Abstract

We examined the effect of body size on locomotor performance and movement behavior in early postmetamorphic toadlets of Fowler's Toad (Anaxyrus fowleri). Dispersal, if strictly density dependent, should be favored among the relatively small toadlets that emerge from crowded growth conditions, but not among the relatively large toadlets that result from low-density conditions; however, smaller toadlets may have less physical capability to disperse than larger toadlets. The net result may thus be that actual dispersal probability is greatest among intermediate-sized toadlets. Using toadlets of various sizes purposefully raised by manipulating their densities as tadpoles, we tested toadlet locomotor jumping endurance in relation to body size. We also compared the animals' initial body size against their overall movements in the wild, determined using capture–recapture methods, over 2 yr as they grew from toadlets to adults. We calculated movement rate and dispersal probability for each individual recaptured more than twice and determined whether successful movement strategies were correlated or uncorrelated. Our results show that toadlets of intermediate size are most likely to disperse farthest, even though they do not necessarily exhibit the highest levels of endurance. Therefore, knowledge of individual life experience across multiple life stages may be necessary to understand dispersal tendencies in amphibians and may be required in future studies aiming to predict dispersal and population dynamics.