WARNING SIGNALS AND CHEMICAL DEFENCE OF ANIMALS By Adrian Kaluka

Escaping predation is essential to survival for most animals and has resulted in the evolution of an amazing diversity of predator avoidance tactics. Conspicuous coloration advertises anti-predator defense across many animals, including invertebrates, fish, amphibians, snakes and birds.

CHEMICAL DEFENCE

Many animals advertise their chemical defense to predators with conspicuous coloration and unpalatability. Chemical defenses are very common in reptile, insects, spiders and amphibians. Most harmless snakes put off predators by releasing a foul-smelling mixture of musk and faeces from their cloaca. They may wipe the stuff all over their bodies by turning in coils. The stuff does not just smell bad, it also tastes vile and is long-lasting.

A striped polecat, if threatened they turn their rump towards the aggressor with the back arched and tail erect , and as a result spray foul smelling fluid from anal glands. The fluid produces a burning sensation in the eyes.These mammals are indicating that they have a foul smelling defense and this is for the benefit of their enemies than can only see in shades of black and white.

Frogs and toads have poisonous glands that produce a foul tasting white substance used to deter possible enemies.

Snakes have venom which is spat or injected on the aggressor e.g. the spitting cobra. King cobra lifts itself 6 feet whilst hissing to frighten the aggressor.A large number of insects secrete a protective formic acid like ants and termites and many emit a strong and very unpleasant smell when disturbed or threatened.

A number of toads and frogs produce a foul tasting milky liquid in order to deter possible predators.

Spiders make use of venom when biting and when stringing. Many animals that make use of chemical defense often use warning signals to deter any possible attack from a predator.

Pangolins have an anal gland that secretes a substance that smells foul when it has seen a predator.

Warning coloration (aposematism) is effectively the opposite of camouflage. Its function is to make the animal highly conspicuous to potential predators, so that it is noticed, remembered and then avoided. Warning colors work by being associated by potential predators with something that makes the warning-coloured animal unpleasant or dangerous. This can be achieved in several ways by distasteful bitter-tasting chemicals in its blood, foul-smelling, for example the skunk can eject a liquid with a long-lasting and powerful odour and poisonous, for example a wasp can deliver a painful sting, while a viper can deliver a fatal bite.

Warning coloration can succeed either through inborn behaviour on the part of potential predators, or through a learned avoidance. 

EXAMPLE FOR CHEMICAL DEFENCE MECHANISM

Kingdom:                    Animalia

Phylum:                       Chordata

Order:                          Tubilidentata

Family:                        Orycteropodidae

Genus:                         Orycteropus

Species:                       afer

Scientific Name:         Orycteropusafer

Common Name:          Aardvark

Local Name:                Inengo (Bemba)

 

WARNING SIGNALS

Animals use color for signaling in several ways, includingwarning, to other animals not to attack and mimicry, taking advantage of another species' warning coloration.Color may divert attacks by startle, surprising a predator e.g. with eyespots or other flashes of color, and by dazzle, confusing a predator's attack by moving a bold pattern (such as zebra stripes) rapidly.

Some animals have evolved dazzle camouflage, whereby instead of attempting to conceal themselves, they are patterned to cause motion dazzle, confusing a predator during an attack, and making it harder to select and track a target. An example is zebras, which stand out in the savannah when stationary, but when moving rapidly, their stripes create a confusing, flickering mass in the eye of a predator such as a lion.

However, a warning signal is only effective when it can be generally recognized. For this reason, groups of poisonous animals all tend to converge on the same kinds of signal, for example, many stinging insects, such as bees and wasps, use the combination of yellow and black to give advance warning.

When large groups of poisonous animals all use the same warning colors to signal that they are poisonous and should not be interfered with, it sends a strong message to their potential predators. But, rather sneakily, the message can be hijacked by perfectly harmless animals that merely pretend to be poisonous.

For example, hoverflies have exactly the same color pattern as wasps but are completely inoffensive. In effect, the harmless creatures use the wasps' color pattern pretending to be
dangerous without actually being so to protect them. Warning colors: Some have conspicuous colors or patterns to advertise a venomous or distasteful nature. In nature, the same color combinations used in our traffic signs are used as warning colors. Red, yellow, black and white in various combinations signal "keep off!”.Many harmless snakes mimic the bright warning colors of venomous snakes especially if they share the same predator or territory.Animals that are brightly colored are warning their possible enemies that they may have a secret weapon that may be; an obnoxious smell, foul-tasting flesh, poison glands, a painful sting or venomous bite.

Displays of color and color-contrasts are found mainly in insects, snakes and other reptiles and in a few mammals.

Insects displaying bright colors do this due to the fact that their predators, which are usually birds, reptiles and some primates, are able to see in color.

EXAMPLE FOR WARNING SIGNALS FOR DEFENCE

Kingdom:                                Animalia

Phylum:                                   Chordata

Class:                                       Mammalia

Order:                                      Artiodactyla

Family:                                    Bovidae

Genus:                                     Syncerus

Species:                                   caffer

Tribe:                                       Bovini

Scientific Name:                     Synceruscaffer

Common Name:                      African Buffalo

Local Name:                            Imboo (Bemba), Njati( Chewa),Munyati Tonga)

LIMITATIONS

• The prey is at high risk of death or to be attacked if the predator ignores the chemical produced by the prey.

• Some predators such as lions do not have a good sense of sight so when they sense an animal; they will keep coming close until they attack and kill.

• Some animals have antihermorphage and antineurotoxin antibodies in their blood such that when they take on poisonous stuff it might not work e.g.Moongoses

• In coloration, animals might not blend well with the environment due to the fact of seasonal changes in vegetation hence prone to attacks.

• During rainy season, animals that produce chemicals may be affected because the chemicals are washed away by the rains e.g. A snake produces musk from its anal gland and in the process when the rains come all the musk will be washed away.

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