In the Region :: Marine
Mammals :: Marine
Turtles :: Strandings
:: Beach Response
 MARINE
ANIMAL STRANDING
What is a stranded marine animal?
A stranded marine animal is generally considered to be an animal
that has been left in a helpless position - one that has come ashore
ill, weak, or simply lost.
Because the shore is not the only place where a marine mammal is
helpless, a stranded animal is routinely defined as one that cannot
cope in its present situation. This can include an arctic seal in
Florida waters, an orphaned dependent offspring, a dolphin swimming
aimlessly, or a whale immobilized after a vessel strike.
Mass Strandings and Single Strandings
Generally, a distinction is made between mass strandings that involve
anywhere from 2-3 animals up to groups of 50, 90, or more, and the
much more common strandings of single animals.
The public hears a lot about mass strandings through the media.
One particular example was the stranding of 57 pilot whales on a
beach in Dennis, MA on July 29, 2002. Headlines in Hamburg, Germany
and reports on the British Broadcast System testify to the international
coverage these events evoke.
However, we hear almost nothing about the more common single strandings.
In each of the last two years, close to 150 dolphins, porpoises
and seals came ashore on Cape Cod, for example, needing help and
over 300 marine turtles stranded in the fall of 1999. Almost all
of the dolphins, porpoises and seals stranded as single animals.
When Marine Mammals Come Ashore . . .
When a marine mammal is not eating, fat from the blubber is released
for energy.
· But when it loses blubber and becomes thin, it must work
harder to stay afloat and keep warm.
· This starts a cycle -- burning more energy that depletes
more fat.
· The spiral tightens rapidly.
The result is that stranded marine mammals are emaciated, dehydrated,
and exhausted. They may also have a disease or injury.
Because marine mammals on the beach are out of their natural environment,
they are usually stressed. Stress can lead to shock and eventually
to death if not reversed. Stranding networks are trained to reduce
stress in the handling of these animals.
Why do marine mammals strand?
Many different theories exist as to why marine animals come ashore.
Sometimes there is a single factor, sometimes a complex of factors.
Frequently the cause may be so far removed from the beach, or of
such short duration, that there are no clear answers.
One publication suggests 11 possible reasons:
1. Complex geographic or oceanic conditions - i.e. confusing salt
marsh passages, extremely high or low tides,
etc.
2. Pollutants and contaminants affecting animal health and well-being
3. Weather conditions - i.e. severe storms that separate young from
mothers or cause panic
4. Pursuit by predators
5. Naturally occurring toxins
6. Geomagnetic disturbances and errors in navigation while following
geomagnetic contours
7. Pursuing prey too close to shore
8. Disease
9. Barriers or disturbances in echo-location in shallow water
10. Social cohesion
11. Human-related injuries
One can see that these 11 reasons fall into two categories: natural
causes and man-made.
 Why
do marine turtles strand?
Sea turtles strand on New England shores generally in the late fall.
Sea turtles are reptiles and cannot regulate their internal temperature
so they live in the warm waters of the Caribbean & southern
US. Scientists believe that, as juveniles, marine turtles follow
the warm Gulf Stream currents north in the summer to eat at the
rich feeding grounds of Stellwagen Banks, just north of the tip
of Cape Cod. Then, when these northern waters turn cold in the fall
the turtles get caught in the area's bays and are unable to return
to the Gulf Stream. They are found on shore "cold stunned".
Their internal organs have "shut down" from the cold.
Marine turtles also strand with wounds from ship strikes, propeller
cuts or entanglements.
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