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Animal Defense against Predators. TIP #2 for Chemical Ecology Phyllis Robinson, Keith Murphy and Melissa Greene. Animal Defense Against Predators. Throughout millions of years of evolution, animals have evolved numerous ways of defending themselves

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Animal Defense against Predators

TIP #2 for Chemical Ecology

Phyllis Robinson, Keith Murphy and Melissa Greene


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Animal Defense Against Predators

Throughout millions of years of evolution, animals

have evolved numerous ways of defending themselves

against predators. Obviously, being able to flee

a predator is the choice of many prey animals we

can consider.

However, there are some often overlooked but

interesting methods of defense which involve deception

and chemistry. These include using toxic chemicals,

camouflage, and mimicry.


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Animal Defense Against Predators

Presented here are several descriptions and

examples of animal defense.


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1. Chemical Defense

  • There are two main ways animals can use chemicals to defend themselves.

  • Animals can synthesize toxin using their own metabolic processes, or they can accumulate toxin from the food they eat.


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1. Chemical Defense

  • Animals which synthesize their own toxin are able to convert chemical compounds in their body to a poison.

  • There are many amphibians that produce skin toxins. The skin toxins are produced by special poison glands, usually located on the animal's back or throughout the skin.

Photo courtesy of Dr. John Daly

The poison dart frog has

poison glands scattered

all over its body.


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1. Chemical Defense

In another example, the fire salamander makes a nerve poison, which it can squirt from glands on its back.

Photo courtesy of Henk Wallays, Cal. Acad. of Sciences.


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1. Chemical Defense

Many animals accumulate toxin from their food rather than synthesizing it from scratch.

For example, the larvae of Monarch butterflies accumulate toxins from the plants they inhabit.  Birds that eat the Monarchs vomit and learn to avoid them in the future. 

Their bright coloration allows birds to remember and avoid them. 

Photo courtesy of T. W. Davies, Cal. Acad. of Sciences.


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1. Chemical Defense

  • Interestingly, many organisms which are distasteful advertise this fact to predators by having bright body colors or markings, as if to say, “Notice me! I’m dangerous!”


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1. Chemical Defense

You can see this in the

bright colors of the Monarch and the poison dart frog.

Photo courtesy of T. W. Davies, Cal. Acad. of Sciences.

Photo courtesy of Dr. John Daly


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1. Chemical Defense

This is called “aposematic

coloration”, and is widely used among the insects

and amphibians.

The Cream-spot Tiger is aposematically colored.


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2. Camouflage

Animals that camouflage themselves pretend to be something they are not. Either their coloration, marking patterns, or entire body resembles something else in their environment, here a leaf, an owl.


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2. Camouflage

Here an aptly named walking stick pretends to be a twig, in an attempt to avoid being seen by a bird or other predator. This is an example of cryptic coloration.

Photo courtesy of Dr. Lloyd Glenn Ingles, Cal. Acad. of Sciences.


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2. Camouflage

In this picture, a four-eyed butterfly fish uses deceptive markings. The large spot near the tail resembles an eye. When predators attack the wrong end, the butterfly fish can swim away in the other direction!


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2. Camouflage

Some predators also depend on camouflage, but this time it is in order to avoid being seen by their prey.

Here, a frogfish resembles

a sponge. Small fish swimming nearby will be engulfed in the frogfish’s enormous mouth!


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3. Mimicry

In mimicry, an organism (the mimic) closely resembles another organism (the model) in order to deceive a third, (the operator). The model and the mimic are not always closely related, but both usually live in the same area. This is similar to camouflage, but in mimicry the model is generally a similar organism rather than a static part of the background environment.


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3. Mimicry

There are several types of mimicry. The two most common types are Batesian mimicry and

Mullerian mimicry.


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3. Mimicry

John H. Tashjian

Batesian mimicryoccurs when an edible mimic resembles an

unpalatable or poisonous model. In this type of mimicry,

only the mimic benefits.

An example of Batesian

mimicry is the scarlet king

snake, a non-poisonous

mimic of the extremely

venemous coral snake.

Photo courtesy of John H. Tashjian,

Cal. Acad. of Sciences.

Above: scarlet king snake

Right: coral snake


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3. Mimicry

Another example of Batesian mimicry is the locust borer.

This insect not only looks like a bee or wasp, it sounds like

one, too!


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3. Mimicry

By contrast, Mullerian mimicry occurs when two (or more) distasteful or poisonous organisms resemble each other. Both species benefit because a predator who learns to avoid one species will most likely avoid the other, too.


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3. Mimicry

The two invertebrates on the left are different species

of sea slugs, while the one on the right is a marine

flatworm. All three secrete noxious substances and

are unpalatable. Notice their similar aposematic

coloring.


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Review and Summary

Three types of defenses that animals can use

against predators include:

• chemical defense

including synthesizing toxins and

accumulating toxins from food;


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Review and Summary

Three types of defenses that animals can use

against predators include:

• chemical defense

• camouflage

including cryptic coloration and

deceptive markings;


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Review and Summary

Three types of defenses that animals can use

against predators include:

• chemical defense

• camouflage

• mimicry

including Batesian and Mullerian

mimicry


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Review and Summary

Three types of defenses that animals can use

against predators include:

•chemical defense

• camouflage

• mimicry

Animals constantly evolve new and improved

characteristics to capture prey or evade predators;

the ongoing “arms race” has produced some of the

wonderful organisms you have just seen!


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