Among naked mole-rats, a royal’s scent keeps the peace

Imagine a superhero that can release a smell so pungent that its enemies stop fighting. For naked mole-rats, the queen wields such power.

Naked mole-rat queens release a calming scent to control their colonies, a new study shows. Other mole-rats exposed to this odor will not fight or mate until the queen and this scent are gone.

Those powers are key to keeping order in a colony. Some mole-rats search for food. Others care for the young. But only the queen reproduces. And she maintains her status by keeping everyone else from mating. When she dies, high-ranking mole-rats start mating. And they fight viciously until one takes over as the new queen.  

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Naked mole-rat queens rule with more than authority. They have chemistry on their side. #molerat #animals #chemistry 🎙️Libby Riddle

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Gary Lewin is a neuroscientist at the Max Delbrück Center in Berlin, Germany. He studies how naked mole-rats use their senses. For instance, he discovered they use scent to identify mole-rats from other colonies. This made him wonder: Do odors matter within a colony, too?

Lewin and his team found one chemical made only by queen mole-rats. It’s called isopropyl myristate (EYE-so-pro-puhl MEER-ih-stayt). The chemical doesn’t smell like anything to people. But it must smell really strong to a naked mole-rat, the researchers realized. It sets off activity in the animals’ olfactory cortex. That’s the brain region that processes smells. 

To test effects of this scent, the team removed a queen from her colony. Then, they applied isopropyl myristate to the colony every day for three months. “In the entire three months, there was no fighting. Everybody was cool with each other … and there was no [mating],” says Lewin.

As soon as the researchers stopped adding the odor, though, the naked mole-rats started fighting. “Within a week we had the first death,” Lewin says. “A few weeks later, we saw mating events — and a new queen emerged.” 

Lewin’s team shared its findings July 15 in Nature.

Long live the queen

The group also turned up a few more clues to how the queen’s special odor works.

In one experiment, Lewin’s team separated pairs of male and female mole-rats from the colony. Then they exposed some pairs to the queen scent. They left other pairs alone. After four weeks, no female exposed to that scent had mated. Five of six from the other pairs, however, were now pregnant.

Blood tests showed that isopropyl myristate affects hormones in female mole-rats. It lowers their levels of progesterone (Proh-JES-tur-own) and raises prolactin. This is what kept them from getting pregnant.

A queen naked mole-rat only produces isopropyl myristate when she’s pregnant or preparing to be, the team showed. If she stops, the other mole-rats know the queen’s not doing her job — which is having babies, Lewin says. So they kill her. This level of teamwork is rare among mammals, he adds. “We think of that as something uniquely human. But it’s actually something that mole-rats have been doing for millions of years — before we even appeared on the scene.”