By Christine Dell’Amore | National Geographic News
Bottlenose dolphins are washing up dead in unusually high numbers along the U.S. East Coast this summer—a “very alarming” situation that has experts scrambling to decipher the cause.
Nearly 120 corpses have washed ashore in coastal states from New York to Virginia in July and the first week of August, which is much higher than the normal number of strandings attributed to natural deaths. Virginia has had the highest mortality, with 64 animals found during that period.
One of the dolphins tested positive for morbillivirus, a measles-like, airborne virus that’s often fatal in dolphins.
A morbillivirus epidemic hit East Coast bottlenose dolphins in 1987 and 1988, wiping out at least 900 animals and striking a major blow to that population of migratory dolphins.
“Because of the sheer number of animals [dying] over multiple states, people are very concerned that this might be a repeat,” said Trevor Spradlin, a marine mammal biologist for the U.S. National Oceanic and Atmospheric Administration’s (NOAA) National Marine Fisheries Service.
Several potential causes of death being investigated include other diseases or pathogens caused by viruses or bacteria; biotoxins caused by harmful algae blooms; pollution or chemicals, especially from concentrated spills; ship strikes; or acoustic trauma from ships or other infrastructure, he said.
“All indications show there’s something serious going on.”
Determining a Cause of Death
The spike follows a general trend in more dolphin strandings—or, in scientific speak, unusual mortality events—that have occurred in recent decades in the United States.
In the northern Gulf of Mexico, for instance, where there’s an ongoing unusual mortality event, 1,031 dolphins and whales have washed up dead since February 2010. (Also see “Dolphin-Baby Die-Off in Gulf Puzzles Scientists.”)
The “concern is we’re doing more and more to protect dolphins from harm, yet dolphin strandings are on the rise,” said Matthew Huelsenbeck, a marine scientist at the nonprofit Oceana.