Carnivorans are important predators in many ecosystems, acting as a "top-down" control on populations of their prey. Many are such an important control on their prey that they act as keystone species, and their removal has drastic consequences for the ecosystem. For example, wolves were recently reintroduced to Yellowstone National Park after being extirpated for nearly 70 years, and their predation on elk has allowed woody plants to recover from overbrowsing.

Carnivores host a wide range of internal and external parasites, including protozoans, nematodes, trematodes, cestodes, fleas, lice, and ticks.

Ecosystem Impact: keystone species

Commensal/Parasitic Species:

• protozoans
• nematodes (Nematoda)
• trematodes (Trematoda)
• cestodes (Cestoda)
• fleas (Siphonaptera)
• lice (Anoplura)
• ticks (Acari)