Michael Zasloff, a researcher at the Georgetown University Medical Center, has discovered that bottlenose dolphins have “miraculous” healing powers: within several weeks they can heal from basketball-sized injuries, without any lasting disfigurements. Moreover, the injuries, presumably from clashes with sharks, don’t seem to cause the animals any apparent pain and don’t become visibly infected. Several abilities seem to be working together to promote healing; for example, Zasloff hypothesizes that bottlenose dolphins prevent bleeding to death by restricting blood flow to certain areas of their bodies, giving large gashes time to clot.
[Read more (and see pictures) at LiveScience.]
A few years ago, scientists observed that some bottle-nosed dolphins held sponges in their beaks as they poked around the ocean floor, flushing out fish they promptly gobbled up—and that mothers taught this trick to their daughters. In a follow-up study published yesterday, the scientists shed some light on why dolphins go to all this trouble: They’re after fatty, energy-rich fish on the seafloor, and the sponges let them scare up a snack without scraping their beaks on sharp rocks or coral.
Here’s a neat dolphin trick that doesn’t involve jumping through hoops. While dolphins sleep overnight (with half their brains and one eye at a time), they begin to show signs of the kind of insulin resistance that marks type 2 diabetes in humans. But when they wake up and have their breakfast, they switch back to their normal state. A research team led by Stephanie Venn-Watson announced the findings at the American Association for the Advancement of Science meeting in San Diego, and said that dolphins’ apparent ability to switch insulin resistance on and off could lead to better understanding of the disease in humans.
Insulin helps people control their levels of blood sugar, and the resistance to it inherent in type 2 diabetes means those levels can get way too high. The dolphins, though, switch on this temporary insulin resistance to their advantage, boosting blood sugar levels overnight. “Bottlenose dolphins have large brains that need sugar,” Dr Venn-Watson explained. Since their diet is very low in sugar, “it works to their advantage to have a condition that keeps blood sugar in the body… to keep the brain well fed” [BBC News].
Bats and dolphins are two of the most celebrated users of echolocation, employing high-frequency sounds to locate prey, find their way, or to communicate. Now a new set of findings in Current Biology show that not only do the two different kinds of mammals use the same method, they also evolved nearly the exact same molecular means for hearing at high frequencies.
That second part was a surprise, study author Stephen Rossiter says: “It’s common on a morphological scale but it’s assumed not to occur at a DNA level because there are so many different ways to arrive at the same solution” [BBC News]. That is, while it’s quite common for different species to separately evolve similar features—like the tusks of elephants and walruses—it’s quite unlikely that natural selection working in separate species would settle an essentially identical gene and protein for growing tusks, hearing high-frequency sounds, or anything else. Or so the thinking went.
Chalk up another unexpected consequence of pumping too much carbon dioxide into the air: According to a new study, the excess CO2 that ends up in seawater is gradually making the oceans noisier.
The changing chemistry of the ocean is one of the major impacts of CO2 emissions. The dissolved gas is changing the pH of the water by making it more acidic, which makes life harder for corals and marine critters with calcium carbonate shells that are corroded by the acidic water. But the new study, published in Nature Geoscience, found that changing the pH of the oceans also reduces the levels of chemicals that absorb sound, like magnesium sulphate and boric acid.
Low-frequency sound in the ocean is produced by natural phenomena such as rain, waves and marine life, and by human activities such as sonar systems, shipping and construction. The sound is absorbed mainly through the viscosity of the water and the presence of certain dissolved chemicals…. But the concentration of chemicals that absorb sound in the oceans has declined as a result of ocean acidification [AFP]. The study found that sound absorption could fall by some 60 percent in high latitudes and deep waters by 2100.
The hunting and killing of bottlenose dolphins in Japanese fishing towns is no longer a quiet secret. The outcry has been growing against the hunt in Taiji, western Japan, since an award-winning American documentary The Cove this year showed dolphins being herded into an inlet and killed by fishermen with spears [AP]. Regardless, hunting season has begun anew, but in a small victory, representatives from the Save Japan Dolphins Coalition said they filmed Japanese fisherman releasing 70 bottlenose dolphins on Sunday.
The released dolphins were part of a catch that netted around 100 animals earlier in the month. The conservationists rejoiced over the release, but considering that the annual hunt in Taiji kills around 2,000, and up to 20,000 dolphins are killed across Japan each year, the group still has some persuading to do.
Dolphin hunting in Japan is a traditional business that many in Taiji rely on to make a living, but the gruesome nature of the killings has turned outsiders against the hunts. Scenes in The Cove graphically depict dolphins being trapped and killed with spears while the waters turn red with blood. This killing may be legal—dolphins and other small marine mammals are not protected by the ban on commercial whaling—but … the methods used are so nonchalantly brutal and gut-churningly primitive that Taiji officials are understandably publicity-shy [The New York Times]. The filmmakers were followed and harassed throughout their shooting, so they had to rely on more covert operations like deploying divers with underwater cameras, flying areal drones, and using thermal imaging and other spy gear to record the hunts.
A new documentary film that has all the intrigue of a thriller is giving the world its first glimpse of what goes on in the scenic waters near the coastal town of Taiji, Japan. The Cove tells the story of a skilled group of activists who reveal the slaughter of dolphins by Japanese fisherman, with scenes so bloody that the cove’s waters are dyed red. This killing may be legal — dolphins and other small marine mammals are not protected by the ban on commercial whaling — but … the methods used are so nonchalantly brutal and gut-churningly primitive that Taiji officials are understandably publicity-shy [The New York Times].
In an effort to keep the dolphin killing off film, mysterious individuals follow, harass, and confront the filmmakers. The cove where the slaughter takes place is private property and strictly off-limits, but the movie makers are more than willing to break the law for their cause. To ensure they get their footage, the team includes a “clandestine operations” organizer, two of the world’s best free-divers, and a former avionics expert with the Canadian Air Force. This cloak-and-dagger crew makes use of such tools as a military infrared camera for night cinematography, unmanned aerial drones, a blimp and fake rocks specially designed by George Lucas’ Industrial Light & Magic to hold secret cameras [Los Angeles Times].
Powerful sonar causes temporary hearing loss in dolphins, a new study has confirmed, and could explain some incidents of mass stranding of the marine mammals. The impact of sonar on dolphins has been debated for years, but for the first time, researchers have played recordings of actual naval sonar to a marine mammal and tested its hearing after progressive step-ups in intensity over a couple of months [ScienceNews].
Tests were conducted at the Hawaii Institute of Marine Biology on a captive dolphin, whose head was fitted with a suction cup attached to a sensor that monitored brainwaves. The dolphin was then exposed to progressively louder pings of mid-frequency sonar…. When the pings reached 203 decibels and were repeated, the neurological data showed the mammal had become deaf, for its brain no longer responded to sound [AFP].
If the U.S. Navy has its way, dolphins and sea lions will soon be patrolling Puget Sound to protect some of the nation’s most sophisticated submarines from possible terrorist attacks. But although the animals have already been through boot camp and are on the job in other parts of the world, Washington State animal lovers and environmentalists are concerned that dolphins and sea lions are ill-suited for conditions in Puget Sound. Animal rights activists are worried dolphins will suffer in the cold waters and environmentalists worry the local habitat may suffer from the droppings of these patrollers [MSNBC]. The Navy is currently holding public hearings in Seattle and towns along the Puget Sound, and has said it will make a decision by October.
The Navy says dolphins and sea lions make great marine sentries, and are more capable of detecting a lone diver approaching a submarine than the most advanced technology. “Their strengths are that they are a mobile sensor: They have the best sensor we know about, and you can have them swim anywhere in the bay. They can outswim any man, they can localize the threat, and they can combine with the sea lions, which have good directional hearing” [Los Angeles Times], says Steve Hugueley, who works with dolphin patrollers at a submarine base in southeast Georgia.
Three pods of killer whales in the Pacific Northwest have now earned the unfortunate title of being the most contaminated wildlife on Earth, according to a new study. These killer whales, known as southern residents, live in the coastal waters near the U.S.-Canadian border and survive almost exclusively on contaminated Chinook salmon. The salmon contain high levels of polychlorinated biphenols (PCBs) and other industrial chemicals, which accumulate in even higher levels in the killer whales. Researcher Peter Ross says whales are particularly sensitive because they eat massive amounts of fish over a long life – killer whales can live for 80 or 90 years – creating a massive buildup of toxins. That means the whales, particularly the southern resident population, have become some of the most contaminated marine mammals in the world [AP].
Researchers estimate that the southern resident killer whales carry 6.6 times more PCBs than a different group of whales just 200 miles to the north, known as the northern residents. They found that the Chinook salmon in the southern waters, including Puget Sound near Washington state, not only had the highest concentrations of contaminants but also the least amount of body fat. This means the southern residents are suffering a “double whammy” because they are forced to eat extra helpings of heavily contaminated salmon. Ross and his colleagues discovered that 97 percent to 99 percent of contaminants in the Chinook eaten by these whales originated from the salmon’s time at sea, in the near-shore waters of the Pacific. Only a small amount came from the time the salmon spent in rivers, although many of the rivers are contaminated, too, Ross said. “Salmon are telling us something about what is happening in the Pacific Ocean,” Ross said. “They are going out to sea and by the time they come back, they have accumulated contaminants over their entire time in the Pacific Ocean” [Scientific American].