We are currently conducting gill-net objects and pinger
experiments each day at Sea World with harbor seals
and Commerson's dolphins. We use gill-net fragments
mounted on a plastic frame which we lower into the
pool. The nets are specially designed so the study
animals don't become accidentally caught and injured.
Commerson's dolphins echolocate at such high frequencies
that we cannot hear their sounds with our human ears.
So we have to record their sounds through a device
that lowers the frequency to something we can hear
and record. We then analyze the tapes to see how echolocation
and communication sounds change in the presence of
gill nets.
Each day, after our subject animals have been fed, we
monitor the animals' behavior with video cameras and
hydrophones for one hour. This is called baseline data collection, and it shows us how
the animals behave normally, when there is no net or
pinger present.
We then place one of our three gill-net objects into the pool, one of which has a pinger.
Next, we observe and record the animals' behavior and
sounds for one to two hours. After the experiment is
over, we take the video and audio tapes back to the
laboratory and analyze how often the different species
approached and touched the net objects.
We will soon be adding California sea lions and bottlenose
dolphins to the study. Eventually our work will encompass
many species and will take us to other Sea World parks
in the United States.
Many questions need to be answered before we can attempt
to solve marine mammal entanglement problems. But we
have the chance to test many theories in our laboratory
setting. The valuable information we gain through the
Novel Objects Project can then be used to reduce entanglements.
We are very excited about our research.
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