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Weird Science: Animal Migration

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Humans are not the only animals who navigate. Many animals migrate across relatively large distances, daily or seasonally, and they do it without a compass, Global Positioning System (GPS) coordinates, or maps! Animals often migrate to find resources like food or shelter that vary throughout the day or year, or to undergo a specific part of their lifecycle.

 

For example, salmon are born in rivers and travel to the ocean as juveniles, where they grow to be adults (SF Fig. 8.1 A). Salmon then navigate back to the river they were born, travel upstream, and finally spawn. Some migrations occur over long distances. Humpback whales undergo long journeys, up to 6500 km, through currents, storms, and waves (SF Fig. 8.1 B). Whales feed in nutrient-rich, polar waters during the summers and then migrate towards the warm tropics during the winter to mate and give birth. Humpback whales have been shown to travel in remarkably straight lines over their migration, deviating from their path less than one degree.

<p><strong>SF Fig. 8.1.</strong> (<strong>A</strong>) Salmon travel upstream to spawn.</p><br />
<p><strong>SF Fig. 8.1.</strong>&nbsp;(<strong>B</strong>) Humpback whales migrate seasonally between polar and tropical regions.</p><br />
<p><strong>SF Fig. 8.1.</strong>&nbsp;(<strong>C</strong>) Some zooplankton engage in daily vertical migration.</p><br />


Not all migrations are across the ocean or land. Some free-swimming, marine zooplankton make daily vertical migrations in the water column (SF Fig. 8.1 C). These zooplankton feed in the upper layers of the ocean at night and then move down to darker waters at depth during the day. Zooplankton most likely use this pattern for predator avoidance; they avoid visual predators during the day by swimming to deeper, darker water where they are less visible.

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.