Dolphins Are Dying off the East Coast and No One Knows Why

While Shark Week has been occupying most of our nautical attention—and outrage—something has been amiss with the bottlenose dolphins off the East Coast. The number of dolphins stranded in July is more than seven times higher than average—89 dolphins according to scientists from the National Oceanic and Atmospheric Administration. As of Wednesday, a total of 35 strandings had occurred already in the month of August. Only seven dolphins have been found while still alive, but they were already beyond treatment, according to Teri Rowles, National Marine Mammal Stranding Coordinator with NOAA Fisheries

As a point of comparison, the BP oil spill saw 186 dead dolphins wash ashore between Louisiana and western Florida over four months in 2011. But without an obvious ecological disaster to blame this summer, researchers are hunting for a cause.

The primary suspect has been morbillivirus, a relative of measles and canine distemper. In 1987, a morbillivirus outbreak killed 740 bottlenose dolphins according to NOAA. Another outbreak in the Mediterranean in 2007 killed more than 100 striped dolphins, that washed ashore in Spain.

While so far one dolphin has tested positive for the virus, the dolphins that have been washing up in 2013 don’t universally exhibit the characteristic skin lesions that accompany morbillivirus. Other specimens will be tested; the virus also leaves lesions on the lung and central nervous system tissue.

News reports state that other dolphins have tested positive for pneumonia, and The New York Times reports that officials estimate it might be weeks before a single cause is found, if one ever is found.