DISSERTATION RESEARCH: Integrating Costs of Investment in Parental Care from Telomeres to Hormones

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Animals can benefit by having many offspring that survive and reproduce. To increase offspring survival, parents may provide extensive parental care and exhibit aggression towards predators or intruders. However, raising and defending a large family can increase stress on parents. Additionally, hormones often regulate expression of behaviors. For example, testosterone is associated with reduced parental care and increased aggression in many birds. High levels of testosterone have been linked to reduced survival in birds, but the mechanisms underlying this link are unknown. One hypothesis is that testosterone shortens telomeres. Telomeres are short sequences of DNA that protect the ends of chromosomes and can affect survival. Stress can also shorten telomere lengths, and shorter telomeres have been associated with reduced lifespan. The researchers have manipulated brood sizes of eastern bluebirds to alter parental care, aggression, and stress, which can all interact with testosterone levels. They will determine how family size, behavior, and hormones affect telomere lengths to impact longevity and survival. The researchers will also develop education programs for local high school students to learn fundamental concepts in the fields of behavioral ecology and physiology.The researchers have found that bluebirds have considerable individual variation in testosterone production. Testosterone is implicated in important, fitness-related behaviors. The costs of elevating testosterone are also well-documented. Although much has been done to elucidate relationships between behaviors and the hormonal mechanisms that regulate them, there is currently very little information about how behavioral and physiological links might be tied to mechanisms that affect survival (i.e., telomere lengths and telomere loss). The researchers will analyze previously collected blood samples to measure testosterone, corticosterone, and telomere lengths. They will relate these physiological measurements to previously recorded behavioral data. By linking costly behaviors mediated by testosterone to telomere lengths, this study will take an integrative approach to answering questions that span the fields of behavioral ecology, endocrinology, and evolution. Data will archived at Oklahoma State University and requests for data will be fulfilled upon approval of the researchers.