Behavioural Ecology

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Behavioural Ecology This subdiscipline studies
the behaviour of individuals in an ecological
context. In general, the behaviours studies are
directed toward food, habitat, and mates. In all
three, genetics and evolution play or have played
key roles in determining the behaviours we
observe. In all three the observed behaviours
frequently result from a mixture of innate and
learned components.
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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 Heres an
experiment demonstrating it Sparrow 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
Normal adult song
The subsong sung at 150 days
The full song
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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.
sign stimulus an insect FAP complex movement
of the tongue to capture the insect
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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 or digger wasps locating their
nests
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Learning Five basic types of learning 1.
Habituation frequent repetition of a signal
leads to a loss of response to it 2.
Imprinting during a short sensitive period
learned behaviour becomes irreversible and
fixed 3. Association stimuli linked to
reward or punishment become associated by
learning 4. Imitation behaviours learned by
mimicking others 5. Problem solving
inventive/innovative behaviours that occur
in response to new situations
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Habituation Do you feel the clothes you are
wearing? Are you aware of the background noise
in your environment? Do you smell the
perfume/cologne the person sitting next to you
is wearing? When a stimulus occurs frequently
enough (or continuously) you respond at first,
but then habituate to it, and response ceases.
When you stop to think about it you can feel
your clothes, hear the background noise, or smell
the scent, but, under usual circumstances, you
lose awareness and response.
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Imprinting Babies recognize their mothers
within a few days of birth, and respond to them
with smiles. The same sort of thing happens in
birds, with the famous picture of Konrad Lorenz
as mother to geese, since he was the first
thing they saw after hatching. Once imprinted, he
was their mother for life.
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Association (or associative learning) One form
is classical conditioning put rats in a
Skinner box where they can press a bar to get
food. Once they associate pressing the bar with
getting food, they press it a lot. Another form
is trial-and-error learning a predator learns
what is good to eat, and what is not. The text
has a painful, but excellent picture if an
error a coyote with a face full
of porcupine quills
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Imitation Thats how the sparrow learns the
normal adult song. If it cant imitate what it
hears from adults, it can produce only the
innate component of normal song. Wolves (and
many other mammalian predators) take their young
(teenage equivalents) along on hunting trips so
that they can learn the proper technique to
successfully capture prey.
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Problem solving Developing a new behaviour to
meet the needs of a novel situation. Dont
think problem solving is limited to primates (and
dolphins). Youve already encountered tool
use by one of Darwins finches, using a cactus
needle to gather insects. The text shows raven
learning how to raise food hung on a
string. Once a problem-solving behaviour has
been discovered, it can be passed on through
imitative learning.
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• There are a few important Categories of behaviour
• 1. Territoriality
• Territoriality is most likely to occur
• When density increases
• When there is increased demand for resources
• When competition increases e.g. for resources or
  mates)
• When resources are aggressively defended
• Of these four reasons, three are related to
  resources, and one to obtaining/keeping mates.

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For any territory based on resources 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. Heres data from one study
Abundant resources- small territories and a
larger number of birds Sparse resources- fewer,
but larger territories to protect sufficient
resources
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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
• 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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Communication can take a number of
forms Chemical pheromones for mating, scent
marking to set territories Visual posing to
attract mates, posing to set dominance
hierarchies, as a portion of mating
rituals Accoustic wolf howls tell members of
a pack how to get home, also tell others the
pack is there cricket chirps (and many other
insect sounds) are related to mate
attraction Tactile many mating rituals involve
the correct touching or rubbing of the
potential mate (and Im not referring to the
human species)
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There are also multiple levels for signals.
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.
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Behaviour involves interactions between/among
individuals. There are four possible outcomes to
interactive behaviour Effect on donor
fitness -- Effect on --
spitefulness selfishness recipient fitness
altruism cooperation
There are numerous observations of cooperation,
both within related groups and among unrelated
individuals. Thats logical from an evolutionary
(fitness) perspective. There are no observations
of spitefulness that I know of. That, too, is
logical. So is selfishness. Altruism is a more
difficult question.
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• There are two kinds of altruism. One, reciprocal
  altruism, is easy to understand.
• Imagine a flock of birds trying to feed.
• When each individual has to defend itself, it
  has to look
• around for predators frequently.
• When the group has rotating sentry duty, group
  defense
• occurs, each individual has to spend only its
  time on duty
• checking for predators frequently.
• Therefore, each can spend more time feeding.
• Each individual expects that others will be as
  vigilant in
• defense as it was while on duty. The effort is
  reciprocal.

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To understand altruism that is not reciprocal,
you need to understand the idea of inclusive
fitness. Evolutionary fitness is measured by the
numbers of copies of your genes in the
subsequent generation compared to those of
others. Note that it doesnt matter whether you
or a relative supplied those genes. An extreme
example You are one of 4 children in a family in
a war zone. You are playing together when someone
throws a live hand grenade through your door.
Would you achieve higher fitness by jumping
through a window or jumping on the hand grenade?
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The answer If you survive, you leave behind
one copy of your genes. If you act in an
altruistic way, each of your siblings shares
(on average) 1/2 of your genes by descent from
the parents. Saving 3 of them would
leave 1½ copies of your genes, and give you
a higher inclusive fitness. Thus, some altruism
is logical and supported by natural selection.
However, truly altruistic acts among unrelated
individuals are much harder (and still
controversial) to explain.