Anecdotal observation of a sexual encounter between two male naked mole-rats

Abstract

Same-sex sexual behaviours (SSBs) are widespread across the animal kingdom, yet little consensus exists regarding their potential adaptive functions or evolutionary history. To fully address questions such as why or how a trait has evolved, it is important to first understand its natural history. Here, we present evidence of SSBs in two male naked mole-rats for the first time. Due to extreme natal philopatry, most naked mole-rats never disperse, making encounters with potential mates valuable in fitness terms. However, in captive colonies of naked mole-rats, a rare disperser morph has been described. We speculate that such dispersing individuals may be indiscriminatory in their mating strategy, copulating with conspecifics regardless of sex, to counter the risk of missed reproductive opportunities. This behavioural strategy would contrast with the common characterisation of naked mole-rats, which describes them as fiercely xenophobic and hostile to unfamiliar individuals. Further, the observation of an indiscriminate mating strategy in a species with limited opportunities for dispersal provides interesting context for the study of the evolution of SSBs.

The evolution of same-sex sexual behaviour in mammals

“…Several hypotheses have been proposed to explain the evolution and prevalence of same-sex sexual behaviour in human and nonhuman animals 2,8,11,17,18 . Some of these hypotheses are non-adaptive, suggesting that same-sex sexual behaviour is the consequence of mistaken identity 19,20 , the limited availability of individuals of the opposite sex [21][22][23] , the consequences of sexual frustration when individuals are refused by members of the other sex 20 , or the byproduct of selection acting on a separate trait, such as high sexual responsiveness 24 . A recently proposed hypothesis that is attracting much attention states that indiscriminate sexual behaviour (that is, the co-occurrence of different-sex sexual behaviour and same-sex sexual behaviour) is the ancestral condition for sexually reproducing animals and this explains the widespread occurrence of same-sex sexual behaviour in animals 3,16 .…”