Animal defense against predators
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Animal Defense against Predators. Diversity of Antipredator Behaviours. Some antipredator adaptations Anti-detection crypsis, camouflage Anti-attack stotting in Thompson’s gazelles warning colouration and mimicry selfish herds Anti-capture run, swim or fly fast vigilance

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Diversity of Antipredator Behaviours

Some antipredator adaptations

Anti-detection crypsis, camouflage

Anti-attack stotting in Thompson’s gazelles

warning colouration and mimicry

selfish herds

Anti-capture run, swim or fly fast

vigilance

body part autotomy (e.g., tail loss in lizards)

Anti-consumption fighting back

releasing noxious chemicals

hard to swallow (e.g., inflation by puffer fish)

feigning death




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Adaptive Significance of Mobbing

Birds sometimes defend their nest or colony by “mobbing”—flying low over a predator, sometimes hitting the predator with their wings or legs, and even defecating or regurgitating food on it. Does mobbing actually deter predation? The data show that it does, presumably by distracting the predators (crows). There is greater mobbing within the colony and this is correlated with lower predation attempt success


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Warning behaviours: springbok antelope

Hypothesis:Stotting is used by gazelle to advertise to the predator that it is “unpalatable” – i.e., you couldn’t catch me so don’t even bother trying

Predict that when stotting occurs predator should abandon pursuit.



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The Selfish Herd. 1

?

Predation selects for bunching up—“selfish herding”





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Group Formation & Vigilance

There can be costs to grouping. Sparrows feeding close to cover are less likely to make a “food here” chirrup call which attracts other sparrows. If predation risk is low they maximise fitness by not calling.


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Chemical Defenses

  • 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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Chemical Defenses

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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Chemical Defenses

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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Warning Coloration

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 bodyresembles something else in their environment, here a leaf, an owl.


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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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Disruptive Coloration

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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Camouflage

Predators

Frogfish resembles

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


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Mimicry

In mimicry, an organism (the mimic) closely resembles another organism (the model) in order to deceive a third, (the operator).

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.

Above: scarlet king snake

Right: coral snake

Photo courtesy of John H. Tashjian,

Cal. Acad. of Sciences.


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Mimicry

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.

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.


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