Naked mole rats may have specific roles, such as “toilet cleaners” and “garbage collectors,” a new study suggests.
The findings, published Wednesday (October 8) in the journal Science Advances, suggest that naked mole rat colonies are even more complex than scientists previously thought.
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Naked mole rats (Heterocepalus glaber) are small, almost hairless rodents that live in underground colonies of about 20 to several hundred individuals. They are one of only two mammal species known to be eusocial, exhibiting a high degree of social organization similar to bees and wasps. In eusocial mammals, the queen reproduces while most other members of the colony, which spans miles of tunnels, are sterile workers.
These workers perform a variety of jobs, including soldiers, tunnelers, gatherers, and caretakers.
However, it was unclear whether individuals changed jobs or tended to stick to specific roles. To investigate, Teruhiro Okuyama, a behavioral neuroscientist at the University of Tokyo, and his colleagues created artificial burrows in their lab. It consisted of nine rooms, each 5.9 by 5.9 inches (15 by 15 centimeters), arranged in a 3 by 3 grid. Adjacent boxes were connected with 6-inch (16 cm) long pipes.
Mole rats designated different rooms for specific uses, such as nesting areas, garbage storage, communal “latrines”, and some compartments with no specific function.
Okuyama and his colleagues studied five colonies, each containing about 20 individuals, for 30 days by implanting mole rats with microchips and installing detectors throughout the colony boxes. This allowed researchers to continuously monitor where the animals went and with whom they spent time.
They found that the breeding queen and several males stayed close to each other most of the time and followed each other around.
However, they found that workers could be classified into six groups based on their movements. “If they weren’t breeding, they were doing other jobs,” Okuyama told Live Science.
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One group moved around a lot and spent the most time in trash cans, leading Okuyama to speculate that they were transportation experts. Another cluster mostly occupied bathroom rooms, leading researchers to suggest that these people may be cleaners.
The third group was less active and usually remained in the nest box. These were often young animals or individuals that were older and past their peak. “I think work is changing little by little depending on age,” says Okuyama.
complex colony
By revealing that naked mole rats may have distinct roles beyond reproduction and general worker roles, this study highlights how much more complex their social organization is than we realize, he added.
“This is a really interesting study,” Chris Fawkes, an evolutionary ecologist at Queen Mary, University of London, who was not involved in the study, told Live Science. “Anyone who has spent time observing naked mole rats will agree that there is a lot going on individually, and that certain animals spend a lot of time in the toilet room, cleaning or digging. This is a good attempt to further quantify these complexities.”
But Markus Zettle, a behavioral ecologist at Linnaeus University in Sweden who was not involved in the study, said it was difficult to draw too many conclusions from the observations.
“This paper shows that there is variation in behavior among helpers. Some helpers are more active, while others are more rested,” he told Live Science. “But that’s what you would expect from a social animal. Some animals are more aggressive, some are more socially aggressive, and some are more timid. Some might call this an animal’s personality, others might call it a caste system.”
Zettl also noted that researchers should be wary of jumping to conclusions about what happens in the wild based on relatively small, simple laboratory burrows with short tunnels. “Given the ecology of these species, the burrows could extend into the area of a soccer field,” he said.
In complex natural burrow systems with long tunnels, different behaviors may emerge because the animals are not fed food, but have to dig to find enough roots to feed dozens or more colony members, he said.
As these animals pass through long tunnels, they often establish their place in the social hierarchy by shoving, touching or avoiding each other as they pass, which influences their behavior within the colony, Fawkes said. But he still believes that research in the lab can give us new insights.
“There’s a hidden complexity in behavior, and within a colony there are groups and individuals that behave very differently and interact in different ways,” he says.
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