Some newborns can take milk from moms other than their own.
In these cases, it’s important to discern whether the mom has a hand in mistakenly identifying an allosuckling pup for her own pup, or whether it’s a case of milk-stealing – a behaviour of the pup that is outside of the awareness of the allonursing mom.
Many mammalian newborns are much more capable than human newborns. They know whether they are being adequately fed – and if they are not, they are capable of sourcing out an alternative mode of nutrition.
Milk-stealing is quite a common occurrence in ungulates like reindeer, camels, and giraffes, and offspring undertaking this risky behaviour have a few common strategies.
First, milk-stealers generally try to suckle from a mom while her own offspring are suckling as well. This works well when there is more than one natural pup in a litter and the milk-stealer selects a position in the middle of the pack.
Second, many milk-thieves will position themselves in an anti-parallel position with respect to the mom so that their back end is closest to the mom’s front end.
Mom is less likely to realize that the intruder is not her own if she isn’t seeing the face. This anti-parallel strategy works especially well if used with the combined feeding method.
A milk-stealer can be successful even if their stealth is not verified, as of course, it’s difficult to conclude whether an infant is actually fooling the mom or whether the mom is simply tolerant of allonursing because of a mutual understanding with the moms in the group.
This post is an adapted excerpt from my book “Wild Moms: Motherhood in the Animal Kingdom“