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Defence mechanism (biology) |
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It has been suggested that this article or section be merged with antipredator adaptation. (Discuss) |
Many plants and animals have developed physical defence mechanisms (British spelling; defense mechanisms in American English).
Grazing mammals often feed in herds. When a predator attacks, the herd runs and may scatter, perhaps confusing the predator and allowing most, if not all, of the prey animals to escape. Alternatively, small animals may freeze in cover or play dead when seen. Smaller animals may not venture too far from their cover in the undergrowth of dense vegetation, where they can quickly hide when danger approaches. Many animals have keen senses of sight, smell, and hearing so that they can detect danger and escape. Some mammals have horns or antlers to fight off predators. Others are active only at night (nocturnal) when it is harder for predators to find them.
Some animals use visual scanning as a defense mechanism, especially in the open. They will typically monitor their surroundings closely to avoid attack by hoping to see a predator before it reaches the critical distance for an attack. This is a standard defense mechanism for animals in open environments, such as grasslands and prairies. It is also common for animals that are arboreal, such as primates, which typically scan the ground around them for terrestrial predators, as well as the sky for aerial predators.
Prey animals may use alarm calls to alert their social group. These are specialized cries that are only used when a predator is sighted or sensed. Such cries are often inherited, though in some cases they are adjusted during early learning. Alarm calls in some social mammals may distinguish between birds, snakes and felines as predators.
Many animals rely on camouflage or the ability to blend in with their surroundings to hide from predators: cryptic coloration. Unpalatable animals often signal by means of bright warning coloration: aposematic coloration.
Some animals use noxious chemicals which they spray from various parts of their bodies to deter predators. A few animals rely on trickery and copy the defences of other animals to protect themselves: mimicry.
Japanese Honeybees isolate and mob Giant Asian Hornets, vibrating their flight muscles in order to raise the temperature around the Asian Hornet scout to lethal levels, rather than allowing the scout to bring others to the Honeybees' hive. This is a rather specialized example of concerted social action: mobbing.
Many plant species have, over the course of their evolutionary history, developed physical and chemical defense mechanisms to deter herbivores. Prickles, spines, and thorns are examples of physical mechanisms. Stinging nettle plants are covered in small hairs that contain chemicals that are a skin irritant to many mammals, including humans.
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