Oxidative Status and Life History Trade-offs in the Cooperatively Breeding Florida Scrub-Jay

Oxidative damage has been linked to several degenerative diseases and, as such, the oxidative status of an organism has been widely used as a proxy for health state. Organisms able to resist attack by reactive oxygen species, or those with high levels of antioxidants, are typically assumed to be in better condition (i.e., better able to withstand oxidative damage to biomolecules). Little work, however, has focused on whether the oxidative status of an organism (particularly oxidative damage in free-living species) influences life history decisions. My research examined the interplay between oxidative status and life history characteristics in a free-living bird, the Florida Scrub-jay (Aphelocoma coerulescens). I addressed the following questions: 1) Does reproductive effort covary with oxidative status? 2) Does supplementation of carotenoids (potentially important antioxidants) alleviate oxidative stress during reproduction? 3) Does supplementation of carotenoids alleviate oxidative stress during development? 4) Is oxidative status predictive of survival during early developmental stages? I found: 1) The oxidative cost of reproduction was sex specific with pre-breeding oxidative damage levels negatively correlated with reproductive effort, however, only in males. Similarly, in males, post-breeding levels of oxidative damage were significantly greater than pre-breeding levels. 2) Supplementation with antioxidants did not significantly change reproductive effort, or affect post-breeding oxidative damage levels. However, there was a relationship between change in oxidative damage levels with reproductive effort and treatment group (i. e., supplemented with antioxidants or not). Interestingly, I found no correlation between two measures of oxidative damage and a third measure of oxidative state (total antioxidant capacity). We emphasize the importance of the assessment of multiple measures of oxidative status in future studies. 3) Supplementation of nestling did not significantly affect growth or oxidative damage measures. 4) Oxidative damage to proteins was significantly lower in older individuals, whereas TAC was significantly higher in older individuals; however, damage to DNA did not significantly differ across ages. Oxidized proteins increased significantly from the nestling to nutritional independence stages (~2 months of age) and then subsequently declines as birds reached ~9 months of age. There were no relationships between oxidized proteins and survival at these early life stages