page_title: Defence against predators
section_title: Methods
hierarchical_section_title: Defence against predators / Secondary defences / Methods
caption_attribution_description: Io moths, Automeris io, female (upper), male (lower). Captured and posed. Location: Durham County, North Carolina, United States
context_page_description: For most animals, defence against predators is vital. Being eaten is not the only threat to life: parasites and diseases may also be fatal. But animals, especially small animals, are often eaten.
  Since life is about reproduction, anything that keeps a creature alive long enough for it to reproduce will be selected for. The next generation comes from the fertilised eggs of the previous generation.
  Not surprisingly, then, animals have developed a wide range of defences against predation. Some of these defences apply also to plants: herbivory on plants can be very damaging, and reduce a plant's fertility. Many plants have some defence against herbivores.
context_section_description: Withdraw to a prepared retreat: many methods. The pearl-fish Carapus apis retreats backwards into the anus, and then into the body cavity of a sea cucumber (Holothuria).ᵖ¹³⁸ It turns out that the fish, when a juvenile, is a parasite on the sea cucumber. Although it is free-living as an adult, it is still able to re-enter the holothurian when danger threatens. Better-known examples include the tortoise, which just withdraws its head and legs under its shell, and the hermit crab, which retreats into its shell when in danger.
  Flee: run or fly away: a popular plan. Animals may flee in a straight line, or zig-zag. Another method is to fly showing some flash colour, and then suddenly settle completely still in camouflage. There are a number of moths with bright hind wings which are covered when at rest.
  Bluff: look threatening or startling (deimatic behaviour). The prey may adopt a posture which causes the predator to pause. This is sometimes called a 'startle display'. The predator may not know whether the display is  a genuine threat or a bluff. Either way, the prey has improved its chance of escape.
  Play dead (thanatosis): many vertebrate predators reject dead animals. Many predators strike to kill only on prey which move. That includes cats, lizards and mantids. A number of insects play dead when attacked. Some larger animals also do this, like the American Opossum. What playing dead does is avoid releasing the predator's inherited killing behaviour.
  Deflect or distract the attack. Many offer a non-essential part of the body, for example, butterflies whose wings have small 'targets' near the edges. Cuttlefish squirt out a cloud of black ink, turn pale and swim fast away from the ink. The Kentish plover, which lays its eggs on the ground, lures attackers away from the eggs. It uses a remarkable impression of being damaged with a broken wing. When the predator is well away from the eggs, the bird flies off.ᵖ¹⁷⁵ Other plovers sit on imaginary nest sites: both methods are distraction displays. Quite a number of animals can break off a non-essential part of their body, and may regenerate it later.ᵖ¹⁷⁹
  Fight back (retaliation or fighting defence): there are a very large number of animal weapons, and many are used for face-to-face fighting. Bombardier beetles squirt hot poisonous liquid at attackers. Large herbivores often carry weapons: Triceratops, Iguanodon, elephants, deer, Rhinoceros, Hippopotamus. Almost always the weapons are used for several functions, not just fighting predators.
  Band together: many animals use defensive groups against predators. Very common in birds and mammals.
caption: Moth Automeris io shows startle display on its rear wings
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop 7.0", "Image DateTime": "2006:05:08 11:02:16", "Image ExifOffset": "156", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "294", "Thumbnail JPEGInterchangeFormatLength": "4401", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "1024", "EXIF ExifImageLength": "564"}