Growing up under the spotlight: effects of tourist visitation on the stress response and sex ratio in Magellanic penguin chicks at San Lorenzo, Argentina

Numerous studies have examined how tourism affects the behavior and physiology of penguins. The majority of these studies focus on adult penguins, with less attention having been focused on chicks - although disturbances and stress to chicks may be particularly problematic during their sensitive developmental period. Here we examine the effects of tourist disturbance on Magellanic penguin (Spheniscus magellanicus) chicks at a colony with an intermediate level of tourist disturbance (San Lorenzo, Argentina with ∼10,000 people/year) and compare these results to our previous findings for a much more intensely disturbed colony (Punta Tombo, Argentina with >120,000 people/year). We examined the development of the hypothalamo-pituitary-adrenal (HPA) axis stress response by measuring the stress hormone corticosterone in chicks in both tourist-visited and undisturbed areas of the San Lorenzo, colony. We additionally determined sex ratio of chicks hatched in both areas of the colony. Although our previous work at Punta Tombo showed tourist disturbance causes early expression of the HPA stress response, chick as San Lorenzo did not show this early expression in either area of the colony. Additionally, there was no difference in sex ratio of chicks between the two areas, and for the colony as a whole, male:female hatch ratio was only slightly skewed towards males. These results suggest that care in examination of tourist disturbance effects on penguins colonies is warranted, and different levels of disturbance may differentially affect penguins’ responses. Additionally, that sex ratio at hatch is nearly equal for male and female Magellanic penguins further suggests that survival post-fledge in these penguins is variable for the sexes, as adult sex ratio is typically highly skewed towards males at colonies in Argentina.