For 36 years, the grass was always greener on the other side of a fence for zebras in Botswana. From 1968 to 2004, a fence designed to protect cattle blocked the zebra's migration route from the Okavango delta to the Makgadikigadi salt pans.
After the removal of the fence, the zebras began to relearn their 360-mile (580 km) round trip migration. As the two-toned travelers returned to their ancient pathways, NASA satellites allowed biologists to watch the zebras and predict their movements based on the greening of the grass along the route. As the rainy season restored life to the Botswana wilderness, the zebra followed the wave of green that appeared on satellite images.
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Zebras generally only live for approximately 12 years in the wild, so they couldn't have remembered the migration route. By monitoring the vegetation changes and the zebras reaction to them, biologists could observe the driving forces behind why migrations occur, beyond the learned behavior of animals simply following a route their have known since youth.
"By comparing the results of the models, it was possible to determine which environmental variables are the most effective in predicting zebra movement, and then use this knowledge to try and infer as to how the zebra make their decisions," said project participant Gil Bohrer of Ohio State University in a press release. "It shows we can figure out very closely what ‘makes the zebra move.'"
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As the planet changes, understanding what drives animal migration decisions can help wildlife managers make conservation decisions.
"We need to know what the fate of those migrations is under climate change," said study author Pieter Beckof the Woods Hole Research Center in a press release. "Understanding when animals might come through, what drives them, what they're looking for sometimes. Being able to predict that into the future is very useful information to managing those landscapes so that migratory animals and humans can coexist."
The Journal of Geophysical Research–Biogeoscences published Beckof's satellite study of zebra migrations.
IMAGE: Plains Zebras, Equus quagga, in Okavango, Botswana in 2002. (Paul Maritz, Wikimedia Commons)