Reproduction triggers adaptive increases in body size in female mole-rats

In social mole-rats, breeding females are larger and more elongated than nonbreeding female helpers. The status-related morphological divergence is thought to arise from modifications of skeletal growth following the death or removal of the previous breeder and the transition of their successors from a nonbreeding to a breeding role. However, it is not clear what changes in growth are involved, whether they are stimulated by the relaxation of reproductive suppression or by changes in breeding status, or whether they are associated with fecundity increases. Here, we show that, in captive Damaraland mole-rats (Fukomys damarensis) where breeding was experimentally controlled in age-matched siblings, individuals changed in size and shape through a lengthening of the lumbar vertebrae when they began breeding. This skeletal remodelling results from changes in breeding status since i) females removed from a group setting and placed solitarily showed no increases in growth, and ii) females disp...