Field observations of snakes preying on endothermic vertebrates are rare and, even rarer, are observations with detailed documentation of the event. Here we present a detailed description of predation by an Amazon Treeboa, Corallus hortulanus (Linnaeus), on a Purple Gallinule (Porphyrio martinica, Rallidae) in Brazil.

Observations were made on Ilha Grande, Piauí, Brazil. This island represents the largest portion on Parnaíba Delta measuring 125 km2. It is bordered to the south by Lontras Creek, to the north by the Atlantic Ocean, to the west by the Rio Parnaíba and to the east by the Rio Igaraçu. The southeast and west of the island are devoted to rice plantations and gallery forest. During December 2012, surveys for Corallus hortulanus were made between 1845 h and 2359 h along a creek known by locals as Igarapé do Baixão. The length of the entire creek is 3.2 km, but only 1.5 km are accessible. On 19 December 2012, during the first-quarter moon, a distress call of a bird was heard at 2046 h and one of us (PdCS) observed an adult Corallus hortulanus 1.20 m total length that had just captured an adult Purple Gallinule of ~34 cm body length, that had apparently been sleeping on the branch of an aquatic macrophyte (Montrichardia linifera) 1.80 m above water level. At 2047 h, it wrapped the bird in two or three coils while grasping the bird’s flank. By 2051 h, the bird was immobile, but the boa continued to constrict and its breathing was audible. Between 2052 h and 2056 h the boa released its jaws from the bird and, while tongue-flicking, re-oriented its body in order to reach the bird’s head. At 2057 h, the boa

commenced head-first swallowing, but it had difficulty getting beyond the beak of the gallinule, and aborted the attempt at 2101 h. At 2102 h, it flicked its tongue once and began a second attempt at head-first swallowing. At 2106 h the snake was hanging vertically and, because of the weight of its body and the bird, it stopped swallowing again and elevated more than half of its body onto a thick branch. At 2109 h with its body well supported it once again grasped the bird’s head (Fig. 1) and by 2113 h the boa had successfully swallowed the head. The entire swallowing process ended at 2129 h. The boa remained in a resting position until 2133 h, and then moved 1.80 m onto a thorn-laden tree branch along the same creek. It remained on that branch for the next 12 days.

Although the actual capture of the gallinule was not witnessed by the senior author, the stealth exhibited by foraging species of Corallus has been documented (e.g., Yorks et al., 2003; da Costa et al., 2012). We can assume that great expenditures of time and energy go into foraging and prey capture, so the tenacity of the boa to overcome the difficulty presented by the head and bill (although certainly not extreme as bills go) is not surprising. Although we do not know when this particular C. hortulanus last fed or how long it had been searching for suitable prey, we do know that, after eating the gallinule, it did not start foraging again for a minimum of 12 days (and possibly longer). Henderson (2002), based on the percentage of preserved C. grenadensis with prey remains, determined that adults fed about every 24 days. Assuming that the C. hortulanus might not feed again over a period of several days to weeks, feeding frequency could be similar to that of C. grenadensis.

The boa’s choice of a tree equipped with thorns while digesting the gallinule is also of interest. Might the snake have choosen that tree because the thorns provided some degree of protection from potential predators while it was at a defensive disadvantage?

Herpetology Notes, volume 6: 233-234 (2013) (published online on 25 May 2013)

Predation on a Purple Gallinule (Porphyrio martinica) by an Amazon Treeboa (Corallus hortulanus)

on Ilha Grande, Piauí, Brazil

Pedro da Costa Silva1 and Robert W. Henderson2*

1Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV. Universidade Federal do Piauí, UFPI, Parnaíba, Piauí – 64202-020, Brazil.

2Milwaukee Public Museum, Milwaukee, Wisconsin 53233 USA

*Corresponding author: henderson@mpm.edu

Pedro da Costa Silva & Robert W. Henderson234

Acknowledgements. The senior author dedicates this paper to Prof. José Roberto S.A. Leite (Universidade Federal do Piauí, Parnaíba) who permitted the use of field equipment in his research. He also thanks people from BIOTEC-UFPI, Campus Ministro Reis Velloso, including Leiz Veras, Yuri Dias Macedo, Dr. Antônio Alvares Tavares, Dr. Anderson Guzzi and personnel from Instituto Butantan in São Paulo: Dra. Maria de Fatima Furtado, Dr. Francisco Luis Franco, Dr. Carlos Jared, Valdir José Germano, Circe Cavalcante, Silvia Cardoso, Dr. Ricardo J. Sawaya and Dr. Otavio Marques.

References

da Costa Silva, P., Henderson, R.W., Alvares Tavares, A., Melo Araújo, S.C., Guzzi, A. (2012): Observations on foraging and new prey records for the Amazon Treeboa (Corallus hortulanus, Squamata, Boidae). Reptiles & Amphibians 19: 187–190.

Henderson, R.W. (2002): Neotropical Treeboas: Natural History of the Corallus hortulanus Complex. - Krieger Publishing Company, Malabar, Florida, USA.

Yorks, D. T., Williamson, K.E, Henderson, R.W., Powell, R., Parmerlee, J.S., Jr. (2003): Foraging behavior in the arboreal boid Corallus grenadensis. Studies on the Neotropical Fauna and Environment 38: 167–172.

Figure 1. Corallus hortulanus in the process of swallowing a Purple Gallinule (Porphyria martinica).

Accepted by Zoltan T. Nagy