Transfer of fatty acids from mothers to their calves during lactation in white whales Delphinapterus leucas

Blubber biopsies, through the entire blubber layer, were collected from the members of 4 mother-calf pairs of white whales Delphinapterus leucas from Storfjorden, Svalbard, Norway. In addition, milk samples were collected from all 4 adult females. The calves ranged in age/size from newborn (with the umbilical cord still attached; 140 cm in length) up to a 1 yr old (body length of 255 cm). Since white whale calves consume only milk during their first year of life, free-living mother-calf pairs provide an interesting opportunity to study the deposition of lipids (calf blubber) when the diet (i.e. milk) is known precisely. The blubber of the newborn calves had fatty-acid (FA) compositions that differed significantly from the FA compositions of both the milk and the blubber of their respective mothers. The FA composition of the blubber of calves changed gradually with age, coming to resemble the FA composition of the blubber of their mothers more closely, rather than shifting towards the FA composition of the milk, i.e. their diet. The largest calf in the study had a blubber FA composition similar to that of the adult whales. Analyses also showed that the FA composition of the milk was significantly different from the FA composition of the maternal blubber.