A study on bird masturbation involving 120 bird species

Amazing stuff!

Notice Oxford University insists in their news release that masturbation should not be punished! How old is Oxford University? 😊

"... In a new study, scientists investigated acts of autosexual behavior in 120 bird species across 22 major groups. The team surveyed bird experts, gathered data from online communities of bird enthusiasts, and combed the relatively scant scientific literature on bird masturbation. “Avian self-pleasure is usually a rather inelegant affair,” they wrote in a piece for The Conversation, which involves a bird rubbing its cloaca against an object, frequently accompanied by wing-flapping and “self-satisfied” vocalizations.

Such behavior, the researchers found, is widespread among bird species and is actually more common in the wild than in captivity. Although slightly more accounts involved males, self-love occurred in both sexes and across all age groups. Species that mate with multiple partners were more likely to engage in the behavior than socially monogamous species or species that form long-term pair bonds, suggesting that it helps increase reproductive success or plays a role in enhancing sexual arousal. ..."

From the abstract:

"Most theories on sexual behaviours are based on adaptive explanations. However, masturbation, a common but scarcely discussed sexual behaviour, appears a Darwinian puzzle.

Why would individuals waste valuable resources such as time, energy and, for males, sperm?

We combined targeted surveys with information from published accounts to test hypotheses about why masturbation occurs, using a phylogenetically broad dataset on the presence or absence of masturbation across 120 bird species.

We find masturbation is widespread in birds, but strongly phylogenetically conserved, typically being fixed (as present or absent) or nearly so within broad clades.

Masturbation is more common in males, though the widespread evidence for masturbation in females suggests that maintaining fresh sperm in testes cannot be the single explanation.

We find no difference in masturbation occurrence between juveniles and adults, further suggesting that it does not solely represent practice copulations before maturity.

Species with indiscriminate matings are more likely to masturbate than socially monogamous species or species with long-term pair bonds.

Importantly, as masturbation is more commonly reported in wild than captive birds, we find it is therefore not a negative or maladaptive response to captivity. Instead, it is part of a wider repertoire of sexual behaviours exhibited in birds. Overall, our data are consistent with masturbation serving as an outlet for increased sexual arousal, a means of increasing reproductive success through postcopulatory selection, or both."

ScienceAdviser

Masturbation in pet birds is natural and should not be punished (original news release)

The Evolution of Masturbation in Birds (open access)

Scientists reveal what drives homosexual behavior in primates

Amazing stuff! The study seems to confirm that homosexual behavior is much more common among different species than previously known.

However, what does homosexual behavior among animals really mean? It might be quite different from that of homosexuality among humans. For example what is the sexual attraction between same sex animals?

"Homosexual behavior in primates has a deep evolutionary basis and is more likely to occur in species that live in harsh environments, are hunted by predators or live in more complex societies ...

Males or females of the same sex mounting or otherwise stimulating each other have been documented across the animal kingdom.

More than 1,500 different species have been observed engaging in same-sex sexual behavior, with some of the earliest reports dating back to the ancient Greek philosopher Aristotle.

But this relatively common behavior was long dismissed by the scientific community as a "Darwinian paradox." ...

More recently, scientists have shown that this behavior can in part be inherited from an animal's parents—and can provide an evolutionary advantage.

"Diversity of sexual behavior is very common in nature, among species and in animal societies—it is as important as caring for offspring, fighting off predators or foraging for food," ...

collected data on 491 non-human primate species.

They identified same-sex sexual behavior in 59 species, including lemurs, great apes and monkeys across the Americas, Africa and Asia.

That the behavior was so widespread indicates it has a "deep evolutionary root," the study said. ...

They found that the behavior was more common in species that lived in harsh environments with limited access to food, such as barbary macaques.

It was also more common in species more likely to be hunted by predators—vervet monkeys, for example, have to avoid all sorts of big cats and snakes in Africa. ..."

"... They found that SSB was more likely in species living in drier climates, with scarce food resources or under greater pressure from predators. Species with noticeable differences between males and females, longer lifespans, or complex social lives were also more likely to engage in SSB.

The findings suggest that same-sex sexual behaviour may play a role in navigating social dynamics, forming alliances, and maintaining cohesion within groups.   ..."

From the abstract:

"Same-sex sexual behaviour (SSB) is widespread across animal species; however, its evolutionary origins and ecological underpinnings remain poorly understood.

In social animals, SSB is probably shaped by both genetic and environmental factors. For instance, a recent study in rhesus macaques indicates that while SSB is partially heritable and genetically based, it is also strongly influenced by environmental and social conditions.

Here we compiled species-level data on 491 non-human primate species, documenting SSB occurrence and prevalence in 59 species, and examined its associations with 15 environmental, life history and social traits using phylogenetic regression and structural equation modelling.

SSB occurrence was more likely in species inhabiting drier environments with increased food scarcity and predation pressure, in species with greater size dimorphism and longer lifespans and in those with more complex social structures and hierarchies.

Structural equation modelling further indicated that environmental and life history traits influence SSB mainly indirectly, whereas social complexity directly promotes its occurrence.

Together, these findings highlight SSB as a context-dependent behaviour shaped by interactions among ecological, life history and social factors, offering insights into the sexual diversity and social evolution of primates."

Scientists reveal what drives homosexual behavior in primates

New research explores ecological and social roots of same-sex sexual behaviour in primates (original news release) "A comprehensive new study of primates reveals that same-sex sexual behaviour (SSB) is widespread and influenced by a combination of environmental and social factors."

Ecological and social pressures drive same-sex sexual behaviour in non-human primates (no public access)

Male chimpanzees exhibiting same-sex sexual behaviour in Kibale Forest, Uganda.

Research suggests (young adult) lovers fit into four categories. Really!

How neat is that! You may have to give the study some credit for trying!

The study is based only on 809 couples from 33 countries, which is in my opinion a small sample. It appears from the news releases that this study mixed hetero- and homosexual couples without distinction.

According to Google Scholar this study was not cited once as of 3/1/2025.

"... The study, published in Personality and Individual Differences, grouped 809 partnered young adults who were in love based on the intensity of romantic love, obsessive thinking, commitment, and frequency of sex per week. 

The results revealed four clusters of romantic lovers:
mild romantic lovers, 

moderate romantic lovers, 

libidinous—or lustful—romantic lovers and 

intense romantic lovers ....

The study used data from the Romantic Love Survey 2022, the world's largest dataset of 1,556 young adults experiencing romantic love. It has participants from 33 countries representing different cultural and ethnic groups. ..."

From the abstract:

"Variation exists in the expression of romantic love, but to date, no studies have specifically investigated this phenomenon. This study employed a TwoStep cluster analysis to group 809 partnered young adults experiencing romantic love from the Romantic Love Survey 2022 according to intensity of romantic love, obsessive thinking, commitment, and frequency of sex per week. 

The results revealed four clusters: 

(i) mild romantic lovers (20.02 %) characterized by the lowest intensity, lowest obsessive thinking, lowest commitment, and lowest frequency of sex;

(ii) moderate romantic lovers (40.91 %), characterized by relatively low intensity, relatively low obsessive thinking, relatively high commitment, and relatively moderate frequency of sex;

(iii) libidinous romantic lovers (9.64 %), characterized by relatively high intensity, relatively high obsessive thinking, relatively high commitment, and exceptionally high frequency of sex; and

(iv) intense romantic lovers (29.42 %), characterized by the highest intensity, highest obsessive thinking, highest commitment, and relatively high frequency of sex.

Each cluster differs on a range of personal and relationship characteristics. The findings can generate theory and hypotheses about romantic love and provide impetus for future research."

Research suggests lovers fit into four categories

Hot, heavy love: if you’re having that much sex, you might be a ‘libidinous’ lover, according to science (this appears to be the original news release)

Variation exists in the expression of romantic love: A cluster analytic study of young adults experiencing romantic love

How a survey of over 2,000 women in the 1920s changed the way Americans thought about female sexuality

Recommendable! This is about what is considered to be the first sexual revolution in the US!

How a survey of over 2,000 women in the 1920s changed the way Americans thought about female sexuality

Katharine Bement Davis was frustrated by the double standard that celebrated men’s sexual experiences and condemned those of women. 

Scientists locate the brain circuit that drives male libido

Amazing stuff!

"“We’ve singled out a circuit in male mammals’ brains that controls sexual recognition, libido, and mating behavior and pleasure,” ...

In the latest study, the team focused on a set of BNST neurons that secrete a slow-acting peptide called Substance P. By stimulating this tract, the circuit reached preoptic hypothalamus neurons with receptors for Substance P, which then initiated the male mating behaviors. When the scientists directly stimulated the Substance P neurons in the pre optic hypothalamus, the male mice that had just completed mating behaviors were driven to immediately resume sexual activity.

It showed that the normal refractory period, in which sex drive and mating capabilities are restored after ejaculation, was completely overwritten. Nearly all mammals require this refractory period to physiologically regroup for sexual activity. ... And on the flip side, suppressing this neural activity can completely erode the male’s libido. ..."

"... For the mice used in this study, the normal refractory period is five days. But directly stimulating just the Substance P receptor-containing neurons of the preoptic hypothalamus via experimental manipulations prompted male mice that had just ejaculated to immediately reprise their sexual mating routine all the way to a second consummation in the presence of a female mouse. ...

The study’s findings could lead to drugs that serve as libidinal rheostats, capable of tamping down sex circuitry in the brains of men with hyperactive sex drives, or, alternatively, boosting sex drive in men who suffer from a lack of desire. ..."

From the highlights and abstract:

"Highlights

• A multisynaptic neural circuit that converts sensory input to male sexual behavior

• An embedded molecular timer delays mating onset following mate recognition

• This neural circuit elicits dopamine release and governs male sexual drive and reward

• This neural circuit governs libido and motor displays of male sexual behavior

Summary

Male sexual behavior is innate and rewarding. Despite its centrality to reproduction, a molecularly specified neural circuit governing innate male sexual behavior and reward remains to be characterized. We have discovered a developmentally wired neural circuit necessary and sufficient for male mating. This circuit connects chemosensory input to BNSTprTac1 neurons, which innervate POATacr1 neurons that project to centers regulating motor output and reward. Epistasis studies demonstrate that BNSTprTac1 neurons are upstream of POATacr1 neurons, and BNSTprTac1-released substance P following mate recognition potentiates activation of POATacr1 neurons through Tacr1 to initiate mating. Experimental activation of POATacr1 neurons triggers mating, even in sexually satiated males, and it is rewarding, eliciting dopamine release and self-stimulation of these cells. Together, we have uncovered a neural circuit that governs the key aspects of innate male sexual behavior: motor displays, drive, and reward."

Sexy mice help scientists uncover the drivers behind male libido Scientists say they've uncovered the neural circuitry behind desire that is responsible for sex drive, behavior and reward.

Stanford Medicine scientists locate key brain circuit containing the seat of male libido A team of Stanford Medicine researchers have shown in male mice that a particular neuronal circuit is responsible for sexual arousal and for the actions and pleasure that ensue, opening avenues for treatment in men.

A neural circuit for male sexual behavior and reward (open access)

Graphical abstract

In this image of a male mouse's brain, pink denotes the bed nucleus of the stria terminalis (BNST); green, the preoptic hypothalamus. The impulse flows from pink to green in the neural circuit governing mating drive, behavior and satisfaction.

Masturbation evolved in primates about 40 million years ago functioning at a macroevolutionary scale

Caution: Taboos! Of course, science can not and should not resist to investigate and examine societal taboos!

Some of the language here seems bombastic!

It maybe healthy and good for fitness for various reasons!

Did you know that male masturbation in the wild is easier to observe than female masturbation?

"Though masturbation is common across the animal kingdom, it seems, at its face, to be an evolutionary paradox: Why would an animal waste time, energy and reproductive resources on self-pleasure instead of copulating with a partner? ...
A new study ... suggests that the evolutionary history of masturbation in primates extends back at least 40 million years, and the behavior might indeed help male primates be ready to mate when they get the chance, and also stay free of disease. ...
To fill gaps in the data due to masturbation not always being easy to observe (or looked for at all) by biologists, [paper researchers] sent out questionnaires to researchers to ask about their observations of primate masturbation that weren’t reported in the literature. This was especially important for information on female masturbation, ... which tends to go unnoticed ...
Male Cape ground squirrels (Geosciurus inauris), for instance, are known to masturbate after sex to cleanse their systems of infectious agents. ..."

From the abstract:

"Masturbation occurs throughout the animal kingdom. At first glance, however, the fitness benefits of this self-directed behaviour are unclear. Regardless, several drivers have been proposed. Non-functional hypotheses posit that masturbation is either a pathology, or a byproduct of high underlying sexual arousal, whereas functional hypotheses argue an adaptive benefit. The Postcopulatory Selection Hypothesis states that masturbation aids the chances of fertilization, while the Pathogen Avoidance Hypothesis states that masturbation helps reduce host infection by flushing pathogens from the genital tract. Here, we present comprehensive new data documenting masturbation across the primate order and use these, in conjunction with phylogenetic comparative methods, to reconstruct the evolutionary pathways and correlates of masturbation. We find that masturbation is an ancient trait within the primate order, becoming a more common aspect of the haplorrhine behavioural repertoire after the split from tarsiers. Our analyses provide support for both the Postcopulatory Selection and Pathogen Avoidance Hypotheses in male primates, suggesting that masturbation may be an adaptive trait, functioning at a macroevolutionary scale."

When and why did masturbation evolve in primates? A new study provides clues The behavior may help males be fertile and disease-free. But data on females are lacking

The evolution of masturbation is associated with postcopulatory selection and pathogen avoidance in primates (open access)

The researchers avoided to use color for their figures in their paper! See example below. 😊

Figure 4. Coevolution between masturbation occurrence (present versus absent; left-hand side of circles in schematic) and pathogens (present versus absent; right-hand side of circles in schematic).

‘A Polar Affair’ delves into a centurylong cover-up of penguin sex

What a story! Monogamy versus polygamy, heterosexual versus homosexual behavior ... How much can we actually compare homosexual behavior among animals with those of humans? 

‘A Polar Affair’ delves into a centurylong cover-up of penguin sex | Science News: In a new book, Lloyd Spencer Davis seeks to understand why an Antarctic explorer kept some of his penguin observations a secret.