Weddell seals (Leptonychotes weddellii) in the Antarctic can lose up to 60% of their body weight during the nursing period. Researchers found that females will begin diving two weeks after giving birth to their pups and the amount of diving varied depending on the body mass of the mother. Thinner seals diving more often and at deeper depths than seals with more body mass, indicates that mothers adjust their diving and foraging behavior to compensate for the energy they lose during lactation of their pups.

[Photo by Skyla Walcott and caption by Karli Chudeau]

Reference

Sato, K., Mitani, Y., Cameron, M.F., Siniff, D.B., Watanabe, Y., Naito, Y. (2002). Deep foraging dives in relation to the energy depletion of Weddell seal (Leptonychotes weddellii) mothers during lactation, Polar Biology, 25(9), 696-702. https://doi.org/10.1007/s00300-002-0406-7.