What is a short story that has animals as the main characters and teaches an…

A fable is a short narrative, in prose or verse, in which animals, plants, or other non-human characters are given human speech and behaviour, and the story closes with an explicit moral lesson stated directly for the reader. Both traits together — non-human protagonists acting like people, and a stated moral — are what mark a story out as a fable rather than any other narrative genre.

The story described in the question is built around animal characters and is written specifically to teach an explicit moral. That exact combination — animal main characters plus an explicit moral — is the defining signature of the fable form, so the story type being asked about is a fable.

Checking this against the other genres offered confirms the choice: fantasy stories are defined by magical or supernatural elements, not specifically by animal characters teaching a moral; science fiction centres on futuristic technology or scientific speculation; and a travelogue is a non-fiction record of a real journey, not a fictional narrative at all. None of these three share the fable's defining combination of animal characters and an explicit moral, so fable is the only genre that fits both conditions in the question.