Habituation of adult Magellanic penguins to human visitation as expressed through behavior and corticosterone secretion.

Ecotourism is increasing worldwide; hence, it is important to know how wildlife are affected behaviorally and physiologically by human visitation. We studied the effects of human visitation on the Magellanic Penguins (Spheniscus magellanicus) at Punta Tombo, Argentina, by monitoring changes in defensive head turns and plasma corticosterone (a hormone secreted in response to stress) for penguins with and without a history of tourist visitation. Habituation to human visitation was rapid. In penguins with no previous exposure to tourists, the number of defensive head turns and level of plasma corticosterone decreased significantly within 5 days of one 15-minute visit/day. Penguins living in tourist-visited and undisturbed areas secreted more corticosterone when captured and restrained than penguins visited by a person. Penguins in tourist areas, however did not show as strong a corticosterone response to capture and restraint as did penguins in areas without tourists. This difference was due to a decreased capability of the adrenocortical tissue to secrete corticosterone in tourist-visited birds. Although our data show no direct negative effects of tourism on Magellanic Penguins at Punta Tombo, consequences of a modification of physiological capabilities (e.g., adrenocortical function) may not become apparent until much later in life. The physiological differences between tourist-visited and undisturbed groups of Magellanic Penguins emphasize the importance of monitoring the effects of anthropogenic disturbances on wildlife at multiple levels.