Intraspecific Allometry of Basal Metabolic Rate: Relations with Body Size, Temperature, Composition, and Circadian Phase in the Kestrel, Falco tinnunculus

Abstract

The relationship between body size and basal metabolic rate (BMR) in homeotherms has been treated in the literature primarily by comparison between species of mammals or birds. This paper focuses on the intraindividual changes in BMR when body mass (W) varies with different maintenance regimens. BMR varied in individual kestrels in proportion to W 1.67 , which is considerably steeper than the mass exponents for homomorphic change (0.667; Heusner, 1984) for interspecific comparison among all birds (0.677) or raptors (0.678), for interindividual comparison of kestrels on ad libitum maintenance regimens (0.786), and for mass proportionality (1.00). The circadian range of telemetered core temperature also varied more strongly with intraindividual than with interspecific (Aschoff, 1981a) variation in mass. This was due to reduced nocturnal core temperature at low-maintenance regimens, which was, however, insufficient to account for the excessive reduction in BMR. Carcass analysis of eight birds sacrificed revealed a disproportionate reduction in heart and kidney lean mass at low-maintenance regimens. We surmise that variation in BMR primarily reflects variation in these metabolically highly active tissues. This may account for positive correlations found between heart, kidney, and BMR residuals relative to interspecific allometric prediction, and between α and p residuals, as expected on the basis of the constant excess of BMR during α above BMR during p (Aschoff & Pohl, 1970a).In the broad diversity of scientific contributions by Jfrgen Aschoff, the one with greatest impact in animal ecology has been his analysis, jointly with Hermann Pohl, of basal metabolic rates (BMRs) in birds and their dependence on body mass and phase of the circadian cycle (Aschoff and Pohl, 1970a, b). This analysis refined earlier allometric relationships established by Kleiber (1947), Brody (1945), and Lasiewski and Dawson (1967 by demonstrating that BMRs, measured in darkness, at rest, at thermoneutral temperature, and without food being digested, were reduced during the circadian rest phase compared with the active phase. BMRs during the rest phase and their allometric relation with body mass soon became a standard for 1. This paper is dedicated to Professor Jürgen Aschoff, whose breadth of scientific interests and warm intellectual support have become an inexhaustible source of inspiration for us.

No Nocturnal Energetic Savings in Response to Hard Work in Free-Living Great Tits

“…This may result in cognitive constraints ('demotivation'), which would reduce foraging activity (FOTHERINGHAM, 1998). If this is actually the case then those birds were starved, and starvation may lead to mass reduction of metabolic active tissue, and subsequently to a decline in BMR (DAAN et al, 1989;PIERSMA et al, 1996).…”

Associations between basal metabolic rate and reproductive performance in C57BL/6J mice

“…between non-breeding and lactating, or between different groups of lactating mice held at different ambient temperatures), they share a dependence on aspects of morphology that limit the uptake of energy or its utilisation. However, support for the existence of such a link at the individual level is sparse (Daan et al, 1989;Daan et al, 1990). In lactating mice, individual variations in BMR do not correlate with individual variation in organ morphology (Krol et al, 2003;Speakman and Johnson, 2000).…”

Limits to sustained energy intake. XIII. Recent progress and future perspectives

“…One interesting idea to emerge from the central limitation hypothesis was that as the system limiting the sustained rate of expenditure (i.e. the alimentary tract including associated processing organs such as the liver) is widely regarded to be expensive to maintain (Daan et al, 1989;Daan et al, 1990;Elia, 1992;Konarzewski and Diamond, 1995;Selman et al, 2001;Brzęk et al, 2007) and makes a substantial contribution to the basal rate of energy expenditure (BMR), increasing sustained rates of expenditure would only be feasible by increasing BMR as well (Konarzewski and Diamond, 1995;Mueller and Diamond, 2001). Consequently, there is predicted to be a limiting ratio between the maximum sustained and basal rates of metabolism -called the 'maximum sustained metabolic scope'.…”