Fig. 5. Relationship between the rate of appearance of glycerol (R_a glycerol=lipolytic rate) and body mass for resting mammals (open squares), exercising mammals (filled squares), resting penguins (triangles) and ruff sandpipers (filled circle). The mean value plotted here for ruff sandpipers is for shivering birds (note that the mean value for non-shivering birds was even higher, although not significantly so; see Table 1). Each point is the mean value from a different study [rat (Kalderon et al., 2000; McClelland et al., 2001), rabbit (Himms-Hagen, 1968; Reidy and Weber, 2002), dog (Issekutz et al., 1975; Shaw et al., 1975), pigmy goat (Weber et al., 1993), sheep (Bergman, 1968), human (Bahr et al., 1990; Mora-Rodriguez et al., 2001; Wolfe et al., 1990) and king penguin (Bernard et al., 2002a; Bernard et al., 2002b; Bernard et al., 2003)]. Lines were fitted by linear regression for resting mammals (broken line; y=–0.31x+21.8; r²=0.333) and exercising mammals (solid line; y=–0.34x+28.8; r²=0.390). Curved dotted lines indicate 95% confidence limits around the values for exercising mammals.