Colony defense in Damaraland mole-rats, Cryptomys damarensis

I examined defense against conspecific intruders in colonies of the Damaraland mole-rat. I introduced foreign animals to captive colonies and examined the effect of the sex and breeding status of the intruder on the sex and breeding status of those that defended. Intruding mole-rats were almost always attacked. Colony defense against intruders was carried out almost exclusively by dominant, reproductive individuals and was directed primarily toward individuals of the same sex. Nonbreeding, subordinate mole-rats participated only rarely. These results contrast sharply with colony defense in the related naked mole-rat and suggest that investment in defense activities in Damaraland mole-rats primarily reflects repulsion of potential competitors for breeding status. Subordinate mole-rats may lack incentive to participate in potentially costly defense, as they are unlikely to gain repro-ductive opportunities within the colony and probably gain fitness primarily through dispersing to breed. Key words: cooperative breeding, Cryptomys damarensis, kin selection, mole-rats, sociality, territorial defense. [Behav Ecol 13:160–162 (2002)] In social animals, defense of communal resources such asterritories or food resources against intrusion by conspe-cifics or predators may involve considerable costs and risks (e.g., Fitzgibbon, 1997; Packer et al., 1990), and willingness to repel intruders may vary according to the benefits so gained (Downs and Ratnieks, 2000; Reeve, 1989). What fitness benefits do individuals gain from costly defense? Breeding in