341
Chapter fifteen: Conclusions and questions
15.5 Lessons from teaching physiology of marine mammals
Most of the authors of this book have taught classes in marine mammal physiology, biochemistry, and anatomy, which have featured prominently in the way we have addressed
many of our chapter topics. There are some questions students ask consistently that we are
still lacking the tools and information to answer in detail and with authority.
15.5.1 Can marine mammals be hurt by loud underwater noise?
Chapter 11 explains many of the issues surrounding marine noise and marine mammal
responses. Increasing background noise in the ocean due to human maritime activity
makes this a particularly contentious area of research. As the Arctic Ocean warms and
human enterprise takes advantage of reduced sea ice, massive efforts are underway to
measure sound levels in an attempt to predict what may cause whales or seals to move or
alter their migration routes. The controversy around Navy SONAR and potential for damage to whales has been decades-long and is at the basis of a great deal of current work on
acoustics.
15.5.2 How do whales find their way during migrations?
The search continues for how whales navigate across great stretches of open ocean. Theories
include navigation by stars, polarized sunlight angles in the water, magnetic sensing,
and acoustics. Luckily, advances in custom telemetry are allowing for dive recorders that
are smaller, more hydrodynamic, and increasingly powerful with additional sensors to
describe the water salinity and temperature. These transmitters are our window into the
whale’s movements up and down coastlines, allowing new analyses of where and when
they spend most of their time, with important information about linkages to prevailing
ocean conditions.
15.5.3 What causes whales to strand?
Every year there are many cases of good intentioned humans attempting to rescue stranded
dolphins or small whales. In most cases, even if they are successful in dislodging the animals from the beach, the animals turn back to shore only to strand again. Sadly, very few
of these rescue attempts are successful. Sound pollution is routinely implicated in stranding events, however animals have beached for eons, long before human noise in the ocean
was a rising concern. Alternative theories include the apparent strong social adhesion of
cetaceans, such that one individual strands due to illness, only to be followed by other
members of their group. Both natural algal bloom events and anthropogenic chemical pollution have been suggested as disorienting factors. The details of each stranding case vary
so widely that we are still many years from identifying the underlying conditions, and
there very well may not be a single unifying principle.
15.5.4 Can species interbreed?
This issue comes up particularly in the context of the changing ice patterns in the Arctic. It
is predicted that polar bears will be forced into ice refugia in the North Eastern Canadian
Arctic within the next century. As they are forced to spend more time on land, there are
suggestions that they may begin to breed with brown bears. While this may occur to some
Chapter fifteen: Conclusions and questions
15.5 Lessons from teaching physiology of marine mammals
Most of the authors of this book have taught classes in marine mammal physiology, biochemistry, and anatomy, which have featured prominently in the way we have addressed
many of our chapter topics. There are some questions students ask consistently that we are
still lacking the tools and information to answer in detail and with authority.
15.5.1 Can marine mammals be hurt by loud underwater noise?
Chapter 11 explains many of the issues surrounding marine noise and marine mammal
responses. Increasing background noise in the ocean due to human maritime activity
makes this a particularly contentious area of research. As the Arctic Ocean warms and
human enterprise takes advantage of reduced sea ice, massive efforts are underway to
measure sound levels in an attempt to predict what may cause whales or seals to move or
alter their migration routes. The controversy around Navy SONAR and potential for damage to whales has been decades-long and is at the basis of a great deal of current work on
acoustics.
15.5.2 How do whales find their way during migrations?
The search continues for how whales navigate across great stretches of open ocean. Theories
include navigation by stars, polarized sunlight angles in the water, magnetic sensing,
and acoustics. Luckily, advances in custom telemetry are allowing for dive recorders that
are smaller, more hydrodynamic, and increasingly powerful with additional sensors to
describe the water salinity and temperature. These transmitters are our window into the
whale’s movements up and down coastlines, allowing new analyses of where and when
they spend most of their time, with important information about linkages to prevailing
ocean conditions.
15.5.3 What causes whales to strand?
Every year there are many cases of good intentioned humans attempting to rescue stranded
dolphins or small whales. In most cases, even if they are successful in dislodging the animals from the beach, the animals turn back to shore only to strand again. Sadly, very few
of these rescue attempts are successful. Sound pollution is routinely implicated in stranding events, however animals have beached for eons, long before human noise in the ocean
was a rising concern. Alternative theories include the apparent strong social adhesion of
cetaceans, such that one individual strands due to illness, only to be followed by other
members of their group. Both natural algal bloom events and anthropogenic chemical pollution have been suggested as disorienting factors. The details of each stranding case vary
so widely that we are still many years from identifying the underlying conditions, and
there very well may not be a single unifying principle.
15.5.4 Can species interbreed?
This issue comes up particularly in the context of the changing ice patterns in the Arctic. It
is predicted that polar bears will be forced into ice refugia in the North Eastern Canadian
Arctic within the next century. As they are forced to spend more time on land, there are
suggestions that they may begin to breed with brown bears. While this may occur to some