In the same way like humans!

Jan 20, 2007 13:00 GMT  ·  By

The word "stress" defines in biology the changes suffered by an organism due to a value too high or too low of an environmental factor that induces tension and exhaustion. In this broad biological meaning, stress means also when we are cold or hot, when we are thirsty or hungry, when do not get sex.But usually, when we talk about stress, we refer to the socio-psychical stress, induced by the too hectic current urban life. Do the animals experience the same type of stress?

"This is an absolutely normal reaction of the whole animal kingdom, from monkey to bee, and the modalities through which the animals search and manage to discharge the stress estates are the most various" said German biologist Vitus Drecher.

Stress emerges when animals are put in situations that threat their survival, when are kept in captivity or when they are pulled out of their normal environment. Let's see some examples.

Gamers trapped in an African national park a giraffe using a lasso. The animal was caged and lifted up on a truck to be sent to a Zoo. All looked good, but when the engine started, the giraffe dropped dead. Diagnostic: death caused by stress.

In fact, many animals are extremely sensitive to the stress of capturing and cannot be kept in captivity because they die from stress at the moment of capture, during the transport or in a short period of captivity.

Gamers in African reserves say that patrolling by helicopter of the herds is harmful for the health of the animals. The noise of the engine over their heads provokes them gastric ulcer.

A worker bee kept isolated from other bees, even if supplied with food, will die soon. It will move restlessly till it drops dead. She won't die by exhaustion but by stress. When kept captive, certain hormones are released in its blood, directing her focusing for the return to the hive.

On the other hand, stress impedes for a while the death, but if the freedom does not come soon, the stress, initially programmed by nature for breaking free, will turn deadly.

A Zoo had, in a large aviarum, a troop of Rhesus Macaque. They bred well and the number of young was steadily increasing. But when nobody expected, a catastrophe triggered: the 90 monkeys, which seemed to have lived in peace and understanding till then, sudden and apparently without reason, rushed one at another, yelling and hurting their neighbors. The keepers put an end to the fight using water jets, but on the battlefield were 17 corpses.

The guilt: stress provoked by overpopulation. The monkeys did not have the possibility of isolating them from their peers not even for a minute. Or, temporary isolation is necessary not only for humans, but for animals, too. Especially for those who are solitary by nature. The stress intensified with each day was released at once: what kept them quiet disappeared and the mayhem started.

What happens inside the body of a mammal found in a stress situation? Senses receive the action of the stress factors and send alarm signals to the brain, more specifically to the hypothalamus, which commands the release of the stress hormone, cortisol. In just a few seconds, cortisol mobilizes the whole body's energy, including, in emergency case, the last reserves, which can have the effect of achieving performances unconceivable in normal situations.

For long was thought that the hare sleeps with the eyes opened. In reality, the hare had already felt the hunting hounds, and, like a race car that in the minutes before the start functions at maximum revolution, being able to begin the race at any moment, so the hare's heart, beating extremely fast, pushes the blood through all the muscles, allowing it, on the moment when the followers are nearby, to flee with maximum speed. The stillness of the animal is apparent; the hare is like a bow stretched to the limit.

Running won't be bad for the animal, but repeated functioning of the heart engine in vain will harm for sure. As a protection measure, the hare can run one-two tours of the field. But it's obvious why repeated stress will harm the health of the animal (and human, too): it will exhaust the heart, and the other inner organs, too. For animals (like for humans, too), physical efforts are important methods for discharging stress.

In an experiment, rats were kept in tiny tight cages. From time to time, the animals received electrical charges, unpleasant but not dangerous. Half of the rats couldn't move, the others could rotate using the front limbs a wheel installed in the cage. The negative effects of the stress, weight loss and gastric ulcer, were less pronounced on the "wheeled" rats.

In fact, we see this often in Zoos, where big cats or other carnivores (like wolves) are in a continuous movement around the perimeter of their cage: that's captivity stress. Another action that seems illogical but serves for discharging stress is the so called "displacement".

For example, cocks can interrupt the fight by beaking grimly the ground beneath their feet and male starlings in a similar situation put an end to the hostilities starting to cleanse their plumage.

This strange behavior at first sight has a profound biological meaning. Fights between the individuals of the same species play only the role of making a hierarchy. When the weakest signals obedience, the fight stops without any killing.

But the accumulated nervous tension (stress) must be removed. This does the replacement, which apparently does not have any connection with the given situation. Displacement is largely found in the human behavior. When somebody hits the table during a talking, he discharges tension.

A fist in a wall discharges stress, when the targeted person can not be touched by various reasons (social or physical). A girl who likes a certain boy will touch her hair when she makes eye contact with him. When you lie to somebody, you won't look into his eyes. Cursing and laughter are very efficient displacement acts.

Bonobo apes are known to use sex as a tool for discharging stress! (photo above) Any conflict is solved by sex parties, and when the tension is high, orgies break out.

Another stress situation for animals is when losing position inside the band, herd, pack, troop. An old elephant, lion, wolf defeated in fight is chased away from the community and bears a lousy existence. Stress makes them extremely aggressive and dangerous, like wanting to prove they were too early "erased from the list". Soon, the lonely animal dies, and it's hard to say if by age or by stress.

In a case in Canada, an old wolf female was chased away from the pack because she did not listen to the younger individuals. Three days later, she returned with the corpse of a deer, like wanting to say "I give you this prey if you let me back in your group". They accepted her, but as a low rank member, and she would not dispute this again. This way, she probably prolonged her life with a few years. We, humans, could prolong the life of our elders if we offer them occupations at their abilities, but which prove them that they are still necessary for those around.

Stress can be applied also for ecosystems. We say a river or lake suffers from stress when wage waters are poured into them.

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