Vampire cannibalism... Yep it's a real thing. It really should be no surprise. The cannibalism between different species isn't anything new. Beings have been eating each other as long as they've been breathing. Sometimes it's out of necessity & sometimes it's just for fun.
One question i get asked a lot is, if a Psy vamp bites/eats a Sang vamp does the Psy vamp get the Sang vamp power? And all scenarios of the whole vamp biting another vamp thing.
Answer: nope. They don't get any super powers from eating each other.
The only thing they gain is a meal. Some vamps love the taste of blood. Some vamps love the taste of flesh. Some kill out of necessity. Some kill for sport.
This really stretches across the board though. Cannibals can be found in humanoid species like Dwarves, Giants, Fae, Elves, & can be found in Werewolves, Chupacabras, Dragons, Gargoyles, etc.
People tend to forget that folklore is not a human thing, it's a widespread phenomena that circulated all civilizations of all species. Because of this the idea that eating something or someone else might give you some special bonus is not singular to the human species.
The act of cannibalism is derived from individual variation via DNA, or through the nurture learned through their local tribe/group. Sometimes it's a practice of ritual, sometimes they are just a group of ruthless, bloodthirsty killers who could care less where their next meal comes from.
Kind of puts things in perspective when it comes to some of the stories of ravenous beings.