By Jessica Taylor | Correspondent
As the days become cooler and shorter, the Outer Banks Center for Dolphin Research slows down our survey effort in Roanoke Sound.
In the fall, we definitely wear more layers out on our boat-based research surveys and a cool “breeze” has a different meaning than it has in summer. Our effort and boat time is dictated by the dolphins; we just don’t see them as much as we do in the summer. Why? Read on to learn about why dolphins enjoy a change of scenery, too!
Temperature: As marine mammals, bottlenose dolphins regulate their own body temperature. Unlike sea turtles whose body temperature will drop to match the temperature of the surrounding water, bottlenose dolphins like to maintain a cozy 96.8-98.6 degrees Fahrenheit, similar to humans.
However, when the water temperature drops, it is harder for dolphins to maintain a stable internal body temperature even with the insulating benefits of blubber below their skin. In response, dolphins will migrate to warmer water. Even moving out to the coastal waters of the Atlantic Ocean will provide warmer water temperatures than the shallow sound, and this is likely where our Roanoke Sound dolphins spend some of their time during the winter. In areas of Florida where dolphins are known to live as year-round residents, dolphins grow thicker blubber layers during the winter to keep themselves warm.
Food: Bottlenose dolphins may be opportunistic foragers, but they love fish that can make some noise. Sound-producing, or soniferous, fish frequent the sound during the summer, yet many species move to coastal waters in the fall. When their food leaves the sound, dolphins simply follow their food. Wouldn’t you follow your food, too? In the future, the Outer Banks Center for Dolphin Research hopes to learn more about how the movements of dolphins and fish in the sound are related. These relationships will become especially important as environmental conditions, such as sea surface temperature and salinity, change over time.
Habitat: There are likely more factors influencing dolphin seasonal movement patterns, such as habitat. The Outer Banks Center for Dolphin Research uses photo-identification aboard our research surveys to study dolphins in Roanoke Sound. By photographing the distinctive markings of each dolphin’s dorsal fin and cataloging these images, we are able to track individuals over time, including who they like to hang out with and where they go.
Dolphins in Roanoke Sound like specific habitats for doing certain things. For example, dolphins are known to feed in areas where the bottom has a steeper slope, such as the edge of the channel. These areas are good for concentrating fish and offer the dolphins more meal opportunities. Perhaps seasonal movements are related to habitat preferences.
The site of the northernmost year-round dolphin community on the east coast is Beaufort, approximately 100 miles south of Roanoke Sound and marks the southern range of the population we frequently see in the Outer Banks. The temperature and food are likely not too different in Beaufort than here. Yet many of our seasonal residents that we know during the summer, such as Onion, Fatlip, and Skylar, are commonly seen in Beaufort coastal waters during the winter.
Perhaps the winter coastal habitat near Beaufort offers something they cannot find in the Outer Banks. Or maybe these movements are a tradition that calves learn from their mothers and continue as they grow older.
Future research and collaborations with scientists along the East Coast will teach us more over time about why dolphins go where they do. Until then, we’ll layer up in our sweatshirts, windbreakers and winter gear hoping to catch a glimpse of dolphins this fall before they leave for their winter coastal water vacations.
If you do happen to see dolphins in the Outer Banks during the winter, please remember these important tips:
Refrain from feeding wild dolphins. Dolphins are federally protected and very good at finding their own food.
Dispose of your trash in the designated area. Littering can be harmful to wildlife, especially at the beach.
Report all dolphin and other marine mammal strandings to the local stranding response team. Even reports of dead animals are useful to learn more about the species.
If you are in Currituck, Dare, or Hyde County, report to the OBX Marine Mammal Stranding Network at 252-455-9654. If you are on Cape Hatteras National Seashore, report to CAHA Stranding Response at 252-216-6892.