All you need is love – oxytocin treatment for lions

Lions are apex predator giant cats that fiercely guard their territories and can mortally wound foes with a single swipe of a paw.

But while this aggression is an advantage for life in the wild, it poses challenges for lions (Panthera leo) living on reserves or in captivity; a number that is growing due to the loss of habitat and the encroachment of cities.

Now, researchers have found that applying the “love hormone” oxytocin through lions’ noses could make big cat meet-cutes at reserves or in captivity a little less life-threatening, according to a new study published in iScience.

The research conducted on a wildlife reserve in Dinokeng, South Africa, showed lions given oxytocin were more tolerant of other lions in their space and displayed less vigilance towards intruders.

“You can see their features soften immediately; they go from wrinkled and aggressive to this totally calm demeanor,” says first author Jessica Burkhart, a Ph.D. candidate with the Lion Research Centre at the University of Minnesota in the US. “They totally chill out. It’s amazing.”

In the summers of 2018 and 2019, a team led by animal biologist Dr Craig Packer and neuroscientist Dr Sarah Heilbronner from the University of Minnesota spent their days using chunks of raw meat to entice lions up to a fence. There, researchers were able to spray oxytocin, or a control containing saline solution, up the lions’ noses with a tool that looks like an antique perfume bottle.

“By spraying the oxytocin directly up the nose, we know it can travel up the trigeminal nerve and the olfactory nerve straight up into the brain,” says Burkhart. “Otherwise the blood-brain barrier could filter it out.”

Oxytocin is a hormone that plays a role in social bonding, and the brain’s oxytocin system has been strongly linked to enhanced prosocial behaviour. African lions are highly social and live in complex social groups, so are a great model for researching the behavioural effects of oxytocin on group dynamics.

To look at the effect of oxytocin on the social tolerance of lions within groups, the researchers administered it or saline (or didn’t administer anything), to all individuals in a group within about 15 minutes of each other.

Then, by observing how close a lion who posessed a desired object – in this case a pumpkin – would let others approach, they found that the lions administered oxytocin were more tolerant of other lions in their vicinity.

“After the lions were treated with oxytocin, and we gave them their favorite pumpkin toy to play with, we saw the average distance between them drop from about 7m with no treatment, to about 3.5m after oxytocin was administered,” says Burkhart.

However, when replacing the toy with food – a frozen blood popsicle – the increase in tolerance was not seen. Understandable, as who would want to share an ice block once you got first dibs?

Yet, they did see a decrease in vigilant behaviour towards potential outside intruders. When recorded roars from unfamiliar lions were played from just outside the enclosure  mimicking a territorial challenge from an intruder, lions administered oxytocin roared significantly less and were also less visibly agitated.

Why is this important?

This kind of treatment may become particularly helpful as cities in southern Africa continue to encroach upon lion territory. As humans move into and change the habitats of wild animals, human-wildlife conflict becomes more common, leading to sometimes deadly consequences.

The 2021 SCINEMA International Science Film Festival Best Online Format winner, How Deadly: World, is an online series by ABC Science which touches on this issue.  In the series, nature journalist Dr Ann Jones explains the sometimes terrifying but often hilarious behaviour of potentially deadly animals from around the world, all while reacting to viral online footage of these animals.

She reacts to interactions between humans and other apex predators such as bears and leopards which occur when humans have encroached on their habitats, explaining the animals’ behaviour and why it isn’t their fault.

You can watch the rest of the series here.

In order to keep lions safe and away from humans in parts of Africa, many have been transported to private fenced reserves. This can often result in lions from different prides mingling with one another.

This research has important implications for the potential welfare and conservation of captive and managed wild lion populations, as oxytocin administration could potentially help ease the adjustment and aid the formation of new prides among unfamiliar individuals.

“Currently we’re working on introductions of animals who have been rescued from circuses. or overseas, or war zones, that now live in sanctuaries,” Burkhart says.

“The hope is that this will translate to animals being relocated in the wild, helping them to become more inclined to their new social environment so they’re more curious and less fearful, leading to more successful bonding.”