Core and body surface temperatures of nesting leatherback turtles (Dermochelys coriacea) Thomas J. Burns n , Dominic J. McCafferty, Malcolm W. Kennedy n Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK article info Article history: Received 27 November 2014 Received in revised form 27 February 2015 Accepted 1 March 2015 Available online 3 March 2015 Keywords: Thermal biology Thermography Non-invasive techniques Core temperature Dermochelys coriacea Eretmochelys imbricata abstract Leatherback turtles (Dermochelys coriacea) are the largest species of marine turtle and the fourth most massive extant reptile. In temperate waters they maintain body temperatures higher than surrounding seawater through a combination of insulation, physiological, and behavioural adaptations. Nesting in- volves physical activity in addition to contact with warm sand and air, potentially presenting thermal challenges in the absence of the cooling effect of water, and data are lacking with which to understand their nesting thermal biology. Using non-contact methods (thermal imaging and infrared thermometry) to avoid any stress-related effects, we investigated core and surface temperature during nesting. The mean 7SE core temperature was 31.4 70.05 °C (newly emerged eggs) and was not correlated with en- vironmental conditions on the nesting beach. Core temperature of leatherbacks was greater than that of hawksbill turtles (Eretmochelys imbricata) nesting at a nearby colony, 30.0 70.13 °C. Body surface tem- peratures of leatherbacks showed regional variation, the lateral and dorsal regions of the head were warmest while the carapace was the coolest surface. Surface temperature increased during the early nesting phases, then levelled off or decreased during later phases with the rates of change varying be- tween body regions. Body region, behavioural phase of nesting and air temperature were found to be the best predictors of surface temperature. Regional variation in surface temperature were likely due to alterations in blood supply, and temporal changes in local muscular activity of flippers during the dif- ferent phases of nesting. Heat exchange from the upper surface of the turtle was dominated by radiative heat loss from all body regions and small convective heat gains to the carapace and front flippers. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction Leatherback turtles (Dermochelys coriacea) are the largest spe- cies of marine turtle, with adult females having a mean mass of around 400 kg (Georges and Fossette, 2006). As adults they inhabit a broad range of water temperatures, migrating between high la- titude, prey-rich temperate waters and the tropics or subtropics, where beaches provide the conditions for laying and development of eggs. Leatherbacks exhibit a range of physiological and beha- vioural adaptations to cope with different environmental tem- peratures, allowing them to remain active in temperate waters and prevent overheating in the tropics. Their thermoregulatory strat- egy likely involves aspects of both gigantothermy due to their large body mass, extensive fatty insulating tissue layers and adaptable blood circulation system (Paladino et al., 1990), and endothermy due to internal heat production (Bostrom et al., 2010; Casey et al., 2014). Thermoregulation is aided by counter-current heat exchangers within the front and rear flippers (Greer et al., 1973), a vascular plexus lining the trachea to reduce respiratory heat loss, analogous to that of nasal turbinates found in birds and mammals (Davenport et al., 2009a), extensive adipose tissues in the head and neck, and major blood vessels buried deep within the insulated neck (Davenport et al., 2009b). In addition to these physiological adaptations for controlling heat loss, behaviour plays a key role in temperature control. Swimming (and the consequent metabolic heating) maintains a high body to water temperature differential (Bostrom and Jones, 2007) and turtles change flipper stroke rate in response to dif- ferent water temperatures (Bostrom et al., 2010). Furthermore, leatherbacks may dive to cooler waters to lose heat in tropical waters (Southwood et al., 2005; Bostrom and Jones, 2007) and, conversely, in temperate seas may bring prey items to the surface to warm them before ingestion (James and Mrosovsky, 2004). Nesting is the only time when female leatherbacks are known to return to land, the process may last over two hours, and requires, with the exception of egg laying, extensive use of the flippers Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jtherbio Journal of Thermal Biology http://dx.doi.org/10.1016/j.jtherbio.2015.03.001 0306-4565/& 2015 Elsevier Ltd. All rights reserved. n Corresponding authors. E-mail addresses: tomb-09@hotmail.co.uk (T.J. Burns), malcolm.kennedy@glasgow.ac.uk (M.W. Kennedy). Journal of Thermal Biology 51 (2015) 15–22