The Insulative Value of Mouse Fur

Abstract

Work reported in the literature has demonstrated the importance of physical insulation as a factor affecting the metabolic response of animals to thermal loads. This paper describes a technique for measuring the thermal insulation of the fur on small pelt samples. The insulation of the fur of the mouse (Mus musculus) was 0-20 (S.D. = 0-04) clo or 1-55 (S.D. =0-46) clo/cm. Special problems relating to the value of the insulation of the fur to small animals such as mice are discussed.THE physical insulation of a mammnal or bird is an important factor determining its 'private climate'. This was clearly demonstrated by Scholander et al. [1950a, b, c] in their investigations of adaptation in mammals and birds exposed to arctic and tropical climates. While the metabolic rates of arctic and tropical mammals and birds were similar, the physical insulation of arctic animals was greater, particularly in species larger than the red fox (Vulpes fulva alascensis). The larger arctic animals showed a lower critical temperature than tropical forms, because of their greater insulation. This interaction between coat insulation, metabolic rate and environment, which has also been stressed by Herrington [1951], suggests that account should be taken of the magnitude of the physical insulation in attempts to specify the standard metabolic rate of fur-bearing species.Scholander et al. (1950a] were unable to measure the thermal insulation of the coat of the shrew (Sorex tundrensis), and were forced to estimate it from the fur thickness. Barnett [1959] used the method of Scholander et al, [1950a] to measure the insulationi of the mouse pelt, but had to use pelts from two different mice at once in order to obtain his measurements.A technique has been developed which enables the thermal insulation of small pelt samples to be measured. The results obtained with the technique described below have also made possible some assessment of the value of the furry coat to small animals such as mice. MATERIALS AND METHODSThe animals used were adult male and female house mice (Mus musculus). Most were outbred, segregating for coat colour, short ear (se), and vestigial tail (vt) genes. Some inbred (C3H) mice were also used. All mice were housed in an air-conditioned room set to a temperature of 220 C, and were exposed continually to a 14 hours light -10 hours darkness cycle. Animals had ad libitum access to Drug Houses of Australia rat and mouse cubes, and water.

Integration of body temperature into the analysis of energy expenditure in the mouse

“…In mice, lack of fur causes a 40–70% increase in light phase metabolic rate [31] . However, mouse fur is only 0.13 cm thick and has a thermal conductivity of 0.0000995 cal/s/cm/°C [63] , meaning that it is a relatively poor insulator [64] . For perspective, in humans a constant temperature is not reached until a tissue depth of 2.5–7 cm [65] .…”