Chap.11 Antipredator Behavior

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

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Antipredator behavior

Avoiding predators Blending into the environment Being quiet Choosing safe habitats

What to do when prey encounter predators Fleeing, approaching predators, feigning death, signaling to predators Fighting back

Predation and foraging trade-offs

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Snake and ground squirrels

Approximately a million years. Strongly selected for ground squirrels to be able to

identify their predators and to respond to them with fine-tuned behaviors.

Squirrel antipredator behavior includes throwing dirt, pebbles, and roots at putative predators, as well as emitting alarm calls that are specifically made when snakes, but not other predators, are present. (Fig. 11.1)

and also immunological defenses (Fig. 11.2)

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Ground squirrel pups emerge from their burrows at about forty days. Shortly before this, there is an increase in their immunological defenses against snakes.

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Ground squirrel pups often face serious predation threat on their first emergence from their burrow.

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Avoiding predators

Blending into the environment Cryptic, hidden through camouflaging,

making their detection by predators unlikely. (Fig. 11.4 Cuttlefish ( 烏賊 ) camouflaging) (A) using uniform color to camouflage itself

against the rocks (B) using a “mottled ( 斑駁的 ) ” camouflage

pattern, with small dark splotches resembling the dark patches or rocks and sand

(C) a “disruptive( 破裂的 )” camouflage pattern

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Disruptive camouflage pattern

Mottled camouflage patternUniform color to camouflage

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Being quiet

Gulf toadfish (prey) (Fig. 11.5)and bottlenose dolphins (predator)

Dolphins orient toward the “boatwhistle” sound produced by male toadfish during breeding season.

Dolphins produce two kinks of sounds, high-frequency whistle for social communication, low-frequency “pops” for foraging.

Fig. 11.6 Gulf toadfish become silent. Playback test

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Wax moth and bat

Subtle differences between male moth sounds and bat echolocating sounds.

Females were indeed able to distinguish between these types of calls and responded appropriately. (playback test) Fanning their wings when they heard

male calls But dramatically decreasing this

behavior when they heard bat echolocation calls.

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Choosing safe habits

Predation and choice of nesting sites in parrots Phylogenies examination showed the ancestral

state was tree cavity nesting. Why the nesting in other cavities had evolved

independently many time in both Australian and Amazonian parrot species?

Whether predation was the key selecting for the shift away from tree cavity nesting? 101 North American species found that a

correlation between the nest predation rate and the length of nesting period.

Therefore, OC nesters should have longer nesting periods.

The data on both Amazonian and Australian parrot species do.

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What to do when prey encounter predators?

Encounters with predator’s dangers are, over the lifetime of an organism (prey), inevitable (Fig. 11.8).

Fig. 11.8 encounter with a predator. A scavenging skua gull descends from the

air in search of penguin eggs or unattended chicks, while these two gentoo penguins attempt to fend it off.

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What to do when prey encounter predators?1. Fleeing

A meta-analysis of flight initiation behavior Tree frog embryos and snakes

2. Approaching predators Thomson’s gazelles minnows

3. Feigning death4. Signaling to predators

Warning coloration in monarch butterflies Tail flagging as a signal

5. Fighting back Chemical defense in beetles Social learning and mobbing in blackbirds

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Fleeing

The most common response of prey that have spotted a predator is to flee for safety. (Fig. 11.9)

Flight initiation distance, how close a predator can approach before prey flee.

Gathered published data from 61 studies of flight initiation in mammals, fish, birds, and reptiles. (meta-analysis) Animals far from of their refuge initiated fleeing

from a predator sooner than animals closer to their refuge.

Animals involved in foraging, mating, or fighting were slower to flee from predators than animals were not currently involved in such behaviors

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Tree frog embryos and snakes

Fig. 11.11 predators that feed on treefrog eggs (A) here a wasp forages on treefrog eggs (B) Snakes are another dangerous predator on

red-eyed treefrog eggs. If terrestrial predation is weak, eggs hatch late

I the season. Warkentin predicted that treefrog eggs would

hatch sooner if predation in the terrestrial environment increased.

Fig. 11.12 wasp predation and the development time of treefrog eggs

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Treefrogs respond to wasp predation by hatching early. Green bar represent hatching rate of clutches that suffered wasp predation, while orange bars indicate undisturbed clutches.

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Snake predation and development time

Fig. 11.13 Snake predation and development time of treefrog eggs. Treefrogs also respond to snake predation

by hatching earlier than normal. Clutches attacked by the snake at (A) five days old and (B) six days old. (C) clutches that were undisturbed by predation.

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five days old six days old

undisturbed by predation

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Proximate cues?

Vibrational cues associated with snake attacks as the proximate cue for when to switch from terrestrial habitats to aquatic ones.

To test the hypothesis, using three kinds of sounds (Fig. 11.14) (playback test) Two kinds of the vibrations associated with

snake attacks and One kind of rainfall The cues associated with snakes resulted

in treefrogs that hatched earlier.

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Snake attack and eats an entire clutch of eggs

Snake eats one or two eggs in s short series of bites

A rainstorm

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Approaching predators

This approach behavior allows prey to gather important information about putative predators and hence reduces their chances of mortality. Approach behavior is often undertaken by

healthy adults. This type of behavior has been extensively

documented in vertebrates, particularly in fish, birds, and mammals.

Prey typically approach a potential predator from a distance in a tentative( 嘗試的 ), jerky( 急動的 ) manner.

Fig.11.15 Gazelle antipredator behavior. (A) Gazelles are constantly vigilant ( 警戒的 ) for potential predators (B) many different species, including the cheetah hunt gazelles.

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Approach behavior in gazelles (Fig. 11.16)

(A) the probability of approach behavior occurring in gazelles is a function of group size, as indicated by the logistic curve.

(B) cheetahs respond to gazelle approach behavior. The distance a cheetah move away in response to gazelle approach behavior is also a function of the gazelles’ group size.

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Interpopulational differences in approach behavior in minnows (Fig. 11.17)

Two different populations of minnows (from the Dorset area and Gwynedd area) Dorset population is under strong predation

pressure from pike predators While pike are absent from the Gwynedd

population of minnows Both populations of minnows increased their

group size when faced with predators in the laboratory, but the Dorset population tended to maintain larger groups.

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(A) Dorset minnow respond to predators by decreasing their predator inspection behavior

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(B) No statistically significant decrease in inspections occurs in the Gwynedd minnow population.

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Feigning death

Faking, or feigning, death is an antipredator behavior seen across a spectrum of species.

Adzuki bean beetle Either fly away or feign death Hypothesized that a negative genetic

correlation existed between the intensity of death feigning and the ability to fly

Artificial selection, longer duration of feign death vs. shortest duration of feign death

• After 8 generations

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The long duration lines are in green and the short duration lines are in orange.

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Signaling to predators

Warning coloration in monarch butterflies Monarch butterflies ingest milkweed plants, which

contain chemicals called cardiac glycosides.• These chemicals, which are toxic to birds, do not harm

the monarchs.

When a naïve predator eats a monarch, the toxins in the butterfly make the predator violently ill- temporarily (Fig. 11.21)

• The color patterns of monarchs act as warning coloration for that predator who now avoids feeding upon monarchs.

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Tail flagging as a signal

Some animals send signals that may serve to notify a predator that is has been spotted.

When the predator is an ambush hunter that relies on surprise, such a signal often cause it to move on the leave the area, and hence clearly benefits the prey.

Fig. 11.22 Tail raising event in White-tailed deer.

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Fighting back

Chemical defense in beetlesFig. 11.23 bombardier defense. When

the bombardier beetle is threatened, it releases chemicals that ward off predators. This bombardier beetle is being attacked

from the front, and so it is directing its chemical spray forward.

They fire the spray backward, when attacked from the rear.

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Social learning and mobbing in blackbirds

Blackbirds undertake a form of attack called predator mobbing. Once a flock of blackbirds spots a

predator, they join together, fly toward the danger, and aggressively attempt to chase it away.

Such group attacks often work well enough to force predators to leave the blackbirds’ area.

Mobbing is a form of cultural transmission. Animals Raised in captivity failed to have

mobbing behavior.

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Predation and foraging trade-offs

Fig. 11.24 foraging-predation trade-off. When animals are being vigilant for predators, it is

often at the cost of other activities. The starlings here can’t be foraging for insects while they scan the sky of hawks.

Foraging is one of the behaviors especially affected by predation. Predation pressure affects virtually every aspect of

foraging– everything from when a forager begins feeding.

Foraging in the gray squirrel (Fig. 11.25)

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Predation and foraging trade-offs

Squirrels alter their foraging choices as a result of predation pressure from redtailed hawks. Squirrels who could either eat their food items

where they found such items or carry the food to cover were more likely to carry items to an area of safe cover, particularly as the distance to safe cover decreased.

The closer the refuge from predation, the more likely they would use such a shelter when foraging.

Squirrels were much more likely to carry larger items to safe areas before continuing to forage.

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(A) Here a squirrel is foraging at a feeding station

(B) A squirrel heads for cover with a food item (a part of a cookie) in its mouth.

Ayo NUTN website:http://myweb.nutn.edu.tw/~hycheng/

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