This is where I can share what I learned in my ecology classes! There’s a concept called the ecological pyramid. The base comprises the primary producers, that is, plants which produce biomass with solar energy through photosynthesis. The next trophic level is the primary consumers, that is, herbivores that eat plant biomass. It’s a pyramid shape because the rule of thumb is that only about 10% of the original solar energy makes it up to the next trophic level.

Guinea pigs are primary consumers. Tigers are secondary or tertiary consumers, eating animals which eat plants, or even animals which eat other organisms which eat plants. Only about 1% of the original solar energy in the plants eaten by the animals the tigers ate goes into making new tiger biomass, compared to 10% of the energy from the plants going into making new guinea pig. And since tigers are much, much bigger, there have to be a lot fewer of them.

A tiger’s size gives it a big enough hunting advantage that, well, the world has tigers in it, but necessarily limits the numbers of the tiger population.