Baseline Corticosterone Is not An Indicator of Population Health during Non-El Niño Conditions in Galapagos Marine Iguanas

25 Pages Posted: 4 May 2023

See all articles by Scott Glaberman

Scott Glaberman

George Mason University

Robert Posont

George Mason University

Hillary Swain

University of South Alabama

Ylenia Chiari

George Mason University

Julien Claude

University of Montpellier - Institut des Sciences de l'Evolution de Montpellier (ISEM)

Date Written: April 28, 2023

Abstract

Glucocorticoids are steroid hormones that are often used to evaluate vertebrate population health. However, glucocorticoid levels can vary widely among individuals and over time, making it challenging to unravel the factors influencing their expression. We examined the relationship between corticosterone – the primary glucocorticoid in reptiles – and various biological and ecological factors in Galapagos marine iguanas (Amblyrhynchus cristatus). Marine iguanas are ideal for studying drivers of physiological stress since they inhabit many isolated islands with varying ecological conditions. We found that baseline corticosterone levels differed among marine iguana populations throughout the Galapagos archipelago, and that females had significantly higher corticosterone values than males. However, we did not find strong relationships between corticosterone and other assessed factors, including body condition, food availability, and blood parasite infection. Our results differ from previous studies, which found that corticosterone is strongly linked to body condition and a good predictor of individual survival probability in marine iguanas. This discrepancy is likely because prior studies were conducted during periods of acute environmental stress, such as an El Niño or oil spill, whereas our work took place during typical non-El Niño conditions when food was abundant. Thus, baseline corticosterone in marine iguanas appears to be a good surrogate for individual health and survival during times of extreme stress but should be used with caution for routine monitoring. Our results add to a growing understanding of the applicability of glucocorticoids for assessing population health.

Keywords: Stress, Hormones, Parasites, Physiology, Reptiles

Suggested Citation

Glaberman, Scott and Posont, Robert and Swain, Hillary and Chiari, Ylenia and Claude, Julien, Baseline Corticosterone Is not An Indicator of Population Health during Non-El Niño Conditions in Galapagos Marine Iguanas (April 28, 2023). Available at SSRN: https://ssrn.com/abstract=4437567 or http://dx.doi.org/10.2139/ssrn.4437567

Scott Glaberman (Contact Author)

George Mason University ( email )

4400 University Drive
Fairfax, VA 22030
United States

Robert Posont

George Mason University ( email )

Hillary Swain

University of South Alabama ( email )

Ylenia Chiari

George Mason University ( email )

Julien Claude

University of Montpellier - Institut des Sciences de l'Evolution de Montpellier (ISEM) ( email )

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