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Do Seasonal Glucocorticoid Changes Depend on Reproductive Investment? A Comparative Approach in Birds
Integrative and Comparative Biology
  • Stefania Casagrande, Max Planck Institute for Ornithology
  • László Zsolt Garamszegi, Estación Biológica de Doñana-CSIC
  • Wolfgang Goymann, Max Planck Institute for Ornithology
  • Jeremy Donald, Trinity University
  • Clinton D. Francis, California Polytechnic State University, San Luis Obispo
  • Matthew J. Fuxjager, Wake Forest University
  • Jerry F. Husak, University of St. Thomas
  • Michele A. Johnson, Trinity University
  • Bonnie Kircher, University of Florida
  • Lynn B. Martin, University of South Florida
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Animals go through different life history stages such as reproduction, moult, or migration, of which some are more energy-demanding than others. Baseline concentrations of glucocorticoid hormones increase during moderate, predictable challenges and thus are expected to be higher when seasonal energy demands increase, such as during reproduction. By contrast, stress-induced glucocorticoids prioritize a survival mode that includes reproductive inhibition. Thus, many species down-regulate stress-induced glucocorticoid concentrations during the breeding season. Interspecific variation in glucocorticoid levels during reproduction has been successfully mapped onto reproductive investment, with species investing strongly in current reproduction (fast pace of life) showing higher baseline and lower stress-induced glucocorticoid concentrations than species that prioritize future reproduction over current attempts (slow pace of life). Here we test the “glucocorticoid seasonal plasticity hypothesis”, in which we propose that interspecific variation in seasonal changes in glucocorticoid concentrations from the non-breeding to the breeding season will be related to the degree of reproductive investment (and thus pace of life). We extracted population means for baseline (for 54 species) and stress-induced glucocorticoids (for 32 species) for the breeding and the non-breeding seasons from the database “HormoneBase”, also calculating seasonal glucocorticoid changes. We focused on birds because this group offered the largest sample size. Using phylogenetic comparative methods, we first showed that species differed consistently in both average glucocorticoid concentrations and their changes between the two seasons, while controlling for sex, latitude, and hemisphere. Second, as predicted seasonal changes in baseline glucocorticoids were explained by clutch size (our proxy for reproductive investment), with species laying larger clutches showing a greater increase during the breeding season—especially in passerine species. In contrast, changes in seasonal stress-induced levels were not explained by clutch size, but sample sizes were more limited. Our findings highlight that seasonal changes in baseline glucocorticoids are associated with a species’ reproductive investment, representing an overlooked physiological trait that may underlie the pace of life.


Complete list of authors: Rosemary Knapp, Eliot T. Miller, Laura A. Schoenle, Maren N. Vitousek, Tony D. Williams, Michaela Hau

Citation / Publisher Attribution

Integrative and Comparative Biology, v. 58, issue 4, p. 739-750

Citation Information
Stefania Casagrande, László Zsolt Garamszegi, Wolfgang Goymann, Jeremy Donald, et al.. "Do Seasonal Glucocorticoid Changes Depend on Reproductive Investment? A Comparative Approach in Birds" Integrative and Comparative Biology Vol. 58 Iss. 4 (2018) p. 739 - 750
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