The ability to discriminate between conspecifics functions in mate choice, kin-selected cooperation and territory defence. In mammals, olfaction plays a key role in such social interactions. Olfactory cues may be particularly important for subterranean mammals, for which visual and acoustic cues are less effective. Damaraland mole-rats live in groups comprising a breeding pair and their nonbreeding offspring. They are xenophobic, obligate outbreeders and independent dispersal represents the usual route to reproduction for both sexes. As yet, little is known about how dispersing individuals locate mates. Using a series of behavioural experiments, we reveal that mole-rats can discriminate between unfamiliar breeding groups and solitary, nonbreeders of the opposite sex by using odour cues. Our experiments showed that subjects spent more time investigating sand taken from other mole-rat groups than control sand, indicating an ability to recognize substrate-borne conspecific odours. Mole-rats also spent more time digging and sweeping in sand taken from the tunnels of unfamiliar, solitary animals of the opposite sex than sand taken from unfamiliar breeding groups and removed a higher volume of this sand during the experiments. Together, these results suggest an olfactory preference in both sexes for solitary, opposite-sex animals over breeding groups. Our results are supported by observations from the field that immigration into breeding groups is rare, with dispersing females typically establishing new groups, where they are subsequently joined by unfamiliar males. This study supports olfaction as a potential recognition cue which may facilitate adaptive dispersal.
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