With oxytocin in the nose, lions become more tolerant

With oxytocin in the nose, lions become more tolerant


Lions tend to become aggressive when they meet their mates, but a squirt of oxytocin in the nose can make these presentations a little less deadly, according to a study. The purpose of this work is to facilitate the integration of new groups within the framework of conservation projects.

Oxytocin is a neuropeptide secreted by the hypothalamus and excreted by the posterior pituitary (neurohypophysis). This hormone acts mainly on the smooth muscles of the uterus and mammary glands. In humans, it also promotes trust, empathy, generosity and sexuality. For this reason, oxytocin is often called the “love”, “happiness” or “attachment” hormone.

In animals, previous research has shown that oxytocin may also play a role in social bonding. In new work, animal biologist Craig Packer and neuroscientist Sarah Heilbronner of the University of Minnesota have looked into the case of lions. Their study has just been published in the journal iScience.

An endangered species

Lion numbers are currently plummeting. There are now only 20,000 individuals, perhaps less, in the wild. These predators are indeed often killed by humans in retaliation for attacks on livestock. They are also targeted by trophy hunters.

Lion conservation efforts often involve relocating individuals to fenced reserves. While these structures help keep animals safe, they also imply a certain closeness between individuals. However, lions are aggressive and very territorial predators. Thus, placing one or more specimens in an area already frequented by another group of lions can lead to conflicts, which is also not in the interest of the species.

As part of this work, the scientists wanted to see if oxytocin would promote social bonds between “rival” lions. To do this, they lured several individuals with meat to a South African wildlife sanctuary, before spraying oxytocin directly into their nostrils.

“In doing so, we knew that oxytocin would go up the trigeminal nerve and the olfactory nerve before arriving directly in the brain”, details Jessica Burkhart in a press release. “Otherwise, the blood-brain barrier could have filtered it.”

Less aggressive lions (except when hungry)

The results showed that the twenty-three lions involved in the study were indeed more tolerant of each other. “You could see their features soften immediately. They went from wrinkled and aggressive to this completely calm demeanor,” continues the researcher. “They were totally relaxing. It was amazing.”

To measure the extent of this tolerance, the researchers then introduced a toy into the cage. While the lions would normally keep a distance of around seven meters from each other, those treated with oxytocin often approached within 3.5 meters of each other.

This new tolerance, however, evaporated in the presence of food. Place a piece of meat in the middle and oxytocin or not, the lions again become intolerant of intruders approaching too close to their food. Nevertheless, this experience turned out to be very encouraging.

Offering oxytocin to lions isn’t exactly unnatural as these predators are by far the most sociable feline species, showing obvious affection towards their companions largely driven by the dangers posed by neighboring groups. However, these social behaviors between members of the same group are very likely to release an oxytocin impulse. What this new study demonstrates is that this territorial response to strangers decreases significantly with more oxytocin.