Many animal populations experience catastrophic population declines which are often caused by natural or human-induced changes in environmental conditions such as climate change or habitat alteration. In response to environment disasters, all vertebrate animals show a stress response that involves the secretion of the stress hormone (corticosterone/cortisol) into the blood. It is so far unclear whether and how a stress response helps individuals to survive, and whether a low or a high stress response is better. The main problem is that it is very hard to study dying animals in the wild. Here professors Wikelski and Romero make use of the fact that Galapagos marine iguanas repeatedly experience natural catastrophes (El Nino weather events) but at the same time are tame and can easily be observed as they die. The researchers will assess the stress response of individuals before a catastrophe and test what kind of a stress response helps individuals most to survive. This research will be put into the context of a 25-year data set that will be made public.
The results of this study will significantly advance the understanding of how vertebrates physiologically deal with catastrophic events in their environment. This project will also educate the public via TV shows and publications, foster scientific exchange between Latin American and US researchers and provide advanced training for undergraduate and graduate students.
Many animal populations experience catastrophic population declines that are often caused by natural or human-induced changes in environmental conditions, such as climate change or habitat alteration. In response to environment disasters, all vertebrate animals show a stress response that involves the secretion of the stress hormone (corticosterone/cortisol) into the blood. Prior to this project, it was unclear whether and how a stress response helps individuals to survive. The main problem is that it is very hard to study dying animals in the wild. This project made use of the fact that Galapagos marine iguanas repeatedly experience natural catastrophes (El Niños) but at the same time are tame and can easily be observed as they die. The goal was to assess the stress response of individuals before an El Niño and then determine what kind of a stress response helped individuals to survive. This is a critical question in ecology. Very little is known about what physiological characteristics allow some individuals to survive while its neighbors die, even though this is an important foundation of natural selection. Perhaps the most exciting finding was that corticosterone responses do indeed help marine iguanas survive. It turned out that the ability to turn off a corticosterone response, (i.e. negative feedback) was a primary predictor of future survival. Iguanas that survived the El Nino turned off their corticosterone responses faster than those that ultimately died. This was a completely novel finding and indicated that the duration of a stress response is more important than its magnitude. A second major finding was the marine iguanas could not cope with introduced predators. Island species are famous for their tameness, but what that meant in terms of physiology was essentially unknown. This project showed that one aspect of tameness is an inability to have an appropriate stress response. Iguanas living on islands with introduced predators (dogs and/or cats) would flee earlier when approached by a different predator (humans) than iguanas living on islands without dogs or cats. However, they still did not flee quickly enough to actually escape a simulated attack by the human. Furthermore, the iguanas living on islands with dogs or cats failed to have a stress response to a human. The conclusion is that neither the behavioral responses nor the stress responses are sufficient to help marine iguanas survive an attack from a novel predator. This seems to explain why island species are so vulnerable to introduced predators. A third contribution was a major review paper that introduced a new way to understand stress responses in animals. The presentation of the "Reactive Scope Model" has the potential of shifting how we think about stress in health and disease. The project also made a major contribution to human resource development. Nine students contribute to the work. Four travelled to the Galapagos and participated directly in data collection. The experience greatly expanded their experience of field biology. Five other students participated in data analysis in the laboratory. They learned how to perform assays, analyze the resultant data, and present the data to peers. These students are co-authors on many of the publications. Finally, the project had a number of broader contributions. The work on tameness has the potential to alter regulatory policies concerning island species and it attracted substantial media coverage. There was also substantial media coverage of the work on stress and survival during El Nino. Both projects were presented in major media outlets as well as numerous websites directed at the general public. The results from these projects were also included in a chapter of a book, "Galapagos: Preserving Darwin’s Legacy," edited by T. De Roy and intended for a general audience. Finally, results of our work formed the basis for a successful lawsuit by the Galapagos National Park against the owners of a boat that spilled oil into the Galapagos waters. Our data on stress and its connection to mortality provided the only solid evidence that wildlife were harmed during the oil spill. The multimillion-dollar judgment will be funneled into conservation and education programs in the Galapagos.
