205
Chapter nine: Thermoregulation
Ultrasound methods work well when the animal in question can be handled. However,
there are many cases where the animals cannot be touched (almost all wild cetaceans) or
where they are not restrained easily (many wild pinnipeds). In those cases, there have
been great advances made in photographic methods to produce images where measurements can be made of width, girth, and so on. Using controls, studies of live and dead
specimens and geometry, values of blubber depth and total body mass can be modeled
using photographic techniques. However, a basic assumption in these methods is that a
marine mammal with large amounts of blubber appears different than the same animal
with less blubber. The concern here is the structural nature of blubber from the protein
matrix. It is possible to remove a great deal of the lipid from blubber without changing its
shape, because of the protein matrix. Therefore, the same whale under low blubber fat and
high blubber fat conditions may appear to have the same width and girth.
9.6.2 Infrared thermography
Similar to the leaps in ultrasound technology, the rapid development of microelectronics has provided research scientists with accurate and inexpensive laser-guided infrared remote thermometers that can be used to measure the skin surface temperature of
all kinds of marine mammals. This is clearly a phenomenal advancement over physically placing a thermometer or thermode on the skin surface of a whale or seal, which
has, by the way, been done (Boyd 2000). However, an even more impressive advancement has been easy-to-use thermal imaging cameras that measure the temperature
profile of the entire animal in a single frame. One of the pioneering a pplications of
this technology to wildlife research was by one of the authors of Chapter 3, where
the differences in heat transfer in elephant ears was defined (Williams 1990). The
method has since been applied to numerous thermoregulatory studies in terrestrial
species (McCafferty et al. 1998, 2013; Tattersall and Cadena 2010). There have been
several applications of thermal imaging specific to pinnipeds, ranging from tracking
the energy budgets of newly weaned gray seals in comparison to their environment
(McCafferty et al. 2005), to the variation in heat loss by territorial male elephant seals
during battle (Norris et al. 2010). The thermal windows mentioned previously provide
evidence beyond the visual that marine mammals can and will use increased blood
flow to the skin to enhance evaporative heat loss (Mauck et al. 2003). With some care,
thermal images of individuals can be used in biophysical modeling to estimate metabolic heat loss (McCafferty et al. 2011).
The Weddell seal is mentioned many times in this chapter, due to their large size,
accessibility during the breeding season, and deep southern environment that provides
an excellent tool for modeling. In a recent study, Mellish et al. (2015) combined both thermal imaging and heat flux sensor deployments in Weddell seals as a thermoregulatory
model for phocid seals in a wide range of mass and condition states. The overall body
surface temperature of the seals was a surprising 14°C on average, despite the below
freezing air temperatures. However, on particularly cold days, there could be as little as
a 2°C–4°C difference between the outer temperature of the skin and the environment,
which according to the Fick principle, would greatly limit the amount of heat lost to the
environment.
The overall temperatures of the seals, in a five-fold range of body mass and threefold range in blubber depth, were largely influenced by a combination of the mass of the
animal, the ambient air temperature, and the wind speed. Unlike more temperate pinniped species, there was no regional difference in heat loss across the body. Using heat
Chapter nine: Thermoregulation
Ultrasound methods work well when the animal in question can be handled. However,
there are many cases where the animals cannot be touched (almost all wild cetaceans) or
where they are not restrained easily (many wild pinnipeds). In those cases, there have
been great advances made in photographic methods to produce images where measurements can be made of width, girth, and so on. Using controls, studies of live and dead
specimens and geometry, values of blubber depth and total body mass can be modeled
using photographic techniques. However, a basic assumption in these methods is that a
marine mammal with large amounts of blubber appears different than the same animal
with less blubber. The concern here is the structural nature of blubber from the protein
matrix. It is possible to remove a great deal of the lipid from blubber without changing its
shape, because of the protein matrix. Therefore, the same whale under low blubber fat and
high blubber fat conditions may appear to have the same width and girth.
9.6.2 Infrared thermography
Similar to the leaps in ultrasound technology, the rapid development of microelectronics has provided research scientists with accurate and inexpensive laser-guided infrared remote thermometers that can be used to measure the skin surface temperature of
all kinds of marine mammals. This is clearly a phenomenal advancement over physically placing a thermometer or thermode on the skin surface of a whale or seal, which
has, by the way, been done (Boyd 2000). However, an even more impressive advancement has been easy-to-use thermal imaging cameras that measure the temperature
profile of the entire animal in a single frame. One of the pioneering a pplications of
this technology to wildlife research was by one of the authors of Chapter 3, where
the differences in heat transfer in elephant ears was defined (Williams 1990). The
method has since been applied to numerous thermoregulatory studies in terrestrial
species (McCafferty et al. 1998, 2013; Tattersall and Cadena 2010). There have been
several applications of thermal imaging specific to pinnipeds, ranging from tracking
the energy budgets of newly weaned gray seals in comparison to their environment
(McCafferty et al. 2005), to the variation in heat loss by territorial male elephant seals
during battle (Norris et al. 2010). The thermal windows mentioned previously provide
evidence beyond the visual that marine mammals can and will use increased blood
flow to the skin to enhance evaporative heat loss (Mauck et al. 2003). With some care,
thermal images of individuals can be used in biophysical modeling to estimate metabolic heat loss (McCafferty et al. 2011).
The Weddell seal is mentioned many times in this chapter, due to their large size,
accessibility during the breeding season, and deep southern environment that provides
an excellent tool for modeling. In a recent study, Mellish et al. (2015) combined both thermal imaging and heat flux sensor deployments in Weddell seals as a thermoregulatory
model for phocid seals in a wide range of mass and condition states. The overall body
surface temperature of the seals was a surprising 14°C on average, despite the below
freezing air temperatures. However, on particularly cold days, there could be as little as
a 2°C–4°C difference between the outer temperature of the skin and the environment,
which according to the Fick principle, would greatly limit the amount of heat lost to the
environment.
The overall temperatures of the seals, in a five-fold range of body mass and threefold range in blubber depth, were largely influenced by a combination of the mass of the
animal, the ambient air temperature, and the wind speed. Unlike more temperate pinniped species, there was no regional difference in heat loss across the body. Using heat