UPSC MainsZOOLOGY-PAPER-I202415 Marks
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Q21.

Explain Aggressive and Territorial behaviour in animals, with suitable examples.

How to Approach

This question requires a detailed understanding of animal behaviour, specifically aggressive and territorial behaviours. The answer should define both behaviours, explain their underlying causes (evolutionary, hormonal, neurological), and provide diverse examples across the animal kingdom. A comparative approach highlighting similarities and differences between the two behaviours would be beneficial. Structure the answer by first defining the behaviours, then discussing the causes, followed by examples categorized under each behaviour, and finally, a brief comparison.

Model Answer

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Introduction

Animal behaviour is a fascinating field that explores the ‘why’ and ‘how’ of animal actions. Aggressive and territorial behaviours are fundamental aspects of this, often crucial for survival and reproduction. These behaviours, while seemingly negative, play vital roles in maintaining social structures, securing resources, and ensuring the propagation of genes. Aggression, broadly defined, involves any behaviour by one animal that threatens or causes harm to another, while territoriality concerns the defense of a specific area against intrusion by others. Understanding these behaviours is key to comprehending animal ecology and evolution.

Aggressive Behaviour

Aggression is a complex behaviour driven by a multitude of factors. It’s not simply ‘random violence’ but often a calculated response to specific stimuli.

Causes of Aggression

  • Competition for Resources: Food, water, mates, and shelter are common triggers.
  • Hormonal Influences: Testosterone, for example, is strongly linked to aggression in many species.
  • Social Hierarchy: Establishing and maintaining dominance within a group often involves aggressive displays.
  • Predator Defense: Protecting oneself or offspring from predators.
  • Frustration-Aggression Hypothesis: Blocked goal-directed behaviour can lead to aggression.

Examples of Aggressive Behaviour

  • Lion prides: Male lions exhibit intense aggression when challenging for dominance and mating rights. Infanticide, where new males kill cubs fathered by previous leaders, is a brutal example of aggressive behaviour securing reproductive success.
  • Honeybees: Worker bees aggressively defend their hive against intruders, using their stingers (resulting in their own death). This is altruistic aggression, benefiting the colony.
  • Red Deer stags: During the rutting season, stags engage in fierce battles using their antlers to establish dominance and access to females.
  • Mandrills: These primates display vibrant facial coloration that intensifies during aggressive encounters, signaling their intent.

Territorial Behaviour

Territoriality involves the establishment and defense of a physical space against encroachment by others, typically of the same species. It’s a form of resource control.

Causes of Territoriality

  • Resource Availability: Territories are established when resources are limited and defensible.
  • Mating Opportunities: Territories often contain prime mating locations or attract mates.
  • Nesting/Breeding Sites: Secure locations for raising offspring are crucial.
  • Reduced Energy Expenditure: Once a territory is established, less energy is spent on constant searching for resources.

Examples of Territorial Behaviour

  • Birds: Many bird species, like robins, fiercely defend their nesting territories through song, displays, and even physical attacks.
  • Fish: Cichlid fish exhibit strong territoriality, defending specific areas of the lakebed for breeding and feeding.
  • Wolves: Wolf packs maintain large territories, marking them with urine and scent glands to warn off other packs.
  • Gorillas: Silverback gorillas defend their harems and territories against rival males, using displays of strength and aggression.

Comparison of Aggression and Territoriality

Feature Aggression Territoriality
Primary Focus Inflicting harm or threat Defending a space
Stimulus Direct challenge, resource competition, frustration Intrusion into a defined area
Duration Often short-lived, episodic Can be long-term, sustained
Outcome Establish dominance, secure resources, defense Resource control, breeding opportunities

While distinct, aggression and territoriality are often intertwined. Territorial defense frequently *involves* aggressive displays, but aggression isn’t always territorial. For example, a lion killing a wildebeest is aggression for food, not territorial defense.

Conclusion

Aggressive and territorial behaviours are fundamental to animal life, shaped by evolutionary pressures and influenced by hormonal and neurological factors. These behaviours, though sometimes appearing brutal, are essential for survival, reproduction, and maintaining ecological balance. Understanding the nuances of these behaviours provides valuable insights into the complex social dynamics and adaptive strategies of the animal kingdom. Further research into the genetic and environmental factors influencing these behaviours will continue to refine our understanding of animal life.

Answer Length

This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.

Additional Resources

Key Definitions

Altruistic Behaviour
Behaviour that benefits another individual at a cost to oneself. Often observed in social animals, it’s explained by kin selection and reciprocal altruism.
Kin Selection
An evolutionary theory that explains altruistic behaviour based on the idea that individuals are more likely to help relatives, as they share genes. This increases the chances of those genes being passed on to future generations.

Key Statistics

Approximately 25% of mammal species and 5% of bird species live in stable social groups exhibiting territoriality (data as of 2020, based on IUCN Red List assessments).

Source: IUCN Red List of Threatened Species (2020)

Studies show that testosterone levels in male deer increase by over 200% during the rutting season, directly correlating with increased aggressive behaviour (Source: Journal of Zoology, 2018).

Source: Journal of Zoology (2018)

Examples

European Robins and Territory

European Robins are renowned for their intense territoriality. They defend territories year-round, even during winter, and will aggressively attack anything that enters their space, including objects resembling rivals (e.g., a red-painted ball).

Frequently Asked Questions

Is aggression always harmful?

No, aggression isn't always physically harmful. It often takes the form of displays – vocalizations, postures, or visual signals – intended to intimidate rivals without resulting in actual combat. These displays are often sufficient to establish dominance or defend resources.

Topics Covered

BiologyZoologyAnimal BehaviorEthologyEvolution