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Rainfall, dispersal and reproductive inhibition in eusocial Damaraland mole-rats (Cryptomys damarensis)

Published online by Cambridge University Press:  14 March 2002

A. J. Molteno
Affiliation:
Department of Zoology & Entomology, University of Pretoria, Pretoria 0002, South Africa
N. C. Bennett
Affiliation:
Department of Zoology & Entomology, University of Pretoria, Pretoria 0002, South Africa Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
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Abstract

Non-reproductive female Damaraland mole-rats Cryptomys damarensis that were caught before a period of good rainfall (during which 90% of the average annual fell) (Group 1), exhibited a significantly lower pituitary sensitivity to gonadotrophin-releasing hormone compared to non-reproductive females (Group 2) caught in the same area, close to the end of the wet period. Group 2 were also significantly heavier than Group 1. Pituitary sensitivity was not significantly correlated to body mass within either group of females, nor within groups of reproductive males and non-reproductive males from a laboratory held colony. This suggests that rainfall may have resulted in the simultaneous, but unrelated, increase in pituitary sensitivity and body mass. Larger size and reduced sexual inhibition assist dispersal and the probability of successful independent reproduction, during periods when environmental constraints on dispersal are relaxed. These findings support the hypothesis that low rainfall may be an important constraint on dispersal and an important factor promoting the evolution of reproductive inhibition, and consequently eusociality, in this species.

Type
Research Article
Copyright
2002 The Zoological Society of London

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