Life Sciences Commons^™

Conservation Implications Of A Lack Of Relationship Between Baseline Glucocorticoids And Fitness In A Wild Passerine, Christine L. Madliger, Oliver P. Love

Integrative Biology Publications

The application of physiological measures to conservation monitoring has been gaining momentum and, while a suite of physiological traits are available to ascertain disturbance and condition in wildlife populations, glucocorticoids (i.e., GCs; cortisol and corticosterone) are the most heavily employed. The interpretation of GC levels as sensitive indicators of population change necessitates that GCs and metrics of population persistence are linked. However, the relationship between GCs and fitness may be highly context-dependent, changing direction, or significance, depending on the GC measure, fitness metric, life history stage, or other intrinsic and extrinsic contexts considered. We examined the relationship between baseline plasma …

Maternal Sleep Loss During Fetal Development Alters Offspring Endocrine Responses To Stress Throughout Life, Audrey Brown

Mahurin Honors College Capstone Experience/Thesis Projects

The hypothalamic-pituitary-adrenal (HPA) axis releases glucocorticoids, including corticosterone (CORT), in response to stress. CORT then negatively feeds back to inhibit its own production by binding to glucocorticoid receptors (GRs) in the hypothalamus and pituitary gland. The HPA axis is subject to “programming” by abnormal stimuli during early development, which may permanently alter how the HPA axis responds to stress. These altered responses have been linked to an increased risk for human psychiatric and metabolic disorders in later life, but the mechanism by which this happens is not fully understood. This study tests the hypothesis that changes to GR expression patterns …

Effects Of Human Disturbance On Physiology, Behavior, And Ornamentation In The Eastern Bluebird, Lauren Marjorie Gillespie

Dissertations

Overall, few studies have focused on anthropogenic disturbance on wildlife physiology. Research has typically focused on how environmentally contaminated areas or anthropogenic disturbance (e.g. noise, human activity) influences biodiversity, community structure and behavior of individual animals. However, understanding how disturbance influences some aspects of physiology can require sacrifice of the animal, prohibiting ecologically relevant measures of behavior and reproductive success. This research strives to examine covariation between testosterone (T) and corticosterone (CORT), plumage ornamentation, and behavior in two populations of eastern bluebirds (Sialia sialis) that differ in degree to which their habitat is modified by human activity.

In …

Employing Individual Measures Of Baseline Glucocorticoids As Population-Level Conservation Biomarkers: Considering Within-Individual Variation In A Breeding Passerine, Christine L. Madliger, Oliver P. Love

Great Lakes Institute for Environmental Research Publications

Labile physiological variables, such as stress hormones [i.e. glucocorticoids (GCs)], allow individuals to react to perturbations in their environment and may therefore reflect the effect of disturbances or positive conservation initiatives in advance of population-level demographic measures. Although the application of GCs as conservation biomarkers has been of extensive interest, few studies have explicitly investigated whether baseline GC concentrations respond to disturbances consistently across individuals. However, confirmation of consistent responses is of paramount importance to assessing the ease of use of GCs in natural systems and to making valid interpretations regarding population-level change (or lack of change) in GC concentrations. …

Temporal Overlap And Repeatability Of Feather Corticosterone Levels: Practical Considerations For Use As A Biomarker, Christopher M. Harris, Christine L. Madliger, Oliver P. Love

Great Lakes Institute for Environmental Research Publications

The measurement of corticosterone (CORT) levels in feathers has recently become an appealing tool for the conservation toolbox, potentially providing a non-invasive, integrated measure of stress activity throughout the time of feather growth. However, because the mechanism of CORT deposition, storage and stability in feathers is not fully understood, it is unclear how reliable this measure may be, especially when there is an extended interval between growth and feather collection. We compared CORT levels of naturally grown feathers from tree swallows (Tachycineta bicolor) that were moulted and regrown concurrently and therefore expected to have similar CORT levels. Specifically, we compared …

Employing Individual Measures Of Baseline Glucocorticoids As Population-Level Conservation Biomarkers: Considering Within-Individual Variation In A Breeding Passerine, Christine L. Madliger, Oliver P. Love

Integrative Biology Publications

Labile physiological variables, such as stress hormones [i.e. glucocorticoids (GCs)], allow individuals to react to perturbations in their environment and may therefore reflect the effect of disturbances or positive conservation initiatives in advance of population-level demographic measures. Although the application of GCs as conservation biomarkers has been of extensive interest, few studies have explicitly investigated whether baseline GC concentrations respond to disturbances consistently across individuals. However, confirmation of consistent responses is of paramount importance to assessing the ease of use of GCs in natural systems and to making valid interpretations regarding population-level change (or lack of change) in GC concentrations. …

Glucocorticoid Manipulations In Free-Living Animals: Considerations Of Dose Delivery, Life-History Context And Reproductive State, Glenn T. Crossin, Oliver P. Love, Steven J. Cooke, Tony D. Williams

Integrative Biology Publications

Experimental glucocorticoid (GC) manipulations can be useful for identifying the mechanisms that drive life-history and fitness variation in free-living animals, but predicting the effects of GC treatment can be complicated. Much of the uncertainty stems from the multi-faceted role of GCs in organismal metabolism, and their variable influence with respect to life-history stage, ecological context, age, sex and individual variation. Glucocorticoid hormones have been implicated in the regulation of parental care in many vertebrate taxa but in two seemingly contradictory ways, which sets up a potential GC-induced 'reproductive conflict'. Circulating GCs mediate adaptive physiological and behavioural responses to stressful events, …

The Impact Of Urban Centers On American Goldfinches (Spinus Tristis) Overwintering At High Latitudes, Corrie Jean Navis

Master's Theses and Doctoral Dissertations

American Goldfinches (Spinus tristis) are partial migrants that overwinter in northern regions where winters can be extreme. To understand the role of urban development in facilitating use of a harsh climate, I conducted winter point count surveys (n = 297) at urban and rural sites across latitudes in Michigan. The following winter I trapped individuals in urban and rural settings to sample baseline and stress-induced plasma corticosterone (CORT) levels. Analyses revealed no interaction of latitude and urbanization in the winter distribution of American Goldfinches. Similarly, CORT concentrations did not differ between individuals trapped in urban and rural settings. …

Temporal Overlap And Repeatability Of Feather Corticosterone Levels: Practical Considerations For Use As A Biomarker, Christopher M. Harris, Christine L. Madliger, Oliver P. Love

Integrative Biology Publications

The measurement of corticosterone (CORT) levels in feathers has recently become an appealing tool for the conservation toolbox, potentially providing a non-invasive, integrated measure of stress activity throughout the time of feather growth. However, because the mechanism of CORT deposition, storage and stability in feathers is not fully understood, it is unclear how reliable this measure may be, especially when there is an extended interval between growth and feather collection. We compared CORT levels of naturally grown feathers from tree swallows (Tachycineta bicolor) that were moulted and regrown concurrently and therefore expected to have similar CORT levels. Specifically, we compared …