Feeding behavior of the Amazonian Water Snake Helicops hagmanni Roux, 1910 (Reptilia: Squamata: Colubridae: Hydropsini)

 

Comportamento alimentar da cobra d'agua amazônica Helicops hagmanni Roux, 1910 (Reptilia: Squamata: Colubridae: Hydropsini)

 

 

Marcelo José Sturaró^I; Jerriane Oliveira Gomes^II

^IMuseu Paraense Emílio Goeldi. Belém, Pará, Brasil (marcelosturaro@gmail.com)
^IIMuseu Paraense Emílio Goeldi. Belém, Pará, Brasil (jerrianegomes@yahoo.com.br)

 Correspondence

 

 

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ABSTRACT

The genus Helicops currently comprises 15 species, of which eleven occur in the Amazon Forest. H. hagmanni feeds on fishes and has nocturnal habits, but detailed data about its diet and behavioral ecology are scarce. Here, we report a H. hagmanni adult female specimen (snout-vent length: 516 mm; weight: 162 g) preying on an adult fish, Rhamdia muelleri (Actinopterygii: Heptapteridae, 215 mm in total length; weight: 70 g), in the creek Caquajó, a tributary of the Anapu River, municipality of Portel, Pará State, Brazil. We found the snake submersed at 20 cm, convoluted around the fish, and shortly after that, started ingesting the fish headfirst. The snake attacked the cat-fish biting the region between the anal and post-anal fins. This information increases the knowledge about the feeding behavior in snakes, especially of the genus Helicops.

Keywords: Water snakes. Helicops. Predation. Cat-fish. Rhamdia muelleri.

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RESUMO

O gênero Helicops inclui, atualmente, 15 espécies, das quais onze ocorrem na floresta amazônica. Helicops hagmanni se alimenta de peixes e apresenta hábitos noturnos, mas dados detalhados sobre seu comportamento alimentar e ecologia são escassos. Neste trabalho, registramos H. hagmanni (fêmea adulta; comprimento rostro-cloacal: 516 mm; massa: 162 g) predando um peixe adulto, Rhamdia muelleri (Actinopterygii, Heptapteridae; comprimento total: 215 mm; massa: 70 g), no igarapé Caquajó, rio Anapu, município de Portel, estado do Pará, Brasil. Encontramos a serpente submersa a 20 cm, enrolada sobre a presa, em seguida, começou a ingeri-lo no sentido ântero-posterior. A serpente atacou o peixe-gato mordendo a região entre o ânus e as nadadeiras anais. Essas informações ampliam o conhecimento sobre o comportamento alimentar das serpentes, especialmente do gênero Helicops.

Palavras-chave: Serpente aquática. Helicops. Predação. Peixe-gato. Rhamdia muelleri.

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The genus Helicops (Colubridae) comprises 15 species of water snakes distributed throughout cis-Andean South America, from Colombia to Argentina. Eleven of those species occur in the Amazonian rain forest (Rossman, 1970, 1973; Frota, 2005). Little is known about the ecology and natural history of Helicops species and the studies available are concentrated in few localities in Amazonia (Cunha & Nascimento, 1978; Duellman, 1978; Cunha & Nascimento, 1993; Silva Jr., 1993; Martins & Oliveira, 1998), caatinga (Vanzolini et al., 1980), pantanal wetland (Ávila et al., 2006), Atlantic rain forest (Sazima & Strüssmann, 1990; Marques et al., 2004; Marques & Sazima, 2004), and southern Brazil (Araujo & Ely, 1980; Sazima & Martins, 1990; Aguiar & Di-Bernardo, 2004; Franz et al., 2007).

Most Helicops species exhibit nocturnal habits, feed upon fishes, anuran tadpoles, and lizards (Cunha & Nascimento, 1978; Duellman, 1978; Vanzolini et al., 1980; Sazima & Martins, 1990; Sazima & Strüssmann, 1990; Cunha & Nascimento, 1993; Silva Jr., 1993; Martins & Oliveira, 1998; Marques et al., 2004; Marques & Sazima, 2004; Ávila et al., 2006), but generally no details are provided about the predatory behaviour in relation to prey type (for example a fish with spines in its fins or not). Sazima & Strüssmann (1990) reported scavenging of H. modestus Günther, 1861 of Geophagus brasiliensis (Quoy & Gaimard, 1824) (Cichlidae) and Astyanax scabripinnis (Jenyns, 1842) (Characidae) in the field in southeastern Brazil. Lema et al. (1983) reported an event of cannibalism among newborn captive H. infrataeniatus Jan, 1865.

Information on food and feeding behavior of Helicops hagmanni is scarce. This species feeds upon fishes and some authors suggested that it is primarily nocturnal (Cunha & Nascimento, 1978, 1993; Silva Jr., 1993; Martins & Oliveira, 1998). In this work, we present an observation of Helicops hagmanni preying on a cat-fish, Rhamdia muelleri (Günther, 1864), in the field.

On September 9, 2007 at 2300h in the creek Caquajó (1^o 57' 36" S, 51^o 36' 55" W; 20 m a.s.l.) ofthe plot of Programa de Pesquisa em Biodiversidade (PPBio), Anapu River, Floresta Nacional de Caxiuaná, municipality of Portel, state of Pará, Brazil, we found an adult female Helicops hagmanni (516 mm snout-vent length and 162 g weight) submersed in water at a depth of 20 cm, which was preying on an adult cat-fish, Rhamdia muelleri (215 mm total length and 70 g weight).

The snake seized the fish biting the prey's posterior body between the anal and post-anal fins (mark of bite on the R. muelleri was observed after the capture), maybe avoiding the fish's pectoral spines. After this, the snake held the prey with anterior, horizontal coils, similar to what has been observed in other colubrid snakes according to Willard (1977) (Figure 1A). Subsequently, the snake extended constriction until the opercula area of the cat-fish (Figure 1B).Thereafter, the snake examined the prey's body and swallowed it (Figure 1C), starting ingestion headfirst (Figure 1D). Aguiar & Di-Bernardo (2004) reported, based on fieldwork, that 92% of the proportionally large preys ingested by H. infrataeniatus (mainly adults) were oriented and swallowed headfirst.

 

 

Greene (1997) pointed out that large preys or preys with a defensive apparatus (spines) require some maneuvering prior to swallowing. We concluded that H. hagmanni assessed the better way to swallow its prey, likely, due to ontogenetic learning, taking into account the presence of pectoral spines and the proportionally large size of the fish (Murphy & Campbell, 1987; Sazima & Martins, 1990). The pectoral spines could obstruct the ingestion if the prey was oriented tailfirst, which would result in damage of the digestive tract, causing lesion, and even leading to death (Aguiar & Di-Bernardo, 2004).

More field observations on the feeding behavior of Helicops and other water snakes are needed to increase our knowledge about how these snakes capture and feed upon their preys.

Both specimens have been deposited in the herpetological (MPEG 22403) and ichthyological (MPEG 13408) collections of the Museu Paraense Emilio Goeldi, Belém, Pará, Brazil.

 

ACKNOWLEDGEMENTS

We thank Marinus S. Hoogmoed and Wolmar B. Wosiacki for snake and fish species identification, respectively. We also thank Adriano O. Maciel; Diogo B. Provete; Gleomar Maschio and Pedro Peloso for critically reading the manuscript. We also thank the Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis for the collecting and transport permits of snake (no 02001.001490/2006-81) and fish (no 02001.001486/2006-12), and the Programa de Pesquisa em Biodiversidade (PPBio) for financial support of the expedition and for the provision of field structures.

 

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Recebido: 20/10/2008
Aprovado: 28/12/2008