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Mighty Migrations: Winter Edition

You might assume that Botswana is a hot country. And, for most of the year, you would be right. But you might also not be surprised to know that winters in the Okavango are much like winters elsewhere on this planet – frosty. During the winter months, overnight temperatures in this desert oasis plummet, sometimes even to below freezing. As they do, the plants that are adapted to living life under the scorching Kalahari sun and have bloomed on the abundance of the rainy season, slowly die away and, thanks to the still-warm days, the floodwaters also begin to evaporate off. It sounds quite miserable, but if you’re a wildlife camera-operator, this is your time! Not only do you not have to deal with the hordes of mosquitoes that sabotaged your sleep during the rainy season, but it’s the best time to spot (and film) big game, whose camouflage is at an all time low and whose abundance reach their annual highs. During this time, the Okavango is swamped with a regular visitor – the Burchell’s zebra - whose epic journey was only recently discovered by science.


Burchell's Zebra arriving in the Okavango Delta. NHFU/Hannah Gormley.


You’re probably well aware that right now the annual Serengeti migration is underway, but you might be surprised to learn that Botswana is home to both the second largest, and longest, overland mammal migration. Perhaps even more remarkable is that this remained a secret for so long. There are two distinct migrations that occur amongst Botswana's resident zebra populations – the first goes between Nxai Pan (a protected area sandwiched between the Moremi and Mgkadikadi Pans National Park) and the Chobe National Park. The second is that which occurs between the Okavango Delta and the Mgkadikadi Pans National Park. So what’s so special about the pans and why do Botswana's zebras travel so far just to get there? As the largest contiguous salt flats in the world, these enormous pans put the Bolivia’s infamous Salar de Uyuni to shame. If you were to visit them during the dry season, you’d be forgiven for thinking they were inhospitable and barren lands, completely devoid of life. But, visit in the wet season and you’ll see this haunting, desolate landscape transform into an ephemeral wetland, dominated by rolling hills of greenery that blossom throughout the park and migrant populations of zebra and wildebeest.


The zebras follow where the grass grows. NHFU/Hannah Gormley.


The allure of the Pans comes in the form of grass. The Delta is remarkably nutrient-void, whereas the palm belt of the Mgkadigkadi provides annual grasses rich in protein and nutrients, which is exactly what the zebra’s need to support the demanding task of producing milk for their foals. The surrounding flat landscape also has a benefit for predator detection, who are never far behind... At the first drops of rain around December, the zebras begin their long march south. They travel as much as 300-miles in search of this paradise and, by the height of the rainy season, it is estimated that the pans are a temporary home to nearly 30,000 zebras. They stay here until March, when the water all but disappears and then begin their arduous journey back again. Now, in mid-winter, the Okavango’s zebra population is at an all-time high. But it is interesting to note that only 55% of the them actually undertake this journey, the others gambling on staying at home – why, as with so much of this story, remains a mystery.


As the zebras migrate, danger is never far behind. NHFU/Hannah Gormley.


So how did this epic migration stay a secret for so long? After a lucrative deal was signed with the European Union shortly after Botswana’s independence, the country developed a large cattle-industry. This, however, was plagued by diseases like foot-and-mouth, with which buffalos were suspected of being major vectors. Huge swathes of fencing was erected around the country, with little understanding of how this could impact wildlife migrations and, as a result, ancient migratory routes and important water sources were suddenly cut-off. Today, Botswana’s thriving tourism industry is both a major employer and a crucial source of income and, thanks to the foresight of a proud country that has always seen the untapped potential in wildlife tourism, the fences were removed in 2004. Tracking collars placed on healthy female zebras saw, for the first time, something astonishing – an epic migration of over 300-miles. By studying the anecdotal evidence, the scientists involved in the study realised that this behaviour had also been documented before the fences. What is remarkable is that they were erected for much longer than the average lifespan of a zebra and, yet, as soon as they were removed, the zebras immediately took up the ancient ancestral pilgrimage that their migratory clocks were telling them to pursue.


The Delta is dissected by ancient migratory trails. NHFU/Hannah Gormley.


This story is a fantastic example of how much we have so much left to learn about our wild animal populations and how, with a little luck, if we reverse the impacts of human interference, they may just come bouncing back. So, next time you read an upsetting story of an animal on the brink of extinction, don't give up - there is still hope. Find out what you can do to make the difference.


Blog by Hannah Gormley