By Postdoctoral Scientist Dr. Jeremy Kiszka
As the humidity returns, the
thermometer rises and the afternoon thunderstorms water south Florida, we are
reminded that the dry season has come to an end. Over the months that spanned the dry season,
however, our lab has been investigating dolphins in the Florida Coastal
Everglades and associated areas of Florida Bay to answer questions about their
behavior, movements and diets.
We have been keeping a
particularly close eye on the dolphins in the waters of the Shark River, Tarpon
Bay, Oyster Bay, Joe River, and a 200 km2 stretch of coastal waters
spanning east from Cape Sable to the Buttonwood Keys. In May, three surveys have were conducted to
increase sample sizes in Shark River and in Florida Bay, that will allow us to
better understand the foraging ecology and ecological roles of dolphins in
these areas. With the 12 new biopsy samples
collected we are up to about 35 samples and various analyses are underway, including
stable isotopes to determine what and where dolphins are eating and persistent
organic pollutants (e.g. PCBs, DDT) and Mercury (Hg). Preliminary results of
stable isotope carbon and nitrogen analyses reveal that bottlenose dolphins
feed in either coastal marine waters, as well as throughout river systems of
the Everglades, from brackish to freshwater environments.
During our expeditions to
the Everglades we have been able to observe some very interesting and unique
behaviors of dolphins including strand feeding, mud ring feeding (solitary and
in groups) and side swimming (in very shallow waters). Biopsy samples taken from these animals may
give us new information about diets specific to these feeding styles and
behaviors.
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| During mud ring feeding, a dolphin swims in a circle around a school of mullet while creating a ring of mud with its tail. The mullet try to jump over the ring of mud and dolphins can catch them out of the air! |
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| The nicks and cuts out of the dorsal fins help us identify individuals. |
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| An osprey grabs a meal. |
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| Some dolphins love to forage right next to - or even under - mangrove trees! |
