What are the conditions for the validity of a wager (Rihan) on a race between animals?

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For a wager (Rihan) concerning animal racing to be valid, the two animals must be of the same species. If they belong to different species, such as a horse and a camel, the wager is invalid because the camel is unlikely to outpace the horse, thus defeating the purpose of the competition. The conditions for the individuals or types of animals are subject to scholarly debate if they are of different breeds within the same species, like an Arabian horse versus a Spanish mule (Bardhun), or different types of camels (Bakhiti versus 'Arabi). One view states it is invalid because the difference in speed is known by custom, resembling different species. Another view validates it because they are of the same species, either can potentially win, and the criterion of species is met, which is sufficient if the underlying wisdom (of testing skill) has a chance of being realized, even remotely.