INTERCOLONIAL ENCOUNTERS AND XENOPHOBIA IN THE COMMON MOLE-RAT, CRYPTOMYS HOTTENTOTUS HOTTENTOTUS (BATHYERGIDAE) - THE EFFECTS OF ARIDITY, SEX, AND REPRODUCTIVE STATUS
Ac. Spinks et al., INTERCOLONIAL ENCOUNTERS AND XENOPHOBIA IN THE COMMON MOLE-RAT, CRYPTOMYS HOTTENTOTUS HOTTENTOTUS (BATHYERGIDAE) - THE EFFECTS OF ARIDITY, SEX, AND REPRODUCTIVE STATUS, Behavioral ecology, 9(4), 1998, pp. 354-359
The ecological constraints prevalent in arid environments have promote
d the evolution of social groups with a high reproductive skew in mole
rat species occurring there. Outbred social bathyergids face conflict
between maintaining colony integrity to enhance personal foraging suc
cess and hence survival, and dispersal to maximize individual lifetime
reproductive success (LRS). This conflict will be a crucial determina
nt of the response of colony members to the presence of foreign conspe
cifics. We investigated how ecological constraints, sex, and reproduct
ive status influence the outcome of meetings between foreign common mo
le rats (Cryptomys hottentotus hottentotus) in a series of dyadic enco
unters. Individuals from two localities, at the extremes of an aridity
gradient, were used to assess the effects of aridity. The effects of
sex and reproductive status were investigated by trials between indivi
duals of differing sex and status. The arid population revealed substa
ntially higher levels of rejection than the mesic population. Sex and
status played a significant role in moderating individual response. Fo
r both populations, encounters between different-sexed individuals pro
duced lower levels of rejection than those between same-sexed individu
als. For the mesic site, rejection was greatest for encounters between
reproductive animals. Conversely, for the arid site, the levels of re
jection were comparatively high and comparable for all combinations of
reproductive status. Ecological constraints, sex, and reproductive st
atus are significant factors in interactions between foreign common mo
le rats, ultimately influencing individual survival, colony integrity
and the differential LRS of all colony members. Our results provide in
sight into the evolution and maintenance of family groups within the b
athyergids.