Swelling populations and evidence of live births among common bottlenose dolphins in the Potomac River could be evidence that the once-filthy “Nation’s River” is the healthiest it has been in many decades.
Once dubbed “a national disgrace” by former President Lyndon Johnson because of its polluted waters, the Potomac has seen a clean and healthy turn in the last several years. Scientists have observed an increase in the population of common bottlenose dolphins in wide areas of the Potomac, particularly near Virginia’s Northern Neck.
Scientists observed about 200 individual dolphins in that area in 2015, but this year they believe there are more than 1,000 animals who occasionally congregate in groups of 200.
“There are dolphins here, and there’s breeding and birthing going on, and this is connected to D.C. — such a populated, urban area,” said Ann-Marie Jacoby, co-director of the Potomac-Chesapeake Dolphin Project. The Potomac-Chesapeake Dolphin Project states that their mission in the area is to “better understand and protect the bottlenose dolphins (Tursiops truncatus) of the Potomac River and Chesapeake Bay. Despite being the largest, and most populated estuary in the U.S., we know almost nothing about the area’s bottlenose dolphins. Yet reports of dolphins in the area date back to the 1800s, with one sighting as far up the Potomac as Washington, DC!”
Sightings of the mammals were indeed recorded as early as the 17th century, with noted population increases in the late 1800s. Rising pollution and litter seemed to drive the dolphins away in the 1940s through the 1960s, but effort over the past few decades to clean up the river after Johnson’s condemnation seem to have paid off.
Janet Mann, a biologist at Georgetown University and founder of Potomac-Chesapeake Dolphin Project, expressed curiosity and uncertainty about the influx of dolphins in the Potomac. “There’s so much we don’t know,” she said. “It’s a challenge of studying marine mammals, in that they dive, and you can’t see everything they’re doing … So much is known about every single species in the Potomac and Chesapeake, except for the charismatic megafauna — bottlenose dolphins. That just astounded me.”
