Whales and dolphins, being marine mammals, exhibit the typical characteristics of mammals: they’re warm-blooded, breathe air, have fur (although only a few hairs or for a limited time period), give birth to live young, and produce milk to feed their offspring. Calves of either whales or dolphins are able to swim shortly after birth, but are unable to hunt and feed and so are fed milk from the mother, with some species nursing for over a year! Without lips, and living in aquatic environment, you can appreciate the inherent difficulties of nursing. You can also appreciate the difficulties involved in us as humans getting closed enough to really see what is happening during nursing. Whale and dolphin calves take frequent short dives beneath the mother for nursing. Whales and dolphins do not have external nipples, instead their nipples are enclosed within mammary slits. Upon stimulation of the calves nudging, the nipple is exposed and the calf positions itself such that the nipple is at the gape of the calf’s jaw for feeding. It is also thought that the tongue is rolled into a tube around the nipple, or rolled into a U-shape and pressed against the upper palate and placed around the nipple, and the mother voluntary ejects milk into the mouth of the calf.
Milk of whales and dolphins varies considerably in fat concentration, but it is much higher than that of human breast milk. The higher fat-content allows for fast growth; it is very important for calves to develop a thick layer of blubber due to the thermoregulatory demands of a marine environment (heat is lost faster in water than in air). The high fat content also allows the milk to travel through the water without breaking up as it is much thicker.
Baleen whales and toothed whales (including dolphins) differ in their milk content and lactation habits. Baleen whales have a relatively short lactation period (5-7 months) during which they fast, or eat very little. On the other hand, toothed whales have a longer lactation period (1-3 years), during which the mothers will feed.
Written by: Minke Tolsma
For further reading:
- Johnson, G., Frantzis, A., Johnson, C., Alexiadou, V., Ridgway, S., & Madsen, P. T. (2010). Evidence that sperm whale (Physeter macrocephalus) calves suckle through their mouth. Marine Mammal Science26: 990-996.
- Oftedal, O.T. 1997. Lactation in whales and dolphins: Evidence of divergence between baleen- and toothed-species: Maternal adaptation to lactation. Journal of Mammary Gland Biology and Neoplasia 2: 205-230.
- Zoidis, A.M., & Lomac-MacNair, K.S. 2017. A note on suckling behavior and laterality in nursing humpback whale calves from underwater observations. Animals 7: 51.