Friday 14th September, Anti Predator Behaviour Flashcards
What is antipredator behavior?
The opposite of ________ behaviour
• General aim is to increase search time and/or handling time of predators to cross over the ‘giving-up’ threshold.
• Key goal: ?
The opposite of foraging behaviour
• General aim is to increase search time and/or handling time of predators to cross over the ‘giving-up’ threshold.
“Annoy predators enough to push them over the ‘giving up’ thereshold so they don’t follow through with eating you by exploting their foraging behaviours”
• Key goal: to exploit foraging behaviour
Predator-defense strategies
At the individual level: ?
(3 things)
At group level: ?
(3 things)
Individual…
– Avoid detection: (cryptic colouration, cryptic behaviour, colour change, minimal scent)
– Avoid capture: (vigilance, speed, deflection markings, warning colouration, startling, autotomy)
– Resist handling: (large size, spines, shells, fighting back with emetics, repellents, playing dead)
Group Level…
– Shared vigilance & alarm signaling
– Dilution effect & confusion effect
– Mobbing
• Strategy: set of adaptations (behaviours/structures) coded by the fittest genes, resulting in highest survival rate of individuals carrying them
Avoiding detection
Background matching
Avoid detection
Disruptive colouratio
- Breaking up body outline can make it harder for predators to detect prey, particularly if looking for a specific shape.
- Humbug damselfish (Dascyllus aruanus) has vertical bars to disrupt their outline.
Avoid detection:
Disruptive colouration
Avoid detection: Polymorphism
- Higher chance of blending in when background is variable
- Lower chances of your predators learning what you look like – i.e. developing a ‘search image’.
- Creates “moving target” for co-adaptation of predators.
Avoid detection: Colour change
• In variable environments, can match a variety of backgrounds - chameleon, cuttlefish, mantis, stick insects.
• Important: colouring may not be for camouflage from predators! Can serve a range of other functions
– i.e., thermoregulation, increasing stealth for hunting, and communication (competition, courtship).
Avoid detection: Cryptic behaviour
Freeze!
- Eyes of searching predators more sensitive to movement than shape Nocturnal activity
- Harder to see in the dark – release from predators that rely on sight
- Nocturnal predators hunt by scent and sound
Avoid capture: Deflection marks
Avoid capture: Autotomy
Detachable tail of many lizards
– also invertebrates & even some mice
- Voluntary mechanism; fracture zone allows effective escape of lizard, with blood vessels that close quickly to reduce bleeding. must balance cost of re-growing lost part.
- Isolated tail attracts attention by movements, colour
Avoid capture: Startle mechanisms
- Sudden change in size or appearance can startle predator.
- Hopefully gives time to escape.
Avoid capture: Fight back
• Use weapons e.g., horns, hooves, poison, etc, to fight off predators.
Avoid capture: Fight back
Avoid capture: Play injured or dead
“Broken wing” distraction display of pied stilt and many plovers.
- Lures predator away from nest.
- Playing possum: originates from possums feigning death.
- Attempt to make predator lose interest
– i.e., avoid triggering predatory behavior of potential predator.
Avoid capture: Warning colouration
Aposematic colouration (Mullerian mimicry)
• Distasteful (or deadly!) prey eaten less if conspicuous
(often red, yellow and black)
- There is selective advantage in truthful advertising
- Depends on real threat; bluffing doesn’t work for long
Avoid capture: Batesian mimicry
False advertising:
Avoid capture: Vigilance
If foraging in the open, animals can’t avoid being seen…
- Stay on constant alert for known danger.
- Some even signal that the predator has been spotted
– this is costly, particularly for ambush predators and can deter an attack
– e.g., tail flagging in ground squirrels deters rattlesnake attacks.
• But also costs energy for prey!
Avoid capture: Escape
• Burrows
– Advantage of familiarity in own home range
– Only (mostly) works against larger predators
• Speed + stamina
– Good for escaping sprinter predators
• Evasion
– Also good for escaping fast predators, even for agile predators.
Avoid capture: Escape
A combination of escape angle (agility) and turning velocity (speed + agility) is needed to escape fast, agile predators.
Resist handling: Large size
• Large prey can be tackled only by large predators, which are rare.
– E.g., rhinos & elephants can ignore lions
– genuine but costly, and doesn’t always work (e.g., pack hunters).
Resist handling: Armor
Spines, shells, etc.
– Effective, but limits agility!
– Also costs energy to produce these structures.
Group anti-predator strategies: Enhanced vigilance & alarm signaling
Allows time for other activities via alarm signals
– can forage, rest etc. while your keep friends watch.
• Increases predator detection
– the more eyes the better.
Group anti-predator strategies: Dilution effect
Works in both space and time
- Lower attack rate per individual due to dilution only.
- Favours synchronous production of young, e.g. periodical cicada
Group anti-predator strategies: Confusion
Particularly useful against chasingpredators.
• Zebras combine numbers with disruptive colouration to evade predators.
Group anti-predator strategies: Mobbing
You might not be able to fight back on your own… so start a gang!
• Fight, harass, annoy & intimidate your predators so they give up.
