Division of Labour
Based on his finding from 40 naked mole-rat colonies
taken from the wild and set up in a lab Jarvis (1981) described three levels
of workers in a
colony:
-Frequent workers: mole rats that frequently participate in nest building and
foraging. These broad behavioral categories include digging, transporting soil,
bringing food to the nest. These naked mole-rats are generally the smallest.
-Infrequent workers: perform the same tasks as frequent workers, but do not
perform these tasks as often as the frequent workers, and are significantly
heavier than the frequent workers.
-Nonworkers: only rarely do any work, but do assist in the care of young. These
naked mole-rats are generally the biggest. This group usually includes the
reproductive individuals (the queen and the reproductive males).
These work descriptions are also supported by other evidence: small naked mole-rats
are more likely to be found with dirt between their incisors suggesting that
they had been digging recently, also in capturing a colony the larger individuals
are caught more quickly, suggesting they were further away from the nest defending
the burrow (Brett, 1991a).
Another behavior that seems to be performed by one type of individual is volcanoing,
which is when a naked mole-rats pushes dirt out of the burrow through a molehill.
Large non-breeding members of the colony are usually the ones to perform this
task. This is a very risky behavior because by volcanoing the naked mole-rat
must turn around so its hindquarters are facing the molehill, thus exposing
himself to a possible attack from a snake, also the act of volcanoing might
attract a predator because there are both visual and acoustic cues from the
dirt spraying up and out of the molehill. Larger individuals might engage in
this behavior because they are strong and more able to push the dirt out of
the burrow, and additional reason why larger individuals might perform this
activity would be for defense purposes.
This web site was completed in partial fulfillment of the requiremtns for Biology 323, Animal Behavior at Davidson College in the Spring Semester of 2003.