Polar bear
From Equestripedia, the Archives of Equestria!
Polar bears are a sub-species of Bears that live in the northern regions of Earth. Pinkie Pie rode a polar bear when she traveled beyond the Northern pass into The Grove while she trekked throughout The Frozen North in order to find the Gift Givers of the Grove.
Like bears, Polar bears seem to be generally harmless and gentle creatures, though it may have simply been because of Pinkie Pie's potential training of it.