Measuring stress in Antarctic seals

Abstract

The term stress is used widely to describe the possible effects of external factors (stressors) on animals at both the individual and population levels. An important question in biology is how animals cope with their environment (Romero and Reed 2005). Assessing this coping mechanism can be done either behaviourally or physiologically or by a combination of both. Stressors include those aspects of everyday life such as energetic and physical demands as well as the more unpredictable events such as habitat loss, predation risk, loss of social status and impacts of human activities. Antarctic animals live in weather conditions that would be considered extreme by most humans and are subject to changes in prey sources and, more recently, to localised disturbance by tourist activities. The Protocol on Environmental Protection to the Antarctic Treaty has highlighted the need to understand the impacts of human activities in Antarctica. An understanding of how Antarctic species cope with their environment is needed if we are to understand how human activities are impacting different species. In the past, human impact studies focused on changes in species' demographic patterns such as breeding success (e.g. Frederick and Collopy 1989; Lord et al. 2001), but more recently attention has been given to the physiological changes that occur in species which are subject to human disturbances (e.g. Romero and Wikelski 2002; Müllner et al. 2004; Walker et al. 2006). Behaviour, heart rate and physiological responses are modulated depending on the type of stressor (Nephew et al. 2003), and so in order to monitor human disturbances in Antarctica, both behavioural and physiological responses should be measured (Walker et al. 2006).