Biologists are investigating an unusual number of humpback whale deaths along the Atlantic Coast since the beginning of 2016, including six in recent months at the mouth of the Chesapeake Bay or along the Delmarva Peninsula.
In all, 41 dead humpback whales have washed ashore between Maine and North Carolina since January 2016, nearly three times more humpback deaths along that stretch than average.
Two of those dead whales were found in Maryland waters, according to the National Oceanic and Atmospheric Administration fisheries department.
Scientists suspect the deaths may be occurring because fish the whales feed on have moved somewhere that exposes the humpbacks to increased shipping traffic. But they don't know why that is.
"It's probably linked to resources," Greg Silber, the large-whale recovery coordinator for NOAA fisheries, told reporters during a conference call Thursday. "Humpback whales follow where the prey is."
Biologists have inspected 20 of the dead whales, and half of them appeared to have died after being struck by a ship or its propellers. Only one or two humpbacks die from ship strikes between Maine and Virginia in an average year.
The deaths have raised alarm around the Mid-Atlantic this year, with five deaths in Virginia waters and six deaths in North Carolina waters in less than five months.
One humpback was found dead in Maryland last year, and another this year, according to NOAA.
Cindy Driscoll, veterinarian for the state Department of Natural Resources, said a badly decomposed whale carcass washed up on shore last year; it was about 30 feet long with no skin or tail on it. According to NOAA data, the carcass was found in the Ocean City area.
The other whale carcass NOAA counts as being found in Maryland actually drifted past the state's coastline well offshore earlier this year and eventually landed on the Virginia coast, Driscoll said. It might have been the same whale carcass that was found on the Virginia side of Assateague Island in late February.
NOAA fisheries declared this week what is known as an "unusual mortality event," a designation triggered when a spike in marine mammal deaths is observed. That launches a formal investigation that involves data collection and analysis, and increased monitoring of any changes to the whales' habitat, including any threats posed by human activity.
There are estimated to be about 10,000 humpback whales in the North Atlantic. They typically mate in the tropical waters of the Caribbean in the winter, though some have been known to spend the season at the mouth of the Chesapeake, seen as far north as Southern Maryland. They then migrate to polar waters for the summer.
Humpback whales had been considered "endangered" under the federal Endangered Species Conservation Act and then the Endangered Species Act since 1970, but were delisted last September. Scientists found there were 14 distinct populations of humpbacks around the world, rather than one global population, and that each of those groups was faring well.
This is the fourth such investigation of North Atlantic humpback deaths since 2003, and in each previous inquiry, biologists were unable to trace a cause.
State officials urge residents who spot whales or sea turtles, alive or dead, to report them by calling 1-800-628-9944.