Transcript Behavioural Ecology

Chapter 51
Behavioural Ecology
Recall...
• Behavioural ecologists distinguish between
proximate and ultimate causes of behaviour
• What are the questions that must be
answered to understand any behaviour?
1. What is the mechanistic basis of the behaviour,
including chemical, anatomical, physiological
mechanisms?
2. How does development of an animal influence
behaviour (sign stimuli)?
3. What is the evolutionary history of the
behaviour?
4. How does behaviour contribute to survival &
reproduction (fitness)?
Behaviours typically studied by ethologists
Fixed Action Patterns
• Fixed action pattern (FAP)
• Imprinting
• Many behaviours have a strong genetic
component –innate behaviours
• Directed movements
– kinesis
– taxis
– migration
• Animal Signals and Communication
• Genetic Influences on Mating and Parental
behaviour
Environment influences the development of
behaviours
• Dietary Influence on Mate Choice behaviour
• Social Environment and Aggressive behaviour
• Learned behaviours
– Habituation
– Spatial learning
– Cognitive maps
– Associative learning
– Cognition
• Concept 51.4: Behavioural traits can evolve
by natural selection
• Because of the influence of genes on behaviour
– natural selection can result in the evolution of
behavioural traits in populations
Behavioural Variation in Natural Populations
• When behavioural variation within a species
– corresponds to variation in the environment, it
may be evidence of past evolution
Variation in Prey Selection
• Differences in prey selection in populations of
garter snakes
– are due to prey availability and are evidence of
behavioural evolution
Figure 51.18a, b
(a) A garter snake (Thamnophis
elegans)
(b) A banana slug (Ariolimus
californicus); not to scale
Variation in Aggressive behaviour
• Funnel spiders living in different habitats
– exhibit differing degrees of aggressiveness in
defense and foraging behaviour
Desert
grassland
population
60
Time to attack (seconds)
50
Riparian
population
40
30
20
10
0
Field
Lab-raised
generation 1
Population
Figure 51.19
Lab-raised
generation 2
Experimental Evidence for behavioural Evolution
• Laboratory and field experiments
– can demonstrate the evolution of behaviour
Laboratory Studies of Drosophila Foraging behaviour
• Studies of Drosophila populations raised in highand low-density conditions
show a clear divergence in behaviour linked to
specific genes
14
Low population
density
12
Average path length (cm)
–
High population
density
10
8
6
4
2
0
L1
L2
L3
H1
H2
D. Melanogaster lineages
Figure 51.20
H3
H4
H5
Migratory Patterns in Blackcaps
• Field and laboratory studies of Blackcap birds
– have documented a change in their migratory
behaviour
• Birds placed in funnel cages
– left marks indicating the direction they were
trying to migrate
(a) Blackcaps placed in a funnel cage left marks indicating the
direction in which they were trying to migrate.
Figure 51.21a
• Migratory orientation of wintering adult birds
captured in Britain
–
was very similar to that of laboratory-raised birds
N
BRITAIN
W
E
S
(b) Wintering blackcaps captured in Britain and their laboratory-raised
offspring had a migratory orientation toward the west, while
young birds from Germany were oriented toward the southwest.
N
Young
from SW
Germany
Mediterranean
Sea
Figure 51.21b
E
W
S
Adults from
Britain and
F1 offspring
of British
adults
• Concept 51.5: Natural selection favours
behaviours that increase survival and
reproductive success
• The genetic components of behaviour
– evolve through natural selection
• Behaviour can affect fitness
– through its influence on foraging and mate
choice
Foraging behaviour
• Optimal foraging theory
– views foraging behaviour as a compromise
between the benefits of nutrition and the costs
of obtaining food
Energy Costs and Benefits
• Reto Zach
– conducted a cost-benefit analysis of feeding
behaviour in crows
• The crows eat molluscs called whelks
– but must drop them from the air to crack the
shells
• Zach determined that the optimal flight height
in foraging behaviour
– correlated with a fewer number of drops,
indicating a trade-off between energy gained
(food) and energy expended
50
Average number of drops
100
40
75
Total flight height
20
Drop height
preferred
by crows
10
0
Figure 51.22
Average number of drops
30
2
3
5
Height of drop (m)
50
25
7
15
Total flight height (number of drops  drop height)
125
60
• In bluegill sunfish
–
prey selection behaviour is related to prey density
Small prey at
middle distance
Small prey at
close distance
Large prey at
far distance
Low prey density
Small prey
Medium prey
Large prey
High prey density
14%
33%
33%
33%
35%
50%
Percentage available
Small prey
Medium prey
Large prey
33%
33%
33%
100%
Predicted percentage in diet
Small prey
Medium prey
Large prey
Figure 51.23
32.5%
32.5%
35%
2%
40%
57%
Observed percentage in diet
Risk of Predation
• Research on mule deer populations
– has shown that predation risk affects where the
deer choose to feed
Predation
risk
Relative deer use
60
15
50
40
10
30
20
5
10
0
0
Open
Figure 51.24
Forest edge
Habitat
Forest interior
Relative deer use
Predation occurrence (%)
70
20
Mating behaviour and Mate Choice
• Mating behaviour
– is the product of a form of natural selection
called sexual selection
Mating Systems and Mate Choice
• The mating relationship between males and
females
– varies a great deal from species to species
• In many species, mating is promiscuous
– with no strong pair-bonds or lasting
relationships
• In monogamous relationships
– one male mates with one female
(a) Since monogamous species, such as these trumpeter swans, are
often monomorphic, males and females are difficult to distinguish
using external characteristics only.
Figure 51.25a
• In a system called polygyny
– one male mates with many females
– the males are often more showy and larger
than the females
Figure 51.25b
(b) Among polygynous species, such as elk, the male (left) is
often highly ornamented.
• In polyandrous systems
–
one female mates with many males
–
the females are often more showy than the males
Figure 51.25c
(c) In polyandrous species, such as these Wilson’s phalaropes, females
(top) are generally more ornamented than males.
• The needs of the young
– are an important factor constraining the
evolution of mating systems
• The certainty of paternity
– influences parental care and mating behaviour
• In species that produce large numbers of
offspring
– parental care is at least as likely to be carried
out by males as females
Eggs
Figure 51.26
Sexual Selection and Mate Choice
• In intersexual selection
– members of one sex choose mates on the basis
of particular characteristics
• Intrasexual selection
– involves competition among members of one
sex for mates
Mate Choice by Females
• Male zebra finches
– are more ornate than females, a trait that may
affect mate choice by the females
Figure 51.27
• Imprinting of female chicks on males with more
ornamentation
Experimental Groups
– affects mate
selection as
adults
Both parents
ornamented
Males
ornamented
Control Group
Females
ornamented
Parents not
ornamented
Results
Females reared by
ornamented parents
or ornamented fathers
preferred ornamented
males as mates.
Females reared by
ornamented mothers or
nonornamented parents
showed no preference
for either ornamented or
nonornamented males.
Males reared by all experimental groups showed no
preference for either ornamented or nonornamented
female mates.
Figure 51.28
• The size of eyestalks in stalk-eyed flies
– affects which males the females choose to mate
with
Figure 51.29
Male Competition for Mates
• Male competition for mates
– is a source of intrasexual selection that can
reduce variation among males
• Such competition may involve agonistic
behaviour
– an often ritualized contest that determines
which competitor gains access to a resource
Figure 51.30
• Morphology affects the mating behaviour
– in isopods of the same species that are
genetically distinct
Large Paracerceis  males
defend harems of females
within intertidal sponges.





Tiny  males are
able to invade
and live within
large harems.
Figure 51.31
 males mimic female morphology and
behaviour and do not elicit a defensive
reponse in  males and so are able to
gain access to guarded harems.
Applying Game Theory
• Game theory evaluates alternative behavioural
strategies in situations
– where the outcome depends on each
individual’s strategy and the strategy of other
individuals
• Mating success of male side-blotched lizards
– was found to be influenced by male
polymorphism and the abundance of different
males in a given area
Figure 51.32
• Concept 51.6: The concept of inclusive fitness
can account for most altruistic social behaviour
• Many social behaviours are selfish
• Natural selection favours behaviour
– that maximizes an individual’s survival and
reproduction
Altruism
• On occasion, some animals
– behave in ways that reduce their individual
fitness but increase the fitness of others
• This kind of behaviour
– is called altruism, or selflessness
• In naked mole rat populations
– nonreproductive individuals may sacrifice their
lives protecting the reproductive individuals
from predators
Figure 51.33
Inclusive Fitness
• Altruistic behaviour can be explained by
inclusive fitness
– the total effect an individual has on proliferating
its genes by producing its own offspring and by
providing aid that enables close relatives to
produce offspring
Hamilton’s Rule and Kin Selection
• Hamilton proposed a quantitative measure
– for predicting when natural selection would
favour altruistic acts among related individuals
• The three key variables in an altruistic act are
– the benefit to the recipient = B
– the cost to the altruist = C
– the coefficient of relatedness = r
• The coefficient of relatedness
– is the probability
that two relatives
may share the
same genes
Parent A
Parent B

OR
1/
1/
(0.5)
probability
Figure 51.34
Sibling 1
(0.5)
probability
2
Sibling 2
2
• Natural selection favours altruism when the
benefit to the recipient
– multiplied by the coefficient of relatedness
exceeds the cost to the altruist
• This inequality
– is called Hamilton’s rule
• Hamilton’s rule = rB > C
– more closely related two individuals are,
greater value of altruism
• Kin selection is the natural selection
– that favours this kind of altruistic behaviour by
enhancing reproductive success of relatives
An example of kin selection and altruism
– is the warning behaviour observed in Belding’s
ground squirrels
Mean distance
moved from
natal burrow
(m)
300
Male
200
100
Female
0
0
Figure 51.35
2
3
4
12
13
14
Age (months)
15
25
26
Reciprocal Altruism
• Altruistic behaviour toward unrelated
individuals
– can be adaptive if the aided individual returns
the favour in the future
• This type of altruism
– is called reciprocal altruism
Social Learning
• Social learning
– forms the roots of culture
• Culture can be defined as a system of
information transfer through observation or
teaching
– that influences the behaviour of individuals in a
population
Mate Choice Copying
• Mate choice copying
– is a behaviour in which individuals in a
population copy the mate choice of others
• This type of behaviour
– has been extensively studied in the guppy
Poecilia reticulata
Control Sample
Male guppies
with varying
degrees of
coloration
Female guppies prefer
males with more orange
coloration.
Experimental Sample
Female model
engaged in
courtship with
less orange
male
Figure 51.36
Female guppies prefer less
orange males that are associated
with another female.
Social Learning of Alarm Calls
• Vervet monkeys
– produce a complex set of alarm calls
• Infant monkeys give undiscriminating alarm
calls at first
– but learn to fine-tune them by the time they
are adults
Figure 51.37
• No other species
–
comes close to matching the social learning and
cultural transmission that occurs among humans
Figure 51.38
Evolution and Human Culture
• Human culture
– is related to evolutionary theory in the distinct
discipline of sociobiology
• Human behaviour, like that of other species
– is the result of interactions between genes and
environment
• However, our social and cultural institutions
– may provide the only feature in which there is
no continuum between humans and other
animals