From our decades of research, we have been able to define the boundaries of several resident dolphin communities.
Different dolphin communities have been identified to the north, to the south, and offshore of the Sarasota community, as well as in other areas.
Within each community is the home range, which defines where an individual dolphin moves.
We have relied primarily on natural markings to identify individual dolphins over the last three decades. Photographs are taken and used to verify dolphin identities.
The menu below has brief summaries of topics important to understanding Dolphin Communities, plus relevant scientific citations.
The area where an animal feeds, breeds, socializes, and travels is called its home range. Bottlenose dolphins are unusual in that different populations have highly variable home ranges in different parts of the species’ range.
Some populations, like the Sarasota dolphins, are permanent residents of their home range. Residents are easiest to study because they can be reliably found in a given area, and many of the Sarasota dolphins have been observed for decades.
Other dolphins have a winter and a summer home range. Populations along the U.S. Atlantic seaboard migrate north in the spring and south in the fall.
Some individual dolphins appear to be transients, staying in an area for a while before moving on. Bottlenose dolphins that live in deep ocean waters remain largely a mystery because they are difficult to study.
In 1970-1971, we began our study of dolphins in Sarasota Bay by putting numbered tags on a few dolphins . We soon found that the same dolphins were seen year round. They were residents. It was a community of dolphins.
During 1975-1976, we tagged more dolphins, and we conducted regular boat surveys to watch for the tagged animals. Photographs verified dolphin identities.
By the late 1970’s we had learned that we could recognize many individuals from natural markings alone, and this has been our primary technique for keeping track of individuals ever since.
Since then, we’ve identified different dolphin communities along Florida’s west coast.
The dolphins within a community share similar home ranges, and they associate together frequently. Home-range boundaries are often marked by inlets between islands, or abrupt changes in water depth.
Neighboring communities often have slightly overlapping home ranges. Dolphins from adjoining communities may interact and sometimes mating also occurs.
While at least five generations of dolphins are known to occupy the same home range, some dolphins may vary their usage seasonally.
For example, Pecan Sandie, is a female dolphin known first from southern Tampa Bay, just north of the Sarasota Bay. She spends her summers in the Sarasota community range, and winters to the north in Tampa Bay.
Relevant SDRP publications
Duffield, D.A. and R.S. Wells. 2002. The molecular profile of a resident community of bottlenose dolphins, Tursiops truncatus. Pp. 3-11 In: C.J. Pfeiffer, ed., Molecular and Cell Biology of Marine Mammals. Krieger Publishing Company, Melbourne, FL.
Irvine, A.B., M.D. Scott, R.S. Wells and J.H. Kaufmann. 1981. Movements and activities of the Atlantic bottlenose dolphin, Tursiops truncatus, near Sarasota, Florida. Fish. Bull. U.S.79:671-688.
Sellas, A.B., R.S. Wells, and P.E. Rosel. 2005. Mitochondrial and nuclear DNA analyses reveal fine scale geographic structure in bottlenose dolphins (Tursiops truncatus) in the Gulf of Mexico. Conservation Genetics.6:715-728.
Urian, K.W., S. Hofmann, R.S. Wells, and A.J. Read. 2009. Fine-scale population structure of bottlenose dolphins, Tursiops truncatus, in Tampa Bay, Florida. Marine Mammal Science 25:619-638.
Wells, R.S. and M.D. Scott. 2009. Common bottlenose dolphin (Tursiops truncatus). Pp. 249-255 In: W.F. Perrin, B. Würsig, and J.G.M. Thewissen, eds., Encyclopedia of Marine Mammals. Second Edition. Elsevier, Inc., San Diego, CA.
All photos © Sarasota Dolphin Research Program under NMFS permit #522-1785