The Lankavatara Sutra: If meat-eaters should be reborn in the animal realm, they would be carnivores for sure. It is because their predilection for meat in this life has left a strong habitual tendency of craving for meat in their alaya consciousness. When they take rebirth, the body may have changed, but the habitual tendencies still remain in the alaya consciousness. We can see that when this tendency is in force, some carnivores, just a few hours after being born, would hunt other small animals for food without ever being taught how to. Because they were meat-eaters in the past, the tendency to eat meat is very strong. Coupled with the fact that being animals now makes them unable to choose right from wrong, they cannot help killing for food again this time around. This is the most terrifying aspect.

[Excerpt from Luminous Wisdom Book Series 1: The Right View ~Why Vegetarian?]