N.W. Kasting; J. Hayward; D. Pemberton; K.G. Hewlett
It is increasing clear that marine mammals are able to live in their cold
water environment because of their excellent insulation and consequent low heat loss. However,
these adaptations for heat retention may become a disadvantage or problem in some circumstances
such as during sustained or vigorous activity; in warm tropical waters; or in the very large
whales with great volume to surface area ratios. Heat loss may also become altered during
illness as in other mammals. Furthermore, attempts to quantify heat loss indicated a heat loss
that was lower than expected considering their metabolic rate. It was the purpose of this study
therefore to examine the whale's surface with infrared thermography to see if uneven or
previously unrecognized areas of heat loss could be detected.
An infrared camera (AGA Thermovision) was used to examine surface heat loss
of a healthy male killer whale (Orcinus orca) that was 6.6 m in length and weighed an
estimated 3420 to 3696 kg.
There were several prominent areas of heat loss detected by this method.
Both sides of the basal pectoral fin had enhanced heat loss relative to the rest of the fin
(greater than 3°C difference) and these changed position on three separate days of
observation. The fluke also showed areas of enhanced heat loss. The dorsal fin showed a
homogeneous low heat loss, as did the majority of the body surface. Other isolated spots of
greater than average heat loss included the melon, eye, two spots on the abdomen and an area
surrounding the genital slit. In conclusion, there are many discrete spots on the killer whale
that could contribute significantly to heat loss but because of their patchy distribution and
changing locations with time, make quantification difficult. Also the pattern may be different
in other cetaceans or in other circumstances. This technique may prove useful in detecting
illness in marine mammals, since it is currently used to screen cattle for illness.