Jpy. Arnould et Ma. Ramsay, MILK-PRODUCTION AND MILK CONSUMPTION IN POLAR BEARS DURING THE ICE-FREE PERIOD IN WESTERN HUDSON-BAY, Canadian journal of zoology, 72(8), 1994, pp. 1365-1370
Milk yield and milk consumption were measured in polar bears (Ursus ma
ritimus) during the summer ice-free period in western Hudson Bay, a pe
riod of severe nutritional restriction. The transfer of milk between a
dult and dependent offspring was measured for five females with cubs (
aged 8 months) and four with yearlings (aged 20 months) by a hydrogen
isotope dilution-transfer method. Females with cubs produced significa
ntly more mill; energy (10.9 MJ.day(-1)) than females with yearlings (
2.6 MJ.day(-1)). Daily milk production represented a greater proportio
n of body mass for females with cubs than females with yearlings but m
ilk production was not correlated with maternal mass or litter mass in
either group. Milk energy consumption was correlated with body mass i
n cubs but not in yearlings. Cubs consumed significantly more milk ene
rgy (7.8 MJ.day(-1)), and displayed a higher relative growth rate, tha
n yearlings (1.5 MJ.day(-1)). However, both age groups lost proportion
ally the same amount of mass during the study period, suggesting that
cubs are less able to survive nutritional restrictions and are more de
pendent on milk for survival than yearlings.