Why are there fewer tertiary consumers than secondary consumers?

The number of individuals at each trophic level decreases as you work your way up the food chain. This phenomenon, called an ecological pyramid, is due to the fact that a significant portion of the energy at each trophic level is lost as heat. This means that there is less energy available to support the organisms at the next trophic level. As a result, there are typically fewer tertiary consumers than secondary consumers, and even fewer quaternary consumers.

To illustrate this, consider the following simplified food chain:

Grass → Grasshopper → Bird → Hawk

In this food chain, the grass produces energy through photosynthesis. The grasshopper eats the grass, and some of the energy from the grass is transferred to the grasshopper. The bird then eats the grasshopper, and some of the energy from the grasshopper is transferred to the bird. Finally, the hawk eats the bird, and some of the energy from the bird is transferred to the hawk.

At each step in this food chain, a significant portion of the energy is lost as heat. This is because the organisms at each trophic level use some of the energy they consume to maintain their own bodies, and the rest is lost as heat. As a result, there is less energy available to support the organisms at the next trophic level.

This is why there are typically fewer tertiary consumers than secondary consumers, and even fewer quaternary consumers. The further you move up the food chain, the less energy is available, and the fewer organisms there are able to survive.