Many animals use dynamic behaviors to cross gaps larger than those they can reach across. Despite the generality of this pattern, the factors that influence the selection of gap-crossing behaviors are not fully understood. In snakes, the relationship between gap distance and behavior has rarely been studied, in part because most species exhibit only one crossing behavior, the cantilever. Here, we examined gap crossing in wild-caught Australian tree snakes (genus: Dendrelaphis). It is possible that these arboreal snakes employ dynamic behaviors to extend their reach, similarly to their sister taxon to the flying snakes (Chrysopelea), who employ jumping to cross large gaps. We hypothesized that tree snakes would transition to a dynamic behavior prior to reaching their maximum cantilever distance (~50% snout-vent length (SVL)), but that larger snakes would transition relatively earlier because of disproportionate mass-related torques. To address this hypothesis, we recorded horizontal gap crossing in 19 specimens from two species (D. punctulatus and D. calligastra), and also collected morphometric data. Video recordings of trials revealed that the largest gap size at which a cantilever was used ranged from 38 to 56% SVL. In absolute terms, this distance scaled approximately 1:1 with snout-vent length. Beyond this distance, both species of Dendrelaphis used dynamic forms of crossing. Because growth is indeterminate in snakes, it is unclear whether this scaling pattern is due to body size or ontogeny, particularly as other behaviors varied between large and small snakes. These data support the general pattern of animals using dynamic behaviors to cross larger gaps, and suggest future directions for identifying factors that play a role in governing gap-crossing behavior selection.