Two species of mole rat (the naked and the Damara) are the insects of the mammal class. Its their social colony structure that makes them “insectlike”. To delve a little bit more into the characters of the mole rat colony:
1) Out of a colony that can reach over 300 individuals, only 1 female (the “queen”) breeds with 1-3 males per litter to create all the progeny of the colony.
– Although the remaining males and females are not infertile, they become nonreproductive. Very little sperm is present in males and estrual cycles are turned off in females. The queen is distinctly larger, with her vertebrae lengthened, than the others of her colony in order to bear the large litter. While she suckles them after birth, the workers care for them. After they are weaned they will join the “workforce” (like us all).
– Some of the young will also join the “workforce” as builders/diggers to expand the colony while others will become soldiers/defenders. These “defenders” are noticeably larger than their construction worker relatives.
– Also, how does one become a queen? It appears that this dominant creature of the colony is chosen through her “stress-related” behaviours she displays such as violent shoving.
2) The progeny is composed of many closely related litters. In fact, incest is common, as most members of the colony will never breed. But why don’t they breed? Like insects, it is thought to serve as a way to maintain their social structure so that all mole rats remain closely related (maintaining similar genetic similarity). By remaining genetically similar, the nonbreeding individuals are guaranteed that their genetic features are passed down.
– This system is highly effective in very dry, arid regions. During times of drought, mole rats are unable to burrow, which is needed for colony expansion and food-seeking, but once rain finally starts to arrive, the colony makes use of their creeds of teamwork: some go off to forage for food (some of which is saved for the next dry season), others remain as soldiers, and the queen with a select few males bear the next litters.
A major way in which they are not like insects in this social behaviour is that they do not seem to communicate with pheromones, chemical hormones that are released to the environment. The entire colony revolves around the reproductive state of the breeding female.
There are suspicions that the reproductive state of the queen is controlled by pheromone release. Just before the queen gives birth, all members of the colony- yes, males AND females- develop teats. In fact, some females become close to reproductive capability. Thus it is believed that there may be a chemical released by the female during this time that primes this behaviour. The cause for this remains unknown.
Ever wonder how these mole rats survive in their underground burrows for so long- especially if they are not the soldiers or food foragers? Namely, where is the water? The high moisture in the food and the humid microclimate of the burrow allows them to get all the water they need. Due to these microclimates, of which the temperature of the burrow remains between 82-86 degrees F (28-30 degrees C), naked mole rats actually appear to have lost the ability to thermoregulate, or modulate their own body temperature. This is particularly important being that the naked mole rat is, well, naked (i.e. hairless).
Wacky naked creatures, right?
FYI News update from Gabby Wild: I, Gabby Wild, am officially a veterinary student! I graduated from Cornell University with a degree in Bachelor of Science (double major in Biology and Animal Science). In August I’ll begin the dream: Cornell University Veterinary School!