Use of Tomahawk traps in freshwater Testudines capture

Transcription

1 Herpetology Notes, volume 11: (2018) (published online on 17 April 2018) Use of Tomahawk traps in freshwater Testudines capture Gabriel Oliveira Garcia-Passos¹, *, Milena Santos Soeiro¹ and Rejâne Maria Lira-da-Silva¹ Abstract. Tomahawk traps are commonly used to sample lizards, and principally small mammals. Prior to this study however, there were no reports of their use in the capture of freshwater Testudines. The objective of this study was to demonstrate the efficiency of tomahawk traps in the capture of freshwater turtles, highlighting an adaptation of the trap to make it float. It was baited with meat and fruit, and seven traps were installed in three ponds on a small island in the Atlantic Forest, six arranged on the bank and a seventh (floating) in the centre of the water body. The species that served as models in this study were Acanthochelys radiolata (Mikan, 1820) (Cágado-pescoço-de-cobra) and Rhinoclemmys punctularia (Daudin, 1801) (Aparema). Rhinoclemmys punctularia (semi-aquatic species) was more efficiently captured by tomahawks when compared to A. radiolata (aquatic species). The small size ( mm of length and mm width carapace) of these animals was a determining factor for the success of captures by Tomahawk traps. Therefore, they are another auxiliary method to sample freshwater turtles, indicated for application together with traditional methods such as active search and capture nets. Keywords: Herpetofauna, Testudines, Acanthochelys radiolata, Rhinoclemmys punctularia, Tomahawk Introduction In the survey and monitoring of reptile species, methods such as interception and fall traps, funnel traps and active visual search are commonly used (Cechin and Martins, 2000; Fogarty and Jones, 2003). In the sampling of freshwater turtles, in addition to the methods already mentioned, equipment is used to assist in captures, such as fishing nets (Gill, Trammel and Fyke Nets), hand nets, floating traps, baited hoop nets, aquatic funnel with guide fences, swing-door boxes, Bal-chatri and even mist nets (Ministry of Environment of Canada, 1998; Akre et al., 2012; Balestra et al., 2015). The main problems in regards to sampling these animals can be attributed to their shy nature, tending to hide in the water when they feel threatened and spending most of their time submerged (Ernst and Barbour, 1989; Bonin et al., 2006). The development of new sampling methods allows an increase of our understanding of 1 Núcleo de Ofiologia e Animais Peçonhentos da Bahia, Instituto de Biologia, Universidade Federal da Bahia, Campus Universitário de Ondina, Salvador, Bahia, Brasil. Cep: * Corresponding author. gabriel_garcia_noap@hotmail.com this group, with a large number of species threatened by anthropic action and climatic change (Dudgeon et al., 2006; Rhodin et al., 2010; Turtle Conservation Coalition, 2011; Quesnelle et al., 2013). Used for the capture of lizards (Mayes, 2006; Vieira et al., 2015) and mainly small mammals (Modesto et al., 2008; Santos-Filho et al., 2015), the Tomahawk cage trap has not yet been reported in chelonian sampling. Thus, the objective of this study is to demonstrate the effectiveness of this trap in the capture of freshwater turtles, as well as three Tomahawk traps adapted for flotation. Materials and Methods The species that served as models in this study were Acanthochelys radiolata (Mikan, 1820) (Cágadopescoço-de-cobra) from the Chelidae family (suborder Pleurodira) and Rhinoclemmys punctularia (Daudin, 1801) (Aparema) from the Geoemydidae family (suborder Cryptodira). Acanthochelys radiolata is considered exclusively carnivorous and aquatic, but may occasionally explore the terrestrial environment to move about, thermoregulate or forage (Ernst and Barbour, 1989; Bonin et al., 2006). Rhinoclemmys punctularia is omnivorous, consuming a wide variety of plants and animals, and is semi-aquatic, exploring both terrestrial and aquatic environments. It inhabits savannahs and

2 286 Gabriel Oliveira Garcia-Passos et al. Figure. 1. Adaptation of a Tomahawk trap for floating in the water using Styrofoam plates (Author of the illustration: Pedro Victor Nogueira Diniz). forests, and occupies all types of freshwater habitats, including marshes, ponds, lakes, rivers and even mangroves, where it can be seen warming itself on floating objects (Ernst and Barbour, 1989; Bonin et al., 2006; Rueda-Almacid et al., 2007; Coy and Lunsford, 2014). The areas studied were three seasonal water bodies (ponds A, B and C) on Monte Cristo Island (IMC) (1.8km²), Saubara, Bahia, Brazil (12º 50 S and 38º 49 W), located in the Paraguaçu River mouth, Atlantic Forest biome. In pond A, three sampling expeditions were carried out, two in the dry season (DS1 between 28 December 2014 and 16 January 2015 and DS2 between 07 and 11 January 2016) and one in the rainy season (RS between 29 July and 10 August 2015). In ponds B and C there was sampling only during the RS. The three ponds have lentic waters, being ideal for Tomahawk traps due to having little water movement to trigger them. The water surface of pond A (PA, 28.2 x 16.5 x 0.76 m in DS1 and 44.6 x 27.8 x 1.44 m in RS) is dominated by the plants Salvinia auriculata Aubl. (Salvínia) and Eleocharis sp. R.Br. (Junco) Pond A was more resistant to long periods of drought compared to pond B (PB, 63.4 x 43 x 1.24 m) and pond C (PC, 116 x 19.5 x 1.05 m), which were practically devoid of aquatic vegetation, and therefore more exposed to solar radiation, consequently drying faster in the absence of rainfall. Thus, in dry seasons there is no water present in ponds B and C. During DS2, the pond A was sampled for only four days with water present, in this case, a large puddle (13.3 x 7.7 x 0.42 m). Three sampling methods were applied: Tomahawk traps, active search and occasional encounters. Six traps (45 x 14.5 x 18.5 cm) were arranged on the PA margin with their back end to the waterline (3 cm maximum depth), while a floating trap was installed in the centre, above the deepest area. The period of activity of the traps in this pond was 16 hours/day for 20 days and 20 hours/day during 4 days, totalling 400 hours of activity (57h8min per trap). Of the 14 traps distributed equally between ponds B and C, 6 were smaller Tomahawk traps (31 x 13 x 15 cm) of the suspended bait type. In these two ponds, the traps remained active for 15 days, for 24 hours a day, totalling 360 hours of activity (51h25min per trap). Thus as in pond A, these two ponds had 6 traps on the shore and one floating in the centre. The floating adaptation (Figure 1) consists of three Styrofoam plates strung externally on the Tomahawk trap (45 x 14.5 x 18.5 cm), two larger ones on the sides and a smaller one on the bottom, at the back (bottom Styrofoam plate). In addition to providing a slope for entry into the water, which facilitates the access of the chelonian into the trap, the lower plate prevents the bait from being consumed from below between the wire. The floating Tomahawk trap must be attached to a wooden rod fixed to the bottom of the water body. All traps were baited with common fruit in the study area (mango, genipap, cashew, guava and palm) and/or meat (bovine lung and liver or fish), and were checked daily. The active search was performed by 7 people over 24 days only in PA, 8 hours/day for 20 days and 4 hours/day for 4 days, totalling 176 hours (25h8min per person). The searches were done during the day shift and crepuscular/nocturnal. In order to attract the turtles, each person carried fishing lines with baits attached, as

3 Use of Tomahawk traps in freshwater Testudines capture % being in DS1 (n = 9) and 5.26% in DS2 (n = 3). Tomahawk traps were responsible for only 3.51% of the samples (n= 2) of this species, both captures being in the RS. There was no record of capture of this species of Pleurodira by the floating trap nor by occasional encounter. Discussion Figure 2. Rhinoclemmys punctularia specimen caught by floating Tomahawk trap in pond A. well as a hand net to assist in the captures, but manual captures also took place. Records of occasional capture consisted in those that occurred in the displacements between the ponds and the base, it was not occurring to the active search. Results In total, 71 R. punctularia (PA = 64, PB = 1 and PC = 6) were caught. For this species, the Tomahawk traps were responsible for most of the captures with 36.62% (n = 26). Were caught 8.45% of the samples in the DS1 (n = 6), 23.94% in the RS (n = 17) and 4.22% in the DS2 (n = 3). The three floating traps were responsible for 12.67% (n = 9) of R. punctularia captures (Figure 2). The 18 traps placed at the margins totalled 23.94% (n = 17). The smaller Tomahawk trap model (Figure 3), which made two captures (2.81%), contained individuals nearly the same width as the trap, one with a carapace width of mm and the other with a width of mm. Manual captures accounted for 35.21% (n = 25), with 1.4% in DS1 (n = 1), 5.63% in RS (n = 4) and 28.17% in DS2 (n = 20). Captures using hand net were 28.17% of the samples (n = 20), with 4.22 for DS1 (n = 3), 1.4% for RS (n = 1) and 22.53% for DS2 (n = 16). Occasional encounters were responsible for 4.22% of the records (n = 3) of the Cryptodira species, all using the hand to capture the turtles. As for A. radiolata, 57 captures were recorded (PA = 56 and PC = 1). The captures with hand net consisted of 75.44% (n = 43), with 36.84% of the samples in DS1 (n = 21), 28.07% in RS (n = 16) and 10.52% in DS2 (n = 6). Manual captures represented 21.05% (n = 12), with Insular populations demonstrate peculiar characteristics in their way of life due to the typical restrictions that this environment places on its fauna (Brown and Lamolino, 2006). In insular environments there are fewer resources available compared to continental environments, which may be a determining factor for the success of baits in the sampling of this R. punctularia population, using Tomahawk traps. The smaller size of the R. punctularia specimens on Monte Cristo Island, compared to the continental populations (Garcia-Passos, Mise and Lirada-Silva, unpublished data), made it possible to use this type of trap for capture. In addition, the efficiency of R. punctularia in exploring the terrestrial environment (Ernst and Barbour, 1989; Bonin et al., 2006; Rueda- Almacid et al., 2007) was a determining factor for the success of its sampling using Tomahawk traps, the trap indicated in the collection of semi-aquatic species. Captures by Tomahawk traps were responsible for 71.87% of R. punctularia sampling until the end of RS (n = 23 of 32). This importance was minimized by the DS2 data, since it was easier to capture this species by hand (n = 20) and with hand net (n = 16) during this expedition due to the low water level in pond A. At the same time, there were only three captures per trap during 80 hours of activity. Figure 3. One of the three R. punctularia individuals caught in the smaller suspended bait type Tomahawk trap.

4 288 The success of the Tomahawk trap was not repeated in sampling the exclusively aquatic A. radiolata (Ernst and Barbour, 1989; Bonin et al., 2006), whose foraging behaviour was incompatible with the character of the bait made available in the trap. Meat baits, submerged in the water and tied to a fishing line were more compatible with A. radiolata foraging behaviour, which was reflected in the expressive sample obtained by hand net. The installation of traps at sites around 5 cm deep can increase the efficiency of collecting more exclusively aquatic species. In the case of the floating Tomahawk trap, the installation of a lower bottom Styrofoam plate 3 or 4 cm in height increases the inclination of the trap entrance, which may increase the chances of this adaptation in capturing more exclusively aquatic species, but this type of use has not been verified. Conclusion The Tomahawk trap is efficient for capturing freshwater turtles, especially small semi-aquatic species ( mm long and mm wide carapace) in lentic water environments. The use of these traps is another auxiliary method for sampling, indicated for joint application together with traditional methods for freshwater turtles such as active search and capture nets. Acknowledgment. The authors wish to thank Sarah Pondé for granting access to Monte Cristo Island for the study. To the team of the Núcleo de Ofiologia e Animais Peçonhentos of the Universidade Federal da Bahia (NOAP/UFBA) for the assistance provided during the collections. To the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio) for the permission to capture and collect the animals. To the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for granting the master s degree grant to carry out this research. 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