L. Michael Romero - US grants

L. Michael Romero
Physiology of Stress in Wild Animals
Proposal Number 0235044

All organisms are faced with noxious stimuli from the environment (such as predators or storms). Vertebrates activate a suite of physiological mechanisms to protect themselves from these stimuli, collectively called the stress response. A vital part of the stress response is the release of the glucocorticoid steroid hormones, but even after more than 60 years of studying stress we still have only a rudimentary idea of how glucocorticoids help wild animals survive. Earlier work indicated that several free-living bird species seasonally regulate glucocorticoid release by varying concentrations of the hormone throughout the year. This proposal builds upon these results to ask the following questions: why do animals seasonally regulate glucocorticoid levels; is there a physiological consequence; and does it affect their susceptibility to chronic stress?
Answering these questions will require an integrated approach of both laboratory and field studies, such as the one proposed here. We will capture wild free-living house sparrows (Passer domesticus) and test how glucocorticoids help regulate blood glucose and triglyceride levels at different times of the year. We anticipate that glucose and triglyceride regulation will depend upon seasonal changes in glucocorticoid levels. We will also bring house sparrows into the laboratory to test whether physiological responses to chronic stress vary seasonally. We anticipate that the magnitude of the negative consequences of chronic stress will depend upon the time of year. These results will help define the physiological consequences of seasonal glucocorticoid release during stress in wild animals, thus having a far-reaching impact on our basic knowledge of the ecological validity of stress responses.
This research will also provide important training for students. Both graduate and undergraduate students will be exposed to, and learn, many important research skills in both the laboratory and field. These findings will be valuable to researchers in diverse fields including Conservation Biology, Endocrinology, and Population Biology, just to mention a few.

Scientific Goals
All organisms are faced with challenges (such as predators or storms) from the environment. Animals mount a stress response in order to survive these challenges, but even after nearly 100 years of studying stress, there is only a basic understanding of how the stress response helps wild animals to survive. This lack of knowledge is of growing significance because man-made noxious events (such as habitat degradation or human disturbance) could cause chronic stress. Although a short-term stress response to a predator or storm is necessary for survival, chronic stress can be very harmful, and if it affects enough individuals, can cause population declines.

This project will use wild European starlings as a model to test two hypotheses: (1) That increased frequency of normal environmental events can result in chronic stress in wild animals; and (2) There will be long-term impacts on offspring whose mothers were exposed to chronic stress. Testing these hypotheses will require an integrated approach of laboratory and field studies on the physiology and behavior of both captive and free-living starlings. The ultimate goal is to create a physiological and endocrinological profile of chronically stressed wild animals. This will provide criteria for identifying chronically stressed individuals in the wild and determining the long-term impact on those individuals and their offspring.

Broader Impacts
Student participation will be vital to accomplishment of the research goals. Graduate students, undergraduate students, and a postdoctoral fellow will receive important training in how to trap animals, take samples, perform assays, write manuscripts, and other important laboratory and field skills. Conservation missions could benefit from additional information to determine whether animals are chronically stressed in the wild.

The vertebrate stress response (the physiological mechanisms involved in protecting an organism from a stressor) is a major mechanism of resilience and an important transducer of biotic interactions (between organisms), and between organisms and their non-living environment (abiotic interactions). It is astonishing, however, that even after nearly 100 years of studying stress, the overall field of stress biology lacks an integrated theory and associated models to enable quantitative and predictive research connecting the multiple mechanisms and outcomes of the stress response. This workshop will include equal numbers of researchers interested in the basic biology of stress in animals (typically funded by NSF) and researchers interested in the role of stress in healthy humans specifically (represented by researchers from NASA). NSF-funded and NASA researchers have substantial common ground. Both communities are interested in how stress biology is manifested in healthy individuals, rather than a cause of disease. However, these two communities do not typically interact owing to the conceptual and methodological constraints on the scope of their research. Both communities see an opportunity to make substantial progress in understanding this complex area of biology by sharing their perspectives and developing multidisciplinary collaborations. The cross-fertilization created by the workshop should yield novel insights about conceptual and technical challenges and opportunities, which will help guide future research in both communities. The overarching aims of the workshop will be to: 1. Identify and surmount bottlenecks that are preventing progress, and 2. Begin to develop specific research approaches to implement integrated studies. This workshop could have profound impacts on the field by facilitating the development of a new conceptual model of stress. Such a model could result in more quantitative, predictive research linking cellular and physiological stress responses with individual-, population- and species-level outcomes. The Principal Investigator anticipates publishing a peer reviewed workshop report. New avenues of research identified by the workshop participants and disseminated by the report will provide a blueprint for further study that should have a broad impact on many scientific fields.