Consequences of heterothermy during development on the physiology and growth of Antarctic storm-petrel chicks

The ability to endure a wide range of body temperatures, called heterothermy, offers many species worldwide the possibility to survive times of malnourishment by lowering metabolic rate and body temperature. During development, facultative hypothermia and therefore lowered body temperatures might have disadvantages. Our study aimed at identifying potential trade-offs between the use of facultative hypothermia and investment into growth, immunity, and nutritional physiology in chicks of an Antarctic seabird, the Wilson's Storm-petrel (Oceanites oceanicus). To answer these questions, we used the irregular occurrence of facultative hypothermia of chicks from a free-living colony breeding on the South Shetland Islands, Antarctica. Our study showed that chicks experiencing lower body temperatures or snowstorms had slower growth, fewer circulating leukocytes, and lower triglyceride concentrations. These findings suggest reduced investment into physiology and growth during events of facultative hypothermia. Patterns of wing growth following facultative hypothermia suggest that chicks may recover within little time after feeding and rewarming. For other parameters, more data of intervals with facultative hypothermic body temperatures followed by normothermy are needed to allow similar conclusions. Our results suggest that while heterothermy seems a beneficial strategy for chick survival in this species, it incurs partially reversible trade-offs with other physiological traits.