Clarke, Frank M.; (1999) Determinants of reproductive status and mate choice in captive colonies of the naked mole-rat, Heterocephalus glaber. Doctoral thesis (Ph.D), UCL (University College London).

Text Determinants of reproductive status and mate choice in captive colonies of the naked mole-rat, Heterocephalus glaber.pdf Download (7MB)

Abstract

Naked mole-rats are small, fossorial, cooperatively breeding rodents with a high reproductive skew. Wild colonies contain around 80 individuals and reproduction is monopolised by a single female, the 'queen', and one to three males. This study investigates the hormonal, behavioural, and genetic correlates of dominance and breeding status in captive colonies. I examine the relationship between dominance rank, reproductive status, and urinary testosterone and cortisol levels, and try to determine whether physiological and behavioural parameters can be used as predictors of succession by experimentally removing breeders. Additionally, Y-maze choice tests were used to investigate kin recognition and female mate choice. Colony social structure is characterised by a linear dominance hierarchy with male and female rank correlated with body weight, age, and testosterone levels. Rank appears the most important determinant of reproductive status. Queens are generally the highest ranking colony member and breeding males the highest ranking males. Both are succeeded by the next highest ranking individuals. Queen succession results in an increase in body weight of colony members, the reproductive activation of one or more females, and often intense dominance-related aggression by females. In contrast, male-male competition over breeding rights is low. This result is interpreted in terms of 'skew theory' and female mate choice. No evidence for a simple relationship between social status and the 'stress' hormone cortisol was found. Furthermore, cortisol does not appear to be causally implicated in suppression of subordinate reproduction. Females discriminate between conspecifics on the basis of familiarity, not through detection of genetic similarity, and discrimination is dependant on their reproductive status. Whereas queens prefer unfamiliar males as mates, reproductively inactive females fail to discriminate. Preferences are interpreted as inbreeding avoidance. Thus, the genetic relationship of males to queens is an important determinant of reproductive status in males.

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