Predation of the hylid frog Bokermannohyla alvarengai ( Bokermann , 1956 ) by the colubrid snake Chironius flavolineatus ( Jan , 1863 ) in a montane rocky grassland

We reported the predation record of the hylid frog Bokermannohyla alvarengai by the colubrid snake Chironius flavolineatus in a montane rocky grassland in Santana do Riacho municipality, Minas Gerais state, southeastern Brazil. Our findings contribute to the biological knowledge of B. alvarengai through identification of one of its natural predators, and of C. flavolineatus by adding an anuran species to its diet, data not previously available in the scientific literature.

haço Mountain Range, Southeastern Brazil.In spite of the species is listed by International Union for Conservation of Nature as "least concern", one should regard that its habitat is under degradation as a consequence of disorderly recreational tourism, livestocks and non-natural fires (Bertoluci & Silvano, 2010).The defensive strategies of B. alvarengai has been poorly studied, but it is known that both tadpoles (Eterovick et al., 2010) and adults (Toledo & Haddad, 2009) make use of cryptic behavior to avoid their detection by predators.
Chironius flavolineatus (Figure 2) is a medium sized colubrid snake (adult snout-vent length ranging from 507 to 894 mm; Pinto et al., 2008), distributed over savannic formations of South America.Although some information on natural history of Chironius species from Atlantic Forest is available, only few studies has focused on its ecology.This snake feed on anurans, mainly hylid frogs (Dixon et al., 1993, Pinto et al., 2008), and its diet seems to be predominantly composed by Hypsiboas Wagler, 1830 and Scinax Wagler, 1830 species (Pombal Jr., 2007;Pinto et al., 2008).
Our casual sampling took place in the montane rocky outcrop habitat in Serra do Cipó (19º17' S, 43º35' W, Datum: WGS 1984), Santana do Riacho municipality, Minas Gerais state, Brazil.On 04 July 2013, at 14:00 h we found an individual of C. flavolineatus presenting a marked medial dilatation of its abdomen.We then, captured the snake and induced it to regurgitate by careful pressing its abdomen with anti-peristaltic movements (Shine, 1995;Mesquita et al., 2013).The individual C. flavolineatus measured 33.0 cm for the snout-vent length, 20.0 cm for the tail length, 13.5 mm for the head length, 8.6 mm for the head width, 5.9 mm for the head height, and had fed on a small B. alvarengai with 23.8 mm of snout-vent length, swallowed headfirst (Figure 3).After the morphometric measurements, the snake was induced to eat the frog again and was released in the site of its capture.
We were able to precisely identify both snake and frog species in view of their diagnostic  characters and geographic distribution.Chironius flavolineatus presents a yellow vertebral stripe along the two anterior thirds of the body (Dixon et al., 1993;Hamdan et al., 2014), and was already recorded to the Serra do Cipó (Assis, 1999).Bokermannohyla alvarengai has a dorsal color pattern that resembles lichens on rocks, with dark brown blotches on a gray background (Bokermann, 1956;Leite et al., 2011), and also has been previously recorded to the Serra do Cipó (Machado & Galdino, 2005).
Individuals B. alvarengai remain motionless thermoregulating unsheltered above the rocks during the daytime period (Tattersall et al., 2006), this fact is notable for the juveniles (CABG obs.pers.).Despite B. alvarengai is criptic against the rocks with lichens (Sazima & Bokermann, 1977), its termoregulatory behavior might exposes individuals to visually oriented predators, as already was confirmed with the predation record by the Chimango Hawk Milvago chimachima (Machado & Galdino, 2005).The case herein reported pres-ents a chemical oriented predator, C. flavolineatus, preying upon B. alvarengai during the sunlight period.Our findings expand the knowledge on biology of B. alvarengai by the identification of other kind of natural predator for the species.