If we place a group of hens not 'known' in the same corral, we will observe the following conduct. At first, the animals prove to be often aggressive some with others. Numerous 'fights' take place to pecks, in general slightly bloody. Nevertheless, as the time is happening the fights are less frequent. What is observed is that the hens have established a 'status' that determines exactly the domination order. If she turns out to be eaten, the domineering animal prefers to sting, then it will make it the following one and then the following one up to the last one. Since it is logical, what it determines the status of every individual it is the result of the different confrontations in the initial phase. Of some form, each one 'knows' the possibilities that it has of gaining a fight, what allows to go away straight to the result, saving itself the aggression in strict sense. The realized experiments, in which it was extracted to an animal of the group and one was returning him to introduce after an interval, they indicate that these remember the hierarchy approximately two weeks. It has been proved that if the social order falters artificially, the animals grow more slowly and put less eggs.
This phenomenon, the picoteo order in the hens, was described for the first time in 1922 by the Swedish scientist Thorleif Schjelderup-Ebbe [1]. It turns out to be curious that this conduct was happening unnoticed during the thousands of previous years, in which the human beings and the funks have had a narrow coexistence. It is clear that the behavior of these animals did not cause too much interest until this investigator began his experiments. Apparently, Schjelderup-Ebbe was a real lover of the hens from his most tender infancy, and they tell that his mother made him construct a henhouse in his house so that he could observe them as much as one wants.
The picoteo order has been observed in hundreds of species of birds and mammals. Since the mammals do not peck, the scientists prefer to use the term ‘hierarchy‘ to name the phenomenon, of which numerous forms and variants exist, although the basic idea is the same in all the cases: some animals dominate on others. For example, between the males of common rat (Rattus norvegicus) exist only two classes: the domineering ones and the dominated ones [2]. The first ones, called an alpha, are animals of strong aspect and they usually do not have injuries signs. These males behave of more trusting form, move freely without being bothered and attack the intruders if they penetrate in his territory. The bloody fights are not frequent between males alpha, although yes the positions of threat and any clashes. The males beta move back when they appear the alpha, do not attack the intruders and behave 'friendly' between them.
The hierarchy system existence usually goes accompanied by rules of threat and submission, which constitute real communication codes between animals and the real aggression acts allow to save themselves. The Swiss R. Schenkel [3] studied in the middle of the XXth century the codes of fight of the wolves (Canis lupus). The animals of top status have a position of typical aggression, with the elevated tail and the stiff paws, while the animal grunts and raises the top lip discovering his canine ones. The subordinated animals adopt submission positions bending the ears and going ‘the tail between the legs’. It is not infrequent to observe these behavior rules in the domestic dogs.
[1] Schjeldrup-Ebbe, T. (1922) “Social Beiträge zur Social-psychologie psychologie des Haushuhns” Z Psicol. 88:226 -[2] Barnett, S.A. “The conduct of the animals and of the man” Publishing Alliance p.192.1972
[3] Schenkel, R. (1947) “Ausdrucks-studien an Wolfen” Behaviour 1:81-129
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