Ecology of the Snake Philodryas patagoniensis (Serpentes, Colubridae) from Northeast Argentina

SOLEDAD M. LOPEZ; ALEJANDRO R. GIRAUDO

JOURNAL OF HERPETOLOGY

Society for the Study of Amphibians and Reptiles

Lugar: Grenville, Ohio; Año: 2008 vol. 42 p. 474 - 480

0022-1511

Information on the natural history and ecology of snakes have been scarcely studied in communities from subtropical and temperate areas of South America. We studied the feeding habits, reproductive biology, sexual dimorphism and seasonal activity of the snake Philodryas patagoniensis in northeastern Argentina, one of the most common snake regionally. There were statistical differences in all scale counts and size measurements between adult males and females. Juveniles showed significant sexual dimorphism in scale counts, tail length and mass. A total of 92 prey items were recorded from 184 specimens, reptiles being the most common prey (58%), mainly lizard Cercosaura schreibersii (26%); however, amphibians also were fairly common in the diet (15%) and mammals (10%) and birds (4%) were taken occasionally. Diet composition did not differ significantly between males and females. An ontogenetic shift from feeding exclusively ectothermic preys (reptiles and amphibians) to feeding endothermic (mammals and birds) and ectothermic preys was demonstrated. Males attained sexual maturity at a shorter snout-vent length (SVL) than females. The reproductive cycle of females was seasonal and the number of eggs was positively correlated with female SVL. Philodryas patagoniensis was active throughout the year, but significantly less so in winter and more so in spring. However, P. patagoniensis is a general predator because it fed different types of prey, the most important prey in its diet was reptiles in Argentina, but its diet varies geographically, presumably in relation to availability.  Reproductive cycle of this snake follows the pattern of temperate region species and it is slightly longer than other population of the same species. Probably the reproduction is relationship with the abundant feeding and a temperature region not extremely colder in winter. The large abundance of P. patagoniensis in South America may be influenced by its foraging plasticity, the abundant feeding and the preys availability and abundance. By these reasons, we think that this species is an important predator in the South American ecosystems.