Meeting Abstract
All sexually reproducing organisms are faced with a fundamental decision: to invest valuable resources and energy in reproduction or in their own survival. This trade-off between reproduction and survival represents the ‘cost of reproduction’ and occurs across a diverse range of organisms. The costs of reproduction are thought to underlie a number of behavioral adaptations, including the evolution of mating and social systems. Although it is widely assumed that cooperative breeding behavior in vertebrates results in part from costly parental care the costs of reproduction in social species have rarely been quantified. We examine the costs of reproduction in a free-living population of cooperatively breeding superb starlings (Lamprotornis superbus), combining proximate and ultimate levels of analysis. Specifically, we show that costs of reproduction have a measurable impact on superb starling fitness, where birds investing in reproduction more frequently throughout their lives have a shorter lifespan (i.e. breeding superb starlings have shorter lives than helpers at the nest, who invest less in caring for young). To better understand the costs of reproduction, we are further examining the physiological mechanisms that link reproduction and survival over a shorter time frame. Specifically, we focused on whether oxidative stress, glucocorticoids, or immune function could play a role in linking reproduction and survival in superb starlings. Preliminary results show that oxidative stress increases with reproductive workload, suggesting that this physiological trait may play a part in linking reproduction to reduced survival. This research demonstrates the importance of integrating across behavioral ecology, endocrinology, immunology and physiology to further understand the costs of reproduction.
