Article for March - April 2012
Dinner Is Served!
by Paula Feldman
photos by Patricia Schaefer
Atlantic bottlenose dolphins are intelligent, social animals, traits they put to effective use while "strand feeding" in groups along the tidal creeks and marshes of the South Carolina Lowcountry.
Suddenly, an explosion of large, silvery fish! Dozens of helpless mullet fling themselves in every direction as Atlantic bottlenose dolphins, in an astonishingly synchronized display, launch themselves onto the sand to feast on their desperate prey. From a distance, you see only a frenzy of splashing, but if you are lucky enough to be standing on the shore in just the right place, you can see the pink underbellies or sleek backs of as many as six dolphins bursting in perfect alignment onto the shore like trained actors in a Sea World show, rather than the wild creatures they are. Then, in a flash, they are gone. The water, once roiled, is still.
Strand feeding, so-called because the prey fish are stranded on the shore, occurs along the East Coast only in South Carolina and Georgia, and has been reported in just a few other places around the world. A sophisticated form of hunting that involves teamwork, communication and expert timing, strand feeding testifies to the intelligence and ingenuity of these extraordinary marine mammals. Underwater, small groups of between two and six dolphins — sometimes more — herd fish tightly together into a "bait ball." Then, forming a line, the dolphins accelerate to create a bow wave that forces their prey onto shore as they, close behind, surge out of the water in unison.
While effective, strand feeding can also be a dangerous foraging technique; sometimes an overeager dolphin will venture too far onto the sand and risk being stranded itself. Although vigorous thrashing will usually allow it to work its way backward into the water, a dolphin that fails to return quickly risks internal injuries, sunburn or even death. There are other downsides as well. No one knows for certain why, but dolphins always strand feed on their right sides. Scientists suspect it has to do with physiology. Over time, the habit of taking fish on sand and mud abrades the teeth on the right side of their jaws. But the rewards must justify the hazards. Strand feeding in a group is mutually beneficial, the very definition of successful "teamwork."
"Two dolphins strand feeding together can make a bigger wave as they rush the shore, thus beaching more fish in the process," observed wildlife biologist Cara M. Gubbins in The Dolphins of Hilton Head: Their Natural History (University of S.C. Press, 2002). Biologists believe this cooperative behavior is learned, rather than innate, and Atlantic bottlenose dolphin mothers have been observed teaching their calves how to strand feed on banks steeper than those preferred by adults, allowing easier and safer re-entry into the water.
Kiawah Island resident Sophia McAllister recalls seeing a mother dolphin teaching a recently born calf the basics of strand feeding along a bank in Bohicket Creek. According to McAllister, despite its mother’s urgings, the still-awkward youngster was only successful in launching itself out of the water about every third try. Calves have never been reported strand feeding with a group of adults, in all likelihood because of the complexity of the coordinated assault and the possibility of being crushed by larger animals.
Dolphins adjust their foraging techniques to their prey species and to their environment, so strand feeding is not always an appropriate tactic. They have many innovative hunting strategies; only some involve cooperative behavior. Most often, dolphins hunt prey independently of one another, even if they are traveling in a group. They take advantage of water currents and steep shorelines to help them herd fish and limit their avenues for escape. Echolocation, a biological sonar adaptation, helps them find prey in murky water, at night, or when feeding on bottom-dwelling species that burrow beneath the sand. When they are pursuing burrowing species in shallow water, you might see their flukes held vertically, waving back and forth.
Sometimes, in winter and spring, when fish swim near the water's surface, individual dolphins might circle them — a technique which Gubbins terms "pinwheeling." Positioned on its side with one pectoral fin out of the water, the dolphin traps fish by swimming in a circle of ever tightening circumference, before it goes in for the kill. Much of the dolphin's body may be visible, and the rapid whirling of fin, fluke and splashing water can give the false impression that there is more than one dolphin feeding. Sometimes two or more dolphins work cooperatively to encircle a school of fish, herd them close together, and then take turns rushing through the tightly compacted school to snatch as many fish as they can.
According to Shelley Dearhart, an educator and biologist at the South Carolina Aquarium, Charleston-area dolphins have been observed "tail whacking," a strategy whereby a dolphin uses its fluke to hit a fish and then eats it while the prey is stunned. "Mud ring feeding" is another ingenious hunting strategy, says Dearhart, which involves a group of dolphins encircling a school of fish in the shallows and slapping their flukes against the mud floor, to create a ring of opaque water. Fish become disoriented and jump over the mud ring right into the waiting jaws of dolphins strategically positioned outside the ring. In another hunting behavior called "kerplunking," a dolphin moves its fluke through shallow sea grass beds, startling fish out of their hiding places, where they become "an easy catch," says Dearhart.
But by far the most awe-inspiring and unforgettable of all bottlenose dolphins' hunting behavior is strand feeding. To see it, ask the locals along the South Carolina or Georgia coast about likely spots, book a trip on a dolphin-watching expedition or follow the birds. Small flocks of pelicans looking for an easy meal may lead you to the dolphins' favorite fishing spots. If you are a careful observer, the dolphins, themselves, may clue you in. As they are preparing to strand feed, they have a tendency to raise their eyes out of the water to check out the territory on shore. Look for strand feeding at low tide (generally within three hours on either side) along exposed mud banks. Dolphins choose their locale carefully to avoid oyster beds, with their razor sharp shells, and to maximize their ability to corral a school of fish. The behavior takes place year round, during both day and night, but it seems more prevalent when mullet are plentiful. September and October are particularly active months.
"You tend to see a leader dolphin, kind of rounding everyone up, communicating with the rest of the herd," says Jake Feary, a naturalist who leads dolphin-watching boat and kayak trips for Kiawah Island Resort. "A couple of what I call worker dolphins are the ones really actively gathering the bait fish up and then you’ve got a lookout dolphin. That's the one that pops his head out of the water and scans the horizon. All of a sudden they all go down and then burst up all at one time on that school of fish."
One instance of strand feeding is often followed by another within minutes. The dolphins re-group, herd more fish and strand feed once more. Sometimes, they use the same location over and over again. At other times, they may move from one side of a tidal creek to another or feed at intervals along one bank.
Adopt a Wild Dolphin!
You can help support the development of marine mammal education and protection programs through a new program at the South Carolina Aquarium. In addition to other benefits, you will receive an "adoption certificate" with a photo of the distinctive dorsal fin of a known Charleston area wild dolphin. For more information, visit the scaquarium.org website. (Click on "Adopt an Animal" under the "Support the Aquarium" tab.)
If you are lucky enough to see strand feeding taking place, try to maintain a distance of at least fifty yards and remain as still as possible. The Federal Marine Mammal Protection Act makes it illegal for anyone to interfere with or discourage dolphins’ natural behaviors. If you are patient, you might be rewarded with an experience you will never forget, for its beauty, exuberance, efficiency and sheer power.
Paula R. Feldman holds the C. Wallace Martin chair in English and the Louise Fry Scudder Chair in Liberal Arts at the University of South Carolina and is an associate faculty member in USC’s School of the Earth, Ocean and Environment.
The photographs accompanying this article were contributed by Charleston-area photographer Patricia Schaefer, who has spent many hours observing and photographing dolphins on Seabrook Island and elsewhere on the South Carolina coast. Some images appeared previously in her self-published book, Dolphin Strand Feeding, available from the Blurb.com online bookstore. To see more of Schaefer’s stunning photos documenting the people and places of the Lowcountry, visit her photography website http://patriciapschaefer.com.
© 2012 South Carolina Wildlife Magazine, March - April 2012 - www.scwildlife.com