Oops - airbending here was meant as "creature of the air".
Predatory relationships continue even when an animal is domesticated. For example, just because farmers began to herd sheep it didn't remove sheep from the food chain - they were still eaten by, well, wolves.
We haven't seen any Wolfbats at the Air Temples, or in the Fire Nation in the case of the new herd, & it is unlikely that the Air Nomads would keep them around if they ate their mounts. As seen with Appa, Flying Bison tended to stay with their masters, who would chase off hungry Wolfbats if able. If unable, well, disappearing Nomads would prompt the Monk Council to do something about it, likely a mass relocation of the offending Wolfbats.
actually, it might offer a possible explanation as to why there are so few flying bison around (aside from being hunted by humans).
However, I can't imagine wolfbats would be a very serious threat on the flying bison population - after all, bison are imaginably very difficult to take down, and i don't think wolfbats would go after them very frequently even if they were, in fact, one their predators
I guess it would make sense being that they would be one of the only animals able to pursue a Sky Bison. The only thing is that they only appear in certain sections of the EK and nowhere near the Air Temples. Even if they were relocated by the Air Nomads, wouldn't they have moved back during the 100 years of no one living in or near the temples?
Wild - I completely agree. If wolfbats ever did go after i bison, i can't imagine them not doing it as a pack due to the size difference. Even then, they may only go after the young, sick, old, etc.
Swamp - their territories may have changed due to the increasing rarity of bison (which i believe to be an outcome of over hunting by humans). If the bison were gone, they may have no more reason to remain there. However, wolfbats were only featured for a brief period, so we know very little about them and there's a lot of room for speculation. Perhaps they do currently, or could have lived near air temples at some point. In any case I imagine they were more widespread in the past, but as human cities expanded out from the lion turtles a lot of the wolfbat population probably suffered from habitat damage, hunting, or loss of prey. This would basically force them into very small areas, such as the cave of two lovers, and make them much less common. I mean, if i were part of an earthkingdom village and there were flying wolves that constantly tried to eat my pigsheep, I'd certainly want to gather some friends and do a bit of "pest control". (not to say that I don't like the idea of wolbats, they and most of the avatar chimeras are pretty cool)
The other problem is the sheer size of sky bison. They're enormous - far, far larger than wolfbats. So, while I'm not saying it's impossible, I do think it unlikely that wolfbats would be able to effectively target an adult sky bison, unless they were to attack in massive numbers - which I suppose is possible.
Far more likely, I think, is that they would try to go after infant and juvenile animals, rather than adults.