Intraspecific interactions

Intra and interspecific interactions between animals

Intraspecific interactions

- between members of the same species

Interspecific interactions

- between members of different species

Aggressive interactions

Aggressive interactions

Co-operative interactions

Co-operative interactions

Intraspecific competition – aggressive behaviour (agonistic

behaviour)• If the size of a population

increases so that resources such as food, shelter and mates become a limiting factor, aggressive behaviour arises as a result of these limiting factors.

Fighting• Because animals of the same species compete for

the same resources, competition is strongest between them.

• Fighting is also a method to keep the gene pool strong. The winner of fights over mates leaves the most offspring, therefore his genes are passed on.

• Fighting to the death can occur, usually to eliminate a stranger from another group

Fighting is unlikely to cause death• When members of the same species fight it is

rare that they fight to the death.• Examples:

1) horned antelope will gore an attacking lion, but will not aim their horns at the exposed flank of the opponent when fighting each other.

2) elephants have tusks, but most elephant fights are pushing matches.

• http://www.youtube.com/watch?v=8_r5EEkBNGI

• Elephants fighting

• http://www.youtube.com/watch?v=n9bd1zMDCbs

• Lions fighting

Territories

• A territory is the area which an animal regards as its own and will therefore defend against intruders.

• The home range is the area in which an animal moves about in search of food. It is not defended.

Territory and Home Range

Adaptive features of territoriality

• It ensures space for each animal. If this is in short supply, and needed for breeding, it keeps the population down

• By spreading out, the animals reduce the spread of disease and parasites, and make it harder for predators to find them.

• The most successful males hold the best territories, and so ensure the best genes are handed on to the offspring.

More adaptive features

• In some species, males without territories cannot attract a mate so fail to breed.

• Territories ensure enough food for the animals and families within them.

• Territories ensure a safe upbringing for the young.

• Once territories have been established, it reduces fighting.

How do animals mark and defend their territories?

• Auditory signals (sounds)

• Olfactory signals (smells)

• Visual signals (sights)

Auditory signals

• Example: Bird song

• A male bird will choose an unoccupied area and begin to sing vigorously within it, thus warning away other males. As it patrols its boundary, it will sing to other males across the boundary - this happens most obviously in early spring as more males arrive in an area and begin to compete for territories. The male who sings the loudest will usually get the largest territory.

• http://www.youtube.com/watch?v=MNmh5w6cj78

Olfactory signals

• Pheromones are substances that are secreted by animals and which influence other members of the same species

• Mammals use pheromones to mark territories and home ranges.

•Examples: Cats, dogs and primates use urine and / or chemicals from scent glands.

• http://www.youtube.com/watch?v=Uynx1sRTInM

Visual displays

• Threat displays usually make the animal look larger and more aggressive.

• Examples: Cats arch their back and their hair stands on end. Dogs look straight at opponent and bares their teeth.

Appeasement displays

Animal adopts a submissive posture. It tries to look smaller, turns its face away, may expose a vulnerable part of its body.