#46 Milk Does A Body Good

A few days ago while on survey we sighted one of the newer North Atlantic right whale mothers, #3360. (Click here to look up #3360 in the North Atlantic Right Whale Catalog.) Though her calf is already a good size, it still has a lot of growing to do by nursing on its mother's rich milk, and we were lucky enough to see some nursing behavior as we circled above the pair. We call the behavior "Probable Nursing" because we can't be sure that the calf is nursing without actually seeing the milk enter the calf's mouth. However the main cue that nursing is probably happening is a calf diving underneath its mother so that its head is just forward of the peduncle, where the body narrows out to the tail (see the accompanying photo). Usually the calf will surface for a breath on the opposite side of its mother from where it originally dove, and then repeat the process, surfacing next on the opposite side of the body again.

Photo Credit: New England Aquarium; Kelly Slivka.

As mammals, whales manage to nurse their young despite the difficulties of suckling underwater with a fixed jaw (allowing for no lip pursing/sucking). Calves need to pack on the pounds immediately after birth in order to build up their blubber layer and stay warm when they accompany their mothers to colder northern waters in spring, and some baleen whales have milk that is 40% fat in order to facilitate quick weight gain. For comparison, human milk is about 5% fat on average. Imagine gulping down milk that is the consistency of thick yogurt or cottage cheese, and you have a good idea of the diet of a right whale calf for about a year after birth!


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