page_title: Pest (organism)
section_title: Animals as pests
hierarchical_section_title: Pest (organism) / Concept / Animals as pests
caption_attribution_description: trafalgar square, pigeon, city of westminster, chordata, animalia, aves, columbidae, columbiformes
context_page_description: A pest is any animal or plant deleterious to humans or human concerns. The term is particularly used for creatures that damage crops, livestock and forestry, or cause a nuisance to people, especially in their homes. Humans have modified the environment for their own purposes and are intolerant of other creatures occupying the same space when their activities impact adversely on human objectives. Thus, an elephant is unobjectionable in its natural habitat but a pest if it tramples crops.
  Some animals are disliked because they bite or sting; snakes, wasps, ants, bed bugs, fleas and ticks belong in this category. Others enter the home thus invading our own private space; these include houseflies, which land on and contaminate food, beetles which tunnel into the woodwork, and other animals that scuttle about on the floor at night, like cockroaches, rats and mice, which are often associated with insanitary conditions.
  Agricultural and horticultural crops are attacked by a wide variety of pests, the most important being insects, mites, nematodes and gastropod molluscs.
context_section_description: Animals are considered pests or vermin when they injure people or damage crops, forestry or buildings. Elephants are regarded as pests by the farmers whose crops they raid and trample. Mosquitoes and ticks are vectors that can transmit ailments, but are also pests because of the distress caused by their bites. Grasshoppers are usually solitary herbivores of little economic importance until the conditions are met for them to enter a swarming phase, become locusts and cause enormous damage. Many people appreciate birds in the countryside and their gardens, but when these accumulate in large masses, they can be a nuisance. Flocks of starlings can consist of hundreds of thousands of individual birds, their roosts can be noisy and their droppings voluminous; the droppings are acidic and can cause corrosion of metals, stonework and brickwork as well as being unsightly. Pigeons in urban settings may be a health hazard, and gulls near the coast can become a nuisance, especially if they become bold enough to snatch food from passers-by. All birds are a risk at airfields where they can be sucked into aircraft engines. Woodpeckers sometimes excavate holes in buildings, fencing and utility poles, causing structural damage; they also drum on various reverberatory structures on buildings such as gutters, down-spouts, chimneys, vents and aluminium sheeting. Jellyfish can form vast swarms which may be responsible for damage to fishing gear, and sometimes clog the cooling systems of power and desalination plants which draw their water from the sea.
  Many of the animals that we regard as pests live in our homes. Before humans built dwellings, these creatures lived in the wider environment, but co-evolved with humans, adapting to the warm, sheltered conditions that a house provides, the wooden timbers, the furnishings, the food supplies and the rubbish dumps. Many no longer exist as free-living organisms in the outside world, and can therefore be considered to be domesticated. The St Kilda house mouse rapidly became extinct when the last islander left the island of St Kilda, Scotland in 1930, but the St Kilda field mouse survived.
caption: Feral pigeons can become very numerous in cities.
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