New research by Dr Chris Faulkes of Queen Mary, University of London draws connections between the breeding habits of mole-rats and stress-related infertility in humans. Dr Faulkes presented his research in Lyons, France this week, at the annual meeting of the European Society of Human Reproduction and Embryology.
The eusocial naked mole-rat (Heterocephalus glaber) lives in colonies of 100-300, where reproduction is dominated by one female - the queen - and a select few males. The chronic infertility of the remainder of the colony gives the species an advantage in semi-arid regions, by allowing the non-breeding majority of the colony to dedicate itself to burrowing and gathering food. It is thought that a key mechanism for suppressing fertility in the species is the aggressive behaviour of the dominating queen, which induces stress in other mole-rats. This stress affects hormone levels, which in turn reduces or even eliminates male sperm production and female ovulation.
More remarkably, the fertility-suppressing mechanism is sufficiently precise and flexible that the queen can revive a fellow mole-rat's fertility as and when necessary. Dr Faulkes explains: 'Despite...hormonal deficiencies in non-breeders that may persist for many years, the block to reproduction is reversible. Non-breeding males and females will rapidly become reproductively active if they are removed from the suppressing influences of their colony and housed singly or in male-female pairs, or if the queen in a colony dies.'
Recent studies have pointed to stress as a significant cause of male and female infertility in humans, and Dr Faulkes suggests that mole-rats may provide a useful model for future research on along these lines. He also points to other species, some of them more biologically similar to humans than mole-rats, which seem to employ a similar mechanism of suppressing fertility by inducing stress: 'Naked mole-rats are at the extreme end of a continuum of examples of socially-induced reproductive suppression among mammals with other examples found in primates, canids and mongooses. Understanding the causes and neuroendocrine/physiological consequences of such 'natural contraception' can also inform studies of stress-related infertility in humans. 'Dr Faulkes adds the important caveat that many of the relevant neurobiological processes are not yet fully understood. Furthermore, the sheer diversity of human social behaviour adds to the difficulty of drawing analogies with animal behaviour.