Over the past decade, bottlenose dolphins have become a more frequent sight north of New Jersey as the lively mammals enjoy the warming shallow waters not far from land in New York Harbor.
A new study from Columbia University and the Wildlife Conservation Society reveals that these migratory marine animals are now avid visitors to the Big Apple, often entering the human-traveled waters between New York and New Jersey for food and socializing. The annual return of these aquatic mammals to the city’s harbor could improve the quality of coastal waters and renew their commitment to protecting local wildlife, even in urban areas.
“It’s kind of like the million-dollar question: If there’s all this human activity in New York Harbor, why do bottlenose dolphins come here,” said Sarah Trabue, a research assistant at the Wildlife Conservation Society and the lead author of the study. study. “It looks like it could be an important feeding area. The prey species here are of a quality or quantity that makes it worthwhile to get into these urbanized areas.”
For two years, Trabue’s team tried to find possible answers to why and how common bottlenose dolphins were in the city’s harbor. They rode in boats, dropped underwater microphones at six different locations, about 30 feet deep, and recorded every hour in 20-minute cycles, for four months, very close to the ocean floor.
The recordings were retrieved, downloaded and run through PAMGUARD, a software program that detects the sounds dolphins make when they echolocate. Rapid clicks mean a dolphin is foraging and about to get its next meal.
“The time between clicks decreases and at some point, when the clicks get so close together, to our ears, it starts to sound like a buzz. That’s what we call the foraging buzz,” Trabue said.
From 2018 to 2020 there was a lot of buzz in the water. Most activity was recorded in the Central Harbor, right at the mouth of the estuary, where the gateway to New York Harbor spans Brooklyn to New Jersey, Sandy Hook and Breezy Point.
During peak season, late summer and fall, these mics picked up quick clicks almost every day. (These highly sociable carnivores spend their winters off the coast of North Carolina.) Experts and study authors believe the reason may be improving habitat due to stricter environmental regulations, such as the Clean Water Act.