What is Predation?

Sun is the ultimate source of enegry for all life on earth. The plants use this energy to make food. This energy is transfered when the plants get consumed by other organims, and eventually, this energy makes its way up the food chain. Predation is a feeding habit where an organism hunts another organism for its sustenance. It is one among the feeding behaviours that includes micro-predation and parasitism and scavengers.


What are Predators?

As stated before, predation involves organisms that hunt other organisms for food. These organisms that hunt are termed as predators. The organisms that are consumed by the predators are known as prey. Typically, we associate predators only with big, apex carnivores like tigers, lions and bears. But this is just half the picture.

Usually, predators are suited to catch specific prey. For instance, plants like Venus flytrap evolved to capture only certain insects like ants, spiders and beetles and grasshoppers. Blue whales for instance, only eat krill and tiny crustaceans called copepods. Sharks like Great Whites prefer to eat seals. Omnivores like humans and bears can consume both animal tissues and plant tissues.

Functional Response

The relationship between the average number of prey consumed by each predator per unit time vs. prey density.

Type I Functional Response

Explanation: Each individual predator takes a fixed fraction of the prey population each time period. If prey density double, the number each predator eats per day doubles Assumptions

Assumptions: Encounter and kill rate is a simple fraction of prey population, No “saturation” or “satiation” of predator. No “handling” or “processing” time. No “switching” from one prey species to another.

Biological Basis: Likely valid for the lower range of prey densities for some species

Type II Functional Response

Explanation: “Saturating functional response” As prey density increases, the number of prey each predator eats per day reaches a constant number.

Assumptions: Encounter rate initially limits predation, but processing/handling time (including digestion) or satiation eventually limits food intake No “switching” from one prey species to another

Biological Basis: Likely applies to most predators, and a nearly Type I response occurs over a lower range of prey density.

Numerical Response

The increase in the number of predators by reproduction and immigration with increases in the prey population. Functional response is usually associated with this factor. Numerical Response has two mechanisms namely, demographic response and the aggregational response.

The demographic response consists of the changes in predator reproduction rates due to changes in the prey population. The aggregational response is the change in predator population due to migration into an area with higher prey population.

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