The active mouse rests within: Energy management among and within individuals

Abstract

The relationship between daily energy expenditure (DEE) and resting metabolic rate (RMR) provides insight into how organisms allocate energy to maintenance versus energetically expensive activities such as locomotor activity. Three models have been devised to describe energy management: the allocation, independent and performance models, which, respectively, predict a DEE–RMR slope of b < 1, b = 1 and b > 1. Here, we took paired repeated metabolic and behavioural measurements in 51 female white‐footed mice to (a) evaluate which energy management models apply at the among‐ and within‐individual levels and to (b) quantify the relationship between metabolic traits and two energetically expensive behaviours. The DEE–RMR slope was different at the among‐ versus within‐individual levels, with values supporting the performance and allocation models at the among‐ and within‐individual levels, respectively. Accordingly, the relationship between voluntary wheel running and RMR was positive at the among‐individual level (r = 0.40 ± 0.21), but negative at the within‐individual level (r = −0.23 ± 0.10). To our knowledge, this is the first study to simultaneously partition the relationship between RMR and behaviour at the among‐ versus within‐individuals levels while determining which energy management models apply at each of these levels. In doing so, we have identified a mechanism through which compensation occurs at the within‐individual level. A free Plain Language Summary can be found within the Supporting Information of this article.

Testing personality—pace-of-life associations via artificial selection: insights from selected lines of rainbow trout on the context-dependence of correlations

“…Since those POLS ideas were presented over a decade ago, there have been many empirical tests of the hypotheses, but few studies have found compelling evidence (e.g. [12][13][14]). Indeed, recent meta-analyses reveal little to no evidence for the POLS predictions at the among individual level ( [15][16][17] but see [18]).…”

CO2 scrubbing, zero gases, Keeling plots, and a mathematical approach to ameliorate the deleterious effects of ambient CO2 during 13C breath testing in humans and animals

“…A typical 25 g laboratory mouse (or similar sized bird) at rest generates $1 mL CO 2 min À1 , [33][34][35][36][37] whereas a resting human (with a body mass 2500-fold larger than that of a mouse) generates $200 mL CO 2 min À1 . [38][39][40] In both of these species, as well as other animals, the actual rates of CO 2 production (hereafter: VCO 2 ) change from minute to minute depending on activity levels (and countless other experimental and physiological factors [41][42][43][44] ). For example, the VCO 2 of a resting mouse can increase by fourfold simply by reducing the ambient temperature from 30 to 10 C and inducing shivering thermogenesis.…”