Naked Mole-Rat Queens Use Chemical Scent to Suppress Colony Reproduction

Chemical Control in Naked Mole-Rat Societies

Naked mole-rats (Heterocephalus glaber) are eusocial mammals that live in underground colonies characterized by a strict division of labor. Similar to ants and bees, a single breeding queen rules over dozens of infertile subordinates who dig tunnels, gather food, and defend the nest. While scientists previously hypothesized that queens maintained this status quo through physical aggression—such as pushing and shoving—this new study suggests that chemical signaling is the primary mechanism for social stability, according to Sciencealert.

The Role of Isopropyl Myristate

Researchers at the Max Delbrück Center for Molecular Medicine in Germany analyzed hundreds of samples from 351 naked mole-rats to map their chemical profiles. They discovered that IPM is highly abundant in queens but almost entirely absent in non-breeding colony members. The compound, which is also used in human cosmetics as a moisturizer and solvent, is odorless to humans.

In queens, IPM levels peak during ovulation and decline during pregnancy and lactation. The study found the compound is most concentrated in vaginal, anal, and mouth secretions. Because queens patrol their tunnels more actively than other members, they likely spread the scent throughout the underground network, creating a pheromone-like effect that regulates the entire colony.

Experimental Evidence of Reproductive Suppression

To confirm that IPM acts as a contraceptive, the team conducted several controlled experiments. When mating pairs were removed from the colony and exposed to daily doses of IPM, the females did not become pregnant, and their progesterone levels remained low. Furthermore, when researchers removed a queen from an established colony and replaced her presence with daily applications of the scent, the colony remained peaceful for three months. No fighting occurred, and no new females attempted to rise to power or reproduce.

Max Delbrück Center Identifies Chemical Queens Use to Suppress Fertility

Conversely, when the researchers ceased the application of IPM, the Game of Thrones style of succession typical of the species resumed. The strongest females began fighting—often to the death—to claim the vacant position of queen, as reported by Ars Technica.

Evolutionary Implications and Future Questions

The findings suggest that naked mole-rat biology is more closely aligned with insect eusociality than previously understood. It’s a relatively simple mechanism that explains a relatively complex behavioral trait, said study co-author Gary Lewin.

While the mechanism is effective in naked mole-rats, researchers are still investigating whether this form of chemical control exists in other mammals. Interestingly, IPM has been detected in the breast secretions of lactating human mothers, though its biological function in humans remains unknown. This molecule or similar molecules may have effects on reproduction in species other than naked mole rats, maybe even including humans. We just don’t know that, Lewin noted.

The study, which involved researchers from the Max Delbrück Center and the University of Pretoria, indicates that the queen’s scent is sufficient to maintain order even in her physical absence. By suppressing the reproductive organs of other females, the queen ensures her status as the sole breeder, a strategy that prevents internal conflict and preserves the colony’s rigid social hierarchy, according to Nature.