Researchers have counted well over 1,000 dolphins in the Potomac River.

Researchers have counted well over 1,000 dolphins in the Potomac River.

Though the Potomac River is indeed cleaner than it was half a century ago, local officials are still not convinced it’s safe to swim in.

So, what does it mean now that dolphins are flocking to the tributary?

We hear from one of the world’s foremost dolphin experts and the president of a local conservancy.

Produced by Julie Depenbrock


  • Janet Mann Director, Potomac-Chesapeake Dolphin Project; Professor of Biology and Psychology, Georgetown University
  • Hedrick Belin President, Potomac Conservancy; @TheNationsRiver.

Potomac-Chesapeake Dolphin Project (NMFS Permit No. 19403)


  • 12:32:15

    KOJO NNAMDIThe Potomac is indeed cleaner than it was half a century ago when President Lyndon Johnson referred to the river as a national disgrace. But local officials are still not convinced the Chesapeake Bay tributary is safe to swim in. So, what does it mean now that bottlenose dolphins are swimming, mating and giving birth in the Potomac River? Are dolphin sightings a harbinger of health, or just another alarming effect of global warming? What do you think? Joining me in studio is Dr. Janet Mann, director of the Potomac-Chesapeake Dolphin Project, and a professor of biology and psychology at Georgetown University. Janet Mann, thank you for joining us.

  • 12:32:52

    JANET MANNThank you. Glad to be here.

  • 12:32:53

    NNAMDIYou have studied dolphins all over the world, for more than three decades. When did you first realize the common bottlenose dolphins are right here in your own backyard?

  • 12:33:03

    MANNWell, I'd heard that they were here in the 1800s, but I didn't know that there were dolphins here until we bought a little cottage on the lower Potomac. And the day we closed on the house...

  • 12:33:14

    NNAMDIIt took a lot of persuasion on your husband's part, too, to get you to participate. (laugh)

  • 12:33:17

    MANNYes. I didn't really want to get a little cottage on the Potomac, and he was trying to get me away from my work, was the irony, because I'm a workaholic. And so he was actually trying to get me away from dolphin research. And the day we closed on the house, there were dolphins swimming in the backyard.

  • 12:33:33

    NNAMDIWhoa. They heard you were coming. (laugh) Tell us more about the Potomac-Chesapeake Dolphin Project.

  • 12:33:41

    MANNSo, that was back in 2012. And then in 2013 to 2015, there was actually a Marbella virus outbreak, which apparently started in the Potomac-Chesapeake. So, there was actually a mass mortality of dolphins that spread along the Eastern Seaboard of the U.S. And so that was what motivated starting the project in 2015. We were still seeing dolphins, but then we started the project in 2015 so that we could better monitor the population that was coming in, and hopefully understand something about the population structure, so that if something else like this happened again, we'd be better prepared.

  • 12:34:21

    NNAMDIHow many dolphins have been identified in the Potomac, and why are they called common bottlenose dolphins?

  • 12:34:28

    MANNWell, the first part is now we've seen over 1,200, (laugh) actually, in the Potomac.

  • 12:34:36

    NNAMDIThey're taking over.

  • 12:34:37

    MANNYeah. So, there's probably thousands in the Potomac-Chesapeake. And we have been seeing about 2 to 300 more individuals per year. So, the numbers are still going up in terms of who we can identify. So, I should say that we identify individuals by the dorsal fins, which I can talk about. But they're called common bottlenose dolphins because they are, in fact, common globally. The genus name is Tursiops truncates, and they're found, you know, from cold waters in northern Scotland all the way to the tropics. So, they have quite a range.

  • 12:35:19

    NNAMDIThese dolphins have some unusual names. What's the purpose behind the naming, and what are some of these dolphins called?

  • 12:35:27

    MANN(laugh) We name them after leaders, social, political and environmental leaders, also abolitionists and suffragists. So, we started with presidents, vice-presidents, founding fathers. And then we've moved to people in Congress and Supreme Court justices and a range of people that we've named the dolphins after.

  • 12:35:53

    NNAMDISo, you're going to have to dig up thousands and thousands more names (laugh) as this population seems to expand over time. But then of course there's no shortage of politicians and public figures here in Washington. So...

  • 12:36:06

    MANNSo, if they have an offspring, then we're naming the offspring after the mother, because we don't know who the fathers are. So, we do have, you know, Chelsea Clinton, and so on. So, they're not all political leaders, so to speak, because we're also naming the offspring.

  • 12:36:25

    NNAMDIAlso joining us in studio is Hedrick Belin. He is the director of Potomac Conservancy, a nonprofit advocating for a cleaner Potomac. Hedrick, good to see you again.

  • 12:36:35

    HEDRICK BELINAlways good to be on the show, Kojo. Thanks for having me.

  • 12:36:37

    NNAMDII'd like to ask you, as president of the Potomac Conservancy -- it's a nonprofit focused on making the river cleaner -- I'm wondering what the presence of dolphins in the Potomac says about the health of the river itself.

  • 12:36:51

    BELINWell, it's a great question, and I think we're seeing the Potomac River making a comeback, but that progress is threatened. And I think the challenge we face is: how do we continue to keep momentum up so we can achieve a fishable swimmable Potomac, one that provides the best home possible for all sorts of wildlife, including dolphins? And, at the end of the day, clean water is good for people, good for native fish and good for dolphins.

  • 12:37:17

    NNAMDISame question to you, Janet: what does this say about the health of the Potomac?

  • 12:37:21

    MANNWell, the dolphins wouldn't be coming here if there wasn't something to eat. (laugh) They have to eat a lot of fish, so that means that the fish populations have to be healthy. And because we're seeing such large groups, at times, we sometimes see a lone dolphin, but sometimes the groups range up to 200 animals. So, that means they have to be big schools of fish.

  • 12:37:41

    NNAMDIHedrick, what is the current state of the Potomac River's health, overall?

  • 12:37:48

    BELINWell, you know, we've seen a lot of progress over the last 50 years, thanks to a lot of hard work that has brought the Potomac back from being a toxic dump to a playground for dolphins and other wildlife. But there certainly are some problems. We can't take the progress we've made over the last 50 years for granted.

  • 12:38:06

    BELINAnd there certainly are a number of threats on the horizon that could undo all this wonderful progress we've made. So, we're going to have to continue to stay focused on how we stop pollution, plastics and other wastes from flowing into our local rivers and streams, and ultimately downstream from here to where the dolphins have been seen, and then on into the Chesapeake Bay, as well.

  • 12:38:30

    NNAMDIWell, back in 2011, the Potomac got a D grade, and last report, it was up to a B. What in particular is threatening the river's progress towards making an A grade?

  • 12:38:42

    BELINYeah, I mean, I think we've seen some really positive trends in the report over the last decade in terms of pollution levels decreasing and fish populations that are important to dolphins rebounding. That also means bald eagles and other wildlife are coming back.

  • 12:38:58

    BELINBut two or three threats that I wanted to highlight today. One, when it comes to achieving clean water, public enemy number one is polluted runoff. Each rainstorm we have here in the metro region delivers a toxic stew of fertilizer, street oil, plastics in our local streams. We're also compounding that, or exasperating polluted runoff is the climate crisis that we're experiencing. And the effects are real.

  • 12:39:26

    BELINYou know, we saw, this past summer, almost four inches of rain fell in less than an hour. And so, again, delivering all sorts of pollution. Many of your listeners probably remember seeing images of cars on Canal Road flooded, or suddenly waterfalls appearing in Metro stations because of all that excess water.

  • 12:39:47

    BELINAnd then I think the third big threat we're seeing right now relates to the Trump Administration's Environmental Protection Agency, which is seeking to remove a lot of protections that have played a major role through the Clean Water Act over the last 50 years, cleaning up these rivers and streams. And they're looking at how to remove protections for critical, ecologically important streams, creeks, wetlands that all have been instrumental in delivering a stronger grade for the Potomac River's health.

  • 12:40:18

    NNAMDIHere now is Stella, on the eastern shore in Maryland. Stella, you're on the air. Go ahead, please.

  • 12:40:24

    STELLA (CALLER_Okay, hi. It's a great topic. Thank you for taking my call. I live over here, but I commute to D.C. on a regular basis, because I'm a teaching assistant there. And I was wondering if callers had a suggestion where people could safely maybe have a good likelihood of observing the dolphins. That will help people to really connect with seeing them there, and continue the work that's been done to make the Potomac, you know, a much better place.

  • 12:40:53

    NNAMDIJanet Mann?

  • 12:40:54

    MANNWell, the dolphins don't tell us where they're going to be, (laugh) unfortunately. We are working on that, but they do really like the lower Potomac. And we know they're going halfway up the tidal (laugh) Potomac. So, they do like the mouths of rivers quite a lot, because those tend to be highly productive areas. But for the rest of the Chesapeake and some -- but we just don't know. People do call in sightings. There is a place to upload people's sightings of dolphins, but that tells us where the people are more than where the dolphins are.

  • 12:41:33

    NNAMDIGot to take a short break. When we come back, we'll be continuing this conversation about dolphins in the Potomac and what that implies. I'm Kojo Nnamdi.

  • 12:42:21

    NNAMDIWelcome back to our conversation about dolphins in the Potomac. We're talking with Dr. Janet Mann, director of the Potomac-Chesapeake Dolphin Project and a professor of biology and psychology at Georgetown University. And Hedrick Belin, he is the director of the Potomac Conservancy, a nonprofit advocating for a cleaner Potomac.

  • 12:42:37

    MANNAnd we got an email from Michael, who says: as the executive director of the Interstate Commission on the Potomac River Basin, I am heartened by the appearance of dolphins in the Potomac River. I would like to ask the panel their opinion on whether they think that their appearance is due to climate change. For example, do you think that temperature changes in the bay maybe driving the dolphins or their food sources up the tributaries of the bay? Janet Mann?

  • 12:43:05

    MANNYes, well, it's hard to say. The dolphins were here in the 1800s, so I do know that they were there before many of the effects of climate change had been felt. And there are changes that will come with climate change, like it being warmer for longer. So, for example, we're still seeing quite a lot of dolphins, and in earlier years, it's been warm. So, they might stay for longer, for example, than historically.

  • 12:43:36

    NNAMDIHere now is Kevin, who is on the water, headed for Cape May. Kevin, you're on the air. Go ahead, please.

  • 12:43:45

    KEVINOh, hey, Kojo. How are you?

  • 12:43:46

    NNAMDII'm doing well.

  • 12:43:48

    KEVINI just wanted to say, you know, my wife and I live on a sailboat, and we sailed up from Florida up to Main this summer. And, during the spring, we were going up the Potomac after a particularly heavy rainstorm. And I noticed a lot of flotsam and jetsam in the water, you know, giant logs, trees and plastic debris. And, you know, I'm happy to see that there's dolphins.

  • 12:44:09

    KEVINWe've seen tons of dolphins all up and down the Atlantic coast. But I'm curious if there's any plans in the works to put one of those river-cleaning boats into service in the Potomac. And, you know, they could grab all that stuff coming off the tributaries, and they scoop it up into a hopper barge behind the boat. And you could put one of those into service after a heavy rain, and I think it'd do a lot to get rid of a lot of that debris before it heads further into the Chesapeake watershed.

  • 12:44:38

    NNAMDIHedrick Belin?

  • 12:44:39

    BELINYeah, it's a great question, and certainly, in these intense storms they deliver all sorts of amazingly large stuff like trees and stumps, as well as a lot of plastic bottles. And so I think there are two solutions that are already underway. In the case of one of the big tributaries, the Anacostia, they have a number of filters called trash traps. They capture, as the caller noted, a lot of debris before it goes into the Potomac.

  • 12:45:03

    BELINIn the D.C. Metro area, D.C. Water has a couple of boats that the caller described, that do try to pick up big stuff. But the challenge is, this is a 15,000 square mile watershed and, you know, there are a ton of tributaries. And with increasingly intense storms, more and more debris is being delivered to the river. And as you get further down from D.C., the river gets actually quite wide. Down near where the dolphins are, it's five to seven miles wide. So, in the Anacostia, it works. In the Potomac, it's too big a river.

  • 12:45:41

    NNAMDII'd like to talk about the coal pollution in the Potomac, in particular the report from a state inspector that a coal-fired plant was violating environmental regulations as coal ash seeped into the Potomac. How common is this kind of contamination?

  • 12:45:54

    BELINWell, I think it's a couple things. Certainly, thanks to the Clean Water Act and a number of its provisions, as I said earlier, over the last 50 years, the number of industrial sites that have pipes that used to discharge all sorts of stuff into our rivers and streams around the country have been turned off or clamped down on. There still are always going to be some bad actors that don't follow the right practices, and so we need to be ever vigilant.

  • 12:46:19

    BELINAnd that's why also doing things to both cut back the efficacy of the Clean Water Act, as well as cut back, in some cases, propose eliminating funding for the Chesapeake Bay cleanup is really troubling by this current administration. But, overall, we've seen a dramatic decrease in pollution coming out of industrial pipes, but there's still work to do. And that's why the Clean Water Act provides the mechanisms to hold polluters accountable.

  • 12:46:49

    NNAMDIJanet, what does this mean for the population of dolphins in the Potomac? I've been reading about lesions on some of the dolphins.

  • 12:46:55

    MANNYes. Well, two things. One is they do go up that far, to where that plant is. It's near the 301 bridge, and we know that dolphins have been documented regularly going up there. And we've had reports of even hundreds of dolphins in that area. So, it's of concern, because of the heavy metals that are being dumped, you know, in the Potomac. Because the dolphins can accumulate that through the fish, and it gets stored in their blubber.

  • 12:47:24

    MANNThey do have a number of lesions. The other site I work at is Unesco World Heritage Site. It's much cleaner, and we just don 't see lesions routinely on the animals. So, those lesions are a sign that something is wrong, and that's something we're working on. I have a team of students who are looking at all the photographs we have of the lesions and trying to understand the long term prospects for those animals.

  • 12:47:50

    NNAMDIHere's Carol in Lottsburg, Virginia. Carol, you're turn.

  • 12:47:54

    CAROLYes, hi. I bought a home in Lottsburg, Virginia, which is the northern neck across the bay from the eastern shore. About 10 years ago -- I'm on Green Creek, which, at the mouth, dumps into the Potomac. We see dolphins all the time off our dock. We swim around that area of the Potomac. It's actually, some days, as much fun as the Caribbean. It's clear, it's beautiful. We see skates and all kinds of wildlife.

  • 12:48:29

    CAROLAnd the thought that someone could change the Clean Water Act at this point, my biggest concern is development in the area that I live along the waterways of converting these farms to high density townhouses, etcetera. How is the Potomac Association Conservancy dealing with these guidelines that we're going to ask developers to follow relative to seawalls and things that are good for the Potomac?

  • 12:49:01


  • 12:49:02

    BELINWell, two thoughts, and it's a great question. I think, you know, most of those land use decisions are made at the local level or the county level. Virginia's a little different in that some of the power is down in Richmond in terms of making land use decisions, compared to Montgomery County. So, we're going to need to make sure that we've, one, got strong rules and regulations on the books in terms of river-friendly development and protecting the environment, protecting clean water.

  • 12:49:25

    BELINAnd, you know, I think it's important for anyone that's in Virginia, like the caller, to remember that there is an election in less than a month, statewide election for all the delegates and senators. And the results are going to have implications for clean water decisions in Richmond over the next four years. And the dolphins that you described living in your Virginia waters are great, but they can't vote. So, we need you to vote for the dolphins and help improve environmentally friendly, river-friendly General Assembly down in Richmond.

  • 12:49:59

    NNAMDIGot an email from Lawrence, who says: we live on the Magothy River just north of Annapolis. We sighted 20 to 30 at the Bay Bridge this summer while out with my wife's sister, niece and grand niece who are visiting from Florida. There is an application called Chesapeake Dolphin Watch where boaters can record sightings. If you look, you can see quite a lot, extending up to and above the Bay Bridge. And, Janet Mann, in August, researchers witnessed a wild dolphin birth. Why is that so significant?

  • 12:50:28

    MANNWell first, births have rarely been seen, even though common bottlenose dolphins are one of the most studied species worldwide. This is the second birth that's been documented by scientists. So, there was one off of Georgia in 2013. And so my graduate student (unintelligible), she was on the water and saw pools of blood, essentially, in the water, and said, look for a baby. Look for a baby. And this tiny, tiny little thing popped up (laugh) next to her mother, and all wrinkly and floppy-looking, as they are when they're first born.

  • 12:51:15

    NNAMDIAnd that's very rare, to see that.

  • 12:51:17

    MANNYes, very rare to see that. I was, unfortunately, stuck onshore. I was quite jealous, because I've been watching dolphins for over 30 years and hadn't seen it. But I was at our cottage, and I did see it later in the day. It did swim in my backyard. (laugh) So, I got to see it from shore.

  • 12:51:34

    NNAMDIYou've talked about how there's still so much mystery around dolphins. What don't we know about them?

  • 12:51:40

    MANNWell, the big question is: why do they have such large brains? Because they're obviously not building cities down there, or anything like that. So, what were the important selections pressures, (laugh) evolutionary pressures, that they have large brains? And, you know, they've had big brains for 30 million years. And humans have only had -- we've only had ours for 1.8 million years. So, the question is, like, why did they evolve such big brains?

  • 12:52:08

    NNAMDIHere now is Jeff in Cape May, New Jersey. Jeff, your turn.

  • 12:52:13

    JEFFYes, hello. First of all, thank you for having me. I'm fascinated that I can pick up your signal. I'm on the other side of the Delaware Bay in New Jersey, the southernmost tip of New Jersey, Cape May. And I'm overlooking Delaware Bay, as we speak. But it's to my delight to see dolphins or any type of animal in their habit. There are lots of fish, you know, a lot more fish that swim beneath the surface, but dolphins are mammals, and they have to come up for air.

  • 12:52:38

    JEFFAnd to see them in their natural habitat is wonderful. Oh, my gosh, it's just a wonderful thing. So, if that's a sign that the environment is changing due to either manmade causes or natural causes, or a combination of both, I hope that the dolphins survive. I hope that we come to our senses and realize that it is incumbent upon all of the people in industry and individuals to learn how to become better stewards and remain good stewards of the Earth.

  • 12:53:05

    NNAMDIThank you very much for sharing that. That links to my last question for Hedrick Belin. And that is: now these dolphins are certainly putting a cute face on a serious issue. What do you think of them as a way into a larger conversation about what's at stake for our waterways?

  • 12:53:21

    BELINWell, we certainly live in a busy world, and we're getting bombarded through all sorts of different media channels with all sorts of different messages. So, being able to cut through all that clutter and noise, dolphins are a great mascot for clean water. But, at the end of the day, we've got to remember, they are one of the top predators, and they're affected by the water quality and the fish populations.

  • 12:53:44

    BELINBut, yeah, it's certainly a charismatic and, as Janet noted, intelligent wildlife species that calls the river home. And so I think we all have a responsibility, as your previous caller said. What can we be doing individually in our daily lives and our daily routines to try to ensure that they have a healthy habitat of clean water in which to splash around with when they're here visiting during this spring, summer and early fall?

  • 12:54:10

    NNAMDII'm afraid that's all the time we have. Hedrick Belin is the director of Potomac Conservancy, a nonprofit advocating for a cleaner Potomac. Hedrick, good to see you.

  • 12:54:17

    BELINThanks for having me, Kojo.

  • 12:54:19

    NNAMDIDr. Janet Mann is director of the Potomac-Chesapeake Dolphin Project and the professor of biology and psychology at Georgetown University. Thank you so much for joining us.

  • 12:54:28

    MANNThank you.

  • 12:54:29

    NNAMDIThis conversation about dolphins in local waterways was produced by Julie Depenbrock. And our earlier discussion about changing demographics around local college campuses was produced by Laura Spitalniak. You go, Laura -- but I digress. Coming up tomorrow, there has been progress in fighting the opioid epidemic in our area, but it remains a crisis. We'll hear about efforts to prevent and reverse overdoses. Plus, after a scathing report, Lowden county schools are confront racism in the classroom. That all starts tomorrow, at noon. Until then, thank you for listening. I'm Kojo Nnamdi.

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