Defence mechanism (biology)

Many plants and animals have developed physical defence mechanisms (American English). (British spelling; defense mechanisms)

Animals

Grazing animals often feed in herds. When a predator attacks, the animals in different directions, often confusing the predator and allowing most, if not all, of the prey animals to escape. Some animals never venture too far from their home in underground dens or thick vegetation and 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 animals have horns or antlers to fight off predators. Some animals are active only at night (nocturnal) when it is harder for predators to find them.

Some animals use visual scanning as a defense mechanism. They will typically monitor their surroundings closely in an effort to prevent an attack by hoping to see a predator before it approaches close enough to attack. This is a common 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 predators.

Animals that use vocalizations often have predator cries. These are specialized cries that are only used when a predator is sighted or sensed. They will typically warn all other animals of the same species to be on the lookout or flee.

Many animals rely on camouflage or the ability to blend in with their surroundings to hide from predators. A few animals are even poisonous or unpleasant-tasting, and predators soon learn to leave such animals alone. These poisonous kinds of animals are often brightly colored, as well, which acts as a warning to predators.

Some animals use 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.

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.

Plants

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.