Photo of Naked Mole Rat in the IZW by Stefan Günther
Life in a naked mole rat “palace” hums along just fine under the firm rule of the queen. But when she dies the succession can be a bloody contest that may end in death for those trying to claim her throne.
Researchers at the Berlin Leibniz Institute for Zoo and Wildlife Research (IZW) in Germany have constructed a palace for a colony of 19 mole rats in their laboratory.
“The naked mole rats did not have to dig their own burrow at the IZW. When they arrived in September 2008 a comfortable tunnel labyrinth with several Plexiglas chambers was waiting for them,” says an IZW news release about the research.
The animal in the photo above looks like a newborn hamster — still naked and blind. But it is not a hamster; it is a naked mole rat and already ten years old, the release says. “These strange creatures live in the semi-deserts of Africa and have a life-span of up to 25 years.
“This way of life is very unusual for mammals: Their subterranean colonies are organized like an insect community around a single breeding queen. The rest of the animals are workers and soldiers.”
At the IZW, unlike in the natural habitat, soldier mole rats are not required as sentinels at the burrow entrance to guard against enemies, IZW says.
“Nevertheless, the workers have a lot to do: They crawl busily over and under each other, moving backwards as fast as they move forward. They transport huge quantities of straw, paper towels and food, scurrying back and forth between the chambers to constantly refurbish the burrow.”
Each chamber in the palace has its own function such as store room, sleeping chamber, or toilet. The occupancy of the different chambers changes from time to time, IZW has observed.
Photo of Naked Mole palace in the IZW by Stefan Günther
“The queen has the most attractive job,” Thomas Hildebrandt, a research director at IZW. “She is somewhat larger and lighter in color than her subjects and is therefore easy to recognize.”
The queen suppresses potential rivals by secreting a messenger substance in her urine that suppresses fertility in other females.
“When the queen dies a palace revolution ensues, as only one female can ascend to the throne. Fierce fighting may occur — sometimes to the death — to determine who will succeed,” IZW’s statement says.
“The winner now takes on the characteristics of the queen. If the colony does not perish during this crisis, it takes about half a year until the new queen is able to reproduce.”
The queen in the IZW is still the uncontested matriarch; to date she has had one litter of five pups.
Reproduction is what interests IZW scientists most about the naked mole rats.
Hildebrandt explains why: “Until now it was generally thought that the distribution of male and female progeny of mammals was completely random. We suspect, however, that the males influence sex ratio by producing more sperm of one sex. It is generally more advantageous for the colony to have female progeny, because as workers they benefit the colony more than male offspring.”
If in another situation the colony needs more males, the sperm composition changes in favor of males, the scientists surmise. “Such a principle may not just apply to naked mole-rats, but also to other mammals,” IZW says.