Naked mole rats may have specific roles, including “bathroom cleaners” and “garbage collectors,” new research suggests.
The findings, published Wednesday (Oct. 8) in the journal Scientific advanceshint that naked mole rat colonies are even more complex than scientists previously thought.
Naked mole rats (Glaber heterocephaly) are small, almost hairless rodents that live in underground colonies of between 20 and several hundred individuals. they are one of only two species of mammals known to be eusocialmeaning they show advanced social organization, similar to bees or wasps. In the case of eusocial mammals, the queen reproduces, while most of the other members of the colony (which can extend over several kilometers of tunnels) are sterile workers.
These workers perform a variety of jobs, including soldiers, tunnel diggers, collectors, and caretakers.
But it was unknown whether individuals changed jobs or tended to stick to specific roles. To investigate, Teruhiro Okuyamabehavioral neuroscientist at the University of Tokyo, and his colleagues created an artificial burrow in their laboratory. It was made up of nine chambers, each 5.9 by 5.9 inches (15 by 15 centimeters), and arranged in a three-by-three grid. Adjacent boxes were connected by 16 cm (6 in) long tubes.
Mole rats designated different chambers for specific uses, including a nesting site, a garbage area, a community “bathroom,” and several compartments without specific functions.
For 30 days, Okuyama and his colleagues studied five colonies, each containing about 20 individuals, implanting microchips in the mole rats and installing detectors throughout the colony box. This allowed the researchers to continually monitor where the animals went and which individuals they spent time with.
They found that the breeding animals (the queen and some males) stayed close to each other most of the time and followed each other.
But they discovered that the workers could be divided into six groups according to their movements. “They did different jobs if they didn’t reproduce,” Okuyama told LiveScience.
One group moved around a lot and spent most of their time in the garbage chamber, so Okuyama speculated that they might be transportation specialists. Another group primarily occupied the bathroom chamber, so the researchers proposed that these individuals could be cleaners.
A third group was less active and generally remained at the nest. These were often younger animals or older individuals who were perhaps past their prime. “I think the job is gradually changing depending on age,” Okuyama said.
Complex colonies
By revealing that there could be different functions for naked mole rats, besides reproducing or being generic workers, the work underscores how much more complex their social organization could be than we thought, he added.
“It’s a really interesting study,” Chris Faulkesan evolutionary ecologist at Queen Mary University of London who was not involved in the work told Live Science. “Anyone who has spent time observing naked mole rats would agree that a lot of individual things happen and that certain animals will spend a lot of time in the bathroom chamber, sweeping or digging. It’s a nice attempt to further quantify these complexities.”
However, Markus ZöttlA behavioral ecologist at Linnaeus University in Sweden who was not involved in the work, said it’s difficult to draw too many conclusions from the observations.
“This article shows that there is variation in behavior among helpers. There are some helpers who are more active, others who rest more,” he told LiveScience. “But that’s what is expected of any social animal. Some would be more proactive; others would be more socially aggressive; others are more shy. Some people might call this animal personality and others would call it caste system.”
We also need to be careful not to jump to conclusions about what happens in nature based on a relatively small, simple laboratory burrow with short tunnels, Zöttl said. “If we think about the ecology of these species, a burrow can extend across the area of a football field,” he said.
Different behaviors could emerge in a complex, natural burrow system with long tunnels where animals need to dig to find enough roots to feed dozens or more colony members, rather than receiving food, he said.
As they travel through these long tunnels, animals often establish their place in the social hierarchy by jostling, interacting or avoiding each other as they pass, Faulkes said, which would then influence their behavior within the colony. However, he still believes that laboratory work gives us new knowledge.
“There is hidden behavioral complexity, and there are groups or individuals that do very different things and interact in different ways within the colony,” he said.
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