Reindeer, or caribou, can outperform all other land animals in their energy efficiency - so are a fitting choice as the legendary Christmas sleigh-pullers! They're more usually seen on their mammoth annual migration to the Arctic during which the North American herds might travel for more than 5,000km - an extraordinary feat that takes them further than any other land mammal. A warm, insulating coat and large hooves are vital to their survival strategy against the extreme cold and snow of the Arctic. Reindeer are the only deer where both males and females sport antlers, complex structures that can reach epic proportions in males.

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