Body reserves influence allocation to immune responses in capital breeding female northern elephant seals

Mounting an immune response requires substantial energy. Ecological immunology theory predicts allocation trade-offs between reproductive effort and immune responses under conditions of energy limitation. Little is known about the impact of capital breeding strategies on energy allocation to immune function in mammals. Northern elephant seals (NES) forage in the marine environment, breed in dense terrestrial colonies and exhibit high rates of energy expenditure for lactation while fasting. Body reserves strongly influence reproductive effort and lactation requires elevation of plasma cortisol for energy mobilization. We characterized immune response by measuring a suite of immune markers including cytokines, an acute phase protein, and immunoglobulins early and late in breeding and moult haul-outs in 197 samples from 129 female NES. We explored potential impacts of breeding, body condition and plasma cortisol on immune function. Immune responses were greater and more varied during br...