Transcript Animal responses to biotic environment

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.
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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
E
Total
0
D
5
5
T
3
7
C
3
5
2
6
12
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 Care
Survival 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
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Sifting the environment with suction and sieves
Dangling baits
Webs and traps
Lying in ambush
– Moving after the prey
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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
Mutualism
When 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).