A combination of body condition measurements is more informative than conventional condition indices: Temporal variation in body condition and corticosterone in brown tree snakes (Boiga irregularis)

Heather L. Waye, Robert T. Mason

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

The body condition index is a common method for quantifying the energy reserves of individual animals. Because good body condition is necessary for reproduction in many species, body condition indices can indicate the potential reproductive output of a population. Body condition is related to glucocorticoid production, in that low body condition is correlated to high concentrations of corticosterone in reptiles. We compared the body condition index and plasma corticosterone levels of brown tree snakes on Guam in 2003 to those collected in 1992/1993 to determine whether that population still showed the chronic stress and poor condition apparent in the earlier study. We also examined the relationship between fat mass, body condition and plasma corticosterone concentrations as indicators of physiological condition of individuals in the population. Body condition was significantly higher in 2003 than in the earlier sample for mature male and female snakes, but not for juveniles. The significantly lower levels of corticosterone in all three groups in 2003 suggests that although juveniles did not have significantly improved energy stores they, along with the mature males and females, were no longer under chronic levels of stress. Although the wet season of 2002 was unusually rainy, low baseline levels of corticosterone measured in 2000 indicate that the improved body condition of snakes in 2003 is likely the result of long-term changes in prey populations rather than annual variation in response to environmental conditions.

Original languageEnglish (US)
Pages (from-to)607-612
Number of pages6
JournalGeneral and Comparative Endocrinology
Volume155
Issue number3
DOIs
StatePublished - Feb 1 2008
Externally publishedYes

Bibliographical note

Funding Information:
Research was conducted under the authority of Oregon State University and University of Guam Institutional Animal Care and Use Committees. We thank Drs. Michael Ehlert, Gregory Witteman and Katharine Lofdahl and Gretchen Grimm of the University of Guam, for their invaluable assistance on Guam, and the snake team at Andersen AFB for letting HLW ride along. Many thanks also to Clay Carlson and Patty Jo Hoff for access to their farm. This research was funded in part by the Department of Zoology, Oregon State University.

Keywords

  • Body condition
  • Brown tree snake
  • Corticosterone

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