Transcript alarm calls

動物行為學 (通識)
國立臺南大學 通識課程 2011年春
T10. 溝通 (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
Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/
溝通 (communication)
 Introduction
 Communication (溝通)
 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
 溝通與誠實
 溝通化解問題 (solves problems)
 How to coordinate group foraging (覓食)
 How to find and secure a mate (伴侶)
 How to warn others about predators (掠食者)
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 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.
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clever house
 Clever house was thought capable of incredible mental feats.
 In fact, clever house was picking up very subtle cues from the
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individual who asked him a question.
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溝通與誠實
 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.
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案例：ptarmigans (雷鳥)
 Both male and female rock ptarmigans are a stark
white against the snow of winter.
 Once spring arrive, females molt quickly, while
males stay white, and as such the males are very
conspicuous against the dark brown background.
 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.
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 Males communicate
ptarmigans (雷鳥)
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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.
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溝通與誠實的案例：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 by large males because of the design of their
vocal system.
 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).
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溝通化解問題 (solves problems)
 How to coordinate group foraging (覓食)
 案例：Food calls in birds
 案例： Honeybees and the waggle dance
 案例： Chemical and vibrational communication in
foraging ants
 How to find and secure a mate (伴侶)
 案例： Birdsong
 案例： Aquatic insects
 How to warn others about predators
 案例： Meerkats (狐獴)
 案例： Alarm calls
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案例： 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.
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The mean number of birds and squeak calls heard two
minutes before and two minutes after insects were flushed by
foraging birds.
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Under certain conditions, ravens emit a loud “yell”
upon uncovering a new food source, such yells
attract other birds.
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Honeybees and the waggle dance
 案例： 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.
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(A) Imagine a patch of flowers that is 1500 meters from a
hive, at an angle 40 degrees to the right of the sun.
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(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.
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(C) The length of the straight run portion of the dance
translates into distance from the hive to the food source.
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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
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When food is very far from a hive,
waggle dance
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案例：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 4methylpyrrol-2-carboxylate and 3-ethyl-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.
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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.
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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.
Stridulating (發出刺耳聲) 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”.
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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 leaf-cutting 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.
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minim workers hitchhiking on a leaf
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How to find and secure a mate (伴侶)
 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.
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案例：Cowbirds
 The role of repertoire size in the mating success of male
brown-headed 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
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Five different song treatments
1.
2.
3.
4.
5.
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Smaller repertoire: s single perched song sung three times
in succession by a male Santa Barbara cowbird.
--- by a male Ventura cowbird.
Larger repertoire: three different perched songs sung in
quick succession by a male Santa Barbara cowbird.
-- by a male Ventura cowbird.
A control: from a different species (song sparrow)
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Copulation solicitation displays (CSDs)
 The length of time that a female displayed ritualized
“copulation solicitation (誘惑) 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
 Female had longer CSDs when they were exposed to three
different songs than to the same song played three times.
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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.
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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)
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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, post-copulation,
sex discrimination, mate guarding, spacing, territoriality,
and food defense.
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Woodpecker alarm calls
• 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
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Development, learning, and alarm call
communication in meerkats (狐獴)
 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.
 age differences in reaction to alarm calls.
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in meerkats, a pup's response to alarm calls was not as
strong as the response seen in adults.
(A) time until reaction after hearing playback of alarm call
(B) duration of response to playback of alarm call
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(C) length of time spent
"scanning" the
environment for predators
after hearing predator
alarm calls.
Adults remain vigilant and
continue to watch out for
predators longer than do
pups.
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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.
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案例：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
low-ranking male who
gave the call.
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Dishonest alarm calls in swallows?
 Male swallow may emit false alarm calls when
they see their mate engaging 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.
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(A) Male barn swallows often give false alarm calls when their fertile mats
leave the nest vicinity
(B) These false alarm calls sometime disrupt extrapair copulations (EPCs)
(C) Moller hypothesized that male swallows would five false alarm calls when
they were at the greatest risk of EPCs to disrupt the EPCs. Colonial breeding
males emitted false alarm calls during the period in which EPCs were most
likely (during egg laying).
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案例：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)
 Heard a recorded alarm call and then saw a
predator (true alarm calls)
 Heard a recorded alarm call. But no predator
(false alarm calls)
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Alarm calls in Richardson's squirrels.
overtime, when predator alarm calls are unreliable,
juvenile squirrels began to ignore such false alarm
cues.
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responses to reliable and unreliable alarm calls.
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問題與討論
Ayo NUTN website:
http://myweb.nutn.edu.tw/~hycheng/