Defensive repertoire of Xenodon dorbignyi (Serpentes, Dipsadidae)

Abstract

The ability of a species to defend itself against a predator is directly correlated with its survivorship. Thus, prey/predator interaction mechanisms are important elements of the natural history of species. In this study, we examined the defensive repertoire of the South-American hognose snake (Xenodon dorbignyi) through simulations of predator attacks in the field. Nine defensive displays were observed. The most frequently observed displays were erratic movements, body flattening, head triangulation and tail display. No differences were detected in the defensive strategies shown by males and females, regardless of their reproductive state. Our findings suggest that X. dorbignyi has the ability to evaluate the level of threat imposed by the aggressor, with cryptic behavior, body flattening and locomotor escape as the primary defensive strategies, with other displays used as secondary responses to a predator attack. Our results support the hypothesis that X. dorbignyi is a mimic of both Micrurus and Bothrops.

Head triangulation as anti-predatory mechanism in snakes

“…These differences between studies may result from the different ecosystems where they were conducted. Head triangulation behavior, recurrently shown in the literature (Tozetti et al 2009, Marques et al 2001a), seems to be an effective strategy that results in a higher survival rate. Lower predations rates are also shown in other mimetic systems.…”

“…However, these results were contested by Valkonen & Mappes (2012). Our hypotheses are: (1) snakes with triangular head suffer less predation pressure; (2) as the snake's head is an important target, the head has higher attack rate (Langkilde et al 2004, Niskanen & Mappes 2005; and (3) snakes with triangular head, supposedly to intimidate visual predators (Tozetti et al 2009), suffer higher attack rate on the head than on other parts of the body, setting up more accurate attacks.…”

“…This ability can be observed in some species of Dipsas, which associated with coloration make them mimetic of Bothrops jararaca, a Viperidae snake widely distributed in Brazil (Tozetti et al 2009). The mimetic behaviors displayed by these snakes, head triangulation and threatening posture, are known for many species of Colubrid snakes (Marques et al 2001a), however, there are controversial data in studies showing their effectiveness against natural predators (Guimarães & Sawaya 2012, Valkonen & Mappes 2012.…”

“…Reptiles exhibit extremely diverse antipredator mechanisms, including cryptic coloration and behavior, mimicry, aposematism and also several ways to intimidate attackers (Pough et al 2004). Many of these anti-predator mechanisms are assumed to be a visual intimidation for predators (Tozetti et al 2009). Snakes are interesting models for defense mechanisms studies because besides having developed defensive behaviors, they are potential prey for many animals such as mammals, birds, other reptiles and invertebrates (Greene 1988).…”

Does human influence on coastal grasslands habitats affect predation pressure on snakes?

“…Reptiles, especially snakes, represent an important food source for a large number of vertebrates, especially birds and mammals (Greene 1997, Hinman et al 1997, Buasso et al 2006, Tozetti et al 2009). However, little is known on how the habitat interferes in predation rates or whether habitat changes can maximize the action of a given type of predator.…”