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5a4 Animal Defenses

Animal Defenses Flight, Fight, Freeze, and More

5a4 Animal Defenses
5a4 Animal Defenses

Animal Defenses Objectives

  • List different types of animal structural and behavioral defenses and provide an example of a species that utilizes each defense.
  • Describe different forms of  camouflage including the species and form of camouflage, and how the camouflage works.
Prey animals are not just waiting to be eaten; they have a variety of defenses that enable them to elude predation.
5a4 Animal Defenses
Species that are vulnerable to predation have a combination of structures and accompanying behaviors to escape being eaten.
This video demonstrates a variety of prey defenses.
This “feigning beetle,” native to southwestern North America, has a response that is similar to opossums.  Watch its response to being picked up and how quickly it recovers.
Sea slugs like terrestrial slugs are mollusks, relatives of snails, clams, and octopuses.  Most seas slugs can release potentially toxic substances when attacked by a potential predator. 
In some cases, prey are defending family members.  This kildeer doesn’t actually have a broken wing, it is flapping an uninjured wing while loudly squawking to draw attention away from its nest, full of eggs.  Once the predator closes in, it will fly out of reach. The kildeer is in danger of being eaten itself, but if its offspring survive, it will pass on its genetic information. 
5a4 Animal Defenses

Camouflage

Camouflage sounds simple: blending in with your surroundings.  However there are diverse forms of camouflage that address particular threats.

5a4 Animal Defenses
Patterns mimicking shade and dappled light enable even large organisms to blend into their surroundings.
Vertical striping can enable herbivores to blend into grass fields, or make it difficult to discern between individuals in a herd.
5a4 Animal Defenses
Vertical striping patterns enable these fish to blend with aquatic plants and algae.
Iridescence in fish and insects may make it difficult for predators to follow prey as they move from light to shadow.
Countershading, different colors on the top and bottom of an animal, allows it to blend with sky from one angle, and ground or water from the other.
5a4 Animal Defenses
Note how color, pattern, and reduced movement work together to camouflage these species.
Some insect species flash a bright color when they are approached by a predator.  This may temporarily startle the predator, enabling the insect to escape.  These are two different moth species that “flash and startle.”
5a4 Animal Defenses
Moth adults and larvae (caterpillars have a variety of forms of camouflage.  This video introduces “eye spots.”
A photo of eyespots on a butterflyfish and the Io moth.
5a4 Animal Defenses
Taking it a step further, these caterpillars have abdomens that look like false snake heads.  They can even inflate them to look more menacing.
5a4 Animal Defenses
Some species, including this skunk and milkweed bugs use bold colors to warn away potential predators.  Bright colors can indicate chemical toxins are present.
5a4 Animal Defenses
5a4 Animal Defenses
Another option is to mimic something a predator is not likely to eat.  This hoverfly looks like a bee, and is less likely to be eaten by birds.  If this hoverfly survives and reproduces, it has a high level of fitness due to its appearance.
The species on the left is unpalatable and unlikely to be eaten by birds.  The species on the right is a mimic: it looks similar enough to the other species, birds will not eat this one either. 
5a4 Animal Defenses
5a4 Animal Defenses
Humans have adopted the idea of mimicry to develop new materials and services.
Biomimicry is designing products that are based on structures found in nature.
Understanding how animal structures relate to their functions has led to the development of human products, a clear connection between science and other fields of study.
This is the end of the Nutrients Guide.  Material from this guide and corresponding lecture, along with the next Predation Guide are assessed on the weekly quiz.
5a4 Animal Defenses
Check your knowledge.  Can you:
  • list different types of animal structural and behavioral defenses and provide an example of a species that utilizes each defense?
  • describe different forms of  camouflage including the species and form of camouflage, and how the camouflage works?
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