The below mentioned article provides a note on vertebrate society.
Definition of Vertebrate Society:
A society has been defined as a grouping of organisms within a population. The vertebrate society, as it appears, is more successful than the invertebrate society.
The success of vertebrate societies lies in the functional versatility of the individuals. In the insect society the reproductive ability of the majority of the members is suppressed. The reproduction of the minority results not only toward the formation of new individuals but also toward new formation of the whole society.
It is evident that amongst social insects, the fate of social institutions is hinged to the fate of a single female and it is her genes that provide the continuity from one social generation to the next. In contrast to that all adult members of a vertebrate society are capable of reproduction and as such the foundation of social continuity is more broad based.
Society has been given an advanced evolutionary status. The insects and vertebrates occupy the zenith of their respective evolutionary lines. Although these societies are different in origin and organisation, similar pattern of social behaviour is evident. Ants and man are unique among animals in making war, practicing slavery and agriculture and in domesticating other animals.
Social hierarchies:
Study of animal behaviour has established the presence of social hierarchies in many species. It has been seen that in a herd of deer an old and experienced female usually acts as leader of the herd. During periods of danger the female leader guides the whole herd.
Dominance—subordination behavior:
Classical studies of peck order in a flock of chicken has revealed the dominance subordination behaviour that occurs in many associations. In a flock of chicken the peck order determines the position of a chicken in that flock. Lowest in that order stands the individual who is pecked at by all. The highest in that order stands the individual who is not pecked at all.
The second highest in the scale is the one who is pecked at by the highest placed individual only. It has been seen that if food, water or a specific standing space is desired by two individuals of the flock, the higher in the peck order simply pecks at the other. The lower on the scale immediately makes room for the dominant one.
Territory:
In most vertebrates there is a tendency to defend certain area against the intrusion by the other individuals of the same species. The dimension of the territory may be a small area like the nest or shelter or may be an extensive one. In many animals territorial behaviour appears only during breeding season.
In some birds the males set up a territory and defend it against the intrusion of other males. Similar behaviour is exhibited by many fishes and mammals.
Communication:
Communication may be defined as an act which influences the activity of one individual by some behaviour of another. The evolution of the techniques of communication in the animal kingdom is progressive but complex in nature. The complex nervous and hormonal systems help in communications between cells and tissues.
In man, communication system ranges from simple body positions and facial expressions like smile, frown to complex and symbolic verbal language. A survey of the communication system in the animals points out that several sensory receptors are involved in the process.
They are:
(a) Odour:
In all probability odour is the primitivemost means of communication. Its role amongst the Invertebrates is little known. The role of scent organs in mammals has been worked out in some details. The musk or other scent glands are useful in marking territories, identifying the members of the same group and also as sex attractant during reproductive seasons.
The secretions of these glands are steroid or steroid-like compounds that might have evolved from the excreted forms of sex hormones.
(b) Tactile communication:
The practice of nose rubbing in many mammals and the rubbing of antennae in many insects is a common feature. By such an act the members belonging to the same society recognise each other.
(c) Visual communication:
Some animals with well-developed vision practise visual communications amongst themselves. Workers on animal behaviour have observed that the various positions of the ear and tail of one wolf have different meanings to other wolves.
(d) Auditory signalling:
The most highly developed means of communication is auditory signalling. Sound production is done in a variety of ways. Some insects produce sounds by rubbing legs or wings. Swim bladder in many fishes is used as sound-producing organ. Vocal cords are well developed in male frogs and mammals. The membrana semilunaris inside the syringeal cavity sub-serve the function of vocal cord in most birds.
(e) Language of the bees:
Amongst the invertebrates the bees have developed a complex language through dancing (Fig. 3.21). Frisch and others have made exhaustive studies on bee communication. In general the bees adopt two mechanisms to. communicate to other bees the information about the source of nectar. They make round dance and wagging dance. A round dance indicates that the food lies near-by.
The round dance consists of small circles made first in one direction and then in the reverse direction. A wagging dance indicates that the food source is further away and it informs other bees of both distance and direction. It is done on a vertical surface inside the hive. It consists of three distinct phases..
In the first phase it makes a semicircular walk, the second phase consists of a straight rush and the final phase consists of another semicircular walk to complete the circle.
The straight rush indicates the direction of the food. Up the side of the hive means towards the sun, down the side of the hive indicates away from the sun and diagonals indicate the angles towards or away from the sun. The frequency of the dance indicates the distance. It has been observed that rhythms of four dances per minute indicate a distance of about 10 km and that 16 per minute refers to a distance of 1 km.
