The interactions among members of the same species are called social behavior. It is also applied to animals of different species. But it excludes predator-prey interactions.
LIVING IN GROUPS
Animal populations are often organized into groups. An aggregation of animals for some simple purpose like feeding, drinking, or mating is called group. Several Drosophila flies live on a piece of rotting fruit. It is an example of an aggregation. A stable group of individuals of the same species that maintains a cooperative social relationship is called animal society. This association typically extends beyond the ‘level of mating and taking care of young. Social behavior has evolved independently in many species of animals.
Therefore, invertebrates and vertebrates have complex social organizations. Advantages of social grouping
There is a major benefit of belonging to a group. It gives protection against predators. There is safety in numbers. Several group members warn each other about an intruder.
Cooperative hunting and capturing of prey increase the feeding efficiency of predators.
Social grouping protects its members from harsh environment. They huddle together in cold weather.
The members of the social groups help each other for finding mate and rearing of young.
Many insects have developed social grouping. These social groups have
evolutionary division of labor. Specific individuals perform specialized tasks.
These tasks are defense, food procurement and feeding of young. Disadvantages of social grouping
There are following disadvantages of social groupings:
Competition for resources developed. between the members of the social groups.
The diseases and parasites spread more rapidly in a group of animals.
They interfere each other for reproduction and rearing of young. The value of group depends on the species and behaviors involved.
AGNOSTIC BEHAVIOR, TERRITORIES, AND DOMINANCE HIERARCHIES
The behavior in which one animal is aggressive or attacks another animal, the other responds by returning the aggression or submitting is called agnostic behavior. A society of animals maintains social structure. Agnostic behavior is lethal in rare cases. Usually the animals are not killed or severely injured.
The males show their aggression in the form of threat displays. The aggression displays involve signals. It warns other males of an intention to defend an area or territory. Agnostic behavior seems antisocial. But it maintains the social order. It is important in the maintenance of territories and dominance hierarchies.
The site defend by territorial animal by agnostic behavior is called territory of the animal. They excluded the competing individuals from this site. Many male birds and mammals occupy a breeding territory. A male actively defends his area against other males. He attracts a female in. his territory and courts (mating) her without interference. Some territories. contain a food supply. Some territories provide shelter. It protects the animal from predators and unfavorable climate.
Dominance hierarchies (grouping)
The organization of group of animals in such a way that some members of the group have greater access to resources like food or mates than others is called dominance hierarchies. Some animals are present near the top of the order. They have first choice of resources. The animals present near the bottom do not get sufficient resources.
Pecking (fight with beaks) order is an example of a dominance hierarchy.
Peck order is present in chickens in a pen. The chickens are placed together. They fight among themselves. Finally, a linear hierarchy of dominance is formed. Higher-ranked chickens are first to eat. They peck lower-ranked chickens. Peaceful coexistence is possible after the setting of the hierarchy. Sometimes, a bird tries to move up in the order. Therefore, occasional fights o Cur.
Dominance hierarchies also exist in many vertebrate groups. The most common dominance hierarchy is present in the form of linear relationships. Sometime, triangular relationships may be formed. The strongest male is highest in the rank order in baboons. But sometimes, older males may form coalitions. They subdue a stronger male and lead the troop.
ALTRUISM (sacrifice for others)
The interaction in which an individual gives up or sacrifices some of its own reproductive potential to benefit another individual is called altruism. Advantages of altruism
An animal produce a large number of Offspring. It makes him successful in a biological sense. Thus it passes its genes to succeeding generations. This animal also shares some genes with its relatives and their young. Therefore, he helps his relative and his young. It increases his reproductive potential or output. Therefore, he helps his relatives in their survival. Thus an individual pass more gen s theoretically to the next generation than by rearing his own young.
1. Altruism in crows: One individual of a group of crows gives an alarm call. It
warns the other individuals of the group of a predator. This call may attract he predator to the sender of the signal.
2. Altruism in Honey bee: Altruism is also present in societies of hymenopteran insects like honeybees. The male drones are haploid. The female workers and queen are diploid. It develops genetic asymmetry. Diploid workers share three fourths of their genes with their full sisters. If they
reproduced, they will share only half of their genes with hypothetical offspring. Thus, female honeybees have more genes common with their sisters than their offspring. The workers help their mother to produce more sisters. Thus the worker passes more genes to the next generation by their mother. Some of their sisters become reproductive queens.
William Hamilton (1936—) proposed the idea of kin (relatives) selection. It explains that selection act on related animals. This selection of related animals can affect the fitness of an individual. A gene that a particular individual carries passes to the next generation through a related animal. Therefore, the fitness of an individual is based on the genes it passes on. It is -also based on those common genes that its relatives pass on. Therefore, altruism is a genetically based tendency. It is passed on by the individual carrying it or by a relative who also carries it. But the individuals of a group must identify its relatives for kin selection to work. It is done by small groups of primates and social insects.