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Chapter 6

LIFESCI 2D03 Chapter Notes - Chapter 6: Olfaction, Aroma Compound


Department
Life Sciences
Course Code
LIFESCI 2D03
Professor
Rashid Khan
Chapter
6

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Chapter 6: Communication
6.1 Communication Occurs When A Specialized Signal From One
Individual Influences The Behaviour of Another
1. Signal: an individual that produces a signal
2. Signal Receiver: an individual that detects a signal
3. Communication: the purpose in which specialised signal produced by one
individuals affects the behaviour of another.
4. Signal: a packet of energy or matter generated from a display or action of a
signaller that travels to a receiver.
HONEYBEES AND THE WAGGLE DANCE
5. When an individual honeybee scout finds a rich food source, it flies back to the
hive and recruits others to help exploit the food. Such communication allows the
colony to rapidly exploit the food resource before competitors do.
6. Von Frish manipulated the location of a distant food source and observed the
behaviour of both scouts and new recruits.
1. Waggle Dance: behaviour performed by a honeybee scout that recruits
workers to a food source.
2. During the waggle dance, the scout moves in figure-eight pattern on a vertical
wall of the honeycomb. During the linear movement of the dance, the scout
vigorously wags it body, and the duration of the wagging, von Frish argued,
indicated the distance to the food.
3. Subsequent work indicated that every 75 msec of waggling translates into a
distance of approximately 100m from the hive. The waggle dance also
describes the direction of the food source, relative to an imaginary line that
runs from the hive to the sun.
1. For instance, if the sun is on the horizon (as at dawn) and the scouts
linear movement is 30 left of vertical, then the food is 30 left of the sun.
4. Von Frisch recognized that odour is used to locate nearby food resources, but
he believed that the waggle dance provides the crucial signal, especially for
food located larger distances away- distances more than, say, 500m.
1. However most recruits take much longer to fly to the food source than
would be expected based on a straight-line route.
7. Wenner and Johnson proposed that the bees doing the waggle dance present the
odour of the food source, not a precise direction and distance; this behaviour then
stimulates recruits to search for food on their own.
1. They suggested that new recruits fly downwind a few hundred meters before
starting their search and use olfaction as a method of locating food by flying
upwind, in a zigzag pattern, back toward the hive.
1. Many insects that rely on only odour cues to find food do fly back and
forth into prevailing wind.
ODOUR OR THE DANCE IN BEES
8. One way to find out if the waggle dance or odour is important is to track the
actual movements of new recruits. Riley and colleagues examined the flight paths

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of recruits that viewed the waggle dance from a hive placed in a large, flat,
mowed field.
1. The field contained few natural sources of nectar or pollen, so the only food
available was located at a feeding station. The station was placed 200m due
east of the hive and contained 0.2-1M sucrose solutions with no artificial
odours.
2. The researchers recorded wind speed and direction at 10-second intervals
from four locations surrounding the field and at the hive to determine their
effect on the flight of the bees.
3. Bees were required to move through a clear plastic tube to enter and leave the
hive, which facilitated bee capture.
1. This setup allowed the researcher to mark most of the bees in the colony
with small numbered tags on their backs. They could then record the
identity and movement of bees into and out of the colony.
4. At the start of the experiment, individual scouts were allowed to visit the
feeder and their identity was recorded. Their waggle dance indicated that
food was located due east of the hive. The researchers captured recruits who
had never previously visited the feeding station and placed small
transponders on their backs that transmitted continuous information about
their location.
1. These individuals were released either at the hive or at one of three
locations 200 to 250m southwest of the hive, and their movements were
tracked.
5. Most of the recruits released at the hive almost immediately began flying east
toward the food station. However, only two of the 9 recruits actually found the
feeding stations.
6. After 200m, most individuals began to follow a more circuitous flight path,
which the researchers interpreted as searching behaviour for the food. In
addition, the 17 bees transported 200-250m southwest of the hive and then
released tended to fly due east for 200m before also adopting a circuitous
flight path.
7. The wind data indicated that no odour from the feeding station was available
to the bees at their release sites. There was no evidence that individuals flew
downwind and then returned in a zigzag pattern to find the food. Instead, the
bees had to fly across the prevailing wind to maintain a due east heading.
8. The flight paths of new recruits confirmed von Frischs hypothesis that the
waggle dance appears to signal the distance and direction of the food.
1. In addition, the data demonstrates that recruits can travel to the area of a
novel food source without odour cues. However, they also show that the
dance signal is not sufficient to allow a recruit to locate a food source
precisely.
2. Additional work has demonstrated that new recruits use odours to
pinpoint the exact location of the food. In sum, the waggle dance in a

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behavioural signal that allows individuals to travel to the area of a distant
food source, but bees then use local odours cues to find the food itself.
AUDITORY SIGNALS: ALARM CALLS
9. Alarm calls: unique vocalizations produced by social animals when a predator is
nearby.
10. Cheney and Seyfarth found that the alarm calls of vervet monkey differ in how
they affect the receivers. Vervet monkeys are attacked by a variety of predators,
including leopards, eagles, and snakes; when a vervet spots one of these animals,
it gives an alarm call that alerts others in its group.
1. However, individuals produce different alarm calls for different types of
predator. Each predator represents a threat that requires a different
behavioural response.
1. For example, leopards attack from the ground. When a leopard is spotted,
a “bark” call is given, and vervets escape attack by moving up into a tree.
“Cough” calls are given when an eagle is sighted. Eagles attack from
above. Avoiding their attack requires moving down from treetops and into
dense bushes. Snakes, in contrast, often hide in dense grass. When a
python or cobra is observed, vervets give a “chutter” call that causes
individuals to stand erect and look into grass clumps.
TITMOUSE ALARM CALLS
11. Courter and Ritchison examined alarm calls in the tufted titmouse, a small
songbird. Titmouse produces an alarm call in response to a perched avian
predator.
1. Vocalization can be visualized in a sonogram, which characterizes
frequencies of sound as a function of time. The titmouse call is composed of
three basic notes, called, Z, A, and D, which are typically produced in
sequence. However, individuals often vary the number of D notes.
1. This call recruits other birds (both con and hetero-specifics) to approach
and mob the predator. Mobbing behaviour, in which birds produce loud
vocalizations, often harasses a predator and can drive it away from an
area.
2. Titmice co-occur with several potential avian predators. Small raptors like
Eastern screech owls, sharp-shinned hawks, and Cooper’s hawks are known
as predators of titmice, while large raptors like great horned rarely attack
titmice.
1. The size of a predator thus correlates negatively with risk of a titmouse.
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