Author: Philip Miller

I had my first shift of the year last week. Going to our beach is always a pleasure, but when I have the opportunity to see wild dolphins and their unique ’Strand Feeding’ behavior, I also feel so very fortunate.

Strand Feeding is when dolphins herd fish up onto the beach by making a wave and then thrust at least half of their bodies up onto the sand, essentially stranding themselves, to catch and eat just one fish. They catch a fish and then quickly return to the water. Usually a group of dolphins, two to five, do this together. The result is a lot of splashing, fish flopping, some noise, a meal for the dolphins and some fascinating viewing. I saw this happen three times during my shift last week.

There are only a handful of places in the world where dolphins Strand Feed. Feeding this way is only one of the methods used to catch fish and is a learned behavior. Young dolphins are taught by their mother if she is one of those who feed this way. After birth, the calf will nurse for more than a year and then typically stays with their mother for three to six years. During that time the calf will learn to Strand Feed.

There are more than 300 dolphins in low country waters around Charleston. Of those, only a few Strand Feed. In the immediate area around Seabrook and Kiawah we have documented only two or three Strand Feeding females. If a mother is harassed or threatened by dogs or people, either in boats or on the beach, she is likely not going to strand feed and may not teach her calf to do so. Since female dolphins calve only once every three or four years, it would not take long for this learned behavior to disappear should mothers stop teaching their calves for any reason.

A group of Seabrook residents, myself included, volunteer to spend up to 4 hours (2 hours before and after low tide) on the beach at the Kiawah River inlet twice a month throughout the spring, summer and fall months. A similar group from Kiawah are on the opposite side of the inlet. We are there to educate people about the dolphins and to record data for scientific research. Lowcountry Marine Mammal Network (LMMN), lead by Lauren Rust, coordinates our activities and teaches us about the dolphins.

I became involved last year after watching a very disturbing Youtube video where someone tried to jump onto the dolphins while they were Strand Feeding. The incident occurred on the same stretch of beach where we now serve as volunteers. For me, if my presence deters such incidents from ever happening again, then it is well worth my time.

If you make the mile+ walk from board walk #1 to the Kiawah River inlet, also known as the ‘Spit’, and you are fortunate enough to see dolphins, please stand back at least 15 yards and do not try to get into the water with them. They may swim near you or even Strand Feed nearby, seemingly oblivious to your presence. But they know you are there and are just as likely to move on to another area or stop feeding altogether. It is not worth the risk of losing this behavior to future generations for a few pictures today. (Besides, with the cameras today and even our phones, the quality and zoom capability makes it very easy to get great pictures from 15 yards away.) Please give the dolphins some space so my grandchildren and yours will be able to see Strand Feeding many years from now.

While you are there a volunteer may approach to encourage you to view from a distance. Our purpose is only to teach people about this rare and wonderful gift we have on Seabrook and Kiawah Islands. If you would rather be left alone, just politely let us know and we will move on.

We hope you have a chance to see these wonderful animals and their unique behavior. It is all too easy to take these sightings for granted. Not long ago I was reminded how special our island is when friends from Canada were visiting and became so excited to see dolphins just a few yards away in the water. Unfortunately, we did not see any Strand Feeding that day. I can only imagine what their reaction would have been.

Here are a few facts about dolphins. Should you encounter a volunteer, I am sure they can share more with you. Just ask.

• Dolphins only strand on their right side.
• A dolphin can swim at speeds of over 30km/hour and dive as deep as 250m.
• They weigh an average of 660 pounds and can reach a length of just over 13 feet.
• A dolphin can hold its breath for 10-15 minutes.
• Bottlenose dolphins, the type we have here at Seabrook, live typically between 30 and 50 years. Dolphins in captivity live much shorter lives than wild dolphins.
• The dolphins in our area Strand Feed at almost anytime, however, the prime time is about an hour before and after low-tide.
• It is a good bet that you will see them in the Kiawah River inlet between Seabrook Island and Seabrook Island.

If you witness dolphins being harassed you should contact either the beach patrol (843-718-6083) or security (843-768-6641). The US Government has passed the Marine Mammal Protection Act which makes it illegal to harass or interfere with the dolphins. Fines can be as much as $100,000. You can learn more about the act here: https://www.fisheries.noaa.gov/topic/laws-policies#marine-mammal-protection-act

Article by: Philip Miller

Credit for the images to Lowcountry Marine Mammal Network, Lauren Rust

How many Charleston individuals? 

Based on our mark-recapture estimates from 2004-06, between 300-400 for CES stock (Charleston Estuarine Stock).

What is their range? 

Depends on sex and area affiliation.  Most females tend to have smaller ranges encompassing a couple rivers and the smaller associated creeks.  Some males can be seen throughout most of stock, from Charleston Harbor to North Edisto.  

Which river(s) are most popular, why?

Stono appears to be the most popular, followed by the Folly and North Edisto. The Ashley, Cooper, and Wando Rivers are popular depending on the time of year. The popular areas are probably due to amount or prey, fewer boats, and proximity to coast.

Male/female ratio? 

According to biopsies, the estimate is around 186 males to 107 females (biased since biopsies always favor males).  According to sightings and research, the estimate is 217 males to 411 females (biased since females are easier to detect (presence of calf) vs males).

Approximately how many births per year? 

Good consistent records from 2005-2009 indicate an average of 35 births/year.

Oldest individuals? 

Animal FB864 was recently spotted in the harbor and is recorded as 36 yrs old. His age was confirmed because he was captured and tagged in the early 2000’s. A tooth was pulled to age him. Oldest known CES dolphins (assuming he is still alive, last seen in 2009) is FB894 who would be 42.  Oldest female (assuming she is still alive, last seen in 2009) is FB805 who would be 41.

Alliances? Male/male? Females/females and calves? 

Yes, male pairs are prevalent.  We’ve noted dozens of them here.  Possibly had a three male “alliance” but not seen together with same frequency as pairs.  Likely a pair and a wanna-be male.  Females tend to stick together especially with calves. Females are known to “babysit” other female calves.

How do they use the harbor-spatially and behaviorally? 

Can be seen throughout the harbor with hot spot behind Fort Sumter.

Main source of food in Charleston Harbor? 

Based on Pate and McFee from 2012, Star Drum was the most abundant prey species for SC dolphins, with Brief Squid the most frequently observed prey item (all from stranded dolphins throughout the state).

What threats do the bottlenose dolphins in the Charleston Harbor face?

There are documented reports of fishery-related mortality and serious injury to the population related to the blue crab pot fishery. During a review of bottlenose dolphin strandings in South Carolina from 1992 to 2003, it was found that 24% of the 42 entanglements of dolphins were associated with crab pots and 19% of entanglements deemed probable to be from interactions with crab pots. Between 2003 and 2007, 12 bottlenose dolphins displayed evidence of being entangled in crab pots. In addition, standings in South Carolina have been greater near urban areas and agricultural input, suggesting negative health effects to bottlenose dolphins in these areas. Reduced immune response has been reported due to an increase in concentrations of several containments, such as mercury, copper, manganese, lead, uranium, and zinc.
Some of the highest concentrations of polychlorinated biphenyls (PCBs) and DDT reported for cetaceans have been founded in the blubber of bottlenose dolphins from the Charleston area.
https://www.nefsc.noaa.gov/publications/tm/tm219/441_BODO_CES.pdf

Do they interact with crab pots a lot? 

Based on strandings and entanglements, they appear to. Dolphins have been seen tugging on crab pot lines.

What makes them unique? 

Strand feeding is probably the most unique feature of CES dolphins, which is seen mostly in SRE (Stono River Estuary). Strand feeding is a unique feeding behavior where dolphins corral fish near sandy shores then create a large wave to push the fish and themselves onto shore to eat the fish before returning to the water. Strand feeding has only been documented in South Carolina and Georgia in the USA. It occurs in several rivers around Charleston. Not all dolphins strand feed and those that do use strand feeding as a secondary feeding behavior. It’s a learned behavior from mom. Dolphins only strand on their right side and typically in small groups (1-3 animals).

Here are some general questions and their answers to help the outreach learn more about Bottlenose Dolphins.

How long is their gestation period?

12 months. The calf will nurse for more than a year and then typically stays with their mother for three to six years.

How fast can they swim?

They can reach speeds of over 30km/hour and dive as deep as 250m.

How much do they weigh? How long are they?

An average of 660 pounds. They can reach a length of just over 13 feet.

What are their different fins used for?

The fluke (tail fin) is used to propel through the water and the pectoral fins (on each side) provide the direction control and the dorsal fin (on top) provides stability.

Do dolphins travel in groups?

Yes. They travel in groups, called ‘pods’. Although, adult males mostly travel alone or with smaller groups and then join the pod for a short time.

What is echolocation?

Bottlenose dolphins produce high-pitched clicks to navigate and find food. When the clicking sound hits an object, it bounces back to the dolphin as echoes, which allows the dolphins to determine the location, size, shape of the object.

What do bottlenose dolphins eat?

They are carnivores so they feed on mostly fish, but can also eat shrimp, crab, or squid. Locally, they eat Star Drum, Menhaden and Mullet.

How long can a dolphin hold its breath for?

10-15 minutes. Dolphins breathe through their blowhole; a muscular flap covers their blowhole while they are underwater.

How do dolphins sleep?

They float just beneath the surface of the water and small movements of their tail flukes propel them to the surface so they can take breaths while sleeping.

Do dolphins mate for life?

Dolphins do not mate for life. Dolphins mate for reasons other than reproductions, similar to humans and when food is scarce, they may not mate at all to focus on survival.

How long do bottlenose dolphins live?

Typically between 30 and 50 years. Dolphins in captivity live much shorter lives than wild dolphins.

What protections are in place to protect them?

Dolphins face various threats around the world, including direct kills, entanglements in fishing gear, live captures for captivity, habitat alteration, boat collisions, and the negative effects of pollution. Fortunately, bottlenose dolphins are protected in U.S. waters under the Marine Mammal Protection Act, which makes it illegal to “take” marine mammals without a permit. A “take” includes harassment, feeding, hunting, capturing, collection, or killing any marine mammal.