Amphibians and reptiles are both important predators and preys in natural ecosystems. Amphibians consume amazing quantities of insects (Toft, 1980; Stewart and Woolbright, 1996), and are prey of diverse invertebrates and vertebrates (Toledo, 2005; Toledo, Ribeiro and Haddad, 2007). Reptiles are also important predators and preys of both invertebrates and vertebrates (Green, 1997; Pianka and Vitt, 2003). Amphibians and reptiles interact between them in a predator–prey dynamic. For instance, there are many reports about snakes eating anurans (Duellman, 2005; Rodriguez et al., 2011; Freitas and Lima, 2012; Moura, Godinho and Feio, 2012; Ribeiro and Freire, 2012; see Toledo, Ribeiro and Haddad, 2007, and Wells, 2007 for a review). However, there are few published reports about snake–anuran interactions where the anuran is successful in their race for survivorship (but see Warkentin, 1995, 2011). Here we report observations of the Cat-eyed snake Leptodeira septentrionalis (Colubridae) attempting to swallow a toad Rhinella humboldti (Bufonidae), where the latter species escapes in spite of apparent lower probabilities for survivorship.

On 10 January 2013, we observed a L. septentrionalis (total length = 685 mm) struggling with an individual of R. humboldti (snout-vent length = 32.2 mm) at Hacienda Pampas, Municipality of Yondó, department of Antioquia, middle Magdalena valley, Colombia (125 m elevation). Specifically, our observation was in a pathway of dry mud located in an open area whose predominant vegetation was grass (Dichanthium aristatum, Hyparrhenia rufa). In this place, the formation of small temporal ponds after rains is common, which are used by both R. humboldti and the

frog Engystomops pustulosus (Leptodactylidae) for breeding purposes. During our observations, we used red lights and avoided to take many pictures to reduce the effects of perturbation in the process registered. The predation event was detected when the toad had already been caught from behind by the snake (22:00 h) (Fig. 1A). During the process, the snake attempted to turn around the toad to swallow its head first, but this was not possible because of the resistance of the toad with one of its hind legs. Additionally, the toad inflated its body. In several occasions, the toad was almost totally swallowed, but repeatedly the snake had to retry its attempts because of toad resistance (Fig. 1B-D). After 113 minutes of this struggle, the snake regurgitated the toad and quickly moved away. The snake was captured to measure its body length and then released. The toad was captured and maintained in a plastic bag with water. The toad was alive and apparently healthy 48h after the attack, despite that Leptodeira snakes have parotid glands to inject venom to preys (Duellman, 1958). We collected the toad and deposited it in the Museo de Zoología at the Universidad de los Andes, Colombia (Andes-A 1390).

Although snakes are able to catch and swallow large preys relative to their body size (Green, 1997), their capacity have a limit imposed by their morphology. In fact, a wrong evaluation of such limits by a given snake can lead to an unnecessary spend of energy, regurgitation of the prey (Bernal and Palma, 2011; Fong, Bignotte and Maure, 2013), or even the death of both predator and prey (Cavalcanti et al., 2012; Caramaschi and Niemeyer, 2012 and references therein). As mentioned above, puffing up the body is a recognized defensive behaviour of amphibians against snake’s predator attempts (Wells, 2007; but see commentaries by Toledo, Sazima and Haddad, 2011). Our observation for R. humboldti might be an example of the effectiveness of that defensive behaviour in toads, but more evidence is necessary to confirm it. We cannot discard a role of the

Herpetology Notes, volume 6: 189-191 (2013) (published online on 20 April 2013)

A race for survivorship: failed predation on the toad Rhinella humboldti (Gallardo, 1965) by the Cat-eyed snake

Leptodeira septentrionalis (Kennicott, 1859)

Fernando Vargas-Salinas1,* and Andrés Aponte-Gutierrez2

1 Department of Biological Sciences, Universidad de los Andes, Cra. 1a No. 18A-10, Lab. 305-J; Bogotá DC, Colombia.

2 Fundación Biodiversa Colombia, Bogotá DC, Colombia.

* Corresponding author; e-mail: vargassalinasf@yahoo.com

Fernando Vargas-Salinas & Andrés Aponte-Gutierrez190

toad cutaneous toxins in the result of the observed event, but it is highly plausible that diverse defensive strategies of the toad act in synergy to deter predators (Toledo, Sazima and Haddad, 2011). Unsuccessful predation events on anurans by snakes may be relatively frequent given the diverse defensive strategies in anurans.

Leptodeira septentrionalis is a nocturnal snake commonly observed eating arboreal egg clutches of frogs such as Agalychnis spurrelli, A. callidryas and Dendropsophus ebracattus (Warkentin, 1995; Vargas-Salinas, Bolaños-L. and Berrio-Baca, 2000; Savage, 2002), and juveniles and adults of diverse frog species in breeding aggregations (Duellman, 1958; Cabrera-Guzmán, Carmona-Torres and Reynoso, 2009; Delhing, 2009; Kaiser, 2010; Olivia et al., 2010; Ortega-Andrade Tobar-Suárez and Arellano, 2011; Rivera-Correa and Gutiérrez-Cárdenas, 2012). Leptodeira septentrionalis also can eat toads (Duellman, 1958), but there are no previous reports on the toad R. humboldti.

Acknowledgements. Observations in this manuscript were made during field work of the agreement between Fundación Biodiversa Colombia and Empresas Agrícola San Bartolo, Inversiones San Bartolo y Productora de Lácteos. We are grateful with F. Arbelaez, J. C. Marín, E. de Jesús Maya and all the people living at Hacienda San Bartolo for their friendship and help in fieldwork. Former version of this manuscript was improved thanks to suggestions by N. Gutierrez-Pinto and P.D. Gutierrez-Cárdenas.

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Figure 1. Predation of the Cat-eyed snake Leptodeira septentrionalis on the toad Rhinella humboldti. A: first observation of the individuals when the snake catched the toad by behind. B-D: race for survivorship of the toad against engulf attempts by the snake. Several times the toad was almost totally swallowed, but finally the snake regurgitated it.

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Accepted by Philip de Pous

191A race for survivorship: failed predation on the toad Rhinella humboldti