New records and notes on defensive behavior of Thamnodynastes rutilus ( Prado 1942 )

Snakes of the genus Thamnodynastes Wagler 1830 are viviparous, opisthoglyphous and have elliptical vertical pupil. Among all of the 11 species that occur in Brazil, T. rutilus is easily diagnosed by having a reddish spot in the sixth infralabial. Information about biology, ecology, distribution and behavior of T. rutilus is very scarce in the literature. Such lack of information leads to poor species management and difficulty for taking conservation measures when needed. Thus, this study brought new insights about T. rutilus geographical distribution, amplifying its previously known occurrence area, as well as providing new data about the species natural defensive behavior.

SHORT COMMUNICATION 1 Universidade Federal de Viçosa.Departamento de Biologia Animal.Museu de Zoologia João Moojen, Vila Gianetti, 32, 36570-000, Viçosa, MG, Brazil.* Corresponding author New records and notes on defensive behavior of Thamnodynastes rutilus (Prado 1942) Novos registros e notas sobre comportamento defensivo de Thamnodynastes rutilus (Prado 1942) Snakes of the genus Thamnodynastes are dipsadids (Costa and Bérnils, 2015) belonging to the subfamily Xenodontinae, which is widely distributed throughout South America (Bailey et al., 2005).They are viviparous, opisthoglyphous and have elliptical vertical pupil (Franco and Ferreira, 2002) (Costa and Bérnils, 2015).Despite the recent contributions to the knowledge of the genus, there are still much confusion about the taxonomic status of the group (Franco and Ferreira, 2002;Bailey and Thomas, 2007).
The species Thamnodynastes rutilus can be easily distinguished from its congeners by having a reddish spot in the sixth infralabial in both sides of the head (Franco and Ferreira, 2002).This species was originally described as Dryophylax rutilus by Prado (1942), which besides the redescription, also discussed the systematic position of the genus Dryophylax.Afterwards, Vanzolini (1948) reviewed Prado's description and placed D. rutilus in the genus Thamnodynastes.The species' geographic distribution is restricted to only a few localities in the states of São Paulo, Minas Gerais, Mato Grosso do Sul, Rio de Janeiro and Distrito Federal (Franco and Ferreira, 2002).Information about the biology, ecology and behavior of this species is very scarce in the literature, with few documented captures, some data without many details about behavior and diet (Marques et al., 2015), and a single observation of parturition in captivity followed by a posterior event of cannibalism, practiced by the only female born in the litter over one of its siblings (Araújo et al., 1998).
Here we provide an updated distributional map of Thamnodynastes rutilus compiled from the literature, online databases [Instituto Butantan (IBSP), Fundação Ezequiel Dias (FUNED) and Universidade Federal de Minas Gerais -Instituto de Ciências Biológicas (UFMG-ICB) collections were accessed through SpeciesLink website; vouchers not examined] (SpeciesLink, 2016) and sporadic records during fieldwork.We considered just those information that contained precise data about the location record.Additionally, following the nomenclature from a few studies regarding behavior of snakes available in the literature (Greene, 1988;Sazima, 1992;Martins and Oliveira, 1998;Tozetti, 2012), we present data about T. rutilus defensive behavior in natural conditions.
We found 14 occurrence localities to T. rutilus through literature (Prado, 1943;Araújo et al., 1998;Franco and Ferreira, 2002;Gonçalves et al., 2007;Condez et al., 2009;Costa et al., 2014), and other five points were added through records from SpeciesLink database.Two records were made through sporadic fieldwork, in 2014 and 2015, respectively.The first record was made on October 26, 2014, during a fieldwork in the Fazenda São Francisco, municipality of Grão Mogol (16°10'36.87"S,42°46'09.55"W;Datum WGS 84; 780m), northern Minas Gerais.A specimen of T. rutilus was recorded by Clodoaldo Lopes de Assis (CLA) around 19:30 h moving on arboreal vegetation on the bank of a stream, approximately 140 centimeters above the ground.The site is embedded in the Espinhaço Mountain Range and has a vegetation mosaic formed by Cerrado, Atlantic Forest and rocky fields.The specimen (male, snout-vent length = 413 mm, tail length = 165 mm) was collected and deposited in the Museu de Zoologia João Moojen at the Universidade Federal de Viçosa (MZUFV 2440).A second record was on February 20, 2015, during a field expedition in the Private Reserve of the Natural Patrimony Vereda Caraíba, located in the municipality of Bonito de Minas (14°45'09.16"S,45°06'14.06"W;Datum WGS 84; 656m), northern Minas Gerais, an adult specimen of T. rutilus was observed and photographed by Douglas Henrique da Silva (DHS) over a vegetation in flooded environment during the night.The site is located in a transition region between Caatinga and Cerrado biomes (Brandão, 1994).
Thamnodynastes rutilus features a relatively wide geographic distribution, mainly for the states of São Paulo (SP) and Minas Gerais (MG), but with scarce records for Mato Grosso do Sul (MS), Rio de Janeiro (RJ) and Dis-trito Federal (DF) (Prado, 1943;Arújo et al., 1998;Franco and Ferreira, 2002;Gonçalves et al., 2007;Condez et al., 2009;Costa et al., 2014).Our results extend its geographical distribution beginning in the nearest points in the literature: Barra do Turvo (SP) extend ca.156 km southwest of Piedade (SP), Bonito de Minas (MG) ca.320 km northeast from Brasilia (DF) and Grão Mogol (MG) ca.428 km northeast from Esmeraldas (MG), these being the limits south, north and east respectively.The material examined by Franco and Ferreira (2002) contains a specimen collected at Sérgio Motta Hydroelectric Plant (IB 61627), in the state of Mato Grosso do Sul, but it does not specify the municipality.Thus we consider the record in Baytaporã (MS), as the westernmost limit of occurrence of the species, extending its distribution ca.113 km southwest of Presidente Epitacio (SP).The current geographic distribution of T. rutilus includes areas of the Cerrado and Atlantic Forest phytophysiognomies, as well transition regions between these two biomes, including rocky fields in the Espinhaço Mountain Range, and also transition areas between the Cerrado and Caatinga biome in its northernmost limit of occurrence (Figure 1 and Table 1).
Both specimens of T. rutilus (Figure 2) recorded by DHS and CLA, respectively, showed defensive posture when disturbed, exhibiting the following behaviors when handled: (1) cloacal discharge, (2) strike with bite and (3) locomotor escape.When set free on the ground, six behaviors were characterized when disturbed: (1) head triangulation, (2) false strike, (3) erratic movements, (4) locomotor escape, (5) S-shaped posture and (6) elevation of the anterior portion of the body.The specimens exhibited a defensive repertoire composed of many different defensive strategies.When the snake did erratic movements or was moving to escape, it always remained with the S-shape posture, triangulation of the head and the posterior third of the body raised.
Marques et al. (2015) described four defensive behaviors for T. rutilus (body flattening, head triangulation, strike and cloacal discharge) of which only body flattening was not observed in this study.Ectothermic animals depend on environmental temperature to carry out their activities and react to stimuli (Goode and Durvall, 1989;Pough et al., 2008).Although we did not consider environmental temperature during observations, the absence of this behavior may be related with it.It has been observed that snakes adjust their defensive behavior according to temperature, being more passive in colder days (Shine et al., 2000).Other possible explanation relies on the fact that snake anti-predator displays are in part heritable and highly variable within populations, so that the individual behavior might not be always consistent (Arnold and Bennett, 1984).In this particular case, the lack of a trigger (e.g., an odor or insight of a particular predator) could also be the reason of why the individuals of T. rutilus did not display the body flattening behavior.New records and notes on defensive behavior of Thamnodynastes rutilus (Prado 1942) Thamnodynastes rutilus presented a diverse set of defensive behaviors, displaying both performances commonly seen in terrestrial species (erratic movements) as those seen in arboreal ones (head lift and neck S-coil) (Martins and Oliveira, 1998;Marques et al., 2015), which is expected for a species that live in both types of microhabitats (Marques et al., 2015) and may be under pressure of different kinds of predators (Greene, 1988).Strike with bite and cloacal discharge were recorded only during the animal manipulation, and possibly is an extreme defensive mechanism to discourage their ingestion by the predator (Tozetti et al., 2009), suggesting that this species is able to adjust their defensive behavior according to the threat level imposed by the predator.Still, the pattern of cryptic coloration and the defensive behavior repertoire (head triangulation, false strike, S-shape posture and elevation of the anterior portion of the body) similar to that described for the genus Bothrops (Sazima, 1988;Araújo and Martins, 2006) suggests that T. rutilus mimics sympatric species of this genus.Other similar cases among colubrid species mimicking viperids or elapids based on the similarity of the color patterns and behavior have been reported (Gans and Latifi, 1973;Sánchez-Herrera et al., 1981;Yanoski and Chani, 1988;Marques and Puorto, 1991), and experiments using models mimicking dangerous species showed that in most cases, such characteristics prevent predators from striking (Dell'Aglio et al., 2012).
In conclusion, T. rutilus is a poorly known Brazilian species, and data about its biology, ecology, distribution and behavior are still very scarce in the literature.Such kinds of information are essential for taking conservation measures, management of species, programs of captive breeding and others.Thus, more studies are still needed in order to fill gaps about the knowledge of this species in a way to better understand its relationship with other organisms and the ecosystem.

Figure 1 .
Figure 1.Geographical distribution of Thamnodynastes rutilus in central and southeastern Brazil.White circles: literature records; yellow circles: new records.

Figure 2 .
Figure 2. Specimens of Thamnodynastes rutilus recorded in Minas Gerais, southeastern Brazil.A: specimen recorded in Bonito de Minas; B, C and D: specimen recorded in Grão Mogol (MZUFV 2440), showing detail of elevation of the anterior portion of the body, triangulation of the head and S-shaped posture.

Table 1 .
Recorded localities for Thamnodynastes rutilus in central and southeastern Brazil.