Research Update: Dolphins give birth in Potomac River and other discoveries

A day with the Potomac River dolphins (and the experts studying them)

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Willis Kliefoth, Potomac Conservancy Communications Manager

On Friday, September 20th, much of the environmental community is skipping work to march in the Global Climate Strike – but good weather for dolphin research must be seized!

That’s why Ann-Marie Jacoby, Assistant Director of the Potomac-Chesapeake Dolphin Project (PCDP), and her two research assistants are gearing up their skiff, the Georgetown University “Ahoya”, at 7:30 am to survey their 37 sq. km research area in the lower Potomac River for the bottlenose dolphins they’ve been seeing all summer. I’m also along for the ride, to hear what they’ve discovered so far.

The georgetown “Ahoya” at smith point harbor in reedville, va.

The georgetown “Ahoya” at smith point harbor in reedville, va.

It’s a calm day in Reedville, VA, a town on the dividing line between the Potomac and Chesapeake Bay and PCDP’s summer research base. Conditions are excellent to spot dolphins - if they’re there. Since the PCDP started in 2015, this is the first year they’ve conducted intensive sampling in September and October. The winds of hurricane season have kept the Ahoya parked at the marina many days in a row and the water temperature has dropped 3°C since the team was last out. How long the dolphins stay in the river before returning to the Atlantic Ocean for the winter is one of many, many questions Jacoby and PCDP Director, Dr. Janet Mann, are attempting to answer about this understudied population.

A Birth in the River!

The Tiny FIn of Gwendolyn Mink! Photo Courtesy of THE PCDP.

The Tiny FIn of Gwendolyn Mink! Photo Courtesy of THE PCDP.

The dolphins made headlines in June when Potomac Conservancy invited the public to name two of the dolphins that PCDP has seen returning to the river summer after summer. “Mac” and “Chessie” were the winning entries (though of course the dolphins, who use their own “signature whistles”, don’t  recognize these names).

Now, the population is generating a more scientifically significant headline: In August, one of them gave birth in the Potomac River. Why is this discovery “beyond exciting” to the team? It’s only the second ever wild birth of a bottlenose dolphin in the scientific literature.

 

Jacoby was following a group of about 50 dolphins in the Potomac River near Lewisetta, Virginia, when she noticed a cloud of blood and shortly afterward a small calf with a “slightly bent and wobbly fin” surfaced and then swam alongside its mother. (At birth, calves’ fins are typically completely flopped over to one side).

She is careful to emphasize that what she witnessed is evidence of a birth, as it's difficult to know definitively whether the birth happened right then or very recently. Nevertheless, she says that the newborn was tiny enough and far enough up the river that she feels certain it was born in the Potomac – and that other dolphins are giving birth in the Potomac too!

Other than Mac and Chessie, PCDP names all the individual dolphins they identify after  political figures. The mother of the newborn is  Patsy Mink, after the former Hawaiian Congresswoman who co-authored the Title IX Amendment of the Higher Education Act. Her calf is named Gwendolyn, after Mink’s  daughter.

Creatures with Charisma

As we travel upstream along the Virginia coast, Jacoby tells me about the birth, how the Potomac dolphins behave differently than other populations, and everything they suspect about why dolphins come to the river. Then, at 8:30 am – fins on the horizon! Soon we’re amid a group of 25-40 dolphins swimming swiftly down river.

 

Researchers use photo catalogues of unique dorsal fins to track individuals, but Jacoby knows many of the resident animals (i.e. the dolphins that seem to spend most of the summer in the region, rather than the hundreds that visit occasionally) by sight. “There’s Chessie!” she yells. We don’t see Patsy, Gwendolyn, or Mac today, but Chessie is with Frederick Douglass, who seems to be his constant friend (it’s common for adult males to form bonds). Many of the females have babies riding in “calf position” which reduces drag. Occasionally, the babies do leap from the water.

It soon becomes clear as the chilly September water how much Jacoby cares about her research subjects. Though a self-described “horse and cat girl” when she started in Dr. Mann’s lab as an undergraduate at Georgetown, Jacoby says the dolphins won her over with their evident intelligence and clearly complex social lives. It’s hard to believe anyone wouldn’t be charmed by these charismatic creatures. Though she is judicious and scientifically rigorous in discussing her research, Jacoby coos to the babies that swim by, responds to their whistles as if in conversation, and waves away the adults that attempt to “bow-ride” the Ahoya.

Dolphins at risk?

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Jacoby photographs dorsal fins for the PCDP’s growing catalogue of potomac river dolphins.

Jacoby photographs dorsal fins for the PCDP’s growing catalogue of potomac river dolphins.

She’s right to be cautious. Through her camera lens, she spots a small calf with several open wounds – slashes on its side and a hole on its peduncle (tail). The injuries could be from boats that get too close (unless you have a research permit from NOAA, do not approach marine mammals within 50 yards) or from discarded fishing gear – a common plastic litter item found up and down the river.

Though there’s nothing we can directly do for the calf, we can all help the population at large. Firstly, the research of the PCDP can be used to advocate for better local protections for dolphins and the fish they eat. Funding can help the team continue their work and investigate exciting discoveries (for example, Jacoby thinks that the Potomac dolphins may have a unique, coordinated feeding behavior like the “silt-netting” strategy of Florida dolphins).

Secondly, working to eliminate pollution upstream, including dangerous plastics, will help keep the dolphins’ downstream nursery safe and clean.

For those of us that live upriver, it can be hard to imagine the Potomac as a playground and home for animals we associate with the open ocean. But as we motor between the Virginia and Maryland coasts in the direction of DC, the blue-green water looks awfully familiar – and it’s full of dolphins.

 
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Help give Potomac dolphins a pollution-free place to raise their babies and support dolphin research:


 

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