Excerpt from the book Animals Evolution Avoided. This book describes 40 animals that ought to exist but don’t, because I made them up.

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Weasels are stealthy and cunning creatures. They know the best way they can achieve what they want. In Sierra Leone, Weasels in the forest live almost exclusively in the trees and rarely venture down to the forest floor where their lives might be in danger. Weasels quickly worked out that to move from tree to tree could be problematical. Jumping from branch to branch might work sometimes, but not always, especially if distances were more than a few feet.

The weasels of Sierra Leone worked out a way of moving around the forest. They hitched rides on the backs of the larger birds such as woodpeckers, parrots, and crows. The birds didn’t enjoy having a passenger on board and tended to fly the shortest distance possible, but this suited the weasel as it invariably meant the weasel was in a tree he hadn’t visited before.

The weasels were very smart and didn’t steal eggs from the nests of the birds who had given them lifts, in the hope the bird would provide a ride to another tree in the future. The birds eventually realised this and gradually the distances the birds took the weasels began to increase. Some birds even waited for the weasel to finish his investigation of a tree before taking the animal somewhere else.

This taxi service provided by the birds to the weasels is unique in the world of nature and is an amazing sight. Although the weasels balance on the backs of the birds, they can in no way steer the bird in a particular direction; the weasel has to go wherever the bird is flying to. A bird ferrying a weasel also gives off a particular call, indicating to other birds that the bird is not being attacked and is not in any danger. These sounds and the spectacle of an animal being ferried around by a bird, adds considerably to the experience of visiting the forests of Sierra Leone.