Testosterone in Tropical Birds: Effects of Environmental and Social Factors

Previous investigations suggest that male tropical birds have lower plasma testosterone concentrations than northern latitude species. To test whether this generalization is valid, we analyzed all currently available plasma testosterone data of tropical birds. We focused on peak breeding testosteron...

Full description

Saved in:
Bibliographic Details
Published in:The American naturalist 2004-09, Vol.164 (3), p.327-334
Main Authors: Goymann, Wolfgang, Moore, Ignacio T., Scheuerlein, Alexander, Hirschenhauser, Katharina, Grafen, Alan, Wingfield, John C.
Format: Article
Language:English
Subjects:
Altitude
Androgens
Animal reproduction
Animals
Aves
Aviculture
Bird nesting
Birds
Birds - genetics
Birds - metabolism
Breeding seasons
Ecosystem
Environment
Male
Male animals
Mating systems
Phylogenetics
Phylogeny
Seasons
Social Behavior
Territoriality
Testosterone
Testosterone - metabolism
Tropical Climate
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Previous investigations suggest that male tropical birds have lower plasma testosterone concentrations than northern latitude species. To test whether this generalization is valid, we analyzed all currently available plasma testosterone data of tropical birds. We focused on peak breeding testosterone levels using phylogenetic and conventional statistics. Explanatory variables considered were social mating system, type of territoriality, breeding season length, and altitude. On average, tropical birds had lower mean peak testosterone levels than northern temperate birds. However, in several tropical species, testosterone levels were well within the range of northern latitude birds. Without controlling for phylogeny, breeding season length, type of territoriality, and altitude explained a significant proportion of the variance in testosterone levels. The shorter the breeding season, the higher the testosterone levels. Tropical birds that defend a breeding season territory had higher testosterone levels than birds that were year‐round territorial or colonial, and testosterone levels were positively correlated with altitude. When controlling for phylogeny, only breeding season length predicted testosterone levels. In conclusion, we propose to refine previous notions of low plasma testosterone levels in tropical birds: short breeding seasons and perhaps environmental conditions at high altitudes precipitate conditions under which high testosterone levels are beneficial in the tropics.
ISSN:0003-0147
1537-5323
DOI:10.1086/422856