Predation of Tropidurus hispidus (Squamata, Tropiduridae) by Siphlophis leucocephalus (Squamata, Dipsadidae)

The discovery of predator-prey relationships are relevant to improve the knowledge regarding ecological processes, such as trophic ecology, mortality sources, and paths of fluxes of matter and energy in ecosystems. Snakes of the genus Siphlophis feed on mammals, birds, frogs, lizards, lizard eggs, and snakes, whereas Tropidurus hispidus lizards are prey for both invertebrates and vertebrates. Here, we report a predator-prey relationship involving T. hispidus and Siphlophis leucocephalus. As a behavioural strategy to reduce the resistance promoted by appendages and body scales, thus diminishing the time and energy expended to swallow the prey, the individual of S. leucocephalus ingested the lizard headfirst. Tropidurus hispidus has mucronate scales that may be difficult to manipulate and swallow. Predators might die because of swallowing lizards with spiny and pointed dermic structures because of perforation of organs and of asphyxia. With this report, we added knowledge about the trophic ecology of S. leucocephalus and mortality sources for T. hispidus, besides reinforcing the idea of the importance of the consumption of lizards by snakes of the tribe Pseudoboini and of the genus Siphlophis.

We collected an individual of S. leucocephalus (Figure 1A), on 25 February of 2013, during the morning, in the district of Igatu, municipality of Andaraí, state of Bahia, northeast Brazil (12º53'57''S, 35º19'21''W, 760 m above sea level).The area is composed by rock outcrops and sandy soils covered by undergrowth, herbaceous and shrubby vegetation.The middle portion of its body was noticeably distended, indicating the presence of a prey in its digestive tract.We dissected the snake for prey identification and found a specimen of Tropidurus hispidus (Figures 1B and 1C) measuring 106.7 mm of snout-vent length and 137.2 mm of tail length and weighing 25 g.The snake measured 675 mm of snout-vent length and 227 mm of tail length and weighed 49.7 g (after dissection).The snake was collected under the permission licence IBAMA/ICMBio nº 17474-1.
The occurrence of saurophagy is common among the Pseudoboini, occurring in species of different genera in this tribe (e.g., Duellman, 1978;Nascimento et al., 1987;Cunha and Nascimento, 1993;Cadle and Greene 1994;Sazima and Argôlo, 1994;Prudente et al., 1998;Neto et al., 2013).Of the seven species of Siphlophis, there is information regarding feeding habits of six of them and all consumed lizards (Duellman, 1978;Nascimento et al., 1987;Sazima and Argôlo, 1994;Prudente et al., 1998;Neto et al., 2013; this study; Table 1), suggesting that these prey is greatly relevant as energy source for these snakes.Species in the family Tropiduridae (particularly in the genus Tropidurus) are among the lizards most commonly consumed by those snakes, having been reported as prey for four species: S. cervinus (Prudente et al., 1998;Martins and Oliveira, 1999), S. compressus (Withworth and Beirne 2011), S. leucocephalus (this study), and S. pulcher (Prudente et al., 1998) (Table 1).Nevertheless, there was no previous record of consumption of T. hispidus by any species of Siphlophis until now.
The individual of S. leucocephalus collected in Igatu ingested the lizard headfirst.Typically, the behaviour of ingesting prey headfirst is a strategy to reduce the resistance promoted by appendages and body scales, thus reducing the time and energy expended to swallow the prey (Greene, 1976;Queiroz and Queiroz, 1987; see also references therein).Tropidurus hispidus has mucronate scales that may be difficult to manipulate and swallow.Predators may die because of swallowing lizards with spiny and pointed dermic structures because of perfora-tion of tissues and organs and of asphyxia (snakes and birds - Pianka and Vitt, 2006;Vitt and Caldwell, 2014).There is information about the ingestion of prey by S. cervinus both starting from the head and from the hind portion of the body, and headfirst ingestion by S. compressus, S. leucocephalus, S. longicaudatus, and S. pulcher (Prudente et al., 1998;Neto et al., 2013;this study).These data is suggestive that the orientation of the prey when swallowed by snakes within this genus may be variable, but predominantly headfirst.
In this report, we revealed the existence of a predatorprey interaction involving S. leucocephalus and T. hispidus, adding knowledge regarding the trophic ecology of the snakes and mortality sources for the lizards and reinforcing the idea of the importance of the consumption of lizards by snakes of the tribe Pseudoboini and of the genus Siphlophis.

Figure 1 .
Figure 1.(A) Individual of Siphlophis leucocephalus collected in Igatu, state of Bahia, northeast Brazil, and the lizard Tropidurus hispidus consumed by the snake in dorsal (B) and ventral (C) views.Note in A the distension in the middle region of the body of the snake due to the presence of the lizard.Photos by Thiago Maia-Carneiro.

Table 1 .
Mabuya and Tropiduridae (including Tropidurus) Prudente et al., 1998Lizard families, genera, and species consumed by snakes of the genus Siphlophis and source of information.