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Marine Mammal Physiology: Requisites for Ocean Living
15.2 Behavior in a physiological box
You have learned about species of marine mammals that can dive for over an hour or
forage for food at over 1000 m depth. Just as with humans, these may be the extremes of
their performance, and daily routines do not include such amazing physiological feats.
Almost every chapter referred to behavioral patterns in marine mammals, and this is
why the physiological box concept becomes important. Biochemistry, physics, and physiology define the limits of how a marine mammal can dive, but it is behavior that places
an animal within that box. An animal will dive to hunt for food, to move from one area
to another, to socialize, to breed, to communicate, or to get away from a predator. All of
those behaviors will determine the pattern of the dives. Physiology and biochemistry set
what the animal is capable of, not what it does from moment-to-moment. For example,
when we were first working on the aerobic dive limit concept many years ago, we discovered that over 95% of the free dives of Weddell seals were under the ADL limit by putting
dive recorders on dozens of seals and then turning them loose to discover their “natural
diving patterns.”
The sea otter is another example we have covered that applies to the physiological box.
The daily behavior of sea otters is driven by a high metabolism, the need to obtain great
amounts of food, and to keep their fur coat waterproof. These are the physiological and
biochemical facts about sea otters. However, the facts do not provide much information
on whether the otter is going to forage at any particular location, or whether it is going to
capture a crab or an urchin. To some extent, the otter is going to capture what it can to eat,
depending on where it is diving. While the physiological box constrains the otter (it cannot hold its breath long enough to go below 30–40 m), what it does inside that constraint
is not really limited by its physiology. What it does inside that box is more determined by
the concept of physiological ecology.
15.3 Physiological ecology
Physiological ecology is at the interface of the energetic needs of the animal and the ecological niche of its environment. As you might imagine, these questions are not easily
answered, particularly for our marine mammal species that spend most or all of their lives
outside of our ability to observe them.
For example, how would you determine how much a blue whale consumes in krill
each day, or how much milk it feeds its calf? Despite the difficulty of finding these answers,
many are at the core of ecological overlap in habitat or resource use by humans. The field of
physiological ecology is essential to most management, Endangered Species Act findings,
and other policy determinations for marine mammals. It is a fascinating area of study, but
one that relies heavily on fundamental limits dictated by physiological and biochemical
rules, combined with physiology in a box theories and knowledge.
Several sections in this book discussed the obvious, and not obvious, conflicts between
fishing and marine mammals. In Alaska, populations of Steller sea lions have been declining for decades. “Is it food?” is not only an important question but has large economic
and social impacts for humans given the billion-dollar fishing industry that is subject to
marine mammal protection regulations. These regulations are based on sometimes very
limited data due to the difficulty of working with these species. Should fisheries around
sea lion rookeries be closed to fishing at the times of year when mothers and pups are
nearby? To obtain part of that answer, scientists deploy dive recorders with satellite tracking so that they can find out the distribution and depth of where the female sea lions
Marine Mammal Physiology: Requisites for Ocean Living
15.2 Behavior in a physiological box
You have learned about species of marine mammals that can dive for over an hour or
forage for food at over 1000 m depth. Just as with humans, these may be the extremes of
their performance, and daily routines do not include such amazing physiological feats.
Almost every chapter referred to behavioral patterns in marine mammals, and this is
why the physiological box concept becomes important. Biochemistry, physics, and physiology define the limits of how a marine mammal can dive, but it is behavior that places
an animal within that box. An animal will dive to hunt for food, to move from one area
to another, to socialize, to breed, to communicate, or to get away from a predator. All of
those behaviors will determine the pattern of the dives. Physiology and biochemistry set
what the animal is capable of, not what it does from moment-to-moment. For example,
when we were first working on the aerobic dive limit concept many years ago, we discovered that over 95% of the free dives of Weddell seals were under the ADL limit by putting
dive recorders on dozens of seals and then turning them loose to discover their “natural
diving patterns.”
The sea otter is another example we have covered that applies to the physiological box.
The daily behavior of sea otters is driven by a high metabolism, the need to obtain great
amounts of food, and to keep their fur coat waterproof. These are the physiological and
biochemical facts about sea otters. However, the facts do not provide much information
on whether the otter is going to forage at any particular location, or whether it is going to
capture a crab or an urchin. To some extent, the otter is going to capture what it can to eat,
depending on where it is diving. While the physiological box constrains the otter (it cannot hold its breath long enough to go below 30–40 m), what it does inside that constraint
is not really limited by its physiology. What it does inside that box is more determined by
the concept of physiological ecology.
15.3 Physiological ecology
Physiological ecology is at the interface of the energetic needs of the animal and the ecological niche of its environment. As you might imagine, these questions are not easily
answered, particularly for our marine mammal species that spend most or all of their lives
outside of our ability to observe them.
For example, how would you determine how much a blue whale consumes in krill
each day, or how much milk it feeds its calf? Despite the difficulty of finding these answers,
many are at the core of ecological overlap in habitat or resource use by humans. The field of
physiological ecology is essential to most management, Endangered Species Act findings,
and other policy determinations for marine mammals. It is a fascinating area of study, but
one that relies heavily on fundamental limits dictated by physiological and biochemical
rules, combined with physiology in a box theories and knowledge.
Several sections in this book discussed the obvious, and not obvious, conflicts between
fishing and marine mammals. In Alaska, populations of Steller sea lions have been declining for decades. “Is it food?” is not only an important question but has large economic
and social impacts for humans given the billion-dollar fishing industry that is subject to
marine mammal protection regulations. These regulations are based on sometimes very
limited data due to the difficulty of working with these species. Should fisheries around
sea lion rookeries be closed to fishing at the times of year when mothers and pups are
nearby? To obtain part of that answer, scientists deploy dive recorders with satellite tracking so that they can find out the distribution and depth of where the female sea lions