Last update: : Tuesday 23 February 2016, by
Par : Dr. Tony Wiliams, Simon Fraser University, Canada - www.sfu.ca/biology/faculty/williams/
Date : vendredi 24 juin 2016 à 13h
Lieu : IPHC, Amphithéâtre Grünewald, bâtiment 25
How hard do free-living animals work? What determines how hard individuals will work on specific activities? Can animals work too hard, such that they pay costs of high levels of activity? It is widely assumed that rearing chicks is “hard work”, otherwise all individuals should be able to rear many, high quality chicks. Also, the idea that a high level of investment in current reproduction can have a negative influence on survival or future fecundity – that there is a ‘cost of reproduction’ – is a central component of evolutionary theory. Central-place foraging associated with parental care (chick-rearing) in birds provided a powerful model for development of optimal foraging theory. However, our knowledge of the physiological basis of individual variation in foraging performance remains rudimentary. Do ‘high quality’ individuals achieve high breeding productivity because they have an ‘innate’ ability to sustain high rates of workload, or perhaps because they can work ‘hard’ without paying costs?
We investigated the physiological basis of individual variation in workload ability (perhaps related to ‘quality’) and putative effects of costs associated with high workload. We obtained repeated measurements of 13 physiological traits in individual, female European starlings (Sturnus vulgaris) during incubation and chick–rearing (low vs. high activity level); including measures of aerobic and metabolic capacity, oxidative stress and muscle damage, intermediary metabolism and energy supply, and immune function. We compared these with measures of workload (provisioning rate, flight distance), current reproduction (brood size), as well as future fecundity (second broods, productivity in year x+1) and survival. We then manipulated workload using a wing-clipping treatment. We use these data to test the following hypotheses: a) that individual variation in “baseline” physiological state predicts breeding success/failure or overall productivity; b) that individual variation in physiological state correlates with individual variation in workload (e.g. nest visit rate) and breeding productivity; and c) that individuals with the highest rates of workload show physiological signatures of ‘costs’.