Edinburgh Napier University

  Harbor seals (Phoca vitulina) live in cold temperate or polar seas and molt annually, renewing their fur over a period of approximately four weeks. Epidermal processes at this time require a warm skin and therefore to avoid an excessive energy cost at sea during the molt, harbour seals and many other pinnipeds increase the proportion of time hauled out on land. We predicted that metabolic rate during haulout would be greater during the molt to sustain an elevated skin temperature in order to optimize skin and hair growth. To examine this, we measured post-haulout oxygen consumption (V̇O2) in captive harbor seals during molt and post-molt periods. We recorded greater V̇O2 of seals while molting than when the molt was complete. Post-haulout V̇O2 increased faster and reached a greater maximum at 40 minutes during the molt. Thereafter, V̇O2 decreased but still remained greater suggesting that while metabolic rate was relatively high throughout haulouts, it was most pronounced in the first 40 minutes. Air temperature, estimated heat increment of feeding (eHIF) and mass also explained 15.5% of V̇O2 variation over 180 minutes post-haulout, suggesting that the environment, feeding state and body size influenced the metabolic rate of individual animals. These results show that moulting seals have greater metabolic rates when hauled out, especially during the early stages of the haulout period. As a consequence, human disturbance that changes the haulout behaviour of molting seals will increase their energy costs and potentially extend the duration of the molt.