They are the largest creatures on earth. They can dive 300 feet or more beneath the ocean surface and remain below for an hour at a time. Even today, much is still unknown about blue whales. So how do scientists hoping to learn more about blue whales track these underwater titans? Like all good scientists, they use empirical evidence—data that can be seen, heard or touched.
“Seeing” under the sea
Scientists with Oregon State University’s Whale Telemetry Group follow the migration patterns of blue whales using tags that send data to orbiting satellites. The radio transmitters are attached to the whales. The transmitters operate for a short while, sending location information up to satellites and allowing scientists to track the blue whales in real time. Because the satellite can “see” many tags across miles of ocean, migratory patterns and animal numbers can be tracked closely in the relative comfort of a lab or office.
Scientists who observe whales from boats also take pictures of the animals as they surface, to record markings. Each blue whale has a unique pattern of light and dark markings, so photographs can help scientists follow individual whales. In addition, some whales show just how rough life in the ocean can be, as their skin reveals scars and markings from everything from shark bites and killer whale encounters to being hit by ships! While unfortunate, all those markings help identify each blue whale.
Blue whales are the loudest animals on earth, with their calls reaching levels higher than the roar of a jet engine.
But most of the time, those loud calls are only underwater, out of earshot of the scientists studying them. Augmenting normal human hearing with technology allows marine biologists to listen to blue whales in three ways.
Hydrophones (underwater microphones) are lowered into the water to listen to and record male blue whale songs—series of clicks, groans, whistles and other utterances that can last for hours, and then be repeated by the whales note for note. Scientists can study these songs to detect patterns of stress in blue whale populations, and have discovered that blue whales are amazingly accurate in the pitch of the notes they produce.
Sonar (sound navigation and ranging) can be used to send a low energy sound wave underwater, where it bounces harmlessly off the bodies of blue whales and returns to the scientists listening for the distinctive “ping.” This is useful for determining the numbers and sizes of blue whales in a pod, or for tracking individual blue whales. The disadvantage of sonar is the need to be close to the animals, which increases the risks to the scientists. Other studies have shown, however, that whales may be incidentally affected by sonar not aimed at them for research purposes, but used instead by the military.
Seismometers—normally used to detect and locate earthquakes—have also been used in recent years to monitor blue and other whales. Because whales often vocalize in very low frequencies, far below the level of human hearing, seismometers can “hear” these sounds when scientists cannot. While humans can hear down to about 20 decibels, blue whales can produce sounds as low as 2 decibels. Low frequency sounds—infrasound—can travel very far underwater. Scientists think blue whales using infrasound can communicate with each other across hundreds of miles of ocean floor seascape.
Blue whales, like other marine mammals, occasionally wash up on beaches. While humans are helpless to aid these large animals at such times, their bodies do provide scientists rare opportunities to study blue whale anatomy and feeding patterns. They can collect samples of the whales’ tissue and analyze the chemical and genetic makeup of these majestic creatures.