It's when the female is fertile and ready for mating, and it's one of nature's more effective tools to ensure survival of the species. (smallanimalchanel.com)
In terms of survival of the species, it doesn't make sense that breastfeeding would only benefit the baby. (breastfeedingtoday-llli.org)
Sirens, the second novel, follows Jake and Em as they fight for survival of their species, both in space and under the sea. (mimshouse.com)