WHY OUR LOCAL DOLPHINS DON’T MIGRATE

Dolphin Explorer LLC is the proprietor of the 10,000 Islands dolphin study program that monitors the social behavior, movement, habits, and abundance of the local bottlenose dolphin population in the waters on the north end of Marco Island. Founded in 2006, the study continues. This program also includes an ecotour that was the recipient of Trip Advisor’s 2020 People’s Choice Award.

More than 100 bottlenose dolphins call the Marco River and surrounding areas their home. The study team on board the Dolphin Explorer knows this because we can identify each and every one of them. Dolphins have a tendency to nip at each other’s fins, causing some knicks and notches to appear, especially on the dorsal fin, the one you see when they come to the surface of the water and breathe. No two dorsal fins are exactly alike so we can tell one individual from another.

With data dating back to the inception of the study in 2006 the current team can continue to track which dolphin is which and monitor their social behavior and habits as well as their travel range and genealogy. We can document where they feed and rest as well as the females’ offspring. Also, we can study their travel range.

Dolphins around the world have a variety of ranges that they utilize and explore, depending upon the type of ecosystem that they call home. For example, the bottlenose dolphins along the Atlantic Coast will head north in the Spring and south again in the Fall. A study at the University of Georgia suggests that these dolphins use water temperature as a cue to turn around in one direction or another. It is still unclear if water temperature is the sole factor that determines their directional patterns. It could also be that there is an increase in prey or more salt density in the water, but they do move.

In other cases, such as the Pacific Coast of Japan and the shoreline of North Carolina, those dolphins follow the seasonal movement of their prey. As their food sources move, so do they.

NOAA actually defines two bottlenose dolphin ecotypes: a shallow water type and a deep-water type. We can also call them inshore and offshore types. Deep water is, well, deep water. Shallow water dolphins tend to inhabit bays, rivers, and estuaries.

Some coastal dolphins have territories that they occupy all year long, with a minimally extended travel range. Such is the case with our dolphins around north Marco Island that take residence in the river and the Rookery Bay estuary as well as the 10,000 Islands estuary.

Since their travel range is minimal the team on board the Dolphin Explorer gets to see the same dolphins on a consistent basis and can catalog the fin markings and define the extent that our dolphins move. Some will cover a range of 5 to 10 miles while others may be a bit longer. One thing is sure - they have plenty of prey here and the variance in water temperature is not substantial enough to cause our population to relocate. They stay here all year long.

So, why does the newer generation stay here as well, and not explore other territories? I personally believe the answer is very simple and logical. Let’s take an example of an adult female named Halfway and her son, Wyatt.

Dolphins are mammals and when Wyatt was born the only source of food and only protection he knew was Halfway. She produced milk for him and provided protection from any unwanted predators. Now, dolphins are very smart and from a young age, before he even developed teeth, Wyatt watched mom feed; how she did it, what she caught and where she caught it. When Wyatt began feeding on his own, next to Halfway’s side, he employed the same technique as mom, in the same location. 

When Wyatt turned three years old his mom, Halfway, had a new calf which meant that he had to face the world on his own. He had great training from mom and was already distancing from mom’s side a year earlier, feeding on his own. Turning five years old this Fall, guess where Wyatt feeds now? You got it…right where Halfway had taught him to catch his meals. There is no reason to travel to other areas or learn new techniques. He has plenty of food right where mom showed him how to survive.

The same holds true for our other resident dolphins. The young are trained to feed here, they know where to get their prey and they rarely leave the travel range that was dictated by their mothers. 

Around the world, feeding styles and habits and travel ranges vary for dolphins based on their ecosystems, water temperature, availability of food and the probability of other factors that we humans have not yet determined. One thing, however, is certain. Our bottlenose dolphins of the Marco River and surrounding estuaries know where their food supply is, and they have been taught by the previous generation how to get it.

We have a healthy ecosystem and a healthy dolphin population. Our Dolphin Explorer team will continue to monitor activities, changes in habits and increases or decreases in overall population. We will continue to do so in the name of science and to educate the general public.

Stay tuned!

BIO: Bob is a Naturalist on board the dolphin study vessel Dolphin Explorer. He is also an owner of Wild Florida Ecotours departing from Port of the Islands. An author of two books, he is an award-winning columnist for Coastal Breeze News. His passion is to educate the public about our ecosystem and its inhabitants. His greatest passion…Bob loves his wife very much!