Government scientists are launching an investigation into an unusually high number of humpback whale deaths from North Carolina to Maine.
The National Oceanic and Atmospheric Administration Marine Fisheries says 41 whales have been stranded in the region in 2016 and so far in 2017.
"These mortalities are unusual because they are a marked increase in magnitude," said Mendy Garron, stranding coordinator for NOAA.
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In an average year, there are about 14 humpback whale strandings between North Carolina and Maine.
The sharp increase in deaths has caused NOAA to declare an “unusual mortality event,” and launch an investigation.
"The designation allows us to bring in experts ... to determine what may be causing it, whether it's natural, or human caused," said Deborah Fauquier, a veterinary medical officer at NOAA.
Officials say 10 of the 20 whales that have been examined so far were killed by collisions with boats. That's far above the average of fewer than two per year, and officials say there's been no spike in boat traffic to explain it.
Humpbacks can grow to 60 feet long. They're popular with whale watchers because of the dramatic way they breach the ocean's surface.
"They are magnificent creatures, who have been mistreated by people," said Chris Cutshall, owner of the Portland-based Odyssey Whale Watch. "You see the scarring on them. You know they come into contact with boats fairly regularly."
NOAA's large whale recovery coordinator, Greg Silber, suspects the humpback whales are swimming closer to vessels, trying to chase prey resources. Silber said the prey may be on the move, due to rising ocean temperatures.
NOAA's Unusual Mortality Event investigation could take months or years to complete.