Recrudescence of sexual activity in a reproductively quiescent colony of the Damaraland mole-rat (Cryptomys damarensis), by the introduction of an unfamiliar and genetically unrelated male—a case of incest avoidance in‘queenless’colonies

Authors

  • C. A. Rickard,

    1. Department of Zoology, University of Cape Town, Rondebosch 7700, Cape Town, South Africa
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  • N. C. Bennett

    Corresponding author
    1. Department of Zoology, University of Cape Town, Rondebosch 7700, Cape Town, South Africa
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    • *

      Dept of Zoology and Entomology, University of Pretoria, Pretoria 0001, South Africa


* Address for correspondence: Dept of Zoology and Entomology, University of Pretoria, Pretoria 0001, South Africa

Abstract

Colonies of the eusocial Damaraland mole-rat, Cryptomys damarensis, are founded from a single reproductive pair of animals genetically unrelated 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, there is a strict incest avoidance and the colony remains reproductively quiescent. Reinstatement of sexual activity in a queenless colony may be brought about in the laboratory by the introduction of an unfamiliar and unrelated adult male.

In the queenless colony under study, there 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. The youngest, but most dominant n on-reproductive female became sexually active and subsequently became pregnant and hence acquired the position of reproductive female. The new reproductive female exhibited heightened progesterone (9nmols/mmol creatinine) and oestradiol (3000pmols/mmol creatinine) concentrations in the urine relative to the other non-reproductive females. These hormone concentrations were indicative of a reproductively active female.

Behavioural and hormonal data are presented to show that sexual activity can be re-instated in queenless colonies of laboratory maintained mole-rats by the introduction of unrelated male mole-rats.

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