Population Interactions – Predation


It is a type of interaction in which members of one species kills and eats up members of the other species.

  • Species that captures is the predator and the species that is killed is the prey.
  • Most animals are predators leaving the scavengers.

  • Insectivorous plants are also predators

e.g., Nepenthes, Utricularia, Dionaea, Drosera.

  • It is nature’s way of transferring energy fixed by plants to higher trophic levels.
  • They help in keeping the prey population under control or due to high population densities they can cause instability in the ecosystem.

Biological control of pests:

  • This relationship is used in Agriculture for biological control of pests.
  • Opuntia introduced in Australia created havoc by spreading rapidly, it was brought under control by introducing its natural herbivore Cactoblastis (cochineal insect).
  • Red Locust menace in Mauritius was controlled by Mynah.
  • Red foxes became top carnivores in New Zealand due to the absence of natural carnivores.

Predators help in maintaining species diversity in a community by reducing competition among competing prey species.


In the rocky intertidal communities of American Pacific coasts, the starfish Pisaster is an important predator. On its removal, more than 10 species of invertebrates became extinct due to interspecific competition.

  • Predators are prudent (careful) as overexploiting its prey would make them extinct and thus the predators too will become extinct.

Preys have developed various defenses to protect themselves from predators.

  • Camouflage – some insects and frogs are cryptically colored so that the predators cannot detect them.
  • E.g., Grasshopper resembles a green leaf.

Praying Mantis resembles twigs.

Stick insect resembles dead leaves.

  • Some are poisonous. E.g., The monarch butterfly is highly distasteful. It acquires the toxic glycosides by feeding on a poisonous milkweed during its caterpillar stage.
  • Herbivores are plant predators.
  • 25% insects are phytophagous feeding on plant sap.
  • Plants too have developed morphological and chemical defenses. E.g., Thorns present in Acacia & Cactus.
  • Weed Calotropis produces highly poisonous cardiac glycosides which make the herbivores sick and may even kill them.
  • Chemical substances produced as a defense against herbivores are Nicotine, caffeine, quinine, strychnine, opium.
  • Mimicry is the resemblance of one species with another to obtain advantage against predation.
  • Batesian mimicry – the mimic is defenseless, it resembles a dangerous animal so that the predator cannot prey upon it,

e.g., Viceroy butterfly mimics Monarch butterfly.

  • Mullerian mimicry–it is the resemblance of two insects, both are harmful to the predators, to their mutual benefit,

e.g., Monarch butterfly and Queen butterfly.













Also read:Ecology Mnemonic


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