MedDocs Publishers ISSN: 2639-4391 Journal of Veterinary Medicine and Animal Sciences Open Access | Research Article Investigating the Thermal Biology and Behaviour of Captive Radiated Tortoises Avraham Terespolsky; James Edward Brereton* University Centre Sparsholt, England *Corresponding Author(s): James Edward Brereton Abstract University Centre Sparsholt, Westley Lane, Sparsholt, Thermoregulation is integral to the maintenance of rep- Winchester, Hampshire, SO21 2NF, England. tile biological function and health, and therefore is a key Email: [email protected] area of investigation for herpetologists. To investigate the relationship between core body temperature and behav- iour, a behavioural study was conducted in which iButton data loggers were placed on a group of captive radiated tor- Received: Nov 09, 2020 toises (Astrochelys radiata) located at Sparsholt College’s Accepted: Jan 04, 2021 Animal Management Centre, in Hampshire, UK. Correla- tions between core body temperature and specific behav- Published Online: Jan 08, 2021 iours were covered. Body mass had a significant effect on Journal: Journal of Veterinary Medicine and Animal Sciences average core body temperature (P= <0.0001) with higher Publisher: MedDocs Publishers LLC average temperatures recorded in larger individuals over Online edition: http://meddocsonline.org/ longer periods. There was a significant positive relationship between mean body temperature and basking behaviour, Copyright: © Brereton JE (2021). This Article is (P= 0.001, r= 0.485), and a negative correlation between distributed under the terms of Creative Commons mean body temperature and feeding (P= 0.006, r= -0.155). Attribution 4.0 International License Temperature did not significantly affect the prevalence of any other behaviours, though a trend toward greater ex- pression of social behaviour, and fewer bouts of aggressive ramming, was observed when tortoises achieved higher body temperatures. Introduction The radiated tortoise (Astrochelys radiata) is categorised as to reach their preferred optimal temperature [2]. The ability to Critically Endangered by the International Union for the Conser- reach this optimal temperature affects tortoise digestion and vation of Nature (IUCN). Endemic to the most southern region immune function [3]. of Madagascar, A. radiata is frequently collected for export for Heat provision presents some challenges for keepers of cap- the pet trade, with seizures of hundreds of illegally imported tive tortoises. The heat source should replicate, as much as pos- animals reported. Given the imminent risk of extinction in the sible, the type that the animal would receive in the wild [1]. wild there is a need to house a sustainable, breeding popula- Many chelonians are heliothermic, and therefore basking lamps tion ofA. radiata in captivity. Many zoos and aquaria have taken are commonly used in captivity as heat sources [4]. Tortoise this reptile’s plight into account: as of August 2020, the Zoo- exhibits should also provide a heat gradient, allowing animals logical Information Management System (ZIMS) (Species360, to control their internal temperature [1]. Most terrestrial tor- 2020) recorded 1,237 A. radiata individuals held in zoos glob- toises operate within preferred ranges and hence exhibits must ally. Temperature regulation in chelonians has been covered in be carefully structured to ensure that the tortoises are able to earlier studies, some dating back to 1939 [1]. As herbivorous achieve their preferred temperature [2]. ectotherms, tortoises must use behavioural thermoregulation Cite this article: Terespolsky A, Brereton JE. Investigating the Thermal Biology and Behaviour of Captive Radiated Tortoises. J Vet Med Animal Sci. 2021; 4(1): 1046. 1 MedDocs Publishers The radiated tortoise is found in a dry region consisting of physical characteristics and a GoPro video camera was used in brush and woodland habitats [5]. A. radiata is herbivorous and tandem with first-person monitoring to ensure accuracy and feeds by grazing on grasses, though it will on occasion feed on identification of behaviour and of each individual. An ethogram fruits and succulents, and it is well documented to indulge on consisting of nine state and six event behaviours was produced invasive Opuntia spp cacti. and refined from the extensive Ethograms provided by [7,8]. This was used to define exhibited behaviours (Table 2). A range While body temperature has been previously researched in of behaviours were observed and recorded in the study. The chelonians [1,2,6], comparisons between body temperature study intended to investigate thermal effects on all aspects of and behaviour would be valuable for animal managers. This tortoise behaviour, rather than just those behaviours which are could allow keepers to determine how behaviour changes as already known to be affected by temperature. body temperature increases toward optimal. Methods The aims of our study were to determine whether the body temperatures of smaller and larger radiated tortoises differed across the normal daily routine in captivity, and to investigate the effect of tortoise body temperature on their activity bud- gets. The study site Five radiated tortoises (two males and 3 females) were lo- cated at Sparsholt College’s Animal Management Centre, and Plate 1: A. radiata enclosure. Basking area with UV on the left, housed in an open-top enclosure within a heated reptile room UV in the middle and cool end to the right. Humid area situated (W93” x D60” x H34”), with a surface area of 3.6 m2. A tempera- above the hot end (Authors own, 2019). ture gradient design is implemented with the use of three heat lamps giving hot spots from between 29-37oC on one side and a heated area at the cool side around 25oC with UVA/B lamps th Table 1: Summary of information pertaining to identification along 3/4 of the enclosure. The substrate consisted of sand number, gender, size and weight of radiated tortoises at the time and small rocks along with a moss section, the animals had ac- of the study. cess to a large hide box in the cool area (Plate 1, Figure 1), a shallow water bowl and two food bowls. The tortoises wee cus- Tortoise Plastron length Body mass Sex tom seizures and therefore exact ages were unknown. Further Identification (Centimetres) (Kilograms) details on sizes and weight can be found on (Table 1). 1 Male 24.7 4.26 Activity and behavioural monitoring 2 Female 26 4.27 Behavioural observations were conducted using instanta- neous focal sampling at 60 second intervals for 1-hour time 3 Male 23 3.28 periods, resulting in 63 hours of observations per tortoise. The 4 Female 20.1 2.15 study took place between 0830-1730 on days with no classes such as weekends or holidays. Each tortoise was identifiable by 5 Female 21 2.51 Table 2: Ethogram used to record state and event behaviours of the radiated tortoises. Adapted from [7,8]. State Behaviours Description Event behaviours Description Eyes open or closed (could be sleeping), static position. limbs Resting Exploratory Sniff Sniffing or putting its beak up to an object. and head out or partially out. While sitting or standing, head elevated or level looking A noise made by the tortoise expelling air Alert Hiss around. from its lungs. Head down, towards the substrate or subject to investigate Foraging Mandible Rub Male places its head on a female’s shell. area of interest. Interaction involved with the process of eating such as biting Feeding Ram A tortoise ramming another. and chewing food items. Includes drinking behaviour. Tortoise standing or sitting under heat source in any position in Two animals are face to face exploring the Basking Social Sniff order to absorb warmth. head/face of the other. Animal in a position to attempt to be out of sight such inside Opens mouth wide, usually momentary. Hiding Yawn its hides, under an object or the substrate. Tortoise is situated in water. Water temperature varied across Soaking the project but was not recorded for this study. Moving at its regular gait. Tortoise is not eating during this Walking time. Journal of Veterinary Medicine and Animal Sciences 2 MedDocs Publishers Temperature temperature, an average of the carapace and plastron was gen- erated for use in statistical tests. Tortoises showed a predictable To investigate the body temperature of the tortoises, tem- increase in body temperature throughout the day (Figure 1). perature/humidity data loggers (iButtons) were attached to both the carapace and plastron on each animal. They were se- cured via surgical tape and located on the 2nd vertebral scute (Figure 2) and on the left abdominal scute in the concavity of the plastron to avoid being scraped off. The data loggers were attached at least 15 minutes before the commencement of the study to avoid interference of behavioural data. The error rate was +/- 0.1oC. Figure 1: Effect of time of day on plastron and carapace tem- perature, +/- standard deviation. Effect of body size on temperature On average, the temperature of the five tortoises used in the study differed. The larger tortoises, 1 and 2, showed consider- ably higher temperature means at 30.75oC and 32.36oC respec- tively. The smaller tortoises 3, 4 and 5 showed lower body tem- perature means at 29.27oC, 29.97oC and 30.5oC. The variance between large and small mean tortoise body temperatures was 1.64oC hotter for larger individuals. Mean body temperature showed a predictable change throughout the course of the day Plate 2: An illustration Showing iButton location placement on the carapace. (Figure 2). Statistical analysis Collated data sheets were produced using means for plastron and carapace temperature and humidity along with behavioural observations per hour per individual. The body temperature of each tortoise was calculated by taking the mean of the carapace and plastron recorded temperatures. State behaviour percent- ages were calculated to present individual and group activity budgets for the tortoises. Statistical analyses were performed using Minitab version 23 and behavioural and temperature data were found to be not Figure 2: Relationship between time of day and average body normally distributed.