Do Hermann's tortoises (Testudo hermanni) discriminate colours? An experiment with natural and artificial stimuli

Abstract

Many animals use chemical and visual cues to obtain reliable information about potential food resources. Most reptiles have evolved highly specialized chemosensory and visual capacities, in particular colour vision, to accomplish this task. By presenting animals with flowers and coloured cardboard discs in two-choice experiments, we examined whether both male and female Hermann's tortoises (Testudo hermanni) were able to distinguish between different colours, and show some preference for certain colours. We found that both sexes responded and discriminated equally between different colours, with some differences between flowers and discs. In particular, the red was preferred in the disc experiment, mainly by males, but was disregarded by both sexes in the flower experiment, where red was represented by poppy, Papaver rhoeas. This suggests that Hermann's tortoise probably relies on a mixed system of olfactory and visual abilities to detect food in order to optimize the intake of essential nutrients as minerals or carotenoids. Our results demonstrate that the most preferred colour by tortoises was the yellow, which might reflect carotenoid content, and we discuss the potential implications of this finding.

Optimal Background Color for Head-Starting Northern River Terrapins (Batagur baska Gray, 1831)

“…Although some evidence of color preferences was reported for turtles or tortoises [7][8][9][10], no significant differences in growth performance of terrapins were found across the five background colors in the current study. Similar observations were also reported for common carp (Cyprinus carpio) [15] and for convict cichlid (Cichlasoma nigrofasciatum) [12] reared with various background colors for 14 and 8 weeks, respectively.…”

“…Therefore, animals from a wide range of taxonomic groups can change their body color based on their background over a range of spatial and temporal scales, since camouflage through color change has ecological significance [5], as well as significance for the physiological processes in response to background stimuli [6]. In turtles and tortoises, some evidence of color preferences has been reported [7][8][9][10], however the majority of such studies have been conducted in fish [11][12][13][14][15]; no prior data are available regarding terrapins.…”

Assessing preferences of two zoo‐housed Aldabran giant tortoises (Aldabrachelys gigantea) for three stimuli using a novel preference test

“…Reptilia (now non‐avian reptiles ) are very under‐researched within the animal welfare, ethology, comparative psychology, and zoo‐animal fields (Goulart et al 2009; Hosey & Melfi, 2014), possibly due to lack of funding, lack of interest in, or lack of understanding of these classes of animals (Lambert et al, 2019). Still, there is a small amount of relevant published research on turtles and tortoises, that has been conducted in zoos, other captive settings, and the wild, which may be drawn upon here (Alba et al, 2017; Gaalema & Benboe, 2008; Gerlach et al, 2013; Gutnick et al, 2019; Kashon & Carlson, 2018; Mehrkam & Dorey, 2014; Mueller‐Paul et al, 2014; Passos et al, 2014; Pellitteri‐Rosa et al, 2010; Tetzlaff et al, 2018; Weiss & Wilson, 2003; Wilkinson, 2015; Wilkinson et al, 2010; Wilkinson et al, 2013). Similarly, some reference books on the wild ecology of Aldabra and the Galapagos Islands may provide relevant insights into the life‐history and some expected behavioural characteristics of the tortoises, that is, behaviour that tortoises have been observed performing in the wild (Pritchard, 1996; Stoddart & Westoll, 1979).…”

The yellow cheek-patches of the Hermann's tortoise (Reptilia, Chelonia): Sexual dimorphism and relationship with body condition

“…Like other Chelonians (e.g. Ammermüller et al 1995;Twig & Perlman 2004;Mathger et al 2007), Hermann's tortoises exhibit good vision, based on a complex type of eye with rods and cones containing multicoloured oil droplets, which enable them to see and clearly distinguish images and to perceive and discriminate colours, particularly the yellow (Pellitteri-Rosa et al 2010). Thus, females with larger cheek patches may actually be more attractive and stimulate males more efficiently, which could result in a larger amount of sperm for fertilising eggs.…”