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Chap.10 Predation
鄭先祐
生態主張者 Ayo工作室
Fig. 10.1 Predation takes many forms
(a) A double crested cormorant actively seeks and
chases its fish prey.
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Fig. 10.1 Predation takes many forms
(b) A little blue heron waits motionless to ambush its
prey. (fish)
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Fig. 10.1 Predation takes many forms
(c) A minke whale feeds on vast numbers of small
crustaceans in the Antarctic ocean.
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Fig. 10.1 Predation takes many forms
(d) A pitcher plant in a bog traps insects in its highly
modified leaves.
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Fig. 10.1 Predation takes many forms
(e) Insect larvae graze on the stems and leaves of
fireweeds..
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Fig. 10.1 Predation takes many forms
(f) A moose feeds in the same patch of fireweed..
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Predation
Carnivorous predation
 Herbivorous predation
 Optimal Foraging theory
 Community-level effects of predation
 Environmental application: Biological
control of pests: Putting predators to work

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Carnivorous predation
Predator adaptations
 Prey detection and recognition
 Tactics for capturing prey
 Prey adaptations
 Avoiding detection
 Avoiding capture
 Disrupting predator handling

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Prey detection and Recognition
Resolving power of a bald eagle’s eye is
approximately that of a pair of 7 x
binoculars.
 Smell (chemoreception)
 Sound (Fig. 10.2 owls)
 Electric fields to detect prey

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Fig. 10.2 The
circles around
the eyes of
many species of
owls are
parabolic
reflectors that
help gather
sound and
channel it to the
ears.
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Fig. 10.3 pulses(solid lines) emitted by a bat and
echoes(dashed lines) received by the bat as it
approaches and object.
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Tactics for capturing prey
分類：
 Ambush its prey or actively seeks them
 Hunts singly or in groups
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Fig. 10.4 Foraging success of captive black-headed
gulls in flocks of different sizes.
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Prey adaptations

Avoiding detection
Fig. 10.5 a white-tailed ptarmigan.
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Ecology 2001 Chap.10 Predation
Fig. 10.5b. The American bitten are examples of
cryptic coloration.
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隱藏的方法
Its color matches the background.
 Its shape is asymmetrical.
 It is counter-shaded (the lower part of the
body is light and upper part is dark)
 Its outline blend into the background.
 Its eyes are hidden.
 It remains motionless.

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Avoiding capture
Antelope 快跑。
 警告聲音。
 停止不動。
 Provide False targets
 Some marine invertebrates use flashes of
bioluminescence to startle predators.
 Safety in numbers strategy.

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Fig. 10.6
increase in musk
ox group size as
a function of
wolf density in
winter and
summer.
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Fig. 10.7 Relative amount of the average total risk of
predation incurred by Atlantic siversides in six positions
within a school under attack by launchers and passers.
F= front; B= back; O= outside; TM = true middle; CM=
confused middle; AA = after attack.
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Fig. 10.7 Relative amount of the average total risk of
predation incurred by Atlantic siversides in six positions
within a school under attack by launchers and passers.
F= front; B= back; O= outside; TM = true middle; CM=
confused middle; AA = after attack.
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Predator swamping
Fig. 10.8 The relationship between average effective brood
size at fledging and hatch date in snow geese.
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Disrupting predator handling
The development of significant defensive
weapons such as antlers, horns, shells, and
chemical deterrents.
 In the newt, Taricha torosa, a potent
neurotoxin called tetrodotoxin acts as a
chemical deterrent to predation.

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Herbivorous predation


1. 植物的生產力和營養成分，隨著季節而有所不同。
掠食者必要把握機會，配合green wave。
2. 植物有anti-grazing strategy。
 Koala 專食eucalyptus trees的樹葉。Eucalyptus樹葉，
營養低，且含有lignin 和tannin，降低消化。Koala
的代謝率低，直腸很長，食物留在腸子的時間很
長(8天)。
 Monarch 蝴蝶的幼蟲，吃食含有毒素的葉子，這
使Monarch蝴蝶的成蟲體內含有毒素。
 Squash 甲蟲使用行為的方法避開植物的化學防衛。
先剪斷葉片的主要葉脈，是其無法傳導入化學物
質，然後再吃葉片。
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Two fundamental groups
Stealthy herbivores and Opportunistic
herbivores
 Stealthy herbivores：專精的覓食方式
 Opportunistic herbivores：大量多樣覓食
的方式。

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Plant adaptations to herbivores


Structural and chemical adaptations
Two hypotheses of the origin of Secondary
compounds.
1.
Secondary compounds, produced as byproducts of plant metabolism and co-opted for
defense because of their toxic nature.
2.
These compounds are evolved de novo in
response to grazing as a selection pressure.
The energetic cost to the plant is high.
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圖10.9
Lotus corniculatus
可產生氰酸的植
物體比率。比較
溫暖的地區，比
率較高。這與掠
食壓力相關。
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範例：


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抗掠食的Secondary compounds 不僅發現在被子
植物和裸子植物，而且也發生在低等植物。
譬如：cyano-bacteria (藍綠藻)，珊瑚礁的藻類，
海草 (Fig. 10-10)。
當有掠食壓力時，Brown alga(Disyota
manstrualis)會產生高濃度的diterpenoid dictyols。
而其旁邊的同種個體，若沒有掠食壓力，則不
會產生。
有蟲吃的Birch，隔年的樹葉，於其樹葉上吃食
的蟲子營養都不良。原因是Birch 產生defense
chemistry.
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圖10.10
海草產生
的六種代
謝物質，
對掠食者
的影響力。
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Allocation of resources to
defense in Plants
1.
2.
3.
4.
Availability of plants to herbivores.
Plant architecture
Seasonal scarcity
Involvement of specialized herbivores
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The effects of herbivores
Consumption of plant parts is known to
have negative effects.
 However, some evidence suggests that the
activity of herbivores has beneficial effects.
 Grazing increases seed production,
increases biomass production, increases
nutrient content.

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範例：Scarlet gilia

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Grazing pressure by mule deer and elk was intense
on their Arizona study sites.
The grazers fed on nearly 75% of all plants and
removed as much as 95% of the above ground
biomass.
When a single stalk was eaten, however, it was
replaced with four new stalks.
被掠食的植物體比沒有被掠食的植物體，可產
生高達3.05倍的種仔。其fitness 比是2.4 : 1。
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圖10.12 Fruit production in matched pairs of plants of Scarlet gilia.
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Optimal foraging theory


Energy maximizers
Time maximizers
Fundamental assumptions of the theory are:
1. Foraging behavior has a genetic basis
2. Fitness is related to the net energy intake.
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Optimal diet
E/h , where E is the energy in the diet
and h is the handling time (or energy)
required to capture, subdue, and consume
the diet.
 E / (s + h), where s is the search time.
 Ei/hi >= E / (s + h)
 i食物的能量價值必要高於目前的平均價
值，掠食者才有可能轉而向i食物。

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Optimal use of food patches
掠食者停留於同一個覓食區的時間長短，
這與移動到另一個覓食區所需要花的時
間(travel time)長短有關。
 Fig. 10.13 Optimal patch theory.

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T1較小，離開的時間
較快。
T2較長，離開的時間
會較慢。
圖10.13 The curve depicts the cumulative amount of energy gained as a
function of the amount of time a predator stays in a patch.
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Environmental application
Biological control of pests: putting
predators to work




Pests and weeds cause tremendous damage to
both natural and agricultural habitats.
Some of these pests are exotic species,
accidentally or intentionally introduced to
regions beyond their natural range.
若是使用殺蟲劑，至少有兩個問題：

1. The targets of the chemicals develop
resistance. (抗藥性)

2. These toxins may themselves pose serious
environmental problems.
因此有所謂的 biological control
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Fig. 10B.1 A classic type of biological control in which the
average abundance of an insect pest is reduced after the
introduction of a predator.
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Integrated pest management

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IPM, a program of carefully selected control
techniques tailored to address each particular
insect pest problem.
Insect numbers are monitored carefully and
population models are used to predict irruptions of
the pest.
Insecticides are used only sparingly and locally in
response to this information.
Natural predators or parasites are released widely
in areas of local infestation.
Sterilization procedures or sex pheromones may
be used.
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範例：運用IPM控制gypsy moth
意外的被引進Massachusetts in 1869.
 The population exploded across the
northeastern US, defoliating many hectares
of forest.
 IPM 包含：pesticides, two species of
parasitic flies and sex pheromones.

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Fig. 10B.2 The rapid
increase in the distribution
of the gypsy moth after its
introduction to North
America.
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 問題與討論！
[email protected]
Ayo 文化站 http://faculty.pccu.edu.tw/~ayo
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