Litter (zoology)

[1] Animals frequently display grouping behavior in herds, swarms, flocks, or colonies, and these multiple births derive similar advantages.

A litter offers some protection from predation, not particularly to the individual young but to the parents' investment in breeding.

With multiple young, predators could eat several and others could still survive to reach maturity, but with only one offspring, its loss could mean a wasted breeding season.

The other significant advantage is the chance for the healthiest young animals to be favored from a group.

Rather than it being a conscious decision on the part of the parents, the fittest and strongest baby competes most successfully for food and space, leaving the weakest young, or runts, to die through lack of care.