A new study suggests that naked mole rats may have specific roles, including “toilet cleaners” and “garbage collectors.”
The results were published Wednesday (October 8) in the journal. Achievements of sciencehint that naked mole rat colonies are even more complex than scientists previously thought.
Naked mole rats (Heterocephalus glaber) are small, almost hairless rodents that live in underground colonies numbering from 20 to several hundred individuals. They are one of only two species of mammals that are known to be eusocialThis means that they exhibit an advanced social organization similar to bees or wasps. In eusocial mammals, the queen reproduces while most other members of the colony, which can extend over several miles of tunnels, are sterile workers.
These workers perform a variety of jobs including soldiers, tunnel diggers, gatherers, and caretakers.
But it was unknown whether people changed jobs or stuck to specific roles. To investigate Teruhiro Okuyamabehavioral neuroscientist at the University of Tokyo and his colleagues created an artificial burrow in their laboratory. It consisted of nine chambers, each measuring 5.9 by 5.9 inches (15 by 15 centimeters), arranged in a three-by-three grid. Adjacent boxes were connected by 6 inches (16 cm) long pipes.
Mole rats have designated different chambers for specific uses, including a nesting site, a trash area, a communal “toilet” and several compartments without specific functions.
Over the course of 30 days, Okuyama and his colleagues studied five colonies, each containing about 20 individuals, implanting mole rats with microchips and installing detectors throughout the colony box. This allowed the researchers to constantly monitor where the animals went and what individuals they spent time with.
They found that the nesting animals—a queen and several males—stayed close to each other most of the time and followed each other.
But they found that workers could be divided into six groups based on their movement patterns. “If they weren't reproducing, they were doing a different job,” Okuyama told Live Science.
One group moved around a lot and spent most of their time in the trash chamber, so Okuyama guessed that they might be transportation specialists. The other group primarily occupied the toilet chamber, leading the researchers to speculate that these people may have been cleaners.
The third group was less active and usually remained in the nest box. These were often younger animals or older individuals who may have passed their prime. “I think work is gradually changing depending on age,” Okuyama said.
Complex Colonies
By revealing that naked mole rats may have different functions beyond just reproducing or working as a general worker, the work highlights how their social organization may be more complex than we thought, he added.
“This is a really interesting study” Chris Faulksan 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 will agree that there are a lot of individual things going on, and some animals will spend a lot of time in the toilet chamber, sweeping or digging. This is a good attempt to further quantify these complexities.”
However, Markus Zettlea behavioral ecologist at Linnaeus University in Sweden, who was not involved in the work, said it was difficult to draw too many conclusions from the observations.
“This paper shows that there are differences in behavior between helpers. There are helpers who are more active, some who rest more,” he told Live Science. “But that’s what you’d expect from any social animal. Some will be more active, others will be more socially aggressive, and others will be more timid. Some people might call it an animal personality, and others might call it a caste system.”
We should also be wary of jumping to conclusions about what happens in the wild based on a relatively small and simple laboratory burrow with short tunnels, Zettle noted. “If you think about the ecology of these species, a burrow could be the size of a football field,” he said.
In a complex natural burrow system with long tunnels that animals must dig to find enough roots to feed dozens or more members of a colony, different behaviors can arise, he said.
As the animals travel through these long tunnels, they often find their place in the social hierarchy by jostling, interacting or avoiding each other, Faulks said, which then influences their behavior within the colony. However, he still believes that laboratory work gives us new ideas.
“There is underlying behavioral complexity, and there are groups or individuals that do very different things and interact differently within the colony,” he said.
