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Botswana's Okavango Delta and the Makgadikgadi Salt Pans are two ends of
the second longest zebra migration on Earth.
Up to five hundred zebras make the 360-mile round trip annually
in search of greener pastures. In this animation
shades of red show dry areas, green represents vegetation,
and the dots show zebras tracked by GPS.
The zebras begin at the Okavango Delta in late September.
After the long dry Southern hemisphere winter, November rains signal
it is time to move. The wet summer months spark the growth of new vegetation.
After a two week trek, the zebras reach the Salt Pans,
which are dotted with flooded oases and nutrient-rich grasses.
As the rain peters out in April, the zebras return to the Okavango Delta,
where floodwaters will support them through the winter.
Fences to keep cattle away from wildlife blocked this zebra migration from
1968 to 2004. But anecdotes about past
migrations proved true when the fences came down and researchers began tracking
zebras with GPS. They compared the zebras' location
to NASA satellite data of rainfall and vegetation. They found
that migrating zebras have quickly learned when to leave the Delta and the Salt Pans
using environmental cues. Researchers then used these cues to predict
when the zebras will be on the move, a powerful tool for conservation.