We’re not just people who are long-term partners. Some bats, wolves, beavers, foxes and lemurs as well. And the brain has a lot to do with it, as published in Scientific Reports magazine. It suggests that the brain circuits that make love last differ depending on the species. Fidelity in animals depends on brain chance.
Monogamia versus Poligamia
The research compares monogamous and promiscuous species within a closely related group of lemurs. Year after year, pairs of red-bellied lemurs and mongoose stick together. They even work together to raise their offspring and defend their territory. They spend much of their time grooming or cuddling next to each other. Your relationships last a third of your life. Other lemur species often change partners.
To biologists, mammalian monogamy in general is a mystery. Only 3-5% are monogamous. But 90% of bird species practice some kind of loyalty to a partner. “This is an unusual practice,” says Nicholas Grebe of Duke University. He is the lead author of the study.
What is the mechanism behind this? It targets two hormones that are released during mating. Oxytocin and vasopressin and how they both work in the brain define fidelity in animals.
The hormones of love
Prairie voles (monogamous) rodents were compared to mountain voles (promiscuous). In the former, oxytocin and vasopressin were attached to parts of the brain’s reward system. Is this the case in the other cases? They mapped the binding sites for oxytocin and vasopressin in the brains of 12 lemurs. Oxytocin and vasopressin act in different parts of the brain in lemurs.
What can lemurs teach us about love? “There are probably several ways that monogamy is instantiated in the brain. And that depends on the animals we are looking at. More things happen than originally thought, ”says Grebe. Oxytocin can be a “love potion” for prairie voles. But other ecological factors can also play a role in creating lasting bonds in lemurs and other primates, including humans. That is why the magic of love still remains a mystery. At least for science.