Predation on Philodryas patagoniensis (Squamata, Colubridae) by an Aplomado falcon (Falconidae: Falco femoralis) in central Argentina

Abstract

The Patagonia Green Racer (Philodryas patagoniensis, Squamata, Colubridae) is a widespread snake that occurs in Argentina, Brazil, eastern Bolivia and Uruguay (Cei, 1993). In Argentina this species ranges from northern (Formosa, Misiones, Corrientes, Salta, Jujuy, Tucumán, Santiago del Estero, Chaco and La Rioja) and central provinces (Mendoza, La Pampa, Córdoba, Santa Fe, Entre Ríos, San Luis) up to northern Patagonia (Neuquén, Rio Negro, Chubut) in the south (Cei, 1993). The Patagonian Green Racer is a medium-sized diurnal colubrid snake that exhibits a territorial behavior, and inhabits mainly open areas as grassland and savannas (Cei, 1993; Scolaro, 2005). Here we present a case of predation on the Patagonian Green Racer by an ornithophagus raptor, the Aplomado Falcon (Falconidae: Falco femoralis). The observation was made in an agricultural landscape from La Pampa province, in central Argentina, during bird?s reproductive season (austral spring). The area consists of a mosaic of different crops and farming lands. The Aplomado Falcon is a medium-sized (average 300 g) falcon of the Americas. This raptor is mainly ornithofagous, being the Ear doves (Zenaida auriculata) its major prey on the study area (Liébana, 2015). Until this report doesn?t exits evidence of depredation by Aplomado Falcon over Patagonian Green Racers or on any other species of Philodryas (Keddy-Hector, 2000; Figueroa and Corales, 2005; Bó et al., 2007; Baladrón et al., 2012). On 10 November 2010 we found remains of a Patagonian Green Racer in an Aplomado Falcon nest containing three nestlings, in Colonia Baron town (36°09′05″ S, 63°51′14″ W; 154 m a.s.l.). The snake remains were situated below the nest, the head and part of the body were possibly consumed by the falcons before falling down to the ground. This was the only occurrence of this prey item on 589 pellets and 278 prey remains analyzed. Remains of colubrid preys (scales) were found on three pellets but they couldn?t be identified to species level. Other reptiles founded in low frequency were Teius oculatus (n=3) and Lioalaemus sp. (n=11). All the reptile preys were identified using references collections and keys (Scolaro, 2005; Scrochi et al., 2010). It has been documented that P. patagoniensis is consumed by a variety of raptor species: the Laughing Falcon (Herpetotheres cachinnas) in Brazil, the Whitetailed Hawk (Buteo albicaudatus) and the Crowned Solitary Eagle (Harpyhialeaetus coronatus) in central Argentina, and it is also probably consumed by the Roadside Hawk (Buteo magnirostris) and the Savanna Hawk (Heterospizias meridionalis) in northern Argentina (De la Peña, 2001; Di Giácomo, 2005; Motta-Junior et al., 2010; Sarasola et al., 2010; Galmes unpublished data). The Patagonian Green Racer is very common in central Argentina; but information about its ecology and potential predators are scarce. Our record presents the Aplomado Falcon as an occasional predator on this colubrid snake.