Integrative assessment of immunity, health-state, growth and survival of Magellanic penguin chicks in a colony exposed to ecotourism

Abstract

Accumulating reports of negative impacts of tourist activities on wildlife emphasize the importance of closely monitoring focal populations. Although some effects are readily noticed, more subtle ones such as changes in physiological functions of individuals might go overlooked. Based on evidence of altered physiology associated with ecotourism on Magellanic penguins Spheniscus magellanicus, here we performed an integrated assessment using a diverse physiological toolkit together with more traditional fitness-related measures to better understand mechanisms and potential consequences. Chicks exposed to tourism showed altered immune condition and elevated flea prevalence, reinforcing previous findings. Tourism-exposed female, but not male, chicks also showed reduced hematocrit and plasma protein levels, providing evidence of sex-specific susceptibility. Physiological alterations detected in tourism-exposed young (week 1-2) chicks were maintained and the effect on flea infestation increased during the study period (week 4-5 of post-hatch). Despite the effects on physiology, these did not seem to translate into immediate fitness costs. No detectable effects of tourism were found on brood sex ratios, chick growth and body condition, and survival until week 5-6 post-hatch. No effects were detected on reproductive output and only a marginal effect on nest survival despite previous reports of tourism-associated alterations in stress indices of adults. This disconnection could result if the physiological changes are not strong enough to impact the measured fitness-related traits and/or only show impacts later in the brooding cycle or even after chick emancipation from their parents. In this respect, a potential link between our results and the previously documented female-biased juvenile mortality in this colony deserves consideration. Integrative assessments of anthropogenic impacts on wildlife should include understanding of physiological mechanisms and individual-level responses to enable the development or tailoring of management measures for effective conservation of exposed populations.