In my last post, I talked about the two varieties of whale stranding and Dr. Gregory D. Bossart 's Science on Tap lecture on the topic at the Georgia Aquarium. This time around, I'm going to run through some of what Bossart had to say about the possible causes behind mass strandings. Sadly, a number of the cases point back to human alteration of the environment.
Pygmy sperm whales: The bottlenose dolphin is the most commonly stranded species, due in large part to the fact that the bottlenose lives close to shore. The pygmy sperm whale, however, is the second most commonly stranded species and it tends to live far from shore.
Pygmy sperm whales are a mysterious species, with needle-sharp teeth for eating squid, and they appear to suffer from a form of heart disease known as cardiomyopathy. In other words, as they wash ashore, they're already dying a slow death due to heart failure. Genetics are certainly partially to blame, but according to Bossart, infectious agents, contaminants and biotoxins are also factors. Scientists don't know exactly why they're dying, but a number of researchers intend to find out -- and see if it all comes back to human pollution and/or climate change.
Hooded seals: Despite being an arctic species, hooded seals have wound up beached as far south as Florida and the Caribbean. A necropsy on one such stranded hooded seal revealed a stomach full of plastic garbage. Scientists are seeing more and more of this, and the theory is that, as the seal's natural food supply shrinks, they're forced to move farther south in search of food. They encounter warmer waters than they've evolved to thrive in, new predators and diseases. It's just one part of what scientists call environmental distress syndrome.
Beaked Whales: The U.S. Navy is currently funding research to discover why beaked whales continue to wash ashore. The reason? Because passive navy sonar might very well be to blame. The Navy uses the sonar in submarine detection training exercises and the theory is that the acoustic energy aggravates gas bubbles in the whale's liver. The result is decompression sickness.
There's something horrifying about a beached whale. It pulls at our heart strings to see these magnificent creatures rendered helpless and dying on shores they abandoned 50 million years ago. How much worse is it to know we might be at fault?
Scientists continue to study both living and dead stranded whales and dolphins in order to answer such troubling questions. The Georgia Aquarium even has its own Dolphin Conservation Field Station now, which you can read about here.