Oceanography | Vol.35, No.1
from two to eight individuals, were
observed first being very active and tar-
geting fish in the middle of a channel
and nearby mudflats and mangroves,”
Jimenez and Alava write. “Then they
started approaching and chasing their
prey, trapping them against the mud-
banks, onto which at least one or two dol-
phins stranded each time and captured
the prey successfully.”
What, if any, signals the dolphins use to
coordinate their bow wave is unknown.
“No one has observed any definitive phys-
ical signal that always precedes strand
feeding, nor has any acoustic signal (whis-
tle or echolocation click) been reliably
associated with strand feeding,” Gubbins
states in The Dolphins of Hilton Head.
“There might be a producer-scrounger
effect: One dolphin initiates the rush, judg-
ing the correct time and place, and nearby
dolphins, with their quick reflexes, simply
follow the leader.”
Two dolphins strand feeding together
can make a bigger wave as they rush the
shore, beaching more fish.
At Captain Sam’s, the behavior hap-
pens every day. With bottlenose dolphins
weighing almost 227 kilograms and mullet
just centimeters long, the dolphins need
to eat a lot of fish. That translates to hours
of strand feeding.
“These dolphins are part of the
Charleston estuarine population,” says
Lauren Rust, executive director of the
Lowcountry Marine Mammal Network.
“They live in brackish waters year-round
and spend a majority of their time in small
areas—their home ranges.” That includes
the Kiawah and Stono Rivers. The Stono
flows southwest of Charleston, South
Carolina, its channel running between
the mainland and Wadmalaw Island and
Johns Island.
“We’ve identified six or seven dolphins
that strand feed pretty consistently in the
Kiawah River,” says Rust. The dolphins
usually feed in groups of three, “but I’ve
seen up to five,” Rust recalls, “and some-
times a single animal. Sometimes they
feed once or twice a day, other days up
to 37 times.”
In the Charleston area, strand feeding
happens year-round, but slows in winter
when mullets go offshore.
The best time to see strand feeding at
Captain Sam’s Spit, according to Feary, is
the four-hour period around low tide. Then
the Kiawah River’s main channel is at its
most shallow and most narrow. The water
level is below that of the marsh grasses,
so mullets are more visible to the dol-
phins. They strand feed on both sides of
the river, wherever there are mudbanks.
MEET THE STRAND
FEEDING DOLPHINS
To learn more about the dolphins’ unusual
feeding technique, the towns of Kiawah
and Seabrook are supporting a bottle-
nose dolphin monitoring program coordi-
nated by the Lowcountry Marine Mammal
Network. Rust has recruited more than
20 volunteers to monitor each side of
the Kiawah River at Captain Sam’s Spit
every day during the summer months,
and on weekends and holidays the rest
of the year.
Data collected so far show that there
are about 25 resident dolphins in the
Kiawah River, with more than a dozen
strand feeders.
Tagging and genetic studies have
revealed information about the diet,
age, sex, and health of the dolphins.
Researchers are using photos of the dol-
phins’ dorsal fins, comparing each fin to
those catalogued in a database, to track
the cetaceans over time. “Identifying
individuals allows us to learn about their
home ranges, family units, new calves,
and associations between individuals,”
Rust says. “That information is important
to understanding the health of the popu-
lation and its habitat.”
One mother dolphin in the Kiawah River,
KoKo, taught her calf, Kai, to strand feed.
“On some days,” says Rust, “the pair spent
more than 20% of its time in the inlet play-
ing, feeding, and likely nursing.” Biologists
have seen at least three mother-calf pairs
frequenting the area, so it may be a safe
place for mothers to bring their young.
A dolphin named Step “is one of the
longest- studied near Charleston, having
first been noted in 1995,” says Rust. “Since
then, she has been spotted more than
70 times in the Stono River.” Low Country
Marine Mammal Network staff members
have also seen her in the Kiawah River, and
have confirmed that she’s a strand feeder.
Researchers spotted her there with at
least five calves. Two, named High Scoops
and Rosie, are strand feeders themselves.
The calves are 16 years old and 11 years
old, respectively, and are independent
from Step. But they’ve been glimpsed