This 'Love Hormone' Makes Fierce Lions Friendlier, New Study Says

Scientists working in a South African wildlife reserve have found that spraying oxytocin, the so-called "love hormone", up the noses of lions makes the big cats much friendlier with their neighbours.

A lion rests under a tree at the Rietspruit Game Reserve in Hoedspruit, South Africa, on December 2, 2021. Scientists found that spraying oxytocin up the noses of lions makes the big cats much friendlier with their neighbors and less prone to roaring at strangers. | AFP

New Delhi: Lions are typically not keen on making new friends, guard their territory fiercely, and can mortally wound an enemy with a single blow. However, aggression poses real challenges for lions on reserves.

Scientists working in a South African wildlife reserve have found that spraying oxytocin, the so-called "love hormone", up the noses of lions makes the big cats much friendlier with their neighbours and less prone to roaring at strangers. 

The study, led by researchers at University of Minnesota, Twin Cities, was recently published in the journal iScience. The researchers found that an intranasal application of the "love hormone" makes lions less life-threatening. Relative to control conditions, oxytocin administration enhanced social proximity, the study said.

What Is Oxytocin?

Oxytocin is a hormone that acts on organs in the body and as a chemical messenger in the brain, controlling key aspects of the reproductive system, and aspects of human behaviour. The hormone modulates mammalian social behaviour. 

The team led by animal biologist Craig Packer and neuroscientist Sarah Heilbronner, spent their summer days of 2018 and 2019 luring lions up to a fence using hunks of raw meat, so that they could spray oxytocin up their noses. They used a tool which appears like an antique perfume bottle.

However, behavioural responses to intranasal oxytocin can vary across species. 

Effects Of Intranasal Administration Of Oxytocin On Social & Non-Social Behaviours

The scientists tested the effects of intranasal administration of oxytocin on social and non-social behaviours within in-group and out-group contexts of African lions. An in-group is a group which one belongs to, while an out-group is the group they do not belong to.  

Jessica Burkhart, the first author of the study, said that by praying the oxytocin directly up the nose, the researchers know it can travel up the trigeminal nerve and the olfactory nerve straight up to into the brain, according to a statement issued by Cell Press, a publisher of scientific journals. 

What Behaviours Did The Big Cats Exhibit?

She said that otherwise, the blood-brain barrier could filter it out. The trigeminal nerve, also known as the fifth cranial nerve, is responsible for sensation in the face and motor functions such as biting and chewing, and for sending pain, touch and temperature sensations from one's face to the brain. 

After subjecting 23 lions to these treatments, the team observed that the big cats were more tolerant of other lions in their space, and displayed less vigilance towards intruders, according to the study.

Quoting Burkhart, the statement said that one can see their features soften immediately, which go from wrinkled and aggressive to a totally calm demeanour. She said that the lions "totally chill out."

The researchers hypothesised that post intranasal oxytocin administration, lions would be in close proximity with fellow group members, whereas out-group stimuli could either produce a heightened vigilance response or an attenuated one, according to the study. 

How Do Researchers Measure Social Tolerance Of Lions?

Researchers observe how close a lion who has a possession of a desired object lets others approach it, in order to measure social tolerance. In this case, the scientists used a toy as the desired object. 

Lions Were Given Their Favourite 'Pumpkin Toy' To Play With

Burkhart said that after the lion's were treated with oxytocin, the team gave them their favourite pumpkin toy to play with. The scientists saw that the average distance between them dropped from about seven metres with no treatment to about 3.5 metres after oxytocin was administered. 

According to study, lions, post oxytocin administration, increased their time spent in close proximity, and decreased vigilance toward out-group intruders, compared to control trials. In other words, the lions reduced their distance to the nearest neighbour, and reduced their vocalisations following a roar-playback. However, no difference was observed when a food object was used.

The authors noted in the study that this kind of treatment may become particularly helpful as cities in Africa encroach upon lions' territory. Many lions have been transported to private fenced reserves,  in order to keep them safe from humans. 

The results not only have important implications for understanding the evolution of social circuitry, but may also have practical applications for conservation efforts, the authors noted in the study.