Meeting Abstract
Pinnipeds forage in the marine environment but aggregate terrestrially for breeding. Little is known about how breeding and associated extended fasts impact immune function. Elephant seals give birth in high-density environments and undergo wide fluctuations in plasma cortisol, a hormone known for immunosuppressive effects, while fasting. Our goal was to characterize immune response across life history stages in adult female elephant seals and explore potential impacts of natural variation in cortisol on immune function. We measured a suite of cytokines, acute phase proteins, and immunoglobulins early and late in breeding and molt haul-outs in 198 samples from 131 female elephant seals taken over 4 years (2011-2014). All immune markers varied significantly with life history stage. In general, immune responses were greater and more varied during the breeding haul-out, particularly in samples closest to parturition. Immune markers were not associated with plasma cortisol levels with one exception. The exception to this pattern was immunoglobulin E, a marker of immune response to parasitic infection. IgE was highest after the post-breeding foraging trip and exhibited a significant negative association with cortisol across all life history stages. This association was strongest directly after foraging trips. IgE also declined significantly over the four study years, despite similar foraging success, suggesting declining parasite exposure or response across the study period. These data suggest that breeding carries an immune cost in female northern elephant seals, but elevation of cortisol in association with breeding fasts does not suppress immune function. In contrast, immune responses to parasites may be influenced by variation in plasma cortisol during foraging.
