Muc Mhara Ireland's Smallest Whale - Marine Institute Open Access ...

LIFE IN THE FAST LANE: ECOLOGY AND BEHAVIOR OF
HARBOR PORPOISES IN THE GULF OF MAINE
Andrew J. Read
Nicholas School of the Environment, Duke University, Beaufort, NC 28516 USA
Plate 1. A harbour porpoise surfaces in the Bay of Fundy, Canada.
Harbour porpoises are the most abundant species of cetacean off the coasts of eastern Canada and
the United States. In addition, these are amongst the best-studied of all whales, dolphins and
porpoises, thanks to a research program that will mark its fortieth anniversary this summer. In
1969, a new faculty member at the University in Guelph in Canada, David Gaskin, began a research
program in the Bay of Fundy to study these enigmatic animals. David’s work revealed some of the
adaptations that allow these small marine mammals to thrive in what seems to us to be a cold, harsh
and unforgiving environment. As one of David’s students, I was fortunate to continue his legacy,
which in turn, is now being led by two of my former students, Andrew Westgate and Heather
Koopman. In this very brief article, I’ll summarize some of the highlights of this long-standing
research program.
One of the most fundamental questions addressed in David’s early research was how these warmblooded
animals manage to stay warm in waters that would quickly stun and kill a human being.
Some early studies suggested that porpoises manage to stay warm by increasing their metabolic rate
(akin to turning up the thermostat in a drafty house). Perhaps not surprisingly, natural selection
resulted in a much more energy-efficient solution. Much of the core body of a harbour porpoise is
wrapped in a 1.5 to 2.5 cm-thick layer of lipid-rich blubber, which insulates the animal in a very
effective manner. The animals do not need to turn up their metabolic furnaces simply to keep
warm.
The blubber of a porpoise is comprised of fat cells suspended in a matrix of collagen fibers; up to
90% of the blubber of a healthy porpoise is made of fat. Heather Koopman’s research showed that
blubber is not a uniform tissue, however, and both its composition and function varies over the
body surface. For example, blubber on the tail stock has more fiber and less fat; this part of the
blubber functions as a biological spring, increasing the efficiency with which the flukes moves up
and down, thus providing more thrust for less energy expenditure. Heather also showed that when
porpoises are unable to feed, they lose fat from the blubber in their thorax and abdomen, but not
from their tail, allowing them keep swimming in search of food. Eventually, of course, a starving
porpoise will succumb to hypothermia or pneumonia – we see many young porpoises in this
condition on the beaches of New England each spring. These starved animals have not learned to
forage effectively on their own after being weaned from their mothers.
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Proceedings of the 2 nd IWDG International Whale Conference: Muc Mhara - Ireland’s smallest whale
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Photo © Ari Friedlaender.