Niyi Osundare's "The Leader and the Led" is a fable because of the use of animals who act as humans. A fable is a short narrative that uses non-human characters - typically animals - who speak, think, and behave like human beings in order to illustrate a moral lesson. This technique is called personification or anthropomorphism.
In "The Leader and the Led," various animals such as the lion, the hyena, the fox, the gazelle, and others come together to choose a leader. Each animal represents a particular human type or political figure: the lion embodies brute force, the hyena represents greed and opportunism, and the fox stands for cunning and deception. Through the animals' debate about leadership, Osundare satirises the politics of leadership selection in human society, particularly in the African context.
While the poem does contain satire and uses relatively simple language, these are not what make it a fable. The defining characteristic of a fable is that animals (or other non-human entities) stand in for humans and act out human situations to teach a lesson. The moral of this poem is that a good leader should be chosen by the people based on character and competence, not by force or deceit.