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Abstract: Although adult crocodilians have few predators (mostly humans and other crocodilians), hatchlings and eggs are killed and consumed by a diverse array of invertebrates, fishes, anurans, reptiles, birds, and mammals. We review published literature to evaluate the incidence of predation in crocodilian populations, and the implications of that mortality for crocodilian life-history evolution. Presumably because predation is size-dependent, small-bodied crocodilian taxa appear to be more vulnerable to predation (across a range of life stages) than are larger-bodied species. Several features of crocodilian biology likely reflect adaptations to reducing vulnerability to predation. For example, the threat of predation may have influenced the evolution of traits such as nest-site selection, maternal care of eggs and hatchlings, crèche behavior in hatchlings, and cryptic coloration and patterning. Even for such large and superficially invulnerable taxa such as crocodilians, the avoidance of predation appears to have been a significant selective force on behavior, morphology, and ecology.
Key words: Alligator; Caiman; Crocodile; Ontogeny; Vulnerability
An organism's vulnerability to predation can play a central role in its biology. For many kinds of animals, predation is a major source of mortality, and hence can influence patterns of distribution and abundance (Sih et al., 1998; Ormerod, 2002). On an evolutionary level, vulnerability to predation can impose selection on traits that influence an organism's rate of encounter with potential predators (e.g., diel patterns of activity, habitat selection [Holomuzki, 1986; Turner and Mittelbach, 1990; Turner, 1996]), its ability to detect the presence of predators (e.g., via visual or olfactory cues [Petranka et al., 1987; Magurran and Seghers, 1990; Lehtiniemi, 2005]), and its ability to escape from a predator's attack (e.g., toxin tolerances, locomotor speeds [Snell et al" 1988; Husak and Fox, 2006]). Although many antipredator tactics clearly have evolved in response to the selective forces imposed by interactions with predators, most of these examples involve species that occupy relatively low positions within trophic webs (e.g., Matsuda et al., 1996; Finke and Denno, 2004; Kondoh, 2007; Carey and Wahl, 2010). In such animals, vulnerability to predation is likely to explain a high proportion of variation in lifetime fitness. However, even adult top predators may occasionally serve as prey (Pienaar, 1969; Hoelzel, 1991). Has the threat of predation acted as a significant selective force even in...