The hairy shrew split from its ancestor to become what you see here. Fur, a great way to lock in heat, began to develop on the hairy shrew, slowly begging to replace its blubber. The shrew still retains some of its blubber, but with less blubber, the hairy shrew was able to grow less bulky. This has allowed it to become a faster, more agile predator. Though not an extremely fast runner, this is still a decent boost in speed for the organism.
Artwork by OviraptorFan