Lions are not known for making new friends easily and will fiercely defend their territory against interlopers.
Their notoriously combative nature has caused problems in sanctuaries throughout South Africa, where lions often become aggressive with their unfamiliar new neighbours.
But scientists may now have a solution: by blowing a love hormone up an angry lion’s nose, it seems you can transform it into something a little closer to an amiable pussycat.
Researchers working on a wildlife reserve in Dinokeng, South Africa, found that an intranasal application of the “love hormone” oxytocin could make encounters between lions who were strangers to each other less life-threatening.
The work was carried out during the summers of 2018 and 2019 by a team who used hunks of raw meat to lure lions close to a fence.
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When the big cats were suitably positioned, the researchers sprayed oxytocin up the animals’ noses with a device 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,” said Jessica Burkhart, the study leader and a PhD candidate working for the Lion Research Center at the University of Minnesota. “Otherwise the blood-brain barrier could filter it out.”
After these treatments, Burkhart and her colleagues observed that the 23 lions who were dosed with 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 demeanour,” she said.
“They totally chill out. It’s amazing.” The researchers measured how relaxed the lions were by seeing how close a cat who held possession of a desired object — a toy pumpkin — would let others approach it.
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“After the lions were treated with oxytocin, and we gave them their favourite pumpkin toy to play with, we saw the average distance between them drop from about 7 meters with no treatment to about 3.5 meters after oxytocin was administered,” Burkhart said.
The hormone-treated lions were also significantly less vigilant toward potential intruders, never roaring in response to recorded roars of unfamiliar lions, whereas untreated lions always roared back.
She added: “Research shows that intranasal oxytocin can last in the system for about four hours. However, oxytocin increases social learning, so even one dose can help the animal ‘learn’ that it is not afraid or anxious and it will remember its positive curiosity, even after the administered dosage is out of the system.
“The most exciting work I’m doing right now are introductions of pairs of unfamiliar lions in sanctuaries throughout South Africa. I am doing both introductions, as well as reconciliations among groups that have been previously housed together but are currently having aggression or avoidance issues.”
Burkhart is also helping to relocate wild cheetahs for conservation. “Cheetahs can easily die from organ failure due to anxiety, and the oxytocin seems to be working brilliantly to decrease their fear and anxiety during moves,” she said.
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Experiments involving other species had already highlighted the effects of oxytocin. Dogs show “increased affiliative behaviours” to human handlers when they have it sprayed up their noses. In marmosets, it increases the tolerance of fathers towards their offspring. And when given to a colony of meerkats, it appeared to promote co-operative behaviour and to reduce aggression.
The researchers believe that the treatment could be useful as cities in Africa encroach further into lion territory. Many of the cats have already been transported to private fenced reserves, which often results in lions from different prides being mixed together.
“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 said.
“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.”
The results were published in the journal iScience.