Bottlenose dolphins in the salt marshes of South Carolina and Georgia deliberately throw themselves onto mud banks at full speed, grab fish off the exposed shore, and slide back into the water. They land on their right side every time. Nobody can fully explain why.
The behavior is called strand feeding. It was first documented in 1971 by H. D. Hoese in the shallow tidal marshes of coastal Georgia. Along the East Coast, it occurs daily only in a roughly hundred-mile stretch of coastline from southern South Carolina through Georgia, nowhere else in the United States. The Lowcountry Marine Mammal Network says the region's pluff mud banks provide the ideal surface: firm enough to slide on, soft enough not to injure a 400-pound animal hitting the ground at speed.
The sequence starts at low tide. Two to six dolphins work together in a narrow tidal creek, using echolocation to track a school of mullet or menhaden through water so murky that nothing is visible from the surface. They circle, tighten, and herd the fish toward an exposed bank. When the school is pinned against the mud, the dolphins make a synchronized rush toward shore. The force of their bodies displacing water creates a bow wave that pushes the fish up and out of the creek onto the bank. The dolphins follow the wave. They surge out of the shallows and slide onto the mud, landing on their right sides, and grab the flopping fish off the ground
Every documented strand-feeding dolphin lands on its right side. The consistency is absolute and unexplained. One hypothesis is that the heart sits on the left side of the body, and landing right-side-down keeps the heart higher and under less compression during the impact. Another is that it relates to lateralized brain function, a preference for processing visual information through the left eye, which faces upward when the dolphin is on its right side. Whatever the reason, the behavior is so uniform that researchers can identify habitual strand feeders by a specific physical marker: the teeth on the right side of their jaws are worn down from repeated contact with abrasive mud. Strand feeders who have done this for years show severe erosion on the right jaw while the left jaw remains normal.
The risk is real. The dolphins must get back into the water within seconds or the mud holds them. The South Carolina Marine Mammal Stranding Network has linked some documented dolphin strandings in the Lowcountry directly to strand feeding gone wrong, particularly when boats or people approach during a feeding event and disrupt the dolphins' ability to slide back in. A controlled three-second beaching becomes a fatal one when something breaks the rhythm.
The behavior is learned. Calves watch their mothers strand feed and begin attempting it in their second or third year. Not all dolphins in the population learn it. Some individuals never strand feed, even though they share the same creeks with dolphins that do it every day. Researchers at Kiawah Island's Captain Sam's Inlet, one of the most closely observed strand-feeding sites, have documented individual dolphins that strand feed consistently across years and others that never attempt it, suggesting the technique passes through specific family lines rather than spreading uniformly through the population.
Wading birds figured it out too. Egrets, herons, and gulls gather along the banks where strand feeding occurs and wait. When the dolphins rush the shore and push fish onto the mud, the birds grab whatever the dolphins miss. A study from Bull Creek in Beaufort County, South Carolina, found that birds stole fish at about 15 percent of all strand-feeding events, though the actual losses to the dolphins were negligible.
It is the only hunting strategy in the dolphin's repertoire that involves leaving the ocean on purpose, catching food on land, and going back in.
Source: Hoese (1971) / South Carolina Aquarium / Lowcountry Marine Mammal Network / National Wildlife Federation / Oceanography (2021).
