Animal responses to biotic environment

categories

Intraspecific aggressive responses

Aggressiveness is a mood, aggression is belligerent behaviour that arises

from competition.

Fighting – agonistic behaviour• Agonistic behaviour is aggressive to wards

another member of the same species involving threat or fighting. Involves a contest to see who gets the resource (food/mate). It can be a test of strength or more commonly a symbolic behaviour they all recognise thus avoiding actual fight. The behaviour leads to submission or appeasement. Scarcer the resource = more intense the fighting.

1. Competition between animals of same species is strongest as want same resource. If for a mate, is within one sex.

2. In-fighting has become ritualised so that one wins and one loses and no-one is too badly hurt.

3. Most vicious fighting is between individuals that cannot really hurt each other (e.g. hornless female antelope)

4. Fighting to the death is non-adaptive to most animals

5. Fighting to death can occur to eliminate a stranger from the group.

Territories

• An area established for feeding, mating or rearing young that is marked/defended. Other members of the same species are excluded from area.

1. Territorial behaviour varies widely. Most animals have a definite home, the area they cover to search for food/mates is called the home range, defended area = territory.

2. Hold territory through aggressive behaviour, strongest attacks are against members of same species and same sex.

3. Many adaptive features of territoriality:

• a) ensures enough space for each animal, if in short supply can keep population down

• b) reduces spread of disease and parasites, harder for predators to find them.

• c) most successful males hols the best territories so best genes are handed on to offspring

• d) once territory established and resources divided loser leave and look elsewhere rather than keep fighting.

• e) in some species males without a territory cannot attract a mate so don’t breed.

• f) territories ensure enough food for animals and families holding them.

• g) ensure a safe protected nest or home for young (or at least a place to breed in a communal breeding ground)

• h) animal is very familiar with area.

4. Territorial behaviour is set, defenders and intruders know their roles which is stabilising behaviour.

Marking and defending territory: most animals regularly patrol their territories and mark them to proclaim ownership.e.g birds sing on boundary, dogs/cats mark with urine, scent in deer, cats and other animals, crabs wave claws at perimeter, howler monkeys ‘howl’ in morning.

Hierarchies• This is the idea of pecking order – the

dominant bird pecks all those below it down to the lowest ranked who doesn’t peck anyone. This is found in many animal groups (alpha males) and is established competitively but once in place cuts down competition and tension.

• Maintained by posture, making self look bigger and subordinates appease them.

• Can be shown by win-loss tables

E D T C Total

E 0

D 5 5

T 3 7 2 12

C 3 5 6 14

• Shaded = no result• C beating T is rare as when dominance is

established there are few changes.

Intraspecific co-operative responses

Three aspects of: group formation, pair bond, parental care.

Group formation• Advantages of:

– 1/ Hunting as a team, can bring down larger game and more of it.

– 2/ defence– 3/protection– 4/ Insect societies, specialised roles coordinated by

the queen.– 5/clumping– 6/ confusion– 7/ breeding

• Disadvantages: when animals crowd together there is competition for resources– Disease can spread quickly through a group

living close together– Parasites spread easier– Increased conflict

Courtship and Pair bonding

• Most animals stay out of another's ‘personal space’, conflicting tendencies are seen in courtship behaviour of wanting to stay away but wanting to come close. The sex act is adaptive as it requires cooperation, temporary halt of aggressive behaviour, a system of communication and species recognition.

Mating appears simple but is fundamental to the survival of the species. Both partners need to be sure they are of the same species, fertile, both fully prepared to mate. Usually the female chooses the male and the male must compete for her. The two ways a male can gain an advantage over another male is a) competing with other males in fighting or ritualised combat or b) compete indirectly by attracting females with special displays and adornments.

Courtship ensures the two animals are of the same species and may be a sign to start nest building or trigger ovulation. Aggression is reduced by dances, calls, movement of body, pheromones or touching. This strengthens the pair bond to allow more intimate behaviour. Important in insects as many females will eat male if not appeased!

• A pair bond is a stable relationship between animals of the opposite sex that ensures cooperative behaviour in mating and rearing young.

Parental CareSurvival of species depends on breeding

population producing adequate numbers to establish a new generation. This is usually achieved by one of two strategies:

1. the r strategy – many relatively unprepared offspring each with low chance of individual survival. No parental care, some should make it, breeding does not affect health of existing generation. (fish, insects, turtles)

2/ the k strategy – produce a few, well prepared offspring with a high chance of individual survival. Parents invest lots of food and effort into them from egg stage to after birth, health of current generation risked for the next generation

Different reproductive strategies

• Monogamy: mate with only one member of the opposite sex. Both parents then raise young – 90% birds.

• Polygyny: male will mate with many females thus having lots of offspring but no parental care (mother or offspring do themselves)

• Polygamy: dominant male has harem of females.

• Polyandry: one female mates with many males but males only mate with one female. Very rare and males do most of the parental care.

• Polygynadry (promiscuity): both males and females mate with several members of the opposite sex. No pair bonds and very little parental care (pukekos).

• Synchronized spawning: all members of species spawn at same time. Coral, worms and some fish.

• Cooperative breeding: mated pair builds nest or base, female has young in it/lays egg. When young arrive are feed by parents or group.

• Kin selection: favours genes that promote altruistic behaviour towards individuals that are genetically related. Rabbits and some birds.

• Social insects: one queen who reproduces, rest infertile but have set jobs (termites, bees, wasps).

Interspecific aggressive responses

Competition for food• Competition is for resources of food, water,

space and breeding sites. Gauses principal: no two species with identical ecological niches can co-exist for long in the same place.

• Different niches can avoid this, nocturnal/diurnal, feed on different parts of tree etc

• Once Interspecific competition is happening there is selection for any differences in niches or one species is driven out and forced to migrate. This leads to adaptive radiation in some species.

Predator-prey relations

• Not a true aggressive relationship as predators can keep prey populations at a health level, predators tend to catch the least adapted, oldest or weakest. This keeps the gene pool strong. Two species depend on each other.

• Adaptations for getting food: – Letting the prey come to the predator

• Sifting the environment with suction and sieves• Dangling baits• Webs and traps• Lying in ambush

– Moving after the prey• Must have right appendages to get at prey• Hunting in swarms• Hunting in teams• Using tools– Parasitizing a prey

Parasite-host relations• In general parasites exist at the expense

of the host. Parasitic invasions tend to be density dependant as crowded conditions make it easier to transfer to a new host. Structures of a parasite are greatly reduced as they depend on the host for many functions so movement can be a problem. Therefore reproduction is highly developed in the hope some offspring will find a new host.

• Ectoparasites are found on the outside of a host (flea) and an endoparasite is found inside.

• Parasitiods are parasites that are only parasitic at one stage of their lifecycle.

Defence strategies against predators• We recognise an animal by three things:

– 1/Its silhouette which can be disguised by• Disruptive colouration (markings that hide the

outline of an animal)• Cryptic colouration (colouration to match the

background)

– 2/ Its eye, which can be disguised by• Making the eye disappear in stripes and blotches• Flaunting a false eye spot in a non-vital part of the

body

3/ Its bulk, which can be disguised by counter shading.– Other defences are:

• Startle the predator by fluffing the body hair or feather to look big

• Pretend to be inedible, look like a stick or a bird dropping.

• Mimicry – an organisms close imitation of a model that is unrelated. Two types: Batesian (a harmless species looks like a toxic one e.g. monarch(toxic) and viceroy(harmless) butterfly look the same), and Mullerian (several poisonous species with the same colouring.

• Warning colouration (aposematic): an animal warns that it is dangerous or poisonous by having bright colours, especially stripes.

• Warning sounds• Firing chemicals (snakes)• Curling up• Retreating into shell• Hiding with camouflage• Escape in large numbers (fish shoals)• Pretending to be dead.

Interspecific co-operative responses

MutualismWhen both animals benefit from the

relationship. Examples are cleaner fish on the larger fish, when mixed groups of animals are grazing the alarm call of one species is heeded by the others, ants care for aphids by guarding them and in return get the honey dew, ruminants and bacteria in gut.

Commensalism• One animal benefits and the other is

neither harmed nor benefits. Examples are remora and shark – remora benefits but has no effect for shark, mussel crabs in mussels

Antibiosis

• One organism is harmed and the other is indifferent (human sewage affecting a river).