Biol. Lett. doi:10.1098/rsbl.2010.0555 (2010)

In groups of banded mongooses, which rear their young together, two-thirds of females give birth on the same night, despite mating on different days.

Sarah Hodge at the University of Exeter, UK, and her colleagues looked at pup survival in 13 groups of Ugandan banded mongooses (Mungos mungo; pictured) over almost 13 years. Synchronous litters suffered fewer deaths before the young mongooses left the den, suggesting that adults who might otherwise kill others' offspring are unlikely to do so when they might risk accidentally killing their own young. Synchronous litters also have fewer pup deaths after they emerge into the world, suggesting that late-born pups lose out in competition for food with bigger littermates. Similar pressures may operate in other species, the authors speculate.

Credit: A. YOUNG