Marco Dolphins – Second Quarter Excerpts

During the first six months of 2023, guests on board the Dolphin Explorer have had the opportunity to watch and engage with the research team on Marco Island as they collect data regarding the local bottlenose dolphin population. These guests are actually “citizen scientists” for three hours as they learn how to identify our dolphins and also become educated on their surroundings.

They watch as we enter information on our survey sheets and record everything about each dolphin sighting during the excursion. Guests are made aware that all of the data is entered into our database after the trips and this info is shared with more than 22 institutions, as far away as Australia.

Here are some excerpts from our second quarter report for the period ending June 30, 2023.

Our habitat is relatively shallow waters with an average depth of about eight feet. The main “highway” for the dolphins is the Marco River, and their secondary travel routes are the bays, estuaries and sandbars and canals adjacent to the river.

Since the waters here are so shallow, there are no large predators here. There are sharks that are a threat to young dolphins, but by the time a dolphin is four years old, it is too big and too fast for a shark to chase. There is no major industry in the area, so the waters are relatively clean as well.

Our dolphins are a “keystone indicator” species which means if they are doing well, typically all other species in the area are also doing well. Our dolphin population has remained steady in the area if not slightly growing. There are more than 120 dolphins that are “residents” to north Marco and surrounding areas, and even more “transient” dolphins that pass through this habitat.

The team engaged in 291 excursions during the first six months of 2023, with 2,875 individual sightings of 128 different dolphins, plus sightings of many “transient” dolphins as well.

Of the 11 new calves born in the Fall of 2022, eight have survived, which is a great record compared to other studies around the world. We have five calves born to first-time mothers that have survived to go on their own at age three in our 17 years of data. Sarasota Bay had one calf of a first-time mom survive that long in its first 30 years of documentation.

There are more adult females than males in our survey region. When a young male leaves its mother’s side at three to four years old, some are often run off from the area by the larger, mature males.

Some males form “pair bonds,” and they will travel together, which allows them to isolate females from single males and give the pair a better chance at mating.

There are three dominant male pair bonds in the area with two more pairs that are just evolving into that society.

The team has a list of 13 females that may be eligible to give birth this Fall. Not all will do so, but the team expects to see eight to 10 new calves from September to December from this group.

Our overall population does not migrate. Calves are born and taught to feed in a “natal” range. Once they leave Mom’s side, they know how to catch fish and where to find them, so they stay in this region. Adult males may have a travel range of 20 to 30 miles throughout a year, while adult females and juveniles, known as subadults, have a range closer to home. 85% of the dolphins documented stay close to home their entire lives.

There does not appear to be any immediate threats regarding habitat loss in this surveyed area. The mangrove forests and estuaries appear to be functioning well. There is no runoff of any algae or nutrients from inland waters that is an immediate danger to our dolphins.

There are plenty of fish for our population to not just survive but thrive. Our dolphins range in weight from 20 pounds at birth to a maximum of 600 pounds for an adult male. On average, this group will eat about one ton of fish each day.

The team was involved in a dolphin rescue on April 25th which resulted in a “life-threatening” fishing line entanglement being successfully removed from a 19-month-old calf. The team was called on June 7th to investigate unusual swimming patterns of something in the water. It turned out to be an eight-foot pygmy whale. Florida Wildlife Commission was immediately notified.

The team will continue to document the daily activities of our bottlenose dolphins, the only species found in north Marco Island waters, and will share its findings quarterly with other dolphin studies, colleges and marine study programs around the world.

Stay tuned for more updates as we approach birthing season!