Herpetology Notes, volume 14: 1137-1139 (2021) (published online on 20 August 2021)
Interaction of the toads Rhinella rubescens (Lutz, 1925) and R. diptycha (Cope, 1862) with artificial road lights in central Brazil
Leonardo P. Fraga1,* and Helga C. Wiederhecker2
The impact of roads on biodiversity starts with In Brazil, the genus Rhinella is represented by 40 habitat destruction, persists through time, and might species (Segalla et al., 2019). Among them, species of the be aggravated by traffic and road characteristics R. marina group (sensu Pramuk, 2006) present cranial (Trombulak and Frissell, 2000; Coffin, 2007). Species crests and distinctive, large parotoid glands (Maciel characteristics may also play an important role, and et al., 2007; Pramuk et al., 2008). In Brasília, Distrito studies contemplating terrestrial vertebrates have Federal, Brazil, the R. marina group is represented by revealed amphibians as particularly vulnerable to three species: R. diptycha (Cope, 1862), R. rubescens traffic (Glista et al., 2007; Healey et al., 2020). Among (Lutz, 1925), and R. cerradensis Maciel et al., 2007 anurans, species that perform massive seasonal (Vaz-Silva et al., 2020). Despite their conspicuous size, migrations for resources, such as food and reproductive information regarding the interaction of these species sites, are particularly affected by traffic (Elzanowski with roads and artificial lights are scarce. Here we et al., 2009; Langen et al., 2009; Beebee, 2013). report on the interaction of individuals of two species of Additionally, some road structures, such as manholes, the R. marina group with the headlights of a car. drains, and basins, can accumulate rainwater, creating The interaction occurred on the 17 November 2019 at temporary bodies of water that attract anurans (Le Viol 19:30 h on a rural road (5 m wide) east of Santa Maria, et al., 2012; Cunnington et al., 2014; Sterrett et al., Distrito Federal, Brazil (16.0082°S, 47.8886°W). It 2019) and increasing mortality associated with roads. was a full moon night with clear sky, air temperature of Artificial light is another element that, when 23.6°C, and relative humidity of 77% (INMET, 2019). associated with roads and traffic, can have negative While driving slowly on the road by car (20 km/h) impacts on anurans (Buchanan, 1993; Mazerolle et during a herpetofauna roadkill monitoring survey, the al., 2005; Van Grunsven et al., 2017). It is known that first author observed three active toads. He stopped the artificial lights attract nocturnal invertebrates, and this car and identified two toads as members ofR. rubescens potential prey source also attracts some anuran species and the third as a member of R. diptycha (Fig. 1A, (Yeager et al., 2014; González-Bernal et al., 2016; B). These species are readily distinguishable by the Ward-Fear et al., 2016). Indeed, studies have showed presence of a large parotoid gland and a tibial gland in the efficiency of luminous traps to attract or capture R. diptycha and a narrow parotoid gland in R. rubescens toads of the genus Rhinella (Yeager et al., 2014; (see Vaz-Silva et al., 2020). As soon as the car stopped, Ward-Fear et al., 2016; Komine et al., 2020; Muller nocturnal invertebrates (mainly alate termites) clustered et al., 2020). As reported for R. icterica (Spix, 1824), around the vehicle’s still-lit headlights. The R. diptycha streetlights may also increase the frequency of road- individual moved towards the vehicle’s headlights killed toads, showcasing the potential negative impact to pursue the termites, on which it preyed with quick of artificial lights on anurans (Coelho et al., 2012). tongue movements (Fig. 1C, D). The two R. rubescens remained further distant from the headlights but were still able to prey on the termites. The first author then 1 Laboratório de Ciências Naturais, Colégio Militar de Brasília, left the car in order to record part of the interaction Brasília, Distrito Federal, 70790-020, Brazil. (17 s, using a Nikon P900 camera; video available 2 Laboratório de Zoologia, Universidade Católica de Brasília, at: https://youtu.be/aZSjAWR3yqA) and to confirm Taguatinga, Distrito Federal, 71966-700, Brazil. species identification of the toads. The individuals of * Corresponding author. E-mail: [email protected] both species were photographed and left at the same site © 2021 Herpetology Notes. Open Access by CC BY-NC-ND 4.0. that they were observed. 1138 Leonardo P. Fraga & Helga C. Wiederhecker
Rhinella diptycha and R. rubescens are generalist group (Meshaka and Powell, 2010; Coelho et al., 2012; species that coexist in the central Brazilian Cerrado González-Bernal et al., 2016). (Brandão and Araújo, 2002; Colli et al., 2002; Frost, Our observation shows that even a transitory car 2020). Rhinella diptycha is a widely distributed species headlight can attract individuals of the Rhinella marina with nocturnal habits and prolonged reproduction during group to a road. This corroborates previous observations the transition between dry and rainy seasons (Colli et that artificial lights attract toads of theR. marina group, al., 2002; Vasconcellos and Colli, 2009). In contrast, R. which in the case of roads and roadway structures rubescens is a Cerrado endemic that reproduces during can increase the risks of road-kills. Because of these the dry season (Vasconcellos and Colli, 2009; Valdujo negative effects on anuran populations, it is necessary et al., 2012). These large-sized toads have a generalist to adopt mitigation strategies such as choosing less and opportunistic diet, which is generally associated attractive light sources for nocturnal arthropods and with dynamic activity patterns and larger home ranges physical barriers to avoid anurans reaching roads, (Lemckert, 2004; Vasconcellos and Colli, 2009). especially when roads cross humid areas, native We verified that R. rubescens and R. diptycha were vegetation, or conservation units (Trombulak and already close to the road before the first author arrived. Frissell, 2000; Beebee, 2013; Jarvis et al., 2019). However, the car headlights ended up concentrating the termites and attracting the observed toads to the References middle of the road. This emphasizes the potential of Beebee, T.J. (2013): Effects of road mortality and mitigation measures artificial lights from roadway structures or traffic lights on amphibian populations. Conservation Biology 27: 657–668. to concentrate anurans in search of prey and increase Brandão, R.A., Araújo, A.F.B. (2002): A herpetofauna associada a the frequency of road-kills (Mazerolle et al., 2005; matas de galeria no Distrito Federal. In: Cerrado: Caracterização Coelho et al., 2012). Indeed, previous studies have e Recuperação de Matas de Galeria, p. 560–604. Ribeiro, J.F., shown that artificial street and road lights can act as Lazarini da Fonseca, C.E., Sousa-Silva, J.C., Eds., Planaltina, Distrito Federal, Brasil, Editora Embrapa. ecological traps for individuals of the Rhinella marina
Figure 1. Standardized images of (A) Rhinella rubescens and (B) R. diptycha from the Brasilia area, Distrito Federal, Brazil. (C, D) Rhinella diptycha opportunistically preying on alate termites (red circles) attracted towards car headlights on a rural road in the Brazilian Cerrado. Photos by Leonardo P. Fraga. Effect of Artificial Road Lights onRhinella rubescens and R. diptycha 1139
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