Abstract
Maximum cold-induced rate of food consumption in cold-acclimated laboratory
house mice (Mus domesticus) averaged 10.4 g/d in females
(body mass before cold exposure = 25.2 g) and 10.7 g/d in males (body mass
= 31.7 g); corresponding maximum rates of energy assimilation were 139
kJ/d in females and 144 kJ/d in males. The traits were highly repeatable:
the intraclass correlation coefficient for three trials at -10 C was greater
than 0.7 for absolute values and greater than 0.6 for values independent
of the initial body mass (residuals from ANCOVA). The estimate of repeatability
of the mass-independent traits depends on which estimate of body mass (initial
or after cold exposure) is used as a covariate in the regression or ANCOVA
model. We conclude that the values of maximum cold-induced food consumption
and energy assimilation are reliable estimates of the performance of individuals
under a specific set of environmental conditions (low ambient temperature,
but not limited access to food) and hence may be subject to phenotypic
natural or artificial selection.