Thermal reference points as an index for monitoring body temperature in marine mammals

Abstract

Background Monitoring body temperature is essential in veterinary care as minor variations may indicate dysfunction. Rectal temperature is widely used as a proxy for body temperature, but measuring it requires special equipment, training or restraining, and it potentially stresses animals. Infrared thermography is an alternative that reduces handling stress, is safer for technicians and works well for untrained animals. This study analysed thermal reference points in five marine mammal species: bottlenose dolphin (Tursiops truncatus); beluga whale (Delphinapterus leucas); Patagonian sea lion (Otaria flavescens); harbour seal (Phoca vitulina); and Pacific walrus (Odobenus rosmarus divergens).ResultsThe thermogram analysis revealed that the internal blowhole mucosa temperature is the most reliable indicator of body temperature in cetaceans. The temperatures taken during voluntary breathing with a camera held perpendicularly were practically identical to the rectal temperature in bottlenose dolphins and were only 1 °C lower than the rectal temperature in beluga whales. In pinnipeds, eye temperature appears the best parameter for temperature control. In these animals, the average times required for temperatures to stabilise after hauling out, and the average steady-state temperature values, differed according to species: Patagonian sea lions, 10 min, 31.13 °C; harbour seals, 10 min, 32.27 °C; Pacific walruses, 5 min, 29.93 °C.ConclusionsThe best thermographic and most stable reference points for monitoring body temperature in marine mammals are open blowhole in cetaceans and eyes in pinnipeds.

Accuracy of the Aspartic Acid Racemization Technique in Age Estimation of Mammals and the Influence of Body Temperature

“…Core body temperature (°C), estimate of 2kAsp and (D/L)0 value and associated SE for four species in this study and published values for another eight species. Average core temperatures (°C) are from Teare (2002), except for records of fin whale (Brodie and Paasche 1985), minke whale (Folkow and Blix 1992), harbour porpoise (Desportes et al (2003), bowhead whales (Rosa et al 2013), narwhal (Heide-Jørgensen et al 2014, and beluga (Melero et al 2015). additional experiments were done in this study to further elucidate this feature, and a full discussion on this topic is beyond the scope of this paper.…”

“…3). The rate of the beluga, however, seem high considering a relatively low core body temperature of 35.7°C (Melero et al 2015). Also the narwhal, the beluga's closest relative, has a racemization rate considerably lower even though core body temperatures of the two species is almost the same (Fig.…”

“…Core body temperatures instead of eyeball temperatures were chosen for the regression for three main reasons: 1) eye temperatures have been shown to be practically the same as or at least correlate with core body temperatures in several mammal species (Melero et al 2015), 2) in situ measurements of whale eyeball temperatures are difficult if not impossible (Rosa et al 2013), NAMMCO Scientific Publications, Volume 10 and 3) published eyeball temperatures for all the 12 species used in this study were not available.…”

Doctor Drone: Non-invasive Measurement of Humpback Whale Vital Signs Using Unoccupied Aerial System Infrared Thermography

“…For example, cetacean blows/spouts will appear as relatively warm IR features when measured from oblique (i.e., near horizontal) angles but relatively cold IR features when measured from perpendicular (i.e., near vertical) angles (Horton et al, 2017, this study). Thus, robust measurement of cetacean thermal reference points, including blowholes (Melero et al, 2015), requires careful consideration of the relationship between imaging angle and emissivity (Horton et al, 2017). Our study helps to overcome this challenge through quantification of cetacean brightness temperatures from low zenith angles.…”

“…Although technological advances in infrared thermography (IRT) and signal processing have facilitated measurement of human vital signs (e.g., Sun et al, 2017), such techniques are not yet widely applied to marine mammals. Although prior marine mammal research has used IRT to measure the dorsal fin surface temperatures of free-swimming bottlenose dolphins (Tursiops truncatus) during small boat surveys (Barbieri et al, 2010) and thermal reference points on captive marine mammals (Melero et al, 2015), airborne IRT has been limited to estimating pinniped colony size using both aircraft (Udevitz et al, 2008) and unoccupied aerial systems (UAS; Seymour et al, 2017). Thus, our overarching goal was to explore the potential utility of UAS-IRT technology as a non-invasive tool for quantifying wild cetacean behaviors and biomedical vital signs.…”