What limits the abundance of top-level carnivores in an ecosystem?
Energy availability limits top carnivores because production decreases at every trophic transfer. Apex predators depend on a broad prey base, require large home ranges, and occur at low population density; a small decline in lower-level production can therefore make their populations nonviable. Competition, climate, and predation can matter locally, but they operate within this energetic constraint. The pattern also explains why habitat fragmentation and prey depletion disproportionately threaten large predators and why their recovery requires restoration of lower trophic levels. The ten-perce
Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 3