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Whales are generally divided into two categories, the toothed whales and baleen whales. Toothed whales include species like sperm whales, narwhals, and orcas. Some examples of baleen whales include the blue whale, humpbacks, grey whale, and fin whales. These whales differ in the way that they use sound for navigation.
Physeter macrocephalous, sperm whale
Balaenoptera musculus, blue whale
Monodon monoceros, narwhal
Toothed Whales
Toothed whales, or Odontoceti, are known to utilize echolocation. Their skull is asymmetrical in the nasal and nasofacial region. These features have thought to have become more exaggerated during the time they evolved the use of echolocation. The asymmetry of the skull makes room for soft tissue that helps produce sound and helps better receive frequencies that bounce back. The shared ancestor of toothed and baleen whales also had an asymmetrical skull, but are thought to not have been able to echolocate. (Geisler, et al 2014) Just beneath the blowhole toothed whales have phonic lips that connect to their nasal passage. When air passes through the nasal passage and into the phonic lips it produces a high frequency sound. The melon is a region of fat that is found between the blowhole and the tip of the snout. It is thought to help focus the sound and help the sound waves travel from the head into the water with less distortion. Echolocation is useful for whales to be able to get a better sense of their environment when diving to depths where light cannot penetrate. The high frequency clicks bounce off of an object, giving the whale a mental picture of its location. Once the echo from the previous click is received the next click will be sent out. The closer to the object the whale gets, the more frequent the clicks become. Sending out sound waves helps them identity landmarks, which assists in building mental paths through the ocean. (Miller, et al 2004)
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Magnetic Navigation
Humpback whales are baleen whales that have been known to migrate distances greater than 6,500 km. Radio tagged whales have been monitored using satellites during their migrations and have been found to follow incredibly precise routes, moving off course by less than 1 degree despite the effects of sea currents. (Travis, et al 2011) How exactly these whales can achieve such precision is still a bit of a mystery. Whales have been found to contain biomagnitite in the retina of their eyes, which is known to make migrating birds sensitive to changes in the earths magnetic field. The intensity of the earth's magnetic field varies around the world, sensing this may help create mental pathways for the animals. Researchers found that most magnetic fields are parallel to the coastline; however, beaches that have high instances of strandings have been found to have a magnetic path that turns towards the shore. This evidence supports the theory that whales can sense the earth's magnetic field, though it has not been definitively proven. (Marks 2006) Given the remarkable precision of their migration routes it, is likely that whales utilize several cues since the earth's magnetic field varies so widely.
Whales are known to spyhop, a behavior in which they surface vertically for about 15 to 30 seconds slowly turning in order to assess what's above the surface. Scientists believe when they are doing this they may be looking out for landmarks, tracking the sun, and utilizing the position of the moon and the stars to get more information on their location and what route to take. When they are underwater sound cues likely also play a role. Researchers theorize that whales might listen out for the sound of snapping shrimp when they are near the coast to cue them in on upcoming rocks. It's also possible that different populations of whales help each other with their migration by communicating through long distance songs. (Allen 1970)
