The tracks that animals left behind
Winter is the season of concerts, ballet performances, rich food and winter sports, but you don’t need to be a skier to enjoy a walk in the snow. There’s a lot to see and even though I used to get cold when on a winter forest walk with my grandfather, he always found something exciting to show me in the snow (and at the end of the walk there always was the hot bouillon in the restaurant). The footprints in the snow (so aptly celebrated in a song by Bill Monroe) left by various animals can actually tell stories. “Here, a marten has chased a squirrel”, my grandfather would point out to me. A little further we’d notice footprints of a deer and then some wild pig. The fox’s prints and the rabbits are the easiest, I remember. And the tiny little ones with a thin line are from rats or mice with their long tails.
Footprints are not restricted to snow, but also visible in sand (Australian Aborigines and African Sān are the world’s best ‘readers’) unless the wind covers them or the rain washes them away. When I was in North Korea I saw a newly married couple write their vows with their fingers into the wet sand of the beach, only to see their semi-secret wishes get erased by the next wave. But there are, of course, beaches that have footprints that did not become erased, but became lithificated, which means they became fossil footprints. Originally made by heavy animals in wet sediments, e.g. mud, they hardened and became preserved and are now visible in various places on Earth. In Scotland the island of Skye is famous for its 165 million year old dinosaur footprints visible at low tide and on the beach near the town of Broome in Western Australia there must have been a real stampede of dinosaurs who left more than 1000 footprints on sandstone 130 million years ago when there was a river delta in that region. The largest ever seen footprint of 1.7 m in diameter probably belonged to a Brontosaurus. It is amazing to read that some ‘collectors’ even tried to dig out some of these prints, which is a highly illegal activity.
Footprints of animals that lived millions of years ago are found in all regions of the world, but apart from the sites mentioned above, those from Portugal, the Andes, Arizona and Sth. Korea are particularly well studied. Several criteria are used to match the footprints and the animals that made them. To determine the age and the type of the sediment is important; size and shape of the imprint are also important and number and lengths of the toes can be a “giveaway”. Web-footed tracks are known from South Korea and three-toed prints (the middle toe being the longest) are typical of the prints from the Scottish island of Skye. The prints not only tell the palaeontologist who has walked along a particular area how many million years ago, but they also provide information on the type of gait used by the animal and whether an individual was a member of a group, was chased by a predator or perhaps was an injured and limping individual. Fossil footprints are known from dinosaurs, birds, mammals, lizards, and even arthropods. Fossil prints from Sth. Korea have even shown that some crocodiles might have moved around on 2 legs.
Of course, all the footprints are the result of depressions in the substrate (one should think). But I observed something peculiar when in Antarctica: my footprints did not leave depressions in the snow, but turned into the opposite: positive, raised footprint reliefs! The reason was that the Polar snow was so fine and powdery that it was immediately blown away by the wind except for the area where the weight of my foot had compressed it. Raised footprints in the snow: a unique feature of Antarctica!
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2020.
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