system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are most of the herbivores mammals like elephants, rhinos, hippos, giraffe, etc. so big in size? Even in the jurassic era the largest dinosaur was a herbivore.
gpt
It's a matter of resources, and how to obtain them. There is a lot of plant matter, which is relatively easy to renew; if an animal is adapted to grazing, the resources are plentiful, and once they get past a certain size, there is basically no carnivore that will prey on them (though their babies may be fair game for predators).


For carnivores, it's a different story: being too large would be detrimental to agility and it may make it impossible to catch prey. There is also less to eat, according to the biological food pyramid, as carnivores are secondary or tertiary consumers. Herbivores are primary consumers.