Biology Reference
In-Depth Information
gration—about four hundred miles over territory she'd probably
never traveled by sea. After all, she came down to Monterey by
road in a truck, so she certainly didn't have any recognizable un-
derwater landmarks on her way back to Humboldt.
Over the years biologists have come to understand quite a bit
about the anatomy and physiology of animals. However, we know
very little about the subtleties of their behavior and we under-
stand even less about the remarkable migrations that some ani-
mals make. Their ability to travel great distances to specific lo-
cations without the use of a compass, clocks, and maps is
something that puzzles us technology-minded humans. We're still
ba›ed by the amazing migration of third-generation monarch
butterflies many hundreds of miles from Canada back to the very
trees in Pacific Grove, California, where their grandparents spent
the winter.
There are many other almost unbelievable examples, such as
the return of the Pacific salmon to the stream of their origin after
spending three years wandering and feeding in the ocean. Or the
return of the adult eel (
Anguilla
) from Europe across the Atlantic
Ocean to its spawning grounds in the Sargasso Sea. We can now
add Big Emma the sevengill shark and her kin to this list of re-
markable migrators.
to them through the water; and on their ampullae of Lorenzini, spe-
cialized organs for detecting the tiny electromagnetic fields produced
by the contracting muscles of all living creatures. The potential prey
doesn't have to be actively swimming to give o¤ these electrical fields;
the beating of the heart is enough. (Except for one other very strange
animal, the duck-billed platypus, this electrical sense is unique to
sharks.)
We found out later that sevengills can be enticed to eat by using the
same fish-on-a-stick technique, but with the feeder standing on the
deck above the water. That was certainly much easier and less time-
consuming.
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