Meeting Abstract
65.8 Jan. 7 Voluntary exercise and aerobic performance in several small mammals CHAPPELL, MA; Univ. of California, Riverside mark.chappell@ucr.edu
The upper limit of sustainable metabolic power output is set by maximum oxygen consumption (VO2max). Physiologists have considerable data on VO2max from a variety of species, but little is known about how frequently animals approach VO2max during voluntary activity, and hence how important this limit is for routine behavior. That information is difficult to attain for free-living animals, but many small mammals readily use running wheels in captivity. I used that propensity to determine voluntary running performance (speed and oxygen consumption) over 24-48 h periods in 4 species of wild-caught small mammals: Belding�s ground squirrel (Spermophilus beldingii), golden-mantled ground squirrel (S. lateralis), least chipmunk (Tamias minimus), Panamint kangaroo rat (Dipodomys panamintinus). The measurements also yielded data on preferred running speeds, energy costs of running, minimal resting metabolism (RMR), and daily energy expenditures. To determine aerobic limits, I also measured VO2max in forced exercise. Tests were done at a field station at 2150 m (ambient pO2 ~ 121 torr). Most animals ran extensively, covering species mean distances of 5.2 � 14.7 km/day, with a maximum of 25 km/day in an S. lateralis. In all species, the relationship between voluntary speed and oxygen consumption (VO2) was linear. For most, maximal VO2 during voluntary exercise was substantially less than VO2max, but golden-mantled ground squirrels regularly ran at speeds that elicited VO2 within 5% of VO2max. Aerobic scope (VO2max /minimal RMR) ranged from 7.2 – 9.6. All species ran at a variety of speeds, contrary to predictions that voluntary running should be at high speeds to minimize incremental costs of transport or predation risk.
