Seasonal variation in vitamin D metabolites in southern elephant seal (Mirounga leonina) females at south Georgia

Southern elephant seals spend two periods on land each year, during breeding and moult, exposed to intensive UV radiation. The time between periods on land are spent at sea, with little exposure to the sun. A study of serum 25-OH-D3 and 1,25(OH)2-D3 on southern elephant seals was carried out at South Georgia. Samples were collected on four different occasions: early and late breeding, and early and late moult. The levels of 25-OH-D3 increased when seals were on land, and decreased when at sea. Two annual peaks of 25-OH-D3 were found, both of which immediately followed periods of intensive exposure of UV radiation. 1,25(OH)2-D3 levels showed a seasonal variation, but no significant changes while being on land were detected. The diving behaviour at sea for southern elephant seals and no detectable change in 25-OH-D3 indicates that the seals feed on prey containing vitamin D.

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