Herpetology Notes, volume 12: 509-511 (2019) (published online on 25 May 2019)

Defensive behaviour in Hyloscirtus larinopygion (Duellman, 1973) (Anura: Hylidae)

Sebastián Duarte-Marín1,2,*, Kevin J. López-Molina1, and Luisa Fernanda Arcila-Pérez2

The interaction sequence between predator and prey 1973), a nocturnal tree frog distributed at elevations can be described as occurring in six phases: localization, between 1950 and 3100 m throughout the central and identification, approach, subjugation, ingestion, and western Andes of Colombia and northern Ecuador digestion (Toledo et al., 2011). During each of these (Coloma et al., 2012; Rivera-Correa and Faivovich, phases, a frog targeted as prey can exhibit diverse 2013). defensive behaviours (e.g., Williams et al., 2000; Wells, We observed six individuals of Hyloscirtus 2007; Toledo et al., 2011). In fact, about 30 different larinopygion on 23 and 25 April 2017 in the Natural types of defensive behaviour have been reported in Reserve “La Patasola,” Salento Municipality, Quindío frogs (Angulo et al., 2007; Toledo et al., 2010). Department, Colombia (4.6830ºN, 75.5500ºW; Shrinking or contracting behaviour has been reported in elevation 2300 m). Those individuals were captured several anuran families (e.g., in members of Bufonidae, and immediately handled for 30–60 s by holding them Dicroglossidae, Hyperoliidae, Leptodactylidae, and at mid-body or by their hind limbs. For recording the Myobatrachidae) as a strategy that helps individuals distress call, we used a Sennheiser ME62 omnidirectional escape from a predator (e.g., Sazima, 1974; Brodie and microphone with K6 powering module connected to a Tumbarello, 1978). This behaviour consists of limb Marantz PMD660 digital recorder. We measured body contraction, body immobility, and ventral flexion of size (snout–vent length) of frogs with a Neiko 01407A the head (Toledo et al., 2010). An additional reported digital calibrator and body temperature with a Fluke 62 defensive behaviour of frogs is the production of distress infrared thermometer. For call analysis, we used RAVEN calls, which consist of acoustic signals that an individual Pro 1.4 software (Bioacoustics Research Program, emits before a predator attack (e.g., Bogert, 1960; Wells, 2011). We digitized recordings at 16-bit resolution using 2007). This type of call is generalized in frogs, except a sampling frequency of 44.1 kHz. Oscillograms and in members of the family Pipidae (Toledo et al., 2010). spectrograms were analysed with a 256-point Fourier Although the occurrence of defensive behaviours Transformation window and applying the Blackman in frogs to avoid predation has been relatively well algorithm. The definition of call parameters follows documented in general terms (e.g., Wells, 2007; Vitt Köhler et al. (2017). Some individuals were collected as and Caldwell, 2013), in many species the behaviour vouchers, euthanized with 2% lidocaine, fixed in 10% has not actually been documented. The purpose of this formaldehyde, and preserved in 70% ethanol (Angulo et work is to describe two previously unreported defensive al., 2006). From each collected individual we removed behaviours of Hyloscirtus larinopygion (Duellman, a piece of tissue from the right hind limb, which was preserved in 96% ethanol as a sample for future genetic analysis according to the protocol of Gonzalez and Arenas-Castro (2017). The individuals collected and their respective tissue samples were deposited in the Colección de Anfibios y Reptiles at the Universidad del 1 Grupo de Herpetología de la Universidad del Quindío, Quindío (ARUQ), in Armenia, Colombia. Programa de Biología, Universidad del Quindío, Armenia, When the frogs were first encountered, their initial Colombia. 2 Grupo de Evolución, Ecología y Conservación, Programa de defensive behaviour was to remain immobile, and they Biología, Universidad del Quindío, Armenia, Colombia. emitted a strong odour when manipulated. Two of six * Corresponding author. E-mail: [email protected] individuals bent their fore- and hind limbs, holding them 510 Sebastián Duarte-Marín et al. close to their body, and remained immobile – even when placed on the ground and manipulated repeatedly (Fig. 1). When we moved the limbs of the individuals into a different position, they did not exhibit any resistance. Individuals remained with their eyes half-way open for up to 1 min. The four other individuals deployed a distress call. The call consisted of a simple note, similar to a “peep” (Fig. 2), with an average duration of 0.114 ± 0.075 s (range 0.054–0.224s), a dominant frequency of 1.292 ± 0.267 kHz (1.033–1.665 kHz), a low frequency of 0.725 ± 0.326 kHz (0.304–1.100 kHz), and a high frequency of 1.979 ± 0.186 kHz (1.708–2.130 kHz). The call exhibits three harmonic bands with dominant average frequencies at 2.268 ± 0.188 kHz (2.095–2.469 kHz), 3.493 ± 0.332 kHz (3.186–3.847 kHz), and 4.700 ± 0.527 kHz (4.105–5.110 kHz). Ours is the first record of shrinking defensive behaviour in H. larinopygion. Toledo et al. (2010) Figure 2. Graphic representations of the single-note distress suggested that this behaviour was characteristic of hylid call emitted by Hyloscirtus larinopygion. (Top) An oscillogram and phyllomedusid species in general and that it was showing the note’s amplitude. (Bottom left) Spectrogram common in species with the capacity for producing skin of the call, showing three different harmonics (yellow and toxins. An experimental study showed that the water green colours). (Bottom right) Power spectrum of the call. snake Liophis miliaris regurgitated a Phyllomedusa Recordings were made at a body temperature of 23.7ºC. The rohdei individual 10–20 min after having been ingested calling individual had a snout–vent length of 49.9 mm. because of the polypeptides secreted by the frog (Sazima, 1974). In addition, Sazima (1974) mentioned that the frog suffered little physical damages, likely due to the contracting behaviour of aligning its limbs tightly is also associated with a skin toxin that produces an with its body. It is possible that the strong odour we unpleasant sensation in potential predators; this may smelled on manipulated individuals of H. larinopygion be a complementary defensive strategy to the shrinking behaviour reported here. Experimental evidence would be necessary to confirm this hypothesis. The distress call we recorded here is slightly shorter and at a lower frequency than the species’ advertisement call (Rivera-Correa et al., 2017). Distress calls are generally characteristic of frogs (Wells, 2007), and they are emitted when frogs are caught by predators or while they attempt to escape (Toledo and Haddad, 2009). Some authors have mentioned that this call may surprise predators and even scare them (Toledo and Haddad, 2009; Hoare and Labra, 2013), or it may serve as an alarm signal for nearby conspecifics (Bogert, 1960; Wells, 2007). However, the acoustic signal remains poorly studied and no report of this behaviour was previously published for species of Hyloscirtus, presenting a line of research to be further developed in Figure 1. Shrinking or contracting behaviour deployed by a the future. treefrog, Hyloscirtus larinopygion (specimen number ARUQ- 773; snout–vent length 51.2 mm). Photos by Sebastián Duarte- Acknowledgements. We thank Julián Ríos-Soto for his Marín. collaboration in the analysis of calls, and the members of the Defensive behaviour in Hyloscirtus larinopygion 511 herpetology group at the University of Quindío, especially Hoare, M., Labra, A. (2013): Searching for the audience of the Cristian C. Gónzalez-Acosta for helping with our fieldwork. weeping lizard’s distress call. 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Accepted by Hinrich Kaiser