Estimating the energy expenditure of endotherms at the species level

Abstract

The ability to account with precision for the quantitative variation in the basal rate of metabolism (BMR) at the species level is explored in four groups of endotherms: arvicoline rodents, ducks, melaphagid honeyeaters, and phyllostomid bats. An effective analysis requires the inclusion of the factors that distinguish species and their responses to the conditions they encounter in the environment. These factors are implemented by changes in body composition and are responsible for the non-conformity of species to a scaling curve. Two concerns may limit an analysis. The factors correlated with energy expenditure often correlate with each other, which usually prevents them from being included together in an analysis, thereby preventing a complete analysis, implying the presence of factors other than mass. Many of the relevant factors, such as food habits and an island residence, are qualitative, which complicates their inclusion in a quantitative analysis, a difficulty that is solved by ANCOVA. The precision of an analysis, based on an inclusive equation, can be determined by comparing its estimates with measurements of the performance of species. Without this comparison, the effectiveness of an analysis cannot be determined, which then simply becomes a suggestion. A proposed standard for a precise estimate is for it to be within 10% of the measured rate.