Plus evolutionary history shows plenty of examples of animals switching from pure carnivore to pure herbivore to omnivores in between, and back the other direction. All birds are descended from a common carnivorous ancestor, but plenty of birds today subsist mostly on seeds or fruit.
If there is a lot of available biomass to be eaten, nature will find a way and some animal is going to fill that niche. Many of the folivores (herbivores specializing in digesting leaves) that descended from carnivores have to deal with the low nutrient/calorie density of their foods by just eating a lot of it, and have varying levels of microbial symbiosis for helping with that digestion.
Plus evolutionary history shows plenty of examples of animals switching from pure carnivore to pure herbivore to omnivores in between, and back the other direction. All birds are descended from a common carnivorous ancestor, but plenty of birds today subsist mostly on seeds or fruit.
If there is a lot of available biomass to be eaten, nature will find a way and some animal is going to fill that niche. Many of the folivores (herbivores specializing in digesting leaves) that descended from carnivores have to deal with the low nutrient/calorie density of their foods by just eating a lot of it, and have varying levels of microbial symbiosis for helping with that digestion.