Abstract:
The social mole-rats of the family Bathyergidae show elaborate social organisation that
may include division of labour between breeders and non-breeders as well as across
non-breeders within their groups. However, comparative behavioural data across the
taxa are rare and contrasts and similarities between species are poorly understood.
Field studies of social bathyergids usually involve capturing all group members until the
entire group is captured. Because each animal is only captured once and traps are
typically placed in close proximity to active foraging areas, the order in which animals
are captured provides an indication of the foraging activity of different individuals and of
the spatial organisation of the group within the burrow system. Here, we compare the
association of capture order with breeding status, sex, and body mass in four species
and subspecies of social bathyergids, which vary in group size and represent all three
social genera within the family Bathyergidae. We show that in naked and Damaraland
mole-rats (Heterocephalus glaber and Fukomys damarensis), male and female breeders
are captured later than non-breeders, whereas in two different subspecies of the
genus Cryptomys only female breeders are captured later than non-breeders. The
effect sizes vary largely and are 10 times larger in naked mole-rats as compared to
Fukomys and 3–4 times larger than in Cryptomys. Among non-breeders, sex effects are
notably absent in all species and body mass predicted capture order in both naked
and Damaraland mole-rats. In naked mole-rats, larger non-breeders were captured
earlier than smaller ones, whereas in Damaraland mole-rats intermediate-sized nonbreeders
were captured first. Our data suggest that there are similarities in behavioural
structure and spatial organisation across all social bathyergid species, though the most
pronounced differences within groups are found in naked mole-rats.
