Behavioural Ecology

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Behavioural Ecology This subdiscipline studies
the behaviour of individuals in an ecological
context. In general, the behaviours studied are
directed toward food, habitat, and mates. In all
three areas, dominance and territoriality are
common occurrences. Also, in all three genetics
and evolution play or have played key roles in
determining the behaviours we observe.
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• What regulates behaviour?
• There are both genetic and environmental
  components (i.e.
• the old nature versus nurture controversy).
• Evidence of the importance of both components is
• wide-spread. One example The learning of bird
  song in
• white-crowned sparrows
• Eggs were gathered in the field and hatched in
  the lab.
• Chicks were separated into 3 groups
• 1. Raised in soundproof chambers unable to
  hear songs
• 2. Chicks allowed to hear songs for 5
  months (still
• immature), then deafened
• 3. Control group

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Males normally begin singing what is termed a
subsong at about 150 days, then the song is
refined and practiced, until at about 200 days
the full song is sung. Here are sonograms of
normal song, the subsong, and full song in the
control group, then what is seen in
experimental groups...
w/exposure to adult song
in isolated birds
The subsong sung at 150 days
Normal adult song -full song in control group
The full song
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You can listen to the song portrayed by the
sonograms at http//birdweb.org/birdweb/bird_det
ails.aspx?id424
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There is a genetic program which produces the
first generalized song, the subsong. If raised
in isolation, the song never changes from
the subsong, which is viewed as a
template. There is a closer match to normal
song, even if the normal song is only heard
before maturation.
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Behaviours that are genetically programmed, and
therefore virtually uniform across all members of
a species, are called innate or instinctual. The
behaviour is termed (by Tinbergen initially)
a FIXED ACTION PATTERN or FAP The FAP is
elicited by a sign stimulus. Particular,
dramatic structures or behaviours may even elicit
stronger responses, and are termed superstimuli.
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At the opposite end of the spectrum are
behaviours that are learned. An example bees
able to communicate the location of food sources
to their hives. The behaviour is called a waggle
dance and communicates both direction and
distance to a food source, as well as the quality
of that source. Heres a diagram youll see it
again later
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• Categories of behaviour
• 1. Territoriality
• Under what conditions does territoriality occur?
• When density increases
• When there is increased demand (and possibly
• competition) for resources
• When competition increases (e.g. for mates)
• When resources are aggressively defended

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Some behaviourists categorize territories
according to their purposes type A - A large
defended area for courtship, mating,
nesting, and food gathering type B - A large
defended area for breeding, but not
foraging type C - A small defended area around
the nest type D - An area for mating, for
courtship activities only type E - An area
defended for roosting or shelter
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For any of these purposes or types of territory
to occur, ANY RESOURCE THAT IS DEFENDED MUST
HAVE AN ECONOMIC GAIN Defending a resource
provides a benefit the value of
the resource. The benefits must exceed the costs
of defending the territory. Otherwise the
resource is not worth defending.
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There is plenty of evidence for the economic
model. Territory size should vary with the amount
of resource available. In type A territories,
there should be a negative correlation between
the abundance of food and territory size.
Heres the re-drawn figure showing this in your
text...
Abundant resources- small territories and a
larger number of birds Sparse resources- fewer,
but larger territories to protect sufficient
resources
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It should also be apparent that a larger animal
needs to hold a larger territory to defend
sufficient food...
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• What determines the size of an animals
  territory?
• Simple models provide a rough answer.
• First, as territory size increases, benefits
  increase, but only
• up to a point. As territory size increases, the
  cost of defense
• also escalates
• there is a larger area to defend
• there is contact (and potentially aggressive
  encounters)
• with a larger number of animals
• the time spent on defense means other functions
  may be
• neglected
• This suggests a cost-benefit model...

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Neither very small nor very large territories are
economically defendable. There is an optimum
size where benefits exceed costs to the greatest
extent.
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How useful is this model in explaining territory
size? In a general sense, the model is
correct. It correctly predicts that very large
and very small territories are too costly.
For example, in some birds low food abundance
(low benefit) causes them to abandon defending
territories. But when food abundance again
increases, territories are again
defended. However, optimal size is very
sensitive to the exact shapes of cost and
benefit curves. Therefore, the model is of
very limited use in making quantitative
predictions.
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• 2. Communication
• In the context of behavioural ecology,
  communication
• means not just the sending of a signal, but its
• reception by another, and that the signal is
  acted upon.
• Communication has many functions. Here are some
• Status - identification of rank
• Begging - solicitation of parental care by
  offspring
• Alarm - warning of the presence of a predator
• Distress - a call for aid
• Threat - Show of imminent aggression
• Appeasement - attempt to dissuade aggression
• Sexual receptivity - identification of
  readiness to mate

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The signal can be communicated in various
ways Chemical Accoustic Visual
Tactile Range long long
medium short Transmission slow fast
fast fast rate Information slow
fast fast fast fadeout time Location of
difficult fairly easy easy easy
sender Energy cost low high low
low to moderate
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Consider two signal communications 1) Photinus
(firefly) flashes - each species has a specific
stereotyped pattern. Males flash, females
signal receptivity by flashing back. This is
a yes-no signal. 2) The honey bee waggle dance
communicates what is called a graded signal,
much more than yes-no. The honey bee flies in
repeated figure-8s inside the hive. Angle to
the vertical communicates the angle between a
food source and the sun. The length of the
straight, middle run indicates distance. The
intensity of the waggle indicates quantity of
food.
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• 3) Aggression
• Aggression has the function of achieving
  dominance by
• either physical violence or the threat of it.
• Aggression can be involved in defense of
  territory, but
• dominance is most important in mating and
  reproduction.
• Aggression associated with mating has obvious
  fitness
• consequences
• in wolves, only the ? male mates. Aggression
  preventing
• other males from mating mean only his genes
  will be
• found in offspring.
• In sea lions, males guard harems of females
  against both
• other males desertion by females

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• Sometimes, aggression is ritualized rather than
  injurious.
• To make evolutionary sense, this must be to the
  advantage
• of both animals. The risk of injury to both
  winner and
• loser is significant. Thus, rapid recognition of
  dominance
• protects both. The loser can try again later,
  having grown
• larger and stronger with time.
• Infanticide is not uncommon
• In lions, when a male takes over a pride, cubs
  are killed
• and the male mates with females, assuring his
  genetic
• contribution to the young he raises.
• In white-footed mice, males that have not sired
  pups are
• infanticidal. Females may also kill pups
  outside their nests.
• This may be a response to apparent high density
  in the
• population.

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• 4) Social Systems - Mating Systems
• Mating systems have 3 components
• the number of mates an individual takes
• whether the male and female form a pair bond
• how long the pair bonding lasts

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The evolution of these 3 components ( mates,
pair bonding, length of bond) is driven
by Sexual selection and Demography Sexual
selection results from the relative investment
in reproduction Males contribute (in most
cases) only sperm Females contribute through egg
production (more costly than sperm),
gestation or incubation, and parental care of
neonates. Thus, sexual selection is normally
female choice of mate(s).
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• At one time mating systems were thought to
  represent
• cooperation between the sexes.
• More recently mating systems have been recognized
  to
• also represent conflict between the sexes.
• The conflict arises because
• males can maximize reproductive success by
• mating many times
• females maximize their reproductive success by
• producing well-adapted, healthy offspring,
• (i.e. picking the best mate, not by mating
  multiple
• times

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Lets compare the energy expenditure on mating
and parental care for (at least) monogamy and
polygamy Mating effort consists of energy spent
on courting, mating, and mate defense or
guarding Parental effort is that spent on
feeding and caring for offspring.
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There are a number of different mating
systems Mating systems in vertebrates Class
Parental Care Mating System Birds male
female monogamy Mammals female polygamy Fish
usually the male polygamy
Amphibians Lizards absent variable
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• Polygyny - males mate with more than 1 female.
• Not all males reproduce, there is important
  variance
• in male reproductive success.
• Likely to evolve when there is clumping, either
  of
• resources or females, and when there is not high
• synchrony in the receptive times of females.

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When females clump, the polygyny is
called female defense polygyny Example female
gorillas travel in groups to avoid predation
by leopards. Males defend these groups from
other males. When resources are clumped, the
polygyny is called resource defense
polygyny Example an African bird, the
orange-rumped honeyguide feeds on beeswax.
Males defend bee colonies from other
males. Females come to the bee colony as a
food source, and copulate with the male
defending it.