Meeting Abstract
30.3 Monday, Jan. 5 Sickness behavior and fever vary among free-living sparrows along a life history gradient ADELMAN, J. S.*; WIKELSKI, M. C.; HAU, M.; Princeton University; Max Planck Institute for Ornithology; Max Planck Institute for Ornithology jsadelma@princeton.edu
Studies in ecological immunology suggest that organisms trade-off the limited resources of time, nutrients, and energy between immune function and other life history traits such as reproductive effort. However, we do not understand which of these resources plays the most important role in shaping such trade-offs. We addressed this question using radio telemetry in free-living song sparrows (Melospiza melodia) at three sites along a latitudinal gradient in reproductive effort (as measured by clutch size and breeding season length). During the early breeding season, we studied three aspects of the acute phase immune response: 1) sickness behavior, specifically inactivity, which represents a significant investment of time, 2) acute phase protein synthesis, which uses both amino acids and energy to build defensive proteins, and 3) fever, which requires substantial energy. Birds were either injected with lipopolysaccharide, a non-pathogenic bacterial cell wall component, or handled but not injected. In the southern population, where reproductive effort per unit time is lowest, treated birds showed an extended time-course and increased severity of sickness behavior when compared to northern populations. Moreover, treated birds in the southern population displayed the lowest levels of territorial aggression in response to conspecific playback. Fever also differed among sites; treated southern birds displayed increased temperatures whereas treated northern birds showed early and transient hypothermia. Acute phase protein synthesis, however, was similar at all latitudes. These results suggest that trade-offs involving time and energy, but not amino acids, help shape the differences in the acute phase response among these populations.
