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In-depth: Whale Navigation
Navigating the Long Way Home
by Robin Marks
Imagine this: You're in Los Angeles, you're hungry and your next meal is in New York City. To get to it, you have to cross the continent. There aren't any maps or road signs, and the weather's constantly foggy, making it hard to see. How will you make your way?
This seemingly impossible scenario is similar to the task that migrating whales face when they make their journeys. They eat very little along the way, it's difficult for them to see and, of course, there aren't any road signs. Or are there? Scientists who study whales believe the animals use a combination of senses to find their path, in a way that helps them "see" the ocean floor, spot landmarks along the way and navigate in the proper direction.
Sounding It Out
Enthusiasts have known for decades that whales use noises to communicate. Whales are divided into two groups, and each uses sound differently. Toothed whales, like
Our understanding of these creatures' use of acoustics began to deepen in the early 1990s, when researchers at Cornell University started using a Cold War spy technology to tune in to baleen whales. The U.S. Navy's Sound
The Cornell researchers learned that the trick to interpreting data gathered by SOSUS is to think about it from a whale's perspective. Water conducts sound much more efficiently than air, and whales can hear much better than humans. When scientists analyzed the sounds picked up by SOSUS - with the scale of the ocean in mind - they discovered that whales send their vocalizations over thousands of miles to communicate and navigate during migration and that their calls took place in a time frame much different from that of human communication. A blue whale, for example, can take up to two minutes to sing just one note of its song. The frequency it sings at is too low to be heard by the human ear, but is one that can travel great distances through water. In essence, a whale's fine-tuned ability to make and use sound is akin to our sense of sight; but it is sound, rather than light, that allows them to "see" the world around them.
There is some evidence that whales use their songs not only to orient themselves, but also to move together as a group. Researchers see pods of whales spread out over many miles moving together as if they were choreographed. Scientists also think whales may have acoustic memories that function like our visual memories. In other words, when they've "heard" a certain route, they can search for familiar landmarks to guide them on their repeat migratory journeys.
Unfortunately, just as scientists are gleaning more new information by listening underwater, they are finding it harder to isolate the whale sounds from the myriad and increasing man-made noises polluting the seas. Sound from shipping vessels, oil exploration, military sonar, and even private boats and whale-watching expeditions is filling in what used to be quiet space in the ocean. And it's affecting the whales. When their songs are drowned out by other noises, the distance their calls can travel shrinks, making the calls less useful for communication and navigation. In addition, some of the sonar used by the military to keep an eye on movements in the ocean is thought to be the same frequency as that of some whale calls, and therefore it might confuse the whales or interfere with their communication.
Noise pollution may even affect whale breeding: The males of some whale species court females by singing to them across many miles. If the males' calls are swallowed up in the din of other undersea noises, the females won't hear them and may miss breeding opportunities.
Along with their sonar, whales have other tricks they employ to keep themselves on track. Many researchers believe that whales and other migrating animals have a magnetic sense that helps them know which direction they're moving. Scientists know that a substance called biomagnitite helps many birds migrate by making them sensitive to changes in the earth's magnetic field. Cetaceans, the animal family to which whales belong, have biomagnitite in the
The intensity of the earth's magnetic field fluctuates across the globe, and an animal able to sense these changes could potentially use them like a map. There is some evidence that toothed whales do this. Most magnetic field lines in the ocean run the same direction as the coastline. But in some places, they turn and run perpendicular to the shore. A whale riding this magnetic "road" might be more likely to strand in areas where the path turns. When researchers studied the magnetic field lines around beaches where groups of whales have repeatedly been found stranded, they found that in each instance, the magnetic paths turned shoreward.
Unfortunately, it's very difficult to study sensitivity to magnetism in whales that are going about their normal business and not stranding on shore, so the question of magnetic navigation remains unclear. But most whale researchers believe it plays some role in navigation.
Last, and possibly least, whales may occasionally surface to take a look around. This behavior is called spyhopping, which is something like when people tread water. The whale tilts its whole body vertically, with its head out of the water, and flaps its tail to keep itself in position. It can stay like this for 15 to 30 seconds, slowly turning and surveying the landscape. These surveys may help the whale see how close it is to shore or to oncoming ships it has been hearing in the distance.
The whale's yearly journey is challenging enough to warrant the recruitment of many senses and skills. It's likely that learned behavior, communication between whales and all of a whale's senses play a role in steering these giants through their
jyi.org: "Whale Songs: Secrets From the Ocean's Depths," Journal of Young Investigators' Science Career Center
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