In October and November, as winter descends, dolphins begin their journey from the coastal waters off Virginia and North Carolina to the waters off northern Florida. On their way, they pass right by the Lowcountry.
That means that if you think you’ve been seeing more of them, you’re right.
November and December are peak months for migrating dolphins to pass through the coastal waters of the Lowcountry according to Wayne McFee, research wildlife biologist with the National Oceanic and Atmospheric Administration’s National Ocean Service.
“South Carolina is a way point for migratory animals,” said McFee. “Usually around November or December you’re going to start seeing larger numbers of dolphins as those animals start moving south, and then again in March and April as they move back.”
That means that right now you have a better chance of seeing dolphins off the Lowcountry coast.
They don’t all leave
Not all dolphins migrate, though, according to McFee. A certain segment of the coastal dolphin population stays put year round, looking to eat fish that swim into warmer coastal waters from estuarine systems as those systems grow cooler.
Dolphins who migrate during the winter and dolphins who don’t are biologically identical, McFee said. Still, they are divided by marine biologists into groups called stocks. The migratory stock heads south in the winter, while the resident stock stays put. The reasons for this are more behavioral than biological.
Different stocks of dolphin are not different species or even different breeds. The differences are simply in how they are grouped. McFee analogizes it to people from different countries or continents. There are people from North and South America, from Europe, Asia, Africa and Australia, but they’re all people, and coastal dolphins are just dolphins.
A stock called the South Carolina/Georgia resident stock makes its home along our shores.
How do you identify a resident?
If migratory and resident dolphins are biologically identical, how can you tell them apart?
According to McFee, resident dolphins can be identified using their dorsal fins. Researchers can take pictures of the fins and then compare them, he said.
Dorsal fins are unique to each dolphin and can be used like fingerprints.
“Doing that over time you can see certain animals that show up all year long, and those are residents,” said McFee
A third stock
A third stock of dolphin, known as the estuarine stock, makes their home in estuary streams and inlets. They are biologically identical to their coastal counterparts.
They don’t migrate, McFee said, but will move closer to warmer coastal waters as their own waters grow cooler.
“It’s likely prey related. So, they’re following prey for the most part,” said McFee. “In the winter time fish move out of the creeks into the sounds. They’re probably following them.”
There are far fewer estuarine dolphins than coastal ones according to McFee. Depending on the estuarine system, their numbers can range from as many as 600 in the Pamlico Sound in North Carolina to as few as 15 or 20 in the North Inlet and Winyah Bay in South Carolina.
Meanwhile, the number of dolphins who make their home along the coast is somewhere between 14,000 and 15,000. McFee said. That number includes both migratory and resident dolphins.
Adapting for winter
Dolphins don’t significantly change during the winter months, McFee said. They don’t hibernate and not all of them migrate.
The one thing that does happen is a trait that people might find identify with, especially around Thanksgiving and Christmas.
“In the winter their blubber layer gets thicker, and it tends to slim down in the summer,” said McFee.