Each burrow system is inhabited by a single colony of mole rats, typically with about twelve members, although colonies can range from as little as two to as many as forty members. The colony is eusocial, consisting of a single breeding pair and their non-reproductive offspring. The non-reproductive members of the colony spend their time foraging and maintaining the tunnel system, in particular closing any breaches that may occur. Intruders from other colonies are generally rejected, although DNA paternity studies show that at least some non-reproductive members of a colony may have been fathered by outsiders. The colony has a clearly defined hierarchy, with the breeding male dominant, followed by the breeding female, then non-reproductive males, and finally non-reproductive females.