Being a weakling and surviving: Keep the fittest siblings close-by when eating.

Weaklings serve as a buffer, allowing an increase in the overall prospect of offspring survival. Whereas birds are able to directly determine which offspring to invest in via selective feeding, multiparous mammals have fewer methods of excluding weaklings from milk provision. In pigs the maternal investment strategy is based on the vigorousness of the progeny, whereby weaklings can suffer hunger due to an inability to sufficiently stimulate the mammary gland. However, the vigorous massage might stimulate higher milk production in the surrounding glands and it is possible that a weakling's survivability is conditioned also by suckling at a position adjacent to heaviest littermate. Results of the present study have confirmed this prediction, showing that the surviving weaklings tended to have the heaviest littermates as nearest neighbours during suckling. It appears, therefore, that weaklings which establish a type of commensal, rather than competitive, relationship with strongest siblings might increase their survivability.