The ecology of gestational growth in a wild cooperative mammal

In wild mammals, early postnatal growth strongly affects offspring
survival and fitness, but little is known about the causes and
consequences of variation in prenatal growth. We investigated whether
gestational weight gains vary according to maternal traits and social and
environmental conditions, and how prenatal growth affects the fates of the
resulting offspring, using an exceptionally large sample of repeated
pregnant body weight records from individually recognisable wild meerkats
(Suricata suricatta). Pregnant meerkats’ body weights remained stable
during the first half of gestation and then increased linearly until they
gave birth. Gestational weight gains were more rapid under favourable
environmental conditions and when mothers were experimentally
food-supplemented, suggesting that nutrition strongly determines prenatal
growth. While social conditions and reproductive competition shape
postnatal growth in many social vertebrates (including meerkats), these
factors had a limited effect on prenatal growth, and adjustments to
gestation lengths were modest and unrelated to social factors. Pups that
grew faster in utero were heavier when they emerged from the birth burrow,
yet this rapid growth was not associated with shortened leukocyte
telomeres, and they were consequently more likely to survive to adulthood.
Broadly, we identified pronounced variation in gestational weight gains,
which is largely driven by food availability and strongly predicts
offspring birth weights and survival. Our findings also highlight
constraints in the flexibility of prenatal growth and gestation lengths in
this species, which may limit adjustments in response to prevailing social
conditions, and enhance selection for flexibility in postnatal growth.