Scientists dosed lions with the love hormone oxytocin to see what effect it would have on this vulnerable apex predator.
Oxytocin is a hormone associated with childbirth, bonding, and breastfeeding in humans. In animals, research over the last few decades suggests that it may play a role in social bonding. For example, research published in 2017 showed how injecting wild seals with oxytocin made them friendlier to each other.
The number of lions is currently declining, with an estimated 20,000 still living in the wild. Lions are hunted by humans in retaliation for attacks on livestock and humans, as well as pre-emptively to protect those living nearby. The species is also targeted by trophy hunters.
Lion conservation efforts often involve translocating individuals from areas where they are endangered by humans and reintroducing them to parks. But lions are aggressive predators and very territorial. This means that bringing a new individual into an area that already has lions can be risky.
University of Minnesota scientists wanted to see if oxytocin promotes social bonding between lions like it does in other species. In their experiment in a game reserve in South Africa, researchers lured lions to a wire fence with pieces of meat. Once close enough, they would spray oxytocin into her nose.
The results showed that the 23 lions that were given oxytocin were more tolerant of others and less territorial. “You can see their facial features soften immediately, going from being wrinkled and aggressive to this completely calm demeanor,” says Jessica Burkhart, lead author of the study published in iscience, said in a statement. “You totally relax. It’s incredible.”
The distance between lions playing with a ball after being given oxytocin halved from about 22 feet to 11 feet, suggesting they were becoming more tolerant of one another. Once food was introduced, the effects of oxytocin disappeared.
Study co-author Craig Packer, from the Department of Ecology, Evolution and Behaviour, narrated news week that lions are by far the most sociable cat species and show obvious affection for their companions. These are behaviors that are highly likely to release a pulse of oxytocin, he said.
“Our previous research on wild lions in the Serengeti has shown that the complex social system of lions stems from a strong ‘us against them’ sentiment – their incredibly close social relationships are largely driven by the dangers posed by neighboring groups – the Larger group victories and pridemates work together to ward off strangers from their territories—but their territorial response to strangers diminishes dramatically under the influence of oxytocin.
“Instead of roaring at a stranger’s roar, they remain silent. Usually, playing a roar is like pushing a button in lions’ territorial response, but oxytocin pretty much shuts it down.”
Sarah Heilbronner, another co-author and neuroscientist, narrates news week There are many reasons why oxytocin might make animals more relaxed in otherwise aggressive social situations. “One possibility is that oxytocin emphasizes the rewarding aspects of social interactions. We know that oxytocin affects reward circuitry,” she said. “Maybe the good parts of social interactions feel really good, and that can overshadow tension or alertness.”
Packer said her work could help wildlife organizations that need to foster social bonding between unidentified lions. “Previous techniques have largely relied on tranquilizers, antidepressants, etc.,” he said. “These work as long as the drugs are administered, but the effects often wear off after a few days or weeks.”
Burkhart now hopes to use oxytocin to help animals rescued from circuses and war zones. “The hope is that this will result in animals being relocated into the wild, which will help them become more acclimated to their new social environment, allowing them to be more curious and less fearful, leading to more successful attachment,” she said in a statement.