Transcript Alarm calls

Chap.12 Communication
鄭先祐 (Ayo) 教授
國立台南大學 環境與生態學院
生態科學與技術學系
環境生態研究所 + 生態旅遊研究所
Chap.12 communication
 Introduction
 Communication
• Defined as the transfer of information from a signaler to
a receiver
 Fig. 12.1 vervet (長尾黑顎猴) alarm calls
 Fig. 12.2 clever house
 Communication and honesty
 Communication solves problems
 How to coordinate group foraging
 How to find and secure a mate
 How to warn others about predators
2
Ayo 2010 Ethology
Fig. 12.1 vervet alarm calls
Vervets give different alarm calls
depending on what type of predator has
been sighted
 (A) here we see vervets standing up after
hearing a “chutter” alarm call indicating
that a snake has been spotted.
 When a leopard (B) is detected, vervets
will give a “barking” alarm call and (C)
climb up trees for safety.
3
Ayo 2010 Ethology
4
Ayo 2010 Ethology
Fig. 12.2 clever house
Clever house was thought capable of
incredible mental feats.
In fact, clever house was picking up
very subtle cues from the individual
who asked him a question.
5
Ayo 2010 Ethology
6
Ayo 2010 Ethology
Communication and honesty
 Selection is thought to favor the most
economical way to share information.
 The natural selection should favor less
exaggerated signals– which was referred to as
“conspirational whispers”(共謀低語).
 This is because signaling often involves some
costs, and natural selection should favor
minimizing these costs during conspirational
whispers and hence reducing the
conspicuousness(惹人注目)of the
communication itself.
 For example, the case of ptarmigans (雷鳥) .
(Fig. 12.3)
 Both male and female rock ptarmigans are a
stark white against the snow of winter.
7
Ayo 2010 Ethology
the case of ptarmigans (雷鳥)
 Once spring arrive, females molt quickly, while
males stay white, and as such the males are
very conspicuous against the dark brown
background (Fig. 12.3). Such conspicuousness
attracts females, but it also attracts predators.
 As the breeding season progresses, rather than
molting, males soil their plumage to become
less conspicuous.
 Males communicate information to females via
coloration, but when the period during which
communication is useful comes to an end, they
shut down the communication system in a
cost-efficient manner– by soiling their white
plumage.
8
Ayo 2010 Ethology
9
Ayo 2010 Ethology
Communication and honesty in toads
 Selection should favor females paying
attention only to those cues that are in fact
true indicators of larger size.
 The case in toads, in whom deep croaks can
only be produced b large males because of the
design of their vocal system. (Fig. 12.4)
 Female toads use the frequency of males’ calls to
gauge their potential mate’s size.
 Honesty is also possible when traits are not
impossible, but merely very costly, to fake.
(handicap principle).
10
Ayo 2010 Ethology
11
Ayo 2010 Ethology
Communication solves problems
 How to coordinate group foraging
 Food calls in birds
 Honeybees and the waggle dance
 Chemical and vibrational communication in
foraging ants
 How to find and secure a mate
 Birdsong
 Aquatic insects
 How to warn others about predators
 Meerkats (狐獴)
 Alarm calls
12
Ayo 2010 Ethology
Food calls in birds
Colonial breeding cliff swallows live in
nests that serve as “information
centers”.
Using both playback experiments and
provision experiments (putting food out
to entice birds), Brown and his team
found that cliff swallows gave off
“squeak(吱吱叫) ” calls, which alerted
conspecifics that a new food patch–
often a swarm of insects– had been
found (Table 12.1).
13
Ayo 2010 Ethology
The mean number of birds and squeak calls heard two minutes before and two
minutes after insects were flushed by foraging birds.
14
Ayo 2010 Ethology
Under certain conditions, ravens emit a loud “yell” upon uncovering a
new food source, such yells attract other birds.
15
Ayo 2010 Ethology
Fig.12.6 yellers are hungry
 In ravens, “yelling” is
often associated with
foraging– in particular,
calling others to a food
bonanza.(富礦帶)
 Immature ravens yell
progressively more as
a function of hunger.
 hungry birds call more
often than satiated(飽
足的) birds.
16
Ayo 2010 Ethology
 Captured birds to a location where there a
new prey item that researchers had placed
into the environment.
 Birds that had learned the location of prey
acted as leaders.
 Fig. 12.7 Raven recruitment.
 The line denotes when the number of ravens that
knew of the prey source equals the number of
ravens at the prey source the next day.
 Green points indicate statistically significant
recruitment
 Orange points indicate that recruitment was not
statistically significant.
17
Ayo 2010 Ethology
18
Ayo 2010 Ethology
Honeybees and the waggle dance
 Fig. 12.8 bee
foraging.
 Honeybee foraging
involves a complex
communication
system, including
waggle dances.
 This dance, along
with other
informational cues,
gives bees in a hive
information about
the relative position
of newly found food
sources.
19
Ayo 2010 Ethology
(A) Imagine a patch of flowers that is 1500 meters from a hive, at an angle 40
degrees to the right of the sun.
(B) when a forager returns, the bee dances in a figure eight pattern. In this
case, the angle between a bee’s “straight run” and vertical line is 40 degrees.
20
Ayo 2010 Ethology
(C) The length of the straight run portion of the dance translates into distance
from the hive to the food source.
21
Ayo 2010 Ethology
Round dance
Sickle dance
Waggle dance
When resources are close to the
hive, honeybee foragers tend to
use round dance.
When resource are at greater
distances, sickle dance
When food is very far from a
hive, waggle dance
22
Ayo 2010 Ethology
The number of “figure
eight” circuits in a waggle
dance when bees were
raised at a temperature of
36℃ or 32℃
Bees from the 32℃
treatment were less likely
to use the waggle dance
when they returned to the
hive than were bees from
other treatments.
Bees from 32℃ treatment
made significantly fewer
“circuits”.
Bees raised in the 36℃
treatment fared much
better in individual
learning tasks.
23
Ayo 2010 Ethology
Foraging ants (leaf-cutter ants)
 Leaves must first be cut, then carried to the
nest, ground up, chewed and treated with
enzymes, placed into a “fungus garden”, and
subsequently cultivated.
 Two chemicals are particularly important,
methyl 4-methylpyrrol-2-carboxylate and 3ethyl-2,5 methylphrazine.
 These substance are produced in the poison
gland and used to recruit fellow workers to
foraging sites.
 Recruitment pheromones are incredibly
powerful.
24
Ayo 2010 Ethology
Leaf-cutter ants can
ravage (毀滅) foliage in
their path. The ants
don’t attack all the
leaves, however, but
instead they often strip
some leaves to the stalk,
were leaving other
leaves untouched.
25
Ayo 2010 Ethology
While only 40% of the ants
stridulated when cutting
tough leaves, the number
increased to 70% when the
leaves were tender, and to
almost 100% when either
type of leaf was dipped in
sugar water.
Fig. 12.13 stridulating communication. A schematic of a leaf-cutter
ant cutting a leaf and stridulating its gaster up and down. the
vibrations were being sent along the length of a leaf in a long
series of vibrational “chirps”.
26
Ayo 2010 Ethology
27
Ayo 2010 Ethology
Fig. 12.14 minim workers hitchhiking on a leaf
 These minim workers cannot cut leaves, but
they are often found hitchhiking rides on
leaves on the backs of leaf-cutters.
 Minim protect these other leaf-cutting ants
from attack by parasitic flies.
 Hitchhiking minims apparently use the
vibrational cues created by stridulating leafcutting nestmates to locate the leaf-cutters.
 The stridulating signals emitted by leaf-cutters
are used in numerous contexts.
 One such venue is between leaf-cutters and
minims, who use these signals to eventually
hitch rides on cut leaves that are carried on
leaf-cutters’ backs.
28
Ayo 2010 Ethology
29
Ayo 2010 Ethology
How to find and secure a mate
The role of
 (1) vocal communication (birdsong)
 (2) tactile communication (insects)
Birdsong:
 In most species of songbirds, males don’t
just learn a single song, they learn many
different songs.
• For example, the song sparrow sings about ten
different songs, the western marsh wren sings
more than a hundred songs, and the brown
thrasher sings an incredible thousand different
songs.
30
Ayo 2010 Ethology
Cowbirds
The role of repertoire size in the
mating success of male brownheaded cowbirds.
Male cowbirds posses between two
to eight different perched songs.
 Earlier studies indicated a correlation
between the size of the perched song
repertoire and mating success.
Whether male repertoire size had
an effect on female mate choice?
 Five different song treatments
31
Ayo 2010 Ethology
Five different song treatments
1. Smaller repertoire: s single
perched song sung three times in
succession by a male Santa
Barbara cowbird.
2. --- by a male Ventura cowbird.
3. Larger repertoire: three different
perched songs sung in quick
succession by a male Santa
Barbara cowbird.
4. -- by a male Ventura cowbird.
5. A control: from a different species
(song sparrow)
32
Ayo 2010 Ethology
Copulation solicitation displays (CSDs)
 Youtube: http://www.youtube.com/watch?v=TQP91a-rhLw
 The length of time that a female displayed
ritualized “copulation solicitation displays”
(CSDs) to different songs was recorded and
used as a measure of female choice.
 Female cowbirds displayed longer CSDs when
they heard cowbird versus song sparrow songs.
 Females show a marked increase in CSD times
when exposed to males with large song
repertoires (Fig.12.15)
 Female had longer CSDs when they were
exposed to three different songs than to the same
song played three times.
33
Ayo 2010 Ethology
34
Ayo 2010 Ethology
Phylogenetic studies of birdsong
Sexual selection operates more strongly
in polygynous mating systems and in
systems that are sexually dimorphic
(Fig. 12.16)
 Across 17 species of blackbirds, the
maximum note length of songs increased
as the size difference between males and
females increased.
There is strong competition for access
to females, natural selection acts
strongly on the many components that
make up male song.
35
Ayo 2010 Ethology
36
Ayo 2010 Ethology
Birdsong from a proximate perspective
 Birdsong is incredibly diverse in terms of
structure, pattern, tempo, frequency, and
repertoire size.
 However, the vocal organ used in birds, the
syrinx, varies little between different species.
 How is it possible that morphological
invariance in the syrinx can translate into
great diversity in birdsong?
 The syrinx has two compartments—left and
right– and that the two sides of a bird’s brain can
control these compartment independently.
37
Ayo 2010 Ethology
Table 12.2 the different ways to sing
 Independent bilateral phonation: Operate
both sides of the syrinx independently without
one side being dominant. (Brown thrasher
and gray catbirds)
 Unilateral dominance: Have one side of the
syrinx dominate song generation. (Canaries)
 Alternating lateralization: Alternate which
side of the syrinx dominates during a song.
(Brown-headed cowbirds)
 Sequential lateralization: Have one side of
the syrinx dominate for certain frequencies,
and the other side dominate for the remainder
of the frequencies used in a song. (Northern
cardinal)
38
Ayo 2010 Ethology
39
Ayo 2010 Ethology
Ripple (波紋) communication and mate
choice
In water striders, ripples are usually
produced by an up-and-down
movement of the legs, with both right
and left legs in synchrony and in
constant contact with the water surface.
The water striders produce different
patterns of ripples for different kinds of
behaviors, including signals for calling
mates, courtship, copulation, postcopulation, sex discrimination, mate
guarding, spacing, territoriality, and
food defense.
40
Ayo 2010 Ethology
41
Ayo 2010 Ethology
Problem: how to warn others about predators
Woodpecker and chickadee(山雀)
alarm calls
Development, learning, and alarm
call communication in meerkats
meerkats
42
 Alarm calls as deceptive
communication
 Male vervets (長尾黑顎猴)
 Dishonest alarm calls in
swallows? (Fig. 12.20)
 Alarm calls in Richardson’s
squirrels (Fig. 12.21)
Ayo 2010 Ethology
While downy
woodpeckers don’t
give alarm calls when
they are paired with
same-sex partners,
they emit such alarm
calls when they are
paired with a member
of the opposite sex
43
Ayo 2010 Ethology
Development, learning, and alarm
call communication in meerkats
Behavior observation indicates,
compared to adults,
 Pups were initially more likely to respond to
alarm calls in the presence of less
dangerous or nondangerous predators,
and they were more likely to ignore alarm
calls emitted in the presence of dangerous
predators.
 Pups don’t react as appropriately to alarm
calls as adults.
 Fig. 12.19 age differences in reaction to
alarm calls.
44
Ayo 2010 Ethology
45
Ayo 2010 Ethology
46
Ayo 2010 Ethology
Alarm calls as deceptive communication
Because alarm calls are a powerful form
of communication– failure to listen
might lead to death– natural selection
should favor paying close attention to
such calls.
Nonetheless, these same selection
pressures set up the possibility of using
alarm calls in a deceptive manner.
 Using alarm calls in a deceptive manner is
probably the exception rather than the rule.
47
Ayo 2010 Ethology
Vervets (長尾黑顎猴)
 Verbets sometimes use deceptive predator
alarm calls during some intergroup
encounters – encounters that can lead to
serious aggression between group members.
 Male verbets five an alarm call when
encountering a new troop, even though no
predator is in the vicinity.
 It was almost always a lowranking male who gave the call.
48
Ayo 2010 Ethology
Dishonest alarm calls in swallows?
Male swallow may emit false alarm calls
when they see their mate engaing in an
extrapair copulation.
These alarm calls break up extrapair
matings.
When females were absent during egg
laying, the males who returned to their
nests almost always gave false alarm
calls.
Male swallow who emitted false alarm
calls during possible periods of extrapair
copulations. (Fig. 12.20)
49
Ayo 2010 Ethology
50
Ayo 2010 Ethology
Alarm calls in Richardson’s squirrels
When alarm calls become less
reliable, natural selection should
favor paying less and less attention
to them.
Two treatment (juveniles of
squirrels) (Fig. 12.22)
 Heard a recorded alarm call and then saw
a predator (true alarm calls)
 Heard a recorded alarm call. But no
predator (false alarm calls)
51
Ayo 2010 Ethology
52
Ayo 2010 Ethology
53
Ayo 2010 Ethology
問題與討論
Ayo NUTN website:
http://myweb.nutn.edu.tw/~hycheng/