Predators can be classified by their
 with their prey. Two factors are considered here: how close the predator and prey (or
host) are, and whether the prey is directly killed by the predator, where true predation and parasitoidism involve certain death.
A true predator is one that kills and eats another living thing. Predators may hunt actively for prey in
pursuit predation, or sit and wait for prey to approach within striking distance in
 Some predators kill large prey and dismember or chew it prior to eating it, as do
humans; others may eat their prey whole, as do
bottlenose dolphins swallowing fish,
white storks swallowing
baleen whales swallowing thousands of
krill or small fish at once.
 Some predators use
venom to subdue their prey before the predator ingests it, as in the
 while the venom of
rattlesnakes and some
spiders also helps to digest the prey.
Seed and egg predation are true predation, as
eggs are potential organisms.
Grazing animals generally do not kill their prey, but like predators, they live by feeding on other organisms. While some herbivores like
zooplankton live on unicellular
phytoplankton and therefore inevitably kill what they eat, in a relationship sometimes called predation,
 many others including
sheep only eat a part of the plants that they graze.
 Many species of plant are adapted to regrow after grazing damage. For example, the growing
grasses are not at the tips as they are in most flowering plants, but at the base of the leaves.
kelp is grazed in subtidal kelp forests, but continuously regrows from a meristem at the base of the blade where it joins the
 Animals may also be 'grazed' upon;
 such as female
mosquitoes land on hosts briefly to feed on blood.
Herbivore-plant interactions, as with predator-prey interactions, have driven plants to evolve defences such as thorns and chemicals to dissuade grazing.
interact with their
, not killing their hosts.
sooner or later kill their hosts, while predators kill their prey immediately. There is a continuum between these feeding strategies.
Parasites, like predators, live by feeding on another organism. The entomologist
E. O. Wilson has characterised parasites as "predators that eat prey in units of less than one".
 Parasites often do not kill their hosts, the exception being
parasitoids which always do, thus blurring the line between parasitism and predation.
 Equally, small parasites such as
mosquitoes exploit their
hosts much as micropredators such as moth
caterpillars on an
oak tree and grazers do, though
endoparasites in particular have a close association with their host species; again there is essentially a continuum between these feeding interactions.
Parasitoids are organisms living in or on their host and feeding directly upon it, eventually leading to its death. They are much like parasites in their close associations with their hosts. Unlike typical parasites, they always kill their hosts, but often not instantly.
Parasitoid wasps are solitary insects that live a free life as adults, laying eggs on or in other insects such as lepidopteran caterpillars. The wasp larvae feed on the growing host, eventually killing it. Parasitoids make up as much as 10% of all insect species.