Social behavior in Heterocephalus glaber, the naked mole-rat.

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What is eusociality? * Which species display eusociality? * What is a naked mole-rat?

There are many different lifestyles in the animal kingdom, some of which are more foreign to us than others. One very specialized lifestyle is that of eusociality, or colony living. This type of behavior is most common in insects, but has evolved at least twice in the mammals. Herein we will discuss eusociality in one of those mammalian species, the naked mole-rat, touching on how its behavior might have evolved, how it is reinforced, how it develops in individual colonies, and why it is an adaptive lifestyle.

Sleeping naked mole-rats(i)

Eusociality is a behavior that maximizes the good of the colony over the good of the individual. It is generally characterized by a single breeding female and her offspring, which are organized in a hierarchical caste system to distribute work in the colony effectively. The individuals that do not breed share duties, including caring for young, foraging, and colony maintenance(1). Eusociality has also been referred to over the years as behavioral altruism(18) and inductive fitness(9). For more on eusociality see the Phylogeny page.

Which species display eusociality?(top)

Eusociality is common in a diverse group of insects, including honeybees, wasps, termites, and ants (2).

Eusociality is less common among vertebrates. Under the most strict definition of eusociality, only two mammals qualify: the naked mole-rat (Heterocephalus glaber) and the Damaraland mole-rat (Cryptomuys damarensis) (3).

A naked mole-rat. Note the giant teeth and tiny eyes and ears.(ii)

Damaraland mole-rats. They look more like 'conventional' rodents.(iii)

What is a naked mole-rat? (top)

Heterocephalus glaber are a small rodent in the Bathyergidae family, native to the deserts of East Africa.(4). They are nearly hairless, nearly blind, and nearly cold-blooded (poikiothermic). They tunnel through the dirt to find and eat tubers that are sparsely scattered through the desert. One tuber can feed a colony of naked mole-rats for months (1). Aside from the queen and her one to three consorts, all animals look the same, with no differences in appearance of external genitalia (5).

This is an excellent video of naked mole-rats in action, narrated by David Attenborough