Since February 1, 2010, 443 dolphins have turned up "stranded"—a word that really, mostly means "dead"—on the beaches of Gulf Coast states. Most of these deaths coincide with the after-effects of the BP oil spill last spring. But not all. In fact, the spill happened on April 20, 2010, but March of that year was the single deadliest month for dolphins, with more than 60 strandings. That detail suggests there's more going on here than simple cause-and-effect oil-spill results.
The NOAA is calling the die-off an "Unusual Mortality Event"—making it rather different from the bird die-offs everybody was talking about earlier this year, which scientists said were common, expected, and had rather mundane explanations.
The NOAA is studying the event, trying to figure out what's happening. On their site, you can see how the deaths this year, and last, stack up against the average monthly dolphin deaths collected between 2002 and 2009. One interesting thing that stands out: March has been a bad month for dolphins for a long time. Over the last decade, it's been the month with the highest number of dolphin deaths. In 2010, that trend continued—it's just that the numbers of deaths in March, and the rest of the year, suddenly got much larger. So far, it's on track to be true for 2011, as well. Clearly, there's a natural mortality cycle that's being enhanced by whatever other factors are affecting the dolphins.
There've been 11 cetacean-centric Unusual Mortality Events in the Gulf since 1991, and 53% of those turned out to be caused by various biotoxin exposure. But, another 40% were never directly attributed to anything. It's difficult to fully understand die-offs like this, and there's a good chance that things will eventually go back to normal without us having ever figured out what's going on.
Read NOAA FAQs on the dolphin Unusual Mortality Event.
Via Kevin Zelnio
Image: Some rights reserved by cmakin
