In zoology, territorial activity refers to how an animal or a group of animals defends their territory from intruders of the same species. Territorial boundaries can be marked by scents such as pheromones secreted by the skin glands of several mammals or sounds such as bird songs. If such a warning does not deter intruders, combat and chases will ensue.

Overview of Territorial Behaviour

A defence form of nest-sites, food sources, or other resources against the other members of similar species. Several animals protect areas of land from intruders, most of whom are of the same genus. Sometimes, this is accomplished by the outright aggression towards intruders, whereas, sometimes, by threat displays, by song (territorial behaviour in birds), and by scent marking (in mammals).

Territorial defence contains both benefits and costs, and animals defend territories only when it is economical to perform so. For example, spotted hyenas (Crocutes crocuta) defend territories in the Ngorongoro crater, where prey is plentiful and predictable, but not in the Serengeti plains, where prey is more seasonal. The hyenas in the Serengeti wander around a wide home range but do not defend territory.

Several animals differ in their defence strategies depending on the food supply. When the food levels become high, intruder pressure increases, and both the squirrels (Sciuridae or the squirrel territorial behaviour) and sunbirds (Nectariniidae) give up their territories due to the defence costs becoming very great. On the other hand, foraging efficiency can plummet to the point that the animal, even with territorial protection, is unable to meet its regular energy requirements. Under these circumstances, the territory has been lost.

A few animals defend territories only during the breeding season (which is the territorial behaviour in animals). In other cases, the male territorial behaviour defends territories, known as leks, where the females come for mating. In some other cases, the territory contains vital resources, which the females need, and the males gain access to females by controlling these resources. For example, in the American bullfrog (the Rana catesbeiana), a few males achieve better mating success compared to others. These are the ones, which are able to defend a territory having the best egg-laying sites.

Adaptivity of Territorial Behaviour

Territorial activity is beneficial in a variety of ways, including allowing an animal to mate without interruption and raise its young in an environment with little competition for food. Also, it can prevent overcrowding by maintaining the optimum distance among the population members. Territories can be seasonal; in several songbirds, the mated pair defends the feeding area and nest until after the young are fledged. In communally nesting birds like gulls, the hummingbird territorial behaviour can just consist of the nest itself.

Function

The ultimate goal of animals defending and inhabiting a territory is to improve the collective or individual health of the animals displaying the action. In this biological sense, fitness relates to the ability of an animal to raise young and survive. The proximate functions of the territory defence differ. For some of the animals, the reason for such protective behaviour is to acquire and protect the food sources, mating areas, nesting sites, or to attract a mate.

Types and Size

Territories have been classified into six types among the birds.

Type A: It is an 'all-purpose territory,' where all activities take place. For example, mating, courtship, foraging, and nesting.
Type B: It is a nesting and mating territory, except for the majority of the foraging area.
Type C: It is a nesting territory that includes the nest, including a small area around it. This is common in colonial water birds.
Type D: It is a mating and pairing territory—the type of this territory defended by males in the lekking species.
Type E: This is a roosting territory.
Type F: Winter territory that typically includes roost sites and foraging areas. It may be equivalent (in the location) to a migratory species or for the Type A territory, maybe on the wintering grounds.

Reports of the territory size may be confused by a lack of distinction between the defended territory and home range. The shape and size of a territory can differ based on its purpose, season, the amount and quality of the resources it has, or geography. Usually, the size is a compromise of defence costs, resource needs, reproductive needs, and predation pressure.

Golden eagles (Aquila chrysaetos) have territories of up to 9,000 hectares (or 22,000 acres), least flycatchers (Epidonax minimus) have territories of up to 600 square metres (or 6,500 square feet), and gulls have territories of only a few square centimetres in the immediate vicinity of the nest.

Territories may be linear. Sanderlings (or the Calidris alba) forage on sand flats and beaches. When on the beaches, they feed either in individual territories or flocks of 10 - 120 meters of shoreline.

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FAQs on Territorial Behaviour: Definition, Types & Adaptations

1. What is meant by territorial behaviour in animals?

Territorial behaviour is a fundamental concept in ethology where an animal or a group of animals claims and defends a specific area, known as a territory, against intruders, particularly members of the same species (conspecifics). This defence is not always through physical fighting; it often involves a series of behaviours like scent marking, vocalizations, and visual displays to advertise ownership and ward off competitors.

2. What are the main types of territories animals defend?

The types of territories animals defend are often classified by their primary function. The main types include:

All-Purpose Territory: An area where the animal performs all its major life activities, including mating, nesting, and foraging. Many songbirds exhibit this type of territoriality.
Mating Territory: A territory defended solely for the purpose of attracting a mate and breeding. A classic example is a lek, where males gather to perform courtship displays in small, defended spaces.
Nesting/Rearing Territory: An area defended only around the nest or den site to protect eggs and raise young from predators and rivals.
Feeding Territory: A specific area defended exclusively for its food resources, which may be separate from the nesting or mating site.

3. How do animals mark and retain their territories?

Animals use a variety of signals, often called 'signposts', to mark and retain their territory, which is more energy-efficient than constant fighting. Key methods include:

Scent Marking: Mammals like wolves and tigers use urine, faeces, or secretions from scent glands to leave chemical signals that inform others about their identity and presence.
Vocalisations: Birds use complex songs, and primates like howler monkeys use loud calls to announce their presence and defend their territory from a distance.
Visual Displays: Animals may use threatening gestures, such as a cat arching its back, a bird spreading its wings, or a lizard displaying its colourful dewlap, to intimidate intruders.

4. Why is territoriality considered an important behavioural adaptation?

Territoriality is a crucial behavioural adaptation because it provides significant survival and reproductive advantages. By defending a territory, an animal secures exclusive access to essential, often limited, resources such as food, water, nesting sites, and mates. This reduces competition, allows for uninterrupted mating and raising of young, and can help control population density, ultimately increasing the animal's overall evolutionary fitness.

5. What is ritualized aggression, and why is it preferred over actual fighting?

Ritualized aggression is a sequence of escalated threat displays—like posturing, vocalizing, or showing off weapons like claws or teeth—without engaging in direct, harmful combat. It is evolutionarily preferred over actual fighting because it serves the same purpose of resolving a territorial dispute while minimizing the high costs of a physical battle. These costs include the risk of serious injury or death and the expenditure of significant energy, both of which would decrease an animal's chances of survival and reproduction.

6. Can you give some examples of territorial behaviour in different animal groups?

Yes, territorial behaviour is widespread across the animal kingdom. For instance:

Birds: A European Robin will aggressively defend its garden territory, which provides food and nesting opportunities, by singing loudly and chasing away intruders.
Mammals: A pack of grey wolves maintains a large hunting territory, marking the boundaries with urine and defending it violently against other packs.
Fish: The male Siamese fighting fish (Betta splendens) will defend a small territory around its bubble nest, flaring its gills and fins to intimidate rivals.
Insects: Many species of dragonflies patrol and defend a stretch of a river or pond from other males to secure mating opportunities with females entering the area.

7. Are there any disadvantages or costs associated with territorial behaviour?

Yes, despite its benefits, territoriality comes with significant costs. The primary disadvantage is the high energy expenditure required to constantly patrol boundaries, mark the area, and perform defensive displays. This behaviour also consumes valuable time that could be spent on other vital activities like foraging, resting, or caring for young. Furthermore, engaging in defensive displays or fights, even ritualized ones, still carries a risk of injury or attracting predators.

8. How does territorial behaviour in humans compare to that in other animals?

While animal territoriality is primarily driven by biological imperatives for survival and reproduction, human territoriality is more complex and influenced by psychology, culture, and social learning. Humans exhibit territoriality over personal space (the area immediately around our body), primary territories (like a home), and secondary territories (like an office desk or a favourite seat). Unlike the often-instinctive scent marking or displays in animals, humans use complex markers like fences, signs, laws, and social customs to define and defend their territories.