Migratory birds and animals travel thousands of miles seasonally, selecting locations best suited for feeding and breeding purposes. Although they are spared the immigration woes that we currently face, their adventurous journeys are not devoid of challenges. How do these creatures manage to accurately navigate their way to their destinations without wasting energy in testing futile ways?
Early navigation and migration studies mainly focused on birds because of their easy availability for experiments. Studies showed that homing pigeons may largely use landmarks, sounds, and smell for finding their way back home after short-distance trips. However, migratory birds traveling thousands of kilometers need further help beyond odor and visual cues. They rely mainly on the position of sun and stars and, most importantly, on the Earth’s magnetic field (1). Researchers found that eyes, beak, and inner ears of birds are together involved in functioning of the sophisticated compass in birds. While the inner ears of birds contain tiny amounts of iron deposits (magnetite) that are influenced by the Earth’s magnetic field, more complex chemicals are apparently present in their eyes, which, when exposed to light, split into molecules that can be influenced magnetically. A study investigating the role of beak in navigation involved cutting the trigeminal nerve connecting the beak to the brain in Eurasian reed warblers and displacing the birds 1000 miles east from their original locations (2). The results showed that birds with intact nerves could re-orient themselves, while those with damaged nerves did not realize their displaced location, although they could still detect north in lab-experiments. This showed that the beak is not involved directly in the ‘compass’, but is important for ‘mapping’ sense in birds.
While migratory birds take over the skies, marine life-forms are not idle either. Whales, among other marine animals, are also known to participate in seasonal migration. Their migration is even more challenging, as visual and solar cues are difficult to decipher below the water surface. Yet, when a group of researchers tracked the migration patterns of 16 humpback whales for a few years, they found that the whales followed their routes with amazing precision, deviating less than 1 degree (3). Curiously, variations solely in position of sun or magnetic field did not affect their sense of navigation. Thus, a combination of different mechanisms enables accurate direction sensing in humpback whales.
Whales are known to communicate with each other via acoustic calls. In fact, theories of these ‘whale songs’ aiding them in mapping out the ocean floor during navigation are also being investigated. Thus, a journey of thousand miles could possibly begin with a song- now, wouldn’t that be cute?
- Kishkinev, Dmitry, et al. “Migratory reed warblers need intact trigeminal nerves to correct for a 1,000 km eastward displacement.” PLoS One 8.6 (2013): e65847.
- Horton, Travis W., et al. “Straight as an arrow: humpback whales swim constant course tracks during long-distance migration.” Biology letters(2011): rsbl20110279.