Fig. 2. Comparison of theoretical predictions with the speeds, stroke frequencies, and force outputs of a wide variety of animals (Iriarte-Diaz, 2002; Drucker and Jensen, 1996; Pennycuik, 1975; Heglund et al., 1974; Marden and Allen, 2002; Taylor et al., 2003; Rohr and Fish, 2004; Bartholomew and Casey, 1978; Marsh, 1988; Wakeling and Ellington, 1997; Marden et al., 1997; Tennekes, 1997; Kiceniuk and Jones, 1977; May, 1995; Arnott et al., 1998; Peake and Farrell, 2004; Muller and Leeuwen, 2004; Bartholomew et al., 1985; Blickhan and Full, 1987; Full and Tu, 1991). The theoretical predictions are based on scale analysis, which neglects factors of order 1 and therefore should be accurate in an order of magnitude sense.