Insulation, radiation, and convection in small arctic mammals

Chappell, Mark

The insulation (I), skin area (A(s)), surface area (A), effective surface area for radiant energy exchange (A(ee)), and convection coefficient (h(c)) were determined for six species of small arctic mammals. Measurements were made under steady-state conditions using pelt-covered, internally heated Wood's metal casts of the animals. Surface areas of the animals studied depended primarily on body mass; shape was of lesser importance. The latter finding was an artifact of different fur lengths - the elongate species studied (weasels) had short fur, whereas more compact animals (lemmings) had much longer coats which greatly increased their diameters and therefore areas. Insulation in blackbody radiation conditions depended primarily on pelage depth but also to some extent on the density of hair growth. Measured values of A(ee) were approximately equal to values of A. Convection coefficients varied directly with wind velocity and inversely with body diameter. Nusselt Number-Reynolds Number plots of convection data revealed that convection from the animals was approximately the same as that from similar-sized cylinders, and that shape and pelage characteristics were not important in determining h(c).

Insulation, radiation, and convection in small arctic mammals

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