Third-level consumers, or tertiary consumers, are carnivores who eat primary and secondary consumers. This almost NEVER happens, but there is sometimes a level higher than the tertiary consumers that eats them. It rarely happens, so often the tertiary consumers do not get eaten. Also, as tertiary consumers eat the primary and secondary consumers, they receive 10% of their energy from the producers. What happens with that 90%? Well, the 90%, most of the time, is lost to the environment as heat. Anyway, there more tertiary consumers besides the red fox, like the eagle, for instance, but there aren't many of the tertiary consumers because there isn't enough energy to get to them, since only 10% is being transferred each time a predator eats a prey in the food chain.