By Jessica Taylor
November 6, 2020
I recently finished downloading dorsal fin photos from a group of dolphins we sighted in Roanoke Sound. These images will allow us to identify individual animals through the distinctive markings on their fins. This is likely to be one of the last sightings that I download for this year.
Although the Outer Banks Center for Dolphin Research will continue our monitoring surveys through the fall, we typically see less dolphins in the sound as the months go on.
Bottlenose dolphins are very seasonal in Roanoke Sound. During the summer, they are drawn in by the warm waters boasting an abundance of prey fish and minimal predators, such as sharks. In the fall, many dolphins leave the sound, likely due to the cool waters and lack of prey. One of my biggest questions when I started studying dolphins on the Outer Banks was, where do they go when they’re not here?
For the past 12 years, the center has completed photo-identification monitoring surveys in Roanoke Sound to learn about the dolphins locally but also to gain a greater understanding of their movement patterns along the East Coast. By contributing our research data to a master catalog curated by the Duke University Marine Lab, known as the Mid-Atlantic Bottlenose Dolphin Catalog, and collaborating with other photo-ID researchers, we’ve learned exactly where some of our local dolphins go and when.
Scientists have found that some marine animals are shifting their ranges north and some northern animals travel further south than usual, such as the seals that are a common sight on our beaches in January. We investigated whether our dolphins travel further north. Over the past four years, we collaborated with researchers in New Jersey, Delaware, Maryland and Virginia. Through countless hours of comparing dorsal fin images to northern catalogs, we found that although these dolphins are known to range as far north as Virginia Beach, Virginia, in the summer, some are straying into northern Virginia and as far north as Maryland! Perhaps they take a short break from their journey by ducking into Roanoke Sound for a snack, then they continue north; however, this still doesn’t answer the question of where our dolphins go in the winter.
During the 1990s, a very distinctive dolphin was sighted near Beaufort, North Carolina. He was a frequent visitor to winter time Beaufort waters, but his summer time residence was a mystery. In 1997, on the maiden voyage of the Nags Head Dolphin Watch, a local eco-tour and collaborator of the Outer Banks Center for Dolphin Research, Rich and Kate Mallon-Day saw the animal, known as Onion, in Roanoke Sound. The Onion sighting provided an important key to our summertime dolphins’ winter whereabouts. When we compared our Outer Banks catalog to photo-ID catalogs near Beaufort, we found many of our “regulars” were seen near Beaufort during winter. Our matching studies are continuing this fall, and we are still finding new dolphins that travel between the Outer Banks and Beaufort.
Roanoke Sound is an important summertime habitat for dolphins as some of these regulars, such as Onion, have frequented our sound for more than 20 years. As the sound waters cool, the days get shorter, and we move deeper into fall, we will continue to survey until the waters are still and there are no dorsal fins breaking the surface. And sometime this month, there will be a message from our collaborators in Beaufort saying that Onion’s group has arrived.
Biologist Jessica Taylor is president of the Outer Banks Center for Dolphin Research. She has a Bachelor of Science in marine science from Rutgers and master’s degree in environmental management from Duke University. She has participated in field research studies of bottlenose dolphins, humpback whales, Steller sea lions and predatory fish in Florida, South Carolina, New Jersey, Alaska and Australia. In 2008, she incorporated the nonprofit Outer Banks Center for Dolphin Research, which is dedicated to conservation of bottlenose dolphins on the Outer Banks. For more info, visit obxdolphins.org.