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Botswana's Okavango Delta and the Makgadikgadi Salt Pans are two ends of

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the second longest zebra migration on Earth.

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Up to five hundred zebras make the 360-mile round trip annually

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in search of greener pastures. In this animation

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shades of red show dry areas, green represents vegetation,

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and the dots show zebras tracked by GPS.

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The zebras begin at the Okavango Delta in late September.

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After the long dry Southern hemisphere winter, November rains signal

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it is time to move. The wet summer months spark the growth of new vegetation.

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After a two week trek, the zebras reach the Salt Pans,

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which are dotted with flooded oases and nutrient-rich grasses.

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As the rain peters out in April, the zebras return to the Okavango Delta,

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where floodwaters will support them through the winter.

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Fences to keep cattle away from wildlife blocked this zebra migration from

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1968 to 2004. But anecdotes about past

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migrations proved true when the fences came down and researchers began tracking

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zebras with GPS. They compared the zebras' location

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to NASA satellite data of rainfall and vegetation. They found

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that migrating zebras have quickly learned when to leave the Delta and the Salt Pans

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using environmental cues. Researchers then used these cues to predict

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when the zebras will be on the move, a powerful tool for conservation.