I wonder why this list specifically and not other animals...? And was this purely for the Vinaya (part of their many vows?) or for lay persons as well?
In the case of elephant flesh, the elephant of King Bimbisāra died and the low caste butchers went to go eat it, along with a few monks. Some people asked the Buddha about this and the rule against eating elephant flash was established. In the case of vultures, as the story goes the monks ate some vulture meat and a bunch of them followed them into the woods, squawking at them, whereupon the Buddha then banned the consumption of vulture flesh.
It was a case by case basis.
Human flesh was apparently used in medicine.