The Escape Behaviour of Wild Greek Tortoises Testudo Graeca with an Emphasis on Geometrical Shape Discrimination Alexandra Glavaschi, Ellen S
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UDORA - University of Derby Online Research Archive Basic and Applied Herpetology 28 (2014): 21-33 The escape behaviour of wild Greek tortoises Testudo graeca with an emphasis on geometrical shape discrimination Alexandra Glavaschi, Ellen S. Beaumont* Department of Biological and Forensic Sciences, University of Derby, Derby, UK. * Correspondence: Department of Biological and Forensic Sciences, University of Derby, Kedleston Road, Derby, DE22 1GB, UK. Phone: +44 (01332) 591156, E-mail:[email protected] Received: 17 December 2013; received in revised form: 11 July 2014; accepted:14 July 2014. Geometrical shape discrimination has been shown to play an important role in the spatial orientation of a wide variety of mammals and birds, while the study of this ability in particular and of cognitive processes in general has been rather neglected in reptiles. The present experiment aims to investigate the ability of wild Greek tortoises Testudo graeca from Topolog forest, Tulcea County, Romania, to discriminate between simple geometrical shapes. Forty-two adult tortoises were subjected to a task consisting of escaping from a square arena through one of the four available doors, each with a geometrical shape attached. Thirty-one individuals completed 10 consecutive trials, requiring significantly less time for the last trial than for the first. This trend suggests that Greek tortoises developed and used an escape strategy, most likely relying on the geometrical shapes provided as cues. This experiment is the first to explore the cognitive processes of this species and fur- ther work should expand on the ecological significance of this ability. Key words: cognitive abilities; navigation; orientation; Romania; Tulcea; visual cues. Conducta de fuga en tortugas moras Testudo graeca salvajes con énfasis en la discriminación de formas geo- métricas. Se ha visto que la discriminación de formas geométricas juega un papel importante en la orienta- ción especial de una gran variedad de mamíferos y aves, pero el estudio en reptiles de esta capacidad en par- ticular, y de los procesos cognitivos en general, ha recibido poca atención. El experimento que aquí se pre- senta tiene por objeto investigar la capacidad de tortugas moras Testudo graeca salvajes procedentes del bos- que Topolog, distrito de Tulcea, Rumanía, de discriminar entre formas geométricas simples. Cuarenta y dos tortugas adultas fueron sometidas a una prueba para escapar de un espacio cuadrado mediante una de las cua- tro puertas disponibles, cada una de las cuales tenía pegada una forma geométrica. Treinta y un individuos completaron tres intentos consecutivos, necesitando para el último intento un tiempo significativamente infe- rior que para el primero. Esta tendencia sugiere que las tortugas moras desarrollaron y utilizaron una estrate- gia de fuga, muy probablemente dependiente de las formas geométricas proporcionadas como señales. Este experimento es el primero en explorar el proceso cognitivo de esta especie, y el significado ecológico de esta capacidad deberá ser investigado en próximos estudios. Key words: capacidades cognitivas; navegación; orientación; Rumanía; señales visuales; Tulcea. Efficient navigation is of obvious importan- visual cues are recognized in studies of spatial ce in an animal’s daily activities and relies on dif- orientation: geometrical cues (the overall shape ferent orientation mechanisms that make use of of the environment, the distinction between left a wide variety of cues, including the sun, moon, and right, angles and distances), and non-geo- stars, polarized light, auditory, chemical, electri- metrical or featural cues (including colour, tex- cal and visual cues (ABLE, 1991). Two types of ture and brightness) (CHENG, 1986). DOI: http://dx.doi.org/10.11160/bah.13019/ 22 GLAVASCHI & BEAUMONT As shown for species like rats (CHENG, by predators, and orientated towards vertical 1986), human children (HERMER & SPELKE, ovals perceived as refuge sites (CHIUSSI & 1996), rhesus monkeys Macaca mulatta DIAZ, 2002). Similarly, some species of her- (GOUTEUX et al., 2001), red tails plitfins mit crabs and mangrove crabs can learn to Xenotoca eiseni (SOVRANO et al., 2002, 2003), associate geometrical shapes with either shel- or Neotropical ants Gygantiops destructor ters (represented by gastropod shells of (WYSTRACH & BEUGNON, 2009), the overall various qualities) or predators, depending on geometry of the environment is used prima- the size and the angle at which the shape is rily in orientation tasks. The importance of positioned (ORIHUELA et al., 1992; DIAZ et al., global geometry for spatial orientation makes 1994, 1995). Cotton-top tamarins (Saguinus sense from an ecological point of view. In an oedipus) subjected to a foraging task in an animal’s natural environment, the overall artificial jungle were not affected by changes layout (shapes and distances between impor- in the overall shape of the environment whe- tant landmarks) remains unchanged across reas alterations of the landmark shape resul- seasons, whereas more local cues such as ted in significant performance disturbance colours, textures, and brightness may change (DEIPOLYI et al., 2001). (for example, due to season change). Thus, Geometrical shape discrimination is also the global geometry is more reliable for ani- reported in several species of fish, such as the mal orientation (CHENG & GALLISTEL, 1984; African cichlid Pseudotropheus sp., which GALLISTEL, 1990; HERMER & SPELKE, 1996). could distinguish between two-dimensional However, smaller, more local cues cannot geometrical shapes of various sizes and diffe- be ignored. The ability to use geometric pro- rentiate between two categories of objects, perties of more specific objects, as opposed to “fish” and “snail” (SCHLUESSEL et al., 2012) the geometry of the environment discussed and the Ambon damselfish, Pomacentrus so far, must be adaptive, as it provides ani- amboinensis, which could rapidly learn to dis- mals with vital information for everyday acti- criminate between bi-dimensional and tri- vity. Various species have been studied in dimensional objects (SIEBECK et al., 2009). terms of their perception of geometrical sha- The experimental design ensured a gradual pes and visual discrimination ability. Sand reduction of the number of stimuli until only fiddler crabs (Uca pugilator) with no previous overall shape remained, which was still training that were presented simultaneously enough for the fish to discriminate accurately with stationary geometrical shapes of equal (SIEBECK et al., 2009). surface areas exhibited various response It has long been assumed that amphibians strengths, in descending order as follows: ver- and reptiles are not capable of learning to an tical rectangle > horizontal rectangle >trian- extent comparable to mammals and birds, gle > square > circle (LANGDON & mainly due to the lack of anatomical structures HERRNKIND, 1985). Moreover, chemically involved in advanced cognitive processes stimulated heaping fiddler crabs (Uca cumu- (SUBOSKI, 1992). However, the interest in repti- lanta) navigated away from striped rectangles le intelligence has a relatively long history (revie- that resembled seagrass meadows inhabited wed in Burghardt, 1977, cited in WILKINSON GEOMETRICAL SHAPE DISCRIMINATION IN GREEK TORTOISES 23 et al., 2007). Reptiles have been found to per- Chelonoidis carbonarius (WILKINSON et al., form similarly to mammals and birds in spatial 2007, 2009, 2013). When provided with geo- orientation tasks (LÓPEZ et al., 2000, 2001) and metrical shapes attached to a curtain surroun- there is a growing body of evidence suggesting ding the test maze, the red-footed tortoise did that the medial cortex of reptiles is equivalent to not use them to navigate (WILKINSON et al., mammalian and avian hippocampus in terms of 2009). By designing a maze of appropriate its role in spatial memory (RODRÍGUEZ et al., complexity and testing a large enough sample 2002; LÓPEZ et al., 2003). to compensate for the limited control, this The most recent information concerning experiment aims to assess whether the ability to cognitive aspects of chelonians comes from discriminate between simple geometrical sha- the study of the red-footed tortoise, pes actually exists in tortoises and explores the Chelonoidis carbonarius. The animals perfor- hypothesis that the subjects will require gra- med above chance in an eight-arm radial dually less time to complete a trial-and-error maze, never re-entering an arm they just exi- test involving escaping from a box with three ted from (WILKINSON et al., 2007) and, when “false” and one “true” exit. available, using extra-maze cues to orient (WILKINSON et al., 2009). Although a solitary MATERIALS AND METHODS species, red-footed tortoises are able to learn to navigate by observing conspecifics Animals and area of study (WILKINSON et al., 2010) and have the capa- city to discriminate between real objects and The Greek tortoise inhabits temperate pictures of them (WILKINSON et al., 2013). and Mediterranean areas and is unevenly dis- The Greek tortoise, Testudo graeca, has tributed in south-east Romania, following been studied in terms of population structu- mixed deciduous forests (TORTOISE & re and dynamics (LAMBERT, 1982; ZNARI et al., FRESHWATER TURTLE SPECIALIST GROUP, 2005), diet (EL MOUDEN et al., 2006) and 1996; COVACIU-MARCOV et al., 2006). The other biological aspects, such as the influence population