• Aggression is a part of agonistic behavior that comprises of everything leading to resolution of conflict between individuals.
• It is used to adjust inter & intra specific conflicts
• Conflict arise when two or more individual compete for some object (food, water & space)
• Aggression is expressed depending upon its intensity from mild to medium, to most pronounce. Facial expression, choosing, grabbing, pushing and lastly fighting and biting all are different forms of aggression.
• Aggressive behavior is formed of 4 components (1) Agonistic (threat) (2) Conflict (fight) (3) appeasement (submission) (4) escape (flee)
• Aggression is formed of complex responses of the animal’s nervous and endocrine system, programme to be used at the time of stage.

Conflict without weapons – Not fatal & exhaust but with weapons can kill each other.
Aggressive is genetically controlled; it has high degree of heritability and has adaptive value.

Types and Causes of Aggression

Aggression is influenced by internal and external stimuli, hunger thirst pain breding and other social circumstances, genetic factors, learning processes and frustrating memories.

1. Xenophobia or aggression towards stranger’s responses to right of stranger esp. Territorial intrudes
2. Crowding or proximate aggression
   • Causes more aggression and more encounter
   • Captive rats lead to behavioral pathologies like fierce fighting and infanticide (Calhoun, 1962)
   • In mice colony a stranger cannot gain entry (Selander, 1970).
   • Knots live in dense flock while Ringed plovers don’t, as crowding knots are more aggressive
   • Female Iguones collect in hundreds and fight for sandy space between rocks, where they bury their eggs.
   • Crowding of sea shores of seals, sea lions, walrus and penguin always increases aggressions in their societies.
3. Spaces or territorial aggression
   • Signalling by male to intruder to keep away from area, but tolerant towards female
   • Strange ants in a colony are enough to raise alarm through phenomenon
   • Appeasement posture in three spined stickle backs during courtship mating by male
   • African baboon fight for sleeping trees
   • Hamadryad baboon fight for water
   • Seal fight for rocky area
4. Seasonal changes or breeding aggression
   • Males threaten or attack rival males and sometimes threaten, bite mating females eg. Hamadryad baboon recruit young females for breeding in their harem by threatening them
   • Most animals put up a show their strength and weapons e.g. Deer show antler, Tiger roar and canine teeth, wolves hauls & full set of teeth
   • Animals look at each other display and decide who is weaker e.g. Grants Gazzles avoid fight.
   • Tiger aggressive towards males but not for female.
   • Rein deer female possive but aggressive before and after birth.
5. Previous experience or pain and aggression
   • Animals behave aggressive in response to pain (Ulrich, 1966)
   • Two rats fight if receive electric shock
   • Puppy dog in isolation beat or scold him, chain him will grow into ferocious dog. Painful experiences make him more aggressive.
6. Social status or dominance aggression
   • Display by dominant animals towards subdominant group members e.g. Strutting walk of Lemmings, toils up by rhesus and facial expression and tail carriage in wolves prevent unnecessary fight among conspecifics.
   • Male mica reared in isolation after wearing are less aggressive, not subjected to dominance as reared in social groups and follow dominant
   • Lion (dominant) in pride eat first
7. Food or feeding aggression
   • Commonly seen in group animal feeding
   • 10 hyena, only 5 can feed zebra, then aggressive
   • Baboon in Africa & Rhesus in Nepal seen fighting for food
   • Clump food rather than homogeneously distributed, fight more
   • Seasonally strong, if source is seasonal eg. Fight at bonanza of fruits and oasis of water
8. Nest or parental aggression
   • 2 types
     • towards nestling
     • towards introducers
   • Parents of birds and mammals direct mild forms of aggression at their offspring
     • To keep them close
     • Or urges them to move
     • To peak up fighting
     • To terminate suckling and
     • At time of weaning
   • All females become aggressive towards intruders when becomes mothers
   • Rhesus or langur can bite at slightest provocation
   • Female crocodile guards her neat ferociously
9. Instinct or Genetic aggression
   • According to Lorenz individuals reared in a non-frustrating environment will still be aggressive. In a study of two stains of mice, A stain was aggressive and B stain was no. Stain A was kept with less aggressive mothers and B with aggressive mother. That means their environments were changed. They were given enough shelter, food and water. It was found out that puppies of aggressive stain remain aggressive in spite of peaceful non-aggressive environment.

Aggressive behavior is not pathological or abdominal, it is very much part of the normal behavioral pattern of almost all animals species.
Darwin explained that stronger, aggressive and healthier animals are selected for reproduction to produces better progeny. The animals are favored for aggression.

Aggressive behavior is essential for animal’s survival. It can take to be accidental (a frustrated pet dog growl at its owner) or intended (a hungry feeding pet dog can snap at owners approaching hand, father can be angry with indisplined child) and physical (though chase, bites, slap) or mental (it relates to feelings only e.g. A person could be smiling but may be feeling angry).

Hess (1953) explored hypothalamus and found that lateral and posterior hypothalamus has centers for aggression, attack, fight or submission. The hypothalamus also plays a role in emotion. The lateral parts are involved with pleasures and rage while the median part is involved with averion, displeasures and a tendency to uncontrollable and loud laughing.

Among vertebrates, it is a generalization that males are more aggressive (Conner, 1972). Castration causes a dramatic decline in aggression. Another important gland (adrenal) when removed, aggressiveness decreases. The aggressive bulls are habitually coast rated to turn them into docile oxen.

Animal weapons

Animals are equipped with specialized weapons for hunting e.g. Snakes have fags; eagle & vulture have sharp beak; big and small cats with retractile claws, sharks and crocodiles with sharp teeth, sheep and deer with horns and antlers, and bees and scorpion have stings.