Higher Biology
Adaptation
Part 5
Adaptation 5
By the end of this lesson you should be
able to:
 Explain what foraging behaviour is.
 Explain the purpose of search patterns to animals.
 Describe the economics of foraging behaviour.
 Understand what is meant by optimal foraging.
 Know the difference between interspecific and
intraspecific competition.
 Explain the advantages of dominance hierarchy.
 Explain the advantages of co-operative hunting.
 Explain territorial behaviour in animals in relation
to competition for food.
2
Foraging behaviour
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Foraging is the term given to the ways in which
animals search for food.
Searching for food requires energy.
It is important that the energy gained from the
food is greater than that involved in
finding/catching it.
Foraging behaviour has evolved so that
Energy Gain
>
Energy Used up
3
Search Patterns
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Some animals have evolved specific search
patterns to help them find food with the least
energy cost to themselves.
E.g.
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Planaria
Ants
Bees
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Planaria
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This is a type of
flatworm which
lives in ponds and
streams and feeds
on the remains of
dead animals!
They are able to
move about freely
and change
direction.
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Planaria

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They tend to move about randomly in the
absence of food- to increase the overall
area covered and so the chance of them
finding food.
Can detect chemicals coming from dead
animals using chemoreceptors so move
towards them (down a concentration
gradient).
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Ants
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Ants leave the colony
and wander about
backwards and forwards
searching for food.
As soon as an ant finds a
food source, it
immediately makes its
way back to the colony,
marking its trail with
scent.
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Ants
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Other ants can then follow the trail and
reinforce the scent marks as long as the
food lasts.
As the scent marks quickly fade, no energy
is wasted following old trails.
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Bees
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Bees are social insects and
the colony is dependent on a
regular food supply.
Once a worker bee has
located a good food source,
she returns to the hive and
performs a waggle dance
which indicates the distance
and direction of the food to
other workers.
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Bees

The duration of the dance indicates the
richness of the food and will reduce as the
richness of the food reduces.
10
Economics of foraging

Foraging is economic when:
Energy Gain

>
Energy Used up
E.g.
Energy used in
finding, catching
& eating food; risk of
being killed by a predator
during feeding
<
Energy Gain
11
Economics of foraging

1.
Factors that affect foraging include:
Time- search time -to locate
pursuit time -to chase, catch & kill
If the search time is short and pursuit time is
long, then animals tend to be selective
e.g. lions can easily find herds of zebra,
however to catch one would take time, so the
lion would select an older or weaker zebra as
its prey.
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Economics of foraging
TimeIf the search time is long but pursuit time is
short, then animals tend not to be selective.
e.g. an anteater may take ages to find an ant
colony, however once it has, it tries to eat as
many ants as it can, as quickly as possible.
1.
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Economics of foraging
2.
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Density and size of prey If the density of prey is low then
predators will be less selective about what it
eats. (& vice versa)
If the prey is small and will not yield much
energy then predators will be less selective
about what it eats.
If the prey is large then more energy will be
spent in catching the prey and it may not be
economical.
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Economics of foraging
2.

Density and size of prey There is an optimal size of prey which will
provide a net energy gain.
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Economics of foraging
3.

Risk of injury It can be better for herbivores to settle
for food in poorer ecosystems rather than
foraging in a food-rich area which exposes
them to attack by predators.
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Competition
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1.
2.
Competition occurs when resources are in
short supply.
There are 2 types of competition:
Interspecific
Intraspecific
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Interspecific Competition
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This is between individuals of different
species which occupy the same ecological
niche.
Usually one species ousts the other and so
the loser must migrate or face extinction.
E.g. red and grey squirrels
rainbow trout and native brown trout
Usually a compromise is reached where the
rivals might eat different foods, or eat at
different times of day. Etc.
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Intraspecific Competition
This is between individuals of the same
species which occupy the same ecological
niche.
 The members of the same species will need
exactly the same resources.
 Intraspecific competition is even more
intense than interspecific competition.
 Intraspecific competition can be reduced
by types of social behaviour.
e.g. dominance hierarchy, co-operative
hunting, territorial behaviour.

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Dominance hierarchy
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This is the type of behaviour occurring in
higher animals living in social groups.
It is based on aggressive behaviour
between individuals which results in a
ranking order, where the higher rank
animals dominate those of a lower rank.
E.g. in birds like hens or pigeons one bird
will emerge as being dominant and will peck
and intimidate others in the group.
This creates a pecking order.
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Dominance hierarchy
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Another example in mammals is wolves.
Wolves hunt in packs and dominance
hierarchy exists amongst the females.
When there is plenty of food- the
dominant female mates and allows others
to mate as well.
However when food is scarce- the
dominant female will mate, but allow fewer
of the others to mate.
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Dominance hierarchy
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This ensures that the dominant females
young will have enough food and be more
likely to survive.
The dominant individual ensures its high
rank by a system of aggressive or threat
displays.
E.g. raising head and staring at other
animals
baring their teeth
raising their ears
fur, ears & tail upright.
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Dominance hierarchy
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All these gestures make the wolves appear
larger and more threatening.
The other individuals show subordinate
displays.
E.g. lowering eyes and head
covering their teeth
lowering their ears
fur, ears & tail lowered.
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Advantages of Dominance hierarchy
1.
2.
3.
4.
5.
6.
Aggression between members becomes
ritualised.
Real fighting is kept to a minimum.
Serious injury is normally avoided.
Energy is conserved.
Experienced leadership is guaranteed.
The most powerful animals are most likely
to pass their genes onto the next
generation.
24
Co-operative hunting
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Predatory animals may hunt co-operatively
to optimise energy gain.
Prey will be larger and less energy will be
used to secure the kill.
The kill will then be shared between all
members of the group, even subordinate
members.
Subordinate members will therefore gain
more food by foraging alone.
25
Co-operative hunting
E.g. wild dogs communicate with each other
using calls and body postures.
 They hunt in packs of 6-30 animals,
roaming over large areas in search of prey
like gazelle or zebra.
Advantages:
1. Larger prey can be tackled and so more
food can be gained.
2. All members, including the subordinate,
benefit- although the dominant ones will
get the larger share of food.

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Territorial behaviour
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A territory is an area that an animal
defends, usually against members of its
own species.
The territory has to contain enough food
for himself and eventually a mate and their
young.
Territories are defended aggressively by
social signals.
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Territorial behaviour
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E.g. a robin sings to proclaim the
boundaries of its territory.
Male lions defend the pride against
intruders- they mark boundaries with urine
and patrol them regularly.
The size of a territory depends on the
species of animal and the resources
available.
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Adaptation 5
Can you do it?
 Explain what foraging behaviour is.
 Explain the purpose of search patterns to animals.
 Describe the economics of foraging behaviour.
 Understand what is meant by optimal foraging.
 Know the difference between interspecific and
intraspecific competition.
 Explain the advantages of dominance hierarchy.
 Explain the advantages of co-operative hunting.
 Explain territorial behaviour in animals in relation
to competition for food
29