Week 5: Anti-predator behavior Flashcards
Swallowtail butterfly
Swallowtail butterflies are middle-to-large in size and very colorful.
The adults are often tailed like the forked tail of some swallows.
Swallowtail butterflies have been the target of butterfly collectors.
Very conspicuous to predators
Avian predators
Are diurnal
Have good vision
Are good fliers
—> Avian predators impose direct threats on diurnal butterflies
—> How do butterflies defend themselves against avian predators?
Sichuan pepper
widely grown and consumed in Asia as a spice
not related to black pepper or to chili pepper
widely used in the cuisine of Sichuan, China, from which it takes its name
alkaline pH and a numbing effect (toxic) on the lips when eaten in larger doses
Chemical defense
Caterpillars of the swallowtail butterflies feed on leaves of the Sichuan trees.
They sequester an extremely potent plant poison in their tissue.
The poison may deter avian predators from attacking swallowtail butterflies and their caterpillars.
Osmeterium
is found in the prothoracic segment of caterpillars of swallowtail butterflies
is normally hidden
can be everted when the caterpillar is threatened
used to emit a foul-smelling secretion containing terpenes
Many of terpenes possess qualities that make them ideal active ingredients as part of natural agricultural pesticides
Effect of monarch butterfly toxins
Any bird that makes the mistake of trying to eat monarchs usually finds the experience most unpleasant.
After vomiting up a noxious monarch just once, a surviving blue jay will avoid this species thereafter.
Such aversive stimuli are rapidly learned and require only a single trial in most cases.
Monarch butterfly
the best known for all North American butterflies
easily recognizable orange and black wing pattern
foul-tasting and poisonous because the caterpillars feed on milkweed
Advertising noxiousness
Prey are noxious and have conspicuous colors and patterns,
which make the prey easy to spot.
A learning process in which predators associate noxiousness with conspicuousness is required
Aposematism
Conspicuousness associated with distastefulness
Conspicuousness is learned by predators to represent noxious prey
Warning signal: bright colours or loud distinctive sounds associated with prey
Examples of warning signals
Coral snakes which are in the same family as cobras possess deadly toxins.
Rattlesnakes rattle and alert the predator of its toxic venom.
Skunks have a black and white pattern and can spray foul-smelling odor.
Batesian mimicry
harmless species resembling the warning signals of a harmful species directed at a common predator.
bumblebees are mimicked by hoverflies
honeybees are also mimicked by overflies
Coral snake is poisonous and is mimicked by the milk snake which is harmless
Müllerian mimicry
two or more harmful species, that are not closely related and share one or more common predators, have come to mimic each other’s signals.
Both forms advertise their unpalatability with bright colors and areas of high contrast on the body or wings.
monarch butterfly and viceroy butterfly
Predator and prey: arms race
Prey are ahead of predator
why?:
- Life vs. dinner principles
- Housefly evades dragonfly’s grasp: fly flies for life, dragonfly for dinner.
- Mistake worse for fly: stronger selection - Generation time
- Often shorter in prey, prey can evolve at a faster rate. - Predators often have several prey
- Predator not sufficiently specialized to drive any one species to extinction
Behavioural adaptations for survival
It is hard to pass on your genes when you are dead.
Not surprisingly, most animals are strongly motivated to stay alive long enough to reproduce.
Predators place their prey under intense selection pressure, favoring those individuals with attributes that postpone death until they have reproduced at least once.
Stages of predation
Predator selected to complete the sequence successfully
Prey selected to interrupt the sequence
detection –> identification –> approach –> capture –> consumption
Stages of predation: detection
Detection of prey as objects which are distinct from the background
antipredator defense:
- Immobility
- Crypsis
- Confusion
Crypsis
the ability of an organism to avoid detection by a potential predator
usually most effective when an animal is still.
very common for both prey and predators
relatively low energy cost
A cryptic animal may do this through camouflage, nocturnality, lifestyle, transparency.
camouflage:
is a method of cryptic or concealing coloration that allows an otherwise visible organism or object to remain indiscernible from the surrounding environment through deception.
Ex) Gray treefrog
Camouflage vs. mimic
Camouflage requires that the “model” be surroundings.
Mimicry requires that the “model” be another organism.
The distinction is arbitrarily defined:
- Animals that resemble twigs, bark, leaves or flowers are often classified as camouflaged (a plant does constitute the “surroundings”), but sometimes classified as mimics (a plant is also an organism). Either way, the animal is considered cryptic.
Does cryptic behavior work?
Blue jays were trained to respond to slides of cryptically colored moths positioned on an appropriate background.
If the jay detected a moth, it pecked at a key, received a food reward, and was quickly shown a new slide.
If the bird pecked incorrectly, it not only failed to secure a food reward, but had to wait a minute for the next evaluation.
Operant conditioning technique
Crysis and background selection should match!
Cryptic coloration depends on background selection.
The body coloration of the Australian thorny devil works only when the lizard is motionless in areas littered with bark and other varicolored debris, not on the roads.
Confusion
makes detection of a single individual more difficult
Disruptive coloration:
- Patterning to interfere with the perception of the true outline
Stages of predation: identification
Identification as profitable or edible prey and decision to attack
antipredator defense :
- Masquerade
- Warning signal
- Müllerian mimicry
- Batesian mimicry
- Honest signaling of unprofitability
Masquerade
special resemblance to inedible objects
Young caterpillars (1st – 4th instars): mimics of bird-droppings
the final 5th instar: camouflage
Honest singling of unprofitability
stotting
When pursued by a cheetah or lion, this antelope may leap several feet into the air while flaring its white rump patch.
Stages of predation: Approach
Approach to attack
antipredator defense:
- Escape by fleeing
- Startle and threat behavior
- Aggregation (dilution effect)
Startle behavior
The hawkmoth larva (right) puffs up its head and thorax when disturbed, when then resemble the head of a small poisonous snake (left).
The dilution effect in butterfly groups
Butterflies aggregate in large, densely packed groups around mud puddles, where they suck up fluid containing valuable mineral nutrients.
They run the risk of being attacked by various birds.
Individuals in large groups experience a lower risk of predation than those in small groups or by themselves.
Stages of predation: Capture
To take by force
antipredator defense:
- Mechanical methods
- Noxiousness
- Group defense
Mechanical methods: Autotomy
Autotomy
- Self amputation is the act whereby an animal severs one or more of its own appendages, usually as a self-defense mechanism designed to elude a predator’s grasp.
- The lost body part may be regenerated later.
- Lizards that are captured by the tail will shed part of the tail structure and thus be able to flee. The detached tail will continue to wiggle, creating a deceptive sense of continued struggle and attracting the predator’s attention away from the fleeing prey animal.
Noxiousness
Bombardier beetle:
- When physically assaulted, bombardier beetles eject a hot chemical spray from the tip of the abdomen.
- The beetle can aim its spray in virtually any direction.
- The spray of bombardier beetles is ejected at 100°C
Group defence in bees
Predatory hornets, Vespa mandarinia, are attacking the honeybee, Apis cerana
More than 500 bees quickly engulf the hornet in a ball
lethal temperature of bees: 48-50 °C
lethal temperature of hornets : 44-46 °C
Stages of predation: consumption
consumption: eating
antipredator defense:
- Safe passage through the gut
Ex) sea snails
