Oxygen Consumption for Locomotion by Caribou Calves

Abstract

Oxygen consumption (VO,, ml/g-hour) by caribou (Rangifer tarandus granti) calves trained to walk on a treadmill was measured using a headstall. Both the standing-resting VO, and the oxygen cost of locomotion (ml 02/g-km) decreased with increasing body weight. Net VO, (walking VO, minus VO, standing at rest) increased linearly with walking velocity, but an upward deflection was noted at velocities >3-5 km/ hour in the younger animals. In all caribou the stride frequency increased linearly with walking velocity between 2 and 7 km/hour. Evidence is presented that the oxygen cost of locomotion is different between Rangifer subspecies and an effect of leg length is implicated. J. WILDL. MANAGE. 50(1):148-152 Caribou usually are born in May-June (Kelsall 1968, Skoog 1968) and must grow to an adequate stature to meet the demands of summer movements, such as dispersal and assembly of nursery groups (Kelsall 1968, Skoog 1968, White et al. 1981). Summer movements are followed by fall migration, winter movements, and a 2nd long migration in spring (Duquette 1984). Consequently, the amount of energy required for locomotion may affect the growth and survival of caribou, especially those in their 1st year of life. The energy costs of movements in caribou are unknown; however, they could be estimated from interspecies prediction equations that show that the energy cost of locomotion/unit body weight declines markedly as body weight increases (Taylor et al. 1970, 1982; Robbins 1983; Parker et al. 1984). These studies suggest that the calf is of particular interest because its cost of locomotion/unit weight may be higher than that of its mother. The prediction of locomotory energy costs from interspecies comparisons must be made with caution since there are species-specific variations in the responses including nonlinear changes in the energy cost as velocity increases (Magaria et al. 1963, Yousef and Dill 1969, Cohen et al. 1978, Parker et al. 1984). The energy cost of locomotion in semidomestic reindeer (R. t. tarandus) walking on tundra surfaces (White and Yousef 1978) or on a treadmill (Nilssen et al. 1984) potentially could be applied to caribou. Yet, application of these data to caribou can be criticized because caribou have longer legs than reindeer and have been under continued selection for migration (Fancy and White 1985). The objective of this study was to determine the energy cost of walking in caribou; special emphasis was placed on calves of varying body size a d on verifying the linearity of the locomotory cost in relation to velocity. A preliminary report of this work was published elsewhere (Luick and White 1983). We acknowledge the assistance of J. L. Davis and P. Valkenburg from the Alaska Dep. Fish and Game for capture of caribou calves. Grants from the Inst. Arct. Biol. and the State of Alaska (Alaska Counc. Sci. and Technol., Grant 46-82) suppor ed equipment construction and testing and the healthcare and feeding of the caribou. We thank L. A. Harbo, K. M. Frisby, P. Line, L. L. Axtel, and S. Dier for their devoted care of animals through the critical period of bottle raising.