Testosterone influences basal metabolic rate in male house sparrows: a new cost of dominance signalling?

Abstract

Sexually selected signals of individual dominance have profound e¡ects on access to resources, mate choice and gene £ow. However, why such signals should honestly re£ect individual quality is poorly understood. Many such signals are known to develop under the in£uence of testosterone. We conducted an experiment in male house sparrows in which testosterone was manipulated independently during two periods: before the onset of the breeding season and prior to the autumn moult. We then measured the e¡ects of these manipulations on basal metabolic rate and on the size of the chest bib, a sexually selected signal. The results demonstrate that testosterone simultaneously a¡ects both signal development and basal metabolic rate in the house sparrow (Passer domesticus). This evidence, therefore, supports a novel conclusion: that testosterone-dependent signals act as honest indicators of male quality possibly because only high-quality individuals can sustain the energetic costs associated with signal development.

The hormonal control of begging and early aggressive behavior: Experiments in black-headed gull chicks

“…Third, androgens may increase metabolic rate. This has been found in two studies (in a songbird, the house sparrow (Passer domesticus): Buchanan et al, 2001; in a cichlid fish: Ros et al, 2004) but not in another study (songbird, whitecrowned sparrow (Zonotrichia leucophrys: Wikelsky et al, 1999). Such an increase in metabolic rate may be due to the building up of relatively costly muscle tissue or immune tissue.…”

Costly steroids: egg testosterone modulates nestling metabolic rate in the zebra finch

“…Alternatively, egg hormone treatment may induce permanent differences in the ability to secrete hormones. We do not know whether egg treatment caused differences in circulating hormone levels in the nestlings, but higher blood levels of testosterone or related steroids may result in higher metabolic rates as has been found in adult birds and fishes (Buchanan et al 2001;Ros et al 2004). Moreover, testosterone is also known to increase anabolic processes at the cellular level ( Tsai & Sapolsky 1996).…”

Seasonal and population variation in male testosterone levels in breeding orange-crowned warblers (Vermivora celata)

“…Elevated testosterone concentrations late in the breeding season can delay or prevent post-breeding molt (Runfeldt and Wingfield, 1985;Nolan et al, 1992;Dawson, 1994), thereby affecting survival in subsequent life history stages. High testosterone concentrations can also increase energy consumption (Wingfield, 1984;Ketterson et al, 1991;Buchanan et al, 2001;but, see Lynn et al, 2000;Buttemer et al, 2008), possibly limiting resources available for self-maintenance. Finally, testosterone may suppress immune function (Greives et al, 2006;Martin et al, 2008), either directly or indirectly by influencing the secretion of other hormones (Owen-Ashley et al, 2004;Poiani et al, 2000).…”