Massive Whales Lack Caution, Explains for Ship Collisions, Say Experts
It's no small secret that ship strikes are a big threat to whales across the globe. Now a new study suggests that the largest of whales - particularly blue whales - may be the most vulnerable of all, as they lack the sort of caution and evasiveness that they would of developed had they ever actually had to worry about predators.
Between 1988 and 2012, there were 100 documented large whale ship strikes along the California coast alone, according to the NOAA, and the agency suspects that the large majority of these incidents remain unreported.
"Evidence of ship strikes comes from a range of sources including direct observations from vessels and examination of whale carcasses found floating at sea," the International Whaling Commission (IWC) reports. "However, for every incident that is observed and reported there will be many others that are missed. This makes assessing the conservation implications of ship strikes very difficult."
Yet despite that admission, the IWC goes on to assert that for right whales in particular - a baleen species only second largest to blues - the ship strike mortality rate is worryingly high.
"It is thought that mortality due to ship strikes may make the difference between extinction and survival for this species," the commission reports. (Scroll to read on...)
That's why researcher Jeremy Golbogen recently led a study of massive baleen whales, looking to blue whales in particular to confirm something he has long suspected.
"It's not part of [large whales'] evolutionary history to have cargo ships killing them, so they haven't developed behavioral responses to this threat," Golbogen, an expert of biology at Stanford Univerwsity's Hopkins Marine Station, explained in a recent statement. "They simply have no compelling response to avoiding these dangerous ships."
And if you think about it, that actually makes a lot of sense. The largest aquatic mammals in the world, blue whales can grow up to 82 feet long and weight a whopping 420,000 pounds as adults. What kind of predator would be crazy enough to attack them?
Without experiencing a fear of being eaten, the blue whale spends its time gleefully siphoning tons and tons of plankton and other small creatures from the ocean with its iconic baleen plates. Recent research has revealed that its physiology even radically changed to help facilitate this sole purpose.
This occored while other species continued to live in an eat-or-be-eaten world, learning appropriate levels of caution from birth and adapting new ways to reflexively avoid a threat.
In a new study recently published in Endangered Species Research, Golbogen and his colleagues argue that this could be why the traditional warning signs supposedly designed to warn whales when a large ship is fast-approaching (flashng lights, sound pings, etc) just don't do the trick.
After tracking the movements of nine blue whales for 24-hour periods, the researchers determined that the closest thing to an avoidance strategy these animals have is a "startle response" in which they essentially play dead. (Scroll to read on...)
"Blue whales have a subtle and not very convincing ability to get out of the way of oncoming ships," said Goldbogen. "Instead of diving, where the animal kicks tail up and goes down vertically, they just sink horizontally. This results in a slow dive and leaves them susceptible to ship strikes."
Whales often have to dive about 30 meters below the surface to avoid a close-encounter with an oncoming ship. Unfortunately, this study revealed that the blue whales sank at about a half a meter per second, and made no move to speed up that decent. This resulted in plenty of near-misses and, while no collisions were observed during the study, the researchers also suspect that this behavior can lead to many ship strikes.
Still, while that's more cause for worry, the researchers add that this revelation is an important step in developing new ways to keep whales and ships from fatally meeting. Next, they plan to expand their work to other large whales, like the iconic humpback whale, in a bid for more behavioral data.
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