Rising global temperatures might mean Father Christmas needs to add an extra reindeer to his line-up.
Reindeer in Norway are now 12% smaller than they were 21 years ago - because the warmer climate is affecting their food supply. Milder weather means more rain than snow, which causes ice sheets to form and trap the animals' food. As smaller females give birth to smaller calves the cycle continues.
The size of reindeer might not seem like a big problem, but it shows how climate change is continuing to affect wildlife.