Naked mole rat (Glaber heterocephaly) queens produce a chemical that prevents other females in their colony from reproducing.

A study published today in Nature suggests that this compound maintains a strict social structure that is dominated by a queen, even when the animal is not present¹. The smell of the chemical disrupts hormone production in other females, stifling their ability to have offspring.

The study is a “game changer,” says Melissa Holmes, a behavioral neuroscientist at the University of Toronto, Canada, because it explains “a long-standing mystery”: why only one female reproduces in a colony of naked mole rats.

all for one

Known for their endurance and unusual longevity, naked mole rats are eusocial, which is extremely rare for mammals. In this social structure, the queen is responsible for all reproduction in her colony, while other infertile individuals raise offspring and complete laborious tasks such as gathering food.

However, unlike other eusocial animals, such as bees, each female naked mole rat can become a queen. But most are stuck in a “stalled phase of puberty,” says Lisa Stowers, a neuroscientist at Scripps Research in San Diego, California. The reproductive organs of these females are poorly developed and the levels of the hormone prolactin are elevated. But it has been a mystery how one woman clings to the throne and stops reproduction in others.

To find out, Mohammed Khallaf, a neuroscientist at the Max Delbrück Center for Molecular Medicine in Berlin, and his colleagues sampled naked mole rats from different social ranks to determine the chemical odors they produced. One chemical, called isopropyl myristate (IPM), was found in abundance in the queens and was almost completely absent in other members of the colony. The production of this compound fluctuates with the queen’s reproductive cycle and peaks during ovulation.

“Actually, our goal was to identify the chemical profile of naked mole rats,” says Khallaf. “I was very excited when we found this compound that only the queen produces.”

Brain imaging showed that IPM exposure stimulated olfactory neurons (cells responsible for processing information about incoming odors) in non-breeding females, suggesting that these individuals react to the smell of the chemical.

To identify the chemical’s effects, the team removed some non-breeding females from the colony and used a drug to block the ability to smell in others. In both cases, the mole rats’ prolactin levels decreased, allowing those paired with males to mate. The presence of MIP alone, even in the absence of a queen, was enough to block reproduction and maintain the status quo in a colony, further experiments showed.

‘Heroic’ effort