RECRUDESCENCE OF SEXUAL-ACTIVITY IN A REPRODUCTIVELY QUIESCENT COLONYOF THE DAMARALAND MOLE-RAT (CRYPTOMYS DAMARENSIS), BY THE INTRODUCTION OF AN UNFAMILIAR AND GENETICALLY UNRELATED MALE - A CASE OF INCEST AVOIDANCE IN QUEENLESS COLONIES

Colonies of the eusocial Damaraland mole-rat, Cryptomys damarensis, ar e founded from a single reproductive pair of animals genetically unrel ated by common descent. All non-reproductive members of the colony are progeny of this reproductive pair. In colonies where the reproductive female has been experimentally removed or has died a natural death, t here is a strict incest avoidance and the colony remains reproductivel y quiescent. Reinstatement of sexual activity in a queenless colony ma y be brought about in the laboratory by the introduction of an unfamil iar and unrelated adult male. In the queenless colony under study, the re was a marked change in social structure with an increase in Landau' s index of linearity from 0.8 to 0.9 on introduction of the new male. The unrelated male became a high ranking dominant reproductive male. T he youngest, but most dominant non-reproductive female became sexually active and subsequently became pregnant and hence acquired the positi on of reproductive female. The new reproductive female exhibited heigh tened progesterone (9 nmols/mmol creatinine) and oestradiol (3000 pmol s/mmol creatinine) concentrations in the urine relative to the other n on-reproductive females. These hormone concentrations were indicative of a reproductively active female. Behavioural and hormonal data are p resented to show that sexual activity can be re-instated in queenless colonies of laboratory maintained mole-rats by the introduction of unr elated male mole-rats.