Data from: 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 dispersing from natural
groups that have not yet bred do not differ in size and shape from helpers
in established groups. Growth patterns consequently resemble other social
vertebrates where contrasts in size and shape follow acquisition of the
breeding role. Our results also suggest that the increases in female body
size provide fecundity benefits. Similar forms of socially responsive
growth might be more prevalent in vertebrates than is currently
recognised, but the extent to which this is the case, and the implications
for the structuring of mammalian dominance hierarchies, is as yet poorly
understood.