Significance of the dorsal zigzag pattern of Vipera latastei gaditana against avian predators

Abstract

Summary 1.Aposematism is an antipredatory strategy in which prey animals conspicuously signal their noxiousness to potential predators. This successful strategy is based on avoidance learning of predators. 2. Most species in the viperid genus Vipera have a characteristic dorsal zigzag pattern. It has previously been suggested that the dorsal zigzag pattern of Vipera berus (the adder) has a cryptic function and thus makes the snake less conspicuous to avian predators. However, a recent experiment suggested that the pattern may function as an aposematic signal rather than being cryptic, and therefore induces active avoidance in avian predators. 3. We conducted a field experiment in Doñana national park in Spain, testing whether the zigzag pattern gives survival value to Vipera latastei gaditana against avian predators. We used two sizes of plasticine models with a zigzag pattern vs. without a zigzag pattern to record attacks by avian predators. The background was controlled (white vs. natural) to exclude the possibility that one morph would be more cryptic to predators than the other one. We also tested size-dependent mortality against the signalling and nonsignalling snakes as aposematic signal is expected to enhance the survival of the aposematic species in a size-dependent manner. 4. Predation pressure against snakes was severe, and on average 39% of models were attacked. Coloration did not enhance the survival of juvenile-sized zigzag-patterned snakes, but significantly increased the survival of adult-sized zigzag-patterned snakes on both backgrounds. 5. Our results provide further support for the aposematism hypothesis of zigzagpatterned noxious snakes, although the advantage due to disruptive coloration is not mutually exclusive.

Head triangulation as anti-predatory mechanism in snakes

“…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.…”

“…Artificial models have been used in several studies as a tool to test anti-predation responses, for example fishes (Kelley & Magurran 2003), amphibians (Saporito et al 2007), birds (Gottfried 1979, Gottfried et al 1985, lizards (Leal & Rodriguez-Robles 1997), mammals (Barros et al 2002, Vignieri et al 2010) and particularly snakes (Brodie & Janzen 1995, Wilgers & Horne 2007, Niskanen & Mappes 2005, Guimarães & Sawaya 2011. Thus, using artificial snakes for studies with mimetic behavior and natural enemies' response seems to be an interesting, valid and effective method.…”

High-model abundance may permit the gradual evolution of Batesian mimicry: an experimental test

“…This method has been employed successfully to document both avian and mammalian predators on at least three continents (e.g. Madsen 1987;Brodie 1993;Brodie & Janzen 1995;Hinman et al 1997;Pfennig et al 2001Pfennig et al , 2007Wü ster et al 2004;Niskanen & Mappes 2005;Buasso et al 2006;, indicating that it is robust to different predator guilds and environments. We constructed our replicas with pre-coloured, non-toxic polymer clay (Polyform Products, Elgin, IL) that were coated with a thin film of clear, low-odour spray latex enamel (Krylon Products Group, Cleveland, OH) to minimize any smell emitted by the clay.…”

El uso de señales aposemáticas en serpientes: contra advertencia no hay engaño

“…Todas las especies de esta familia poseen un sistema de envenenamiento neurotóxico con pequeños colmillos frontales fijos (proteroglífos) (Jackson, 2003). Sin embargo, las especies de los géneros Micrurus y Micruroides son las que presentan un patrón de coloración conspicuo que es empleado como señal visual de advertencia asociado con su toxicidad (Niskanen y Mappes, 2005). Asimismo, el modo como está constituida la coloración mediante anillos en estas serpientes y la indiferenciación de su cuello con la cabeza las protege porque confunde al depredador y le dificulta la ubicación de esta parte vital.…”

“…En el caso de los vipéridos los patrones de manchas dorsales, la forma de la cabeza y su sistema de envenenamiento con largos colmillos móviles (solenoglífos) (Jackson, 2003) son características que funcionan conjuntamente como señales aposemáticas (Bechtel, 1978;Niskanen y Mappes, 2005;Dell'Aglio et al, 2012;Rojas et al, 2015). Se sabe que los patrones en zigzag de las manchas dorsales presentes en algunos vipéridos (figura 2) funcionan como señales de Nota: ejemplares del Herpetario Reptilium del Zoológico de Zacango.…”