APS 209 Animal Behaviour

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APS 209 Animal Behaviour
Lecture 5. The Development of Behaviour
Neural Mechanisms

• Fixed Action Patterns
• Cortical focus of senses
• Stimulus Filtering
• Navigation

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Aims Objectives
Aims 1. To show how an animal simplifies the
outside world by responding specifically to
certain key stimuli, and how the properties of an
animals nervous system are tuned to the demands
of its lifestyle and environment. 2. To present
examples of this in fixed action patterns, the
response of moths to sound, measuring distance by
bees etc Objectives 1. Lean the examples above.
2. Understand why it can be adaptive for an
animal to concentrate on just a few key stimuli.
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Fixed Action Patterns
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Tinbergens Herring gull work
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Fixed Action Pattern Releaser Stimuli
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Comparing Releaser Stimuli
A gull chick will peck at the bill of a parent in
a stereotyped way (Fixed Action Pattern). The
beak releases (Releaser Stimulus) the FAP. This
study determines which features of an adult bill
are involved. The red dot contrasting with the
rest of the bill is the key feature. An
artificial object with very little resemblance to
the actual bill, but with the right releaser
stimuli in abundance, is very effective.
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Supernormal Stimulus
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Egg Retrieval in Greylag Geese
The geese retrieve eggs with a stereotyped
behaviour (FAP), rolling them back into the nest.
Any object that is roughly egg shaped will be
retrieved. If a researcher removes the object
during the FAP, the behaviour continues even
though the object is no longer there.
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Hypothesized Neural Mechanisms in Brain
The brain of the chick must have some mechanism
for detecting the releaser stimulus and
triggering the response the begging FAP. The FAP
of the gull chick is instinctive. Therefore, the
brain circuitry behind the FAP must have been
encoded in the chicks genes rather than learned.
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Parasite Exploiting Releaser Behaviour
Atemeles beetles are one of the many insects that
are parasites in ant nests. The ants respond to
the beetles as if to other ants, feeding them.
Larvae of Large Blue butterflies (Maculinea
arion) are also parasites in ant nests preying on
larvae. However, in species of Maculinea found in
Europe, the caterpillars do not prey on the
larvae but are fed by worker ants similar to
Atemeles.
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Honey Bee When Flower Colour is Learned
The herring gull chick has a stereotyped response
to the parents bill. Honey bees also show a
stereotyped learning response to flowers. The
flowers colour is learned as the bee lands. The
bee does not notice if the colour of the flower
is experimentally changed after landing.
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Unusual Senses
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Emperor Moth
The Emperor moth is a silk moth found in Britain.
The males can detect females from miles away. The
antenna of the male (left) are larger due to the
importance of the antennae in detecting the
female sex attraction pheromone. Many animals
have sensory systems that detect stimuli that
humans cannot detect (e.g., UV light), or are bad
at detecting (chemicals).
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Star-Nosed Mole
Lives underground in wet marshy soil, tiny eyes,
highly modified nose.
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Star-Nosed Mole
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Star-Nosed Mole
Researchers have determined how much of the
animals brain cortex is involved in processing
signals from each pair of nose appendages.
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Noctuid Moth Ear
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Noctuid Moth
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Ear of Noctuid Moth
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Moth Anatomy
The moth ear is a good example of how what seems
to be rather a simple sensory organ can still be
very effective in giving the animal useful
information about its environment. By our
standards a moth ear is crude. It has just a few
receptors and cannot detect the pitch of the
sound. But it can detect bat sonar, and the
direction from which this is coming, thereby
helping the moth escape. Because the signal
picked up by the moth is not an echo (the bat has
to pick up echos) the sound that the moth hears
is much louder than the sound that the bat hears,
so moths can probably detect bats before bats
detect moths.
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Neural Activity of Receptors
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Neurology of Moth Ears
Tympanum vibrates
BAT ULTRASOUND SIGNAL
Mechanical stimulation of receptor cells
Stretch-sensitive channels open in membrane of RC
Na flow in and change the electrical charge
inside the cell relative to that outside
If change is great, an action potential occurs
all or nothing response
AVOIDING ACTION BY MOTH
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Nerve Cells Connected Together
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Advantage of Having Two Sensory Cells
Range over which ear is sensitive to change in
intensity
max. rate
less sensitive neuron
more sensitive neuron
Firing rate of sensory neuron
min. rate
Sound intensity
If the two sensory cells in the moth ear are not
equally sensitive, as is the case, then this will
increase the range over which the moth ear is
sensitive to variation in sound intensity.
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Detecting Where Bat is
A. Bat to one side. One ear stimulated more than
the other. B. Bat behind. Both ears stimulated
equally. C. Bat above. Ears stimulated more when
wings are up.
A)
B)
C)
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Some Simple Physics
d
Green Bat sonar Red Echo
echo
2d
The intensity of sound, gravity, light etc,
decreases by the square of the distance. Thus, if
the moth is twice as far away the sound of the
bat will diminish 4-fold (i.e., according to
1/d2). But the echo will diminish 16 fold (i.e.,
according to 1/(d2 x d2)). Thus, a simple moth
ear may be able to detect a bats sonar at a
greater distance than the much more sophisticated
bat ear can hear the echo. In addition, only a
small amount of the call will be reflected back
to the bat from the moth.
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Radar Equation
The amount of power Pr returning to the receiving
antenna is given by the radar equation. In the
common case where the transmitter and receiver
are at the same location, Rt Rr and the term
Rt2 Rr2 can be replaced by R4, where R is the
range. This shows that the received power
declines as the fourth power of the range, which
means that the reflected power from distant
targets is very, very small. http//en.wikipedia.o
rg/wiki/Radar Boiling the radar equation down,
the ability of the bat to detect the moth is
proportional to (sonar loudness x reflection of
target x sensitivity of ear)/(distance4) In other
words, louder sonar, a more reflective (larger)
insect, and a more sensitive ear all help. But
the biggest factor is distance. This is because
sensitivity depends inversely on the 4th power or
distance, but only on the 1st power of the other
factors.
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Why Bats Have Squeaky Voices
Wavelength small relative to target good
resolution
Wavelength large relative to target poor
resolution
A wave can only detect (be reflected) by an
object that is larger than half the wavelength.
This is why ultra-violet or electron microscopes
are used to see small objects, as UV and high
energy electrons have a smaller wavelength than
visible light. Similarly, high pitched sounds
reflect better from small insects. Bat species
which specialise on larger insects have deeper
calls. Sound travels at 340ms-1 at sea level.
Thus, sound of 340Hz (a womans voice) will have
a wavelengh of 1m. Sound of 34,000Hz (ultrasound
beyond human hearing will have a wavelength of
1cm. Bat sonar is typically 40,000-120,000Hz,
meaning wavelengths of c. 2-8mm. (Hz Hertz,
cycles per second).
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Stimulus Filtering
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Stimulus Filtering
The world is full of information that may or may
not be relevant to an animal. Stimulus filtering
is a universal feature of sensory systems, which
typically focus on information relevant to the
animals survival or reproduction. Emperor
moth Antennae are tuned to the female
pheromone Star nosed mole Has senses tuned to
detecting prey in the dark Noctuid moth Ears
function well as bat detectors, but would not do
very well in picking up the nuances of human
music. Humans What environmental stimuli do are
sense organs detect or not detect? How does this
compare to other animals? What patterns does the
brain detect when processing input from sense
organs?
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Stimulus Filtering Ormia Flies
Ormia ochracea is a parasitoid fly. Females
deposit larvae on male crickets. The fly larvae
burrow into and eat the cricket. Female flies
ready to deposit larvae are attracted to speakers
playing cricket sounds. The female fly, but not
the male, is maximally sensitive to sounds of the
same frequency as those made by the cricket prey.
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Stimulus Filtering Therobia Flies
Therobia leonidei is another parasitoid fly of
crickets. As in Ormia, the female is more
sensitive that the male to the prey call. But
note that the frequency is very different to that
of Ormia.
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Special Reading Measuring Distance In the Honey
Bee
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Honey Bee Waggle Dance
Dancer (forager)
Dance Followers (unemployed foragers)
The waggle dance of the honey bee can be used to
determine how bees measure distance. By dancing,
the worker bee tells the researcher (and other
bees) how far it thinks it has flown. Bees who
fly down tunnels with random patterns think they
have flown further than bees who have flown down
the same tunnels marked with parallel stripes.
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Waggle Dance Distance Information
Duration of entire circuit
Duration of waggle run
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Types of Waggle Dance
The waggle dance occurs in two forms. Most often
you will see the figure of eight form, but if the
food is very close to the hive the bees will make
the round form, especially the Italian
subspecies. Round waggle dance Food close to
hive, c. lt50m in the Italian subspecies of Apis
mellifera studied. Figure of eight waggle
dance Food further from hive (c. gt50m).
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Round Waggle Dance
If food is close (lt50m) the bees perform a round
dance
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Figure of Eight Waggle Dance
Dances are performed in nest on vertical combs in
darkness.
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Tunnel Down Which Bees Fly
Top covered with insect netting when in use
Tunnel shown is 1 x 1cm random pattern. The
tunnel can also have 1cm parallel stripes running
lengthwise (not shown).
Photo courtesy of M. Srinivasan
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Experimental Design
round dances
6m
35m
87 Ex. 1
dances
10 Ex. 2
Obs. hive
87 Ex. 3
6m
tunnel
13 Ex. 4
Four experiments were performed using marked bees
from the same observation hive. Bees were trained
to a syrup feeder at either the beginning (Ex.1)
or end of the tunnel (Ex. 2-4). The tunnel had
either a random (Ex. 1,2,4) or parallel pattern
of black and white on the inside. The image
motion hypothesis predicts that foragers in
Experiments 2 and 4 are less likely to make round
dances, which normally indicate distances of less
than 50 metres. The data support this
prediction. Srinivasan et al. 2000. Science 287
851-853.
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Ant Navigation
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Foraging Track of Desert Ant
Worker desert ants, Cataglyphis, forage
individually looking for dead insects. An ant
makes a meandering foraging trip. When it finds
some food it has the ability to walk straight
back to the nest. The ant knows where it is at
all times by integrating the distance and
direction it has moved. It can measure distance
by the amount of walking it does, and direction
by the position of the sun or polarised light
patterns in the sky. It can allow for movement of
the sun. As a result it can walk straight back to
the nest.
Food
Meandering path looking for food
Direct return trip to nest
Nest
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Cataglyphis fortis
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Navigation
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The Sun As a Landmark
The sun has one major disadvantage as a
landmarkit moves (360 degrees per day). (In fact
it is the Earth that rotates, or more exactly the
relative positions of Sun and Earth change.)
Animals that navigate by the sun correct for
shifting sun position.
Honeybee waggle dance gives directional
information relative to the suns azimuth. They
adjust the direction in accordance to where the
sun is. Bees dancing inside the nest allow for
the movement of the sun when making their dances.
They dont just use the position of the sun when
they returned from their foraging trip. The
animal has a clock by which it can measure
time. Honeybees must also have a stopwatch to
measure short periods of time as used in the
waggle run of their dance.
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Navigation
Navigation steering a course from place to
place Very useful for many animals, including
humans To navigate effectively you need to
combine sensory information with effective
neurological processing In many animals
hippocampus is the location of stored mental maps
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Hippocampus and Navigation
Human subjects explored a virtual town. The aim
was to get to the goal as soon as possible.
Brains were scanned with MRI. There was a
correlation between navigational ability and
hippocampal activity.
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Hippocampus and Navigation
Human subjects explored a virtual town. The aim
was to get to the goal as soon as possible.
Brains were scanned with MRI. There was a
correlation between navigational ability and
hippocampal activity.