I agree with Rusty. The physical description of the bull as a black-haired one is literal, since there must be also brown bulls.
I also agree that "fighting bulls" or "fierce bulls" may be used for "toros bravos", because the tame ones (there are) can't be used for bull fighting. It's important that the business that breed bulls for this activity "guarantee" that the bull will actually charge against the toreador; the ones that won't be interested are boring to watch for the fans.
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