Passage 60
Until recently, scientists did not know of a close verte-
brate analogue to the extreme form of altruism abserved in
eusocial insects like ants and bees, whereby individuals
cooperate, sometimes even sacrificing their own oppor-
( 5) tunities to survive and reproduce, for the good of others.
However, such a vertebrate society may exist among under-
ground colonies of the highly social rodent Heterocephalus
glaber, the naked mole rat.
A naked mole rat colony, like a beehive, wasp’s nest, or
(10) termite mound, is ruled by its queen, or reproducing
female. Other adult female mole rats neither ovulate nor
breed. The queen of the largest member of the colony, and
she maintains her breeding status through a mixture of
behavioral and, presumably, chemical control. Queens have
(15) been long-lived in captivity, and when they die or are
removed from a colony one sees violent fighting for breed-
ing status among the larger remaining females, leading to a
takeover by a new queen.
Eusocial insect societies have rigid caste systems, each
(20) insects’s role being defined by its behavior, body shape, and
physiology. In naked mole rat societies, on the other hand,
differences in behavior are related primarily to reproductive
status (reproduction being limited to the queen and a few
males), body size, and perhaps age. Smaller nonbreeding
(25) members, both male and female, seem to participate pri-
marily in gathering food, transporting nest material, and
tunneling. Larger nonreaders are active in defending the