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

Crossmodal association between visual and acoustic cues in a tortoise (Testudo hermanni)

Humans spontaneously match information coming from different senses, in what we call crossmodal associations. For instance, high-pitched sounds are preferentially associated with small objects, and low-pitched sounds with larger ones. Although previous studies reported crossmodal associations in mammalian species, evidence for other taxa is scarce, hindering an evolutionary understanding of this phenomenon. Here, we provide evidence of pitch-size correspondence in a reptile, the tortoise Testudo hermanni. Tortoises showed a spontaneous preference to associate a small disc (i.e. visual information about size) with a high-pitch sound (i.e. auditory information) and a larger disc to a low-pitched sound. These results suggest that crossmodal associations may be an evolutionary ancient phenomenon, potentially an organizing principle of the vertebrate brain.

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

Recent research has uncovered many complex cognitive traits and affective processes in many reptile species, such as the ability to make choices that are rewarding or pleasurable. The investigation herein was initiated after many years of anecdotal reports, and preliminary observations, that the two male Aldabran giant tortoises (Aldabrachelys gigantea), Wilbur and Little John, at Melbourne Zoo (Melbourne, Australia) would approach the fence-line of their enclosure, sometimes multiple times daily, to "solicit" interactions from zoo visitors and/or zoo staff. Following other research with Galapagos giant tortoises (Geochelone nigra), this experiment was a novel preference test with two male Aldabran giant tortoises to assess their individual preferences for three stimuli: (1) human interaction (shell and neck rubs provided using hands); (2) food (highly palatable carrot pieces); and (3) an "enrichment" ball (a red "boomer ball"). The results found that Wilbur highly preferred human interaction and food over the ball; whereas Little John preferred food, and showed some initial interest in the ball, but did not approach the human on any of his 13 human interaction trials. These results reflect previous published findings, that human interaction is a preferred "enrichment," but is dependent upon a multitude of other contextual factors, and is not preferred at all times by all individuals. Individual variation may be very important to understand to have greater positive effect on the welfare-related needs of each giant tortoise housed in captivity. Further research is clearly required to enhance the welfare and well-being of many types of zoo-housed reptiles.

The Matter of Non-Avian Reptile Sentience, and Why It "Matters" to Them: A Conceptual, Ethical and Scientific Review

The concept of sentience, how it is characterised and which non-human animals possess it have long been of contention in academic and intellectual debates. Many have argued that there is no way to empirically know that animals have conscious experiences. Yet others argue that consciousness, awareness and sentience in non-human animals can be quite obvious, and can indeed be measured empirically. Most modern declarations of animal sentience from official organisations and governments now include all vertebrate animals as sentient beings, including reptiles and fish. Some declarations also include some invertebrate species. This conceptual, ethical and scientific review first focuses on conceptual components and definitions of consciousness, awareness and sentience. It then specifically discusses how cognitive, neurobiological, ethological and comparative psychological research in non-avian reptiles over the last century has evidenced many capacities that historically were denied to this class of animals. Non-avian reptiles do indeed possess all of the necessary capacities to be declared as sentient beings, at least in the small proportion of reptile species that have actually been empirically investigated so far. It is suggested that much innovative future research will continue to uncover evidence of capabilities linked to sentience within a wide range of species, including non-avian reptiles, fish and invertebrates.

Frugivory and seed dispersal by chelonians: a review and synthesis

In recent years, it has become clear that frugivory and seed dispersal (FSD) by turtles and tortoises is much more common than previously thought. We here review published and unpublished records of chelonian FSD, and assess the role of chelonians as seed dispersers, from individual species to the community level. We first discuss the distribution of chelonian FSD and the characteristics of the fruit and/or seed species eaten and dispersed by chelonians. We then use the seed dispersal efficiency framework to explore the quantitative and qualitative components of seed dispersal by tortoises and turtles, embarking on a journey from when the fruits and/or seeds are consumed, to when and where they are deposited, and assess how efficient chelonians are as seed dispersers. We finally discuss chelonian FSD in the context of communities and of chelonians as megafauna. A substantial proportion of the world's aquatic and terrestrial turtles and a major part of testudinid tortoises (71 species in 12 families) include fruits and/or seeds in their diet; fruits of at least 588 plant species in 121 families are ingested and/or dispersed by chelonians. For some chelonians, overall or in certain seasons, fruit may even form the largest part of their diet. Contrary to seed dispersal by lizards, the other major reptilian frugivores, chelonian FSD is not an island phenomenon in terms of geographic distribution. Nevertheless, on islands tortoises are often among the largest native terrestrial vertebrates - or were until humans arrived. We synthesise our knowledge of chelonian FSD, and discuss the relevance of our findings for conservation and restoration, especially in relation to rewilding with large and giant tortoises.

Frugivory and seed dispersal by chelonians: a review and synthesis

In recent years, it has become clear that frugivory and seed dispersal (FSD) by turtles and tortoises is much more common than previously thought. We here review published and unpublished records of chelonian FSD, and assess the role of chelonians as seed dispersers, from individual species to the community level. We first discuss the distribution of chelonian FSD and the characteristics of the fruit and/or seed species eaten and dispersed by chelonians. We then use the seed dispersal efficiency framework to explore the quantitative and qualitative components of seed dispersal by tortoises and turtles, embarking on a journey from when the fruits and/or seeds are consumed, to when and where they are deposited, and assess how efficient chelonians are as seed dispersers. We finally discuss chelonian FSD in the context of communities and of chelonians as megafauna. A substantial proportion of the world's aquatic and terrestrial turtles and a major part of testudinid tortoises (71 species in 12 families) include fruits and/or seeds in their diet; fruits of at least 588 plant species in 121 families are ingested and/or dispersed by chelonians. For some chelonians, overall or in certain seasons, fruit may even form the largest part of their diet. Contrary to seed dispersal by lizards, the other major reptilian frugivores, chelonian FSD is not an island phenomenon in terms of geographic distribution. Nevertheless, on islands tortoises are often among the largest native terrestrial vertebrates - or were until humans arrived. We synthesise our knowledge of chelonian FSD, and discuss the relevance of our findings for conservation and restoration, especially in relation to rewilding with large and giant tortoises.

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

Simple Summary

Substrate color is an important physical condition affecting the lifestyle of reared animals. However, no prior data are available regarding northern river terrapins. In this study, the terrapins were reared in five types of colored tanks (transparent, green, red, blue, and black) for twelve weeks. Based on parameters assessing survival, growth, feed utilization, and health, the blue background is more suitable for rearing terrapins relative to other colored tanks. The findings from the current study could be applied to wall, pond, or aquaria decoration to support the head-starting programs of northern river terrapins before release to natural habitat, as well as in public displays, such as aquaria and zoos.

Abstract

Background color has significant effects on the lifestyles of various animal species. In this study, the effects of wall background color on growth, feed utilization, specific activity of gastric and pancreatic enzymes in fecal samples, fecal thermal properties, carapace elemental profile, and hematological parameters were investigated in northern river terrapin (Batagur baska Gray, 1831) in order to optimize the head-starting conditions. The terrapins (70.13 ± 0.04 g initial weight) were completely randomized into five types of colored tanks (transparent, green, red, blue, and black) and reared for twelve weeks. At the end of the experiment, tank color had no effect on survival and growth performance, but had significant effects on feeding rate, feed conversion ratio, and protein efficiency ratio (p < 0.05). Terrapins reared with black, red, or blue backgrounds had the highest feed utilization among the treatments. Among these three groups, analysis of specific activity of gastric and pancreatic enzymes in fecal samples and fecal thermal properties suggested improved digestive functionality in terrapins reared with a blue background relative to the other treatments. Carapace elemental composition and hematological parameters indicated no negative effects on health status of the terrapins reared with this optimal treatment. Findings from the current study support the head-starting program of northern river terrapins before release to natural habitats, and could also be applied in aquaria or zoos for public display.

Assessing colour preference in Aldabra giant tortoises (Geochelone gigantea)

Tortoises perceive different colours and rely on the visual system to find food. However, few studies have considered colour preference in tortoises, especially in land species. The aim of this study is to investigate whether Aldabra giant tortoises (Geochelone gigantea) housed in Parco Natura Viva (VR), an Italian zoological garden, show a specific colour preference in their social context. The study was divided into two different periods in which red and yellow balls of the same size were scattered around in the outdoor enclosure. In the first period, pieces of carrots were placed behind each ball whereas in the second period, carrots were replaced with apples. Data on the frequencies of interaction with red and yellow balls were collected. First, tortoises interacted more with the balls when pieces of apples rather than carrots were hidden behind them. No significant group-level colour preference was found; however, individual-level variation in colour preference was reported. In addition, tortoises interacted significantly more with the yellow balls in the second than in the first period. Food typology seems therefore to play an important role in determining colour preference in chelonians. Research aimed at identifying individual differences in animal preferences might be valuable to improve captive animal husbandry (e.g.: development of enrichment programmes, diets and rewards).

The effect of growth rate and ageing on colour variation of European pond turtles

Many chelonians have colourful dots, patches and stripes throughout their body that are made up, at least in part, of carotenoids. Therefore, turtles are very suitable models to study the evolution and functionality of carotenoid-based colouration. Recent studies suggested a close link between colouration and immune system in these taxa. However, more research is needed to understand the role of these colourful stripes and patches in turtle visual signalling. The purpose of this study was to explore the relationship between growth rate and colouration in European pond turtles. In particular, we wanted to answer the question of whether there is a trade-off between growth and colour expression. We also aimed to explore the effect of body size and age on colour variation. Turtles from a reintroduction-breeding program were recaptured, weighed and measured over an 8-year period to estimate their growth rates and age. We also measured with a spectrometer the reflectance of colour patches in two different body parts: shell and forelimb. We found that turtles with a faster growth rate had brighter limb stripes independently of their age. On the other hand, shell colouration was related to body size with larger turtles having brighter shell stripes and higher values of carotenoid chroma. Our results suggest that fast-growers may afford to express intense colourful limb stripes likely due to their higher intake of carotenoids that would modulate both growth and colour expression. However, shell colouration was related to body size probably due to ontogenetic differences in the diet, as juveniles are strictly carnivorous while adults are omnivorous. Alternatively, shell colouration might be involved in crypsis as the shell is visually exposed to predators.

Using operant conditioning and desensitization to facilitate veterinary care with captive reptiles

In addition to being a large component of most zoological collections, reptile species are becoming more popular as family pets. Reptiles have the cognitive ability to be trained to facilitate daily husbandry and veterinary care. Desensitization and operant conditioning can alleviate some of the behavioral and physiological challenges of treating these species. A survey of reptile training programs at zoos in the United States and worldwide reveals that there are many successful training programs to facilitate veterinary care and minimize stress to the animal. Many of the techniques being used to train reptiles in zoological settings are transferable to the exotic pet clinician.