In his extensive publications, the ecologist Paul Colinvaux explains that rarity of the big and fierce animals is as a result of natural ecological order referred to as Eltonian Pyramids (Colinvaux, 1990). The concept of Eltonian Pyramids (put forward by Charles Elton) explains that the amount of energy or amount of biomass or number of individuals present at the base of a food chain are comparatively abundant and this declines to the top of the trophic levels (Fulbright, 2007). This is because food webs can only support fewer apex predators because the transfer or conversion of energy from one level to the next is inefficient, resulting to decline of energies consumed up the food web.
Large Fierce animals usually fall at the apex of the Eltonian Pyramid. Mostly carnivorous, they require more food to survive but at the tertiary level of ecological pyramid, there isn't enough food to support their demand due to inefficiencies of converting energies consumed up the food web. This means that they can only be fewer of such a species at this level of ecological pyramid (Krogh, 2002). In actual fact, research studies estimate that only 1/1000th of the energy found at the bottom of the ecological system (brought in by plant photosynthesis of solar energy) essentially makes it to the owl or hawk at the apex of the ecological system.
However, it is not only the inefficiencies in converting energies that limits the abundance of the large fierce animals today. The direct and indirect negative interference of humans have led to their decline (Ray, 2005). Hunters simply over-killed these animals (and/or their prey) for many reasons including protecting their livestock and pets, and for their own safety. Humans also killed simply to assert their "machismo" or superiority over everything found in their surrounding. Today, these animals are still being hunted to sell their parts such as fur, teeth, heads, horns/tusks, etc. Additionally, indirect human activities induce changes to the ecosystem (Fulbright, 2007). Such activities include forest clearing, environmental pollution, habitat destruction and fragmentation, fires etc. causes population declines of the large fierce animals. Encroachment of their natural habitats by humans reduces their natural roaming areas making it harder for them to survive.