespread among bird species, forming part of a broader repertoire of sexual behaviors exhibited in birds. This is coupled with findings that masturbation is more prevalent in wild birds and those that are reared by their parents (as opposed to humans).
With both data from targeted surveys and published reports, researchers have created a dataset of 120 bird species across 22 major avian groups, including both captive and wild populations. With this data, they sought to probe a simple but mostly intangible question: why do birds masturbate?
The explanation is somewhat multifaceted. Although masturbation is prevalent among birds, it also exhibits phylogenetic conservatism (species within a broad evolutionary lineage either always display the behavior or do not).
While the study determined that males masturbated more than females, there was still female data available to substantiate the commonality of masturbation. In particular, male records reported masturbation on 55% of occasions, while female records reported it on 36% of occasions. This is inconsistent with the hypothesis that the behavior only serves to protect sperm from degradation during its time in the testes. If females are involved, the basic rationale has to be wider.
Nor is it simply “practice” for mating. The researchers found no difference between juveniles and adults (100% and 97%, respectively), suggesting that masturbation is not just rehearsal before sexual maturity.
Among their most interesting findings were that species habitually mating with multiple partners, an obvious form of promiscuity, were more prone to masturbation than socially monogamous species or those maintaining long‑term pair bonds. Importantly, this pattern tends to be consistent with one or both of the two competitive mating situations implicating masturbation in causing reproductive strategies either by helping individuals adjust sexual arousal or increasing reproductive success.
In particular, masturbation was noted more often in wild birds than in captive populations. This conclusion refutes the notion that the behavior is merely a maladaptive response to confinement, instead suggesting that it may more likely constitute an appropriate component of the avian sexual repertoire.
As for what functional purpose it plays, the researchers proposed two main options: Sexual release – sexual pleasure without mating ability; Postcopulatory selection: a fine-tuning strategy for reproductive success, potentially by mediating sperm competition or other physiological preparedness.
This study rewrites the definition of masturbation not as a biological curiosity but, instead, wipes that concern away altogether and demonstrates it to be part of legitimate avian sex by recording instances across a wide range of species.
It also presents a challenge for researchers to consider how evolutionary explanations may need to be reinterpreted in light of non-reproductive sexual behaviors. Besides the promising implications for captive breeding and conservation efforts, this new perspective has important practical consequences in terms of animal welfare, as it expands our understanding of complex mating dynamics in birds.
Chloe said, “Through enhancing our biological understanding of this unusual trait, our research can give owners, breeders, and conservationists more clarity if birds in their care display this behavior, by highlighting that veterinary interventions trying to stop masturbation may actually be causing more harm to birds. I hope that our research can trigger a shift in the current advice that vets give to bird owners and ultimately improve animal welfare.”
In the words of the researchers, masturbation is “part of a wider repertoire of sexual behaviors exhibited in birds.”
Journal Reference:
- Chloe Heys, Kevin Arbuckle, Matilda Brindle, Tom A. R. Price. The Evolution of Masturbation in Birds. Ecology and Evolution. DOI: 10.1002/ece3.73693
Amit Malewar
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