To capture fish, bottlenose dolphins have many special tricks. They can round them up by disturbing the sediment on the seafloor, creating “mud nets,” or may chase fish toward the shore, trapping their prey before also partially beaching themselves and chowing down.
The cetaceans also have a slightly more brutal tactic: Smacking or flipping fish with their tail flippers, sending them flying into the air. The dolphins then swim over to the stunned fish for an easy bite.
This technique, which has been observed among several types of dolphins in areas as disparate as the U.S. Gulf Coast and New Zealand, has the fancy technical name of “fish-kicking” or “fish-whacking,” explains Stefanie Gazda, a biologist at the University of Florida who studies the animals at Cedar Key, north of Tampa Bay.
Self-proclaimed animal lover Michael McCarthy has been watching bottlenose dolphins do this for years near his home in Seminole, Florida, about 160 kilometres to the south. He says that it’s the most common feeding technique that he observes among local bottlenoses—and his recent video of the phenomenon provides new insights into the behaviour for people who aren’t lucky enough to live near the animals.
McCarthy filmed the behaviour while seated in one of the transparent boats made by his company, SeeThroughCanoe, and captured through the zoom lens of a GoPro mounted on a drone.
“It’s very spectacular video” that clearly shows this fish-whacking, Gazda says, adding the behaviour is likely learned by dolphins from their parents or other adults.
But it has also clearly arisen independently several different times, as it’s seen in many areas, she says—an intriguing example of how a successful hunting strategy can evolve in multiple places.
Shannon Gowans, a behavioural ecologist who studies the animals at Eckerd College in St. Petersburg, says she sees the behaviour often. “It doesn’t seem to be every individual doing it,” she says, but rather a few key dolphins do it quite a lot.
These animals have a range of behaviours, with different individuals specialising in different techniques. “One dolphin does this, another does that,” she says.
“This helps reduce competition between individuals, and gives the [fish-kickers] an advantage over those doing the same thing as everybody else.”
Before thinking about using a drone, it’s important to know the limitations and risks involved with filming wildlife.
McCarthy told National Geographic that he’s careful not to harass the dolphins by getting too close with his Mavic 2 drone, which he said he specifically chose because it’s designed to be relatively quiet. To film these videos, he maneuvered the drone about 152 to 182 metres away from the animals at a height of 30 metres or more and zoomed in using the GoPro, he says.
If the drone is close enough to be noticeable, “you ruin the opportunity and you annoy the dolphin, and that’s never good,” he says.
Indo-Pacific bottlenose dolphins swim off Jeju Island, South Korea.
PHOTOGRAPH BY BRIAN SKERRY, NAT GEO IMAGE COLLECTION
Harassing these and other aquatic animals is also against the law, a violation of the Marine Mammal Protection Act, which can result in fines or worse. When viewing dolphins or other animals from directly above, any type of “aircraft” is not supposed to go below a thousand feet, according to recommendations by the National Oceanic and Atmospheric Administration.
This specific altitude, however, comes from the aforementioned act, which was written in the early 1990s before drones were widely available. Meanwhile, according to the Federal Aviation Administration, drones cannot usually be flown higher than 120 metres so as to not interfere with helicopters and airplanes.
Thus, the use of drones to film wildlife falls into a bit of a legal gray area. Technically, researchers that use drones should apply for permits that allow them to briefly come closer than 120 metres.
Regardless, NOAA asks observers not to approach within 45 metres of animals in a boat, says Stacey Horstman, the agency’s bottlenose dolphin conservation coordinator.
“When viewing dolphins,” she says, “it is important to practice responsible viewing to prevent interrupting critical behaviours like feeding and maternal care.”
Lead Image: Bottlenose dolphins, seen here in the Bahamas with one Atlantic spotted dolphin, are known for kicking fish into the air before feeding on them.
PHOTOGRAPH BY BRIAN J. SKERRY, NAT GEO IMAGE COLLECTION