Abstract

Killer whales are an important sentinel species, and non-invasive methods for health assessment provide insight for investigating ecosystem health. Rectal temperature is a proxy for core temperature in managed-care cetaceans, however, this measurement is impractical for free-ranging cetaceans. Infrared thermography (IR) of blowhole temperature is reportedly nearly identical to rectal temperature in dolphins and approximately 1°C (1.8°F) lower than rectal temperature in belugas.¹

IR video was recorded from blowholes of thirteen (n=13) healthy killer whales. Rectal temperatures were documented at depths of 70 cm, 60, 50, 40, 30, 20, and 10 cm. Temperatures were compared using a repeated measures Bland-Altman method,² and multivariate multiple regression. Rectal temperature was significantly affected by sex, weight, and air temperature. Blowhole temperature was significantly affected by weight, air temperature, and water temperature. Maximum rectal temperatures were most frequently observed at 40–50 cm depth and depth was significantly affected by sex. While most data points fell within limits of agreement, blowhole temperature had weak agreement with rectal temperature, and a -1.38°C (-2.49°F) bias. Significant proportional bias was observed; the difference in the two temperatures decreased as mean temperature increased. Normal ranges for blowhole (n=156, 13 individuals) and rectal temperatures (n=583, 18 individuals) were also generated.

Acknowledgements

The authors wish to thank the animal care staff of SeaWorld San Diego and SeaWorld San Antonio.

References

1.  Melero M, Rodriguez-Prieto V, Rubio-Garcia A, Garcia-Parraga D, Sanchez-Vizcaino JM. 2015. Thermal reference points as an index for monitoring body temperature in marine mammals. BMC Res Notes. 8:411.

2.  Myles PS, Cui J. 2007. Using the Bland-Altman method to measure agreement with repeated measures. Br J Anaesth. 99:309–311.