The “love drug” oxytocin has been found to have a positive effect on big cat bonding in captivity. Lions and their giant murder mittens have a tendency to get aggressive when introduced to other lions, but a spritz up the nose of oxytocin was able to make these mammals’ meet-cutes a little less deadly.

The novel treatment for non-lethal lion speed dating was devised by animal biologist Craig Packer and neuroscientist Sarah Heilbronner from the University of Minnesota who published their findings in iScience.

Apex predators aren’t the easiest patients when trying to squirt something up the nose, but the pair, working with a team at the wildlife reserve in Dinokeng, South Africa, were able to use the lions’ bloodthirst for good. They lured them to a fence with a large piece of meat so that they could safely get close enough to sneak a squirt of oxytocin up their nostrils

A tricky task, but the nasal placement served a purpose beyond getting the researchers’ heart rates up.

“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,” first author Jessica Burkhart said in a statement. “Otherwise the blood-brain barrier could filter it out.”

Lions that received the treatment (23 in total) instantly showed signs of mellowing and became more tolerant of and less aggressive towards fellow lions.

“You can see their features soften immediately, they go from wrinkled and aggressive to this totally calm demeanor,” Burkhart said in a statement. “They totally chill out. It’s amazing.”

To test the drug’s efficacy and measure the extent of their tolerance the researchers then introduced a favorite pumpkin toy to play with. Vigilant lions would keep a distance of around 7 meters (23 feet) even with the lure of the pumpkin, but oxytocin lions got within 3.5 meters (11.5 feet) of one another.

The tolerance however evaporated in the presence of food, with lions being intolerant of intruders getting too close to their meat even on oxytocin.

Finding ways to improve relations among lions living in close quarters has benefits beyond captive scenarios, as human encroachment on lion territories often sees animals moved to fenced-in reserves. While the reserves keep the animals safe, they put them in closer proximity to other lions than is ideal for these cantankerous cats.

“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.”