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The influence of animal physiology on population processes:
Population cycles in arvicoline rodents (voles and lemmings) are a fascinating ecological phenomenon that have been studied since the 1920s. Many different populations of these rodents go through cyclic peaks and crashes in population density over a ~3 year period. In some cases, population crashes cannot be explained by predators, food supplies, or disease. This has inspired the hypothesis that crashes can be driven by changes in the animals themselves, including suppressed or delayed reproduction at high density, called "intrinsic regulation" or population self-regulation. We are investigating differences in the reproduction, behavior, and epigenetic signatures of voles and other animals born in different population densities to determine if there are physiological mechanisms that can cause this self-regulation, with major implications for the fundamental understanding of population dynamics in these ecological model organisms. The influence of the social environment on physiology and phenotype:
The social environment can profoundly shape individuals. Individuals born in different social environments can be drastically different as adults, and we are interested in the physiological mechanisms that drive these changes. For animals that live in groups, position in the social hierarchy can be a factor that shapes an individual. One hypothesis is that in some types of social groups, individuals that have low social status experience chronic stress. We found that in eusocial naked mole-rats, this is not the case; individuals show no social status differences in cortisol levels. However, individuals that were isolated from the social group show marked increases in cortisol levels. We continue to explore the relationship between social environment and physiology in other species, and how changes in landscape use can influence both animal social dynamics and internal physiology. The relationship between cortisol and reproduction:
Glucocorticoid hormones, including cortisol and corticosterone, are released when an organism experiences a stressful event to redirect energy reserves towards process that are immediately beneficial for survival. During extreme stress, reproduction can be suppressed as it is not necessary to support immediate survival. However, glucocorticoids have many other functions related to energy allocation and act as transcription factors for numerous genes. These other functions have not been as well explored as their role in the stress response. We study the relationship between cortisol and reproductive state to see when reproductive suppression occurs, and when cortisol may have beneficial energy allocation functions related to reproductive processes. |
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