9. Predator Prey Behaviours

Antipredator Behaviour - Individuals

• NS favors evolution of efficient foraging behaviours -increase fitness by having more energy available for reproduction

• NS also favours evolution of behaviours that allow animals to successfuly avoid being captured

• Animals perform number of behaviours that lower their risk of predation

• Antipredator behaviour - any behaviour that decreases the probability that organisms will be depredated

• Behaviours can be categorized as making detection, capture, and attack less likley

1. Avoid Detection: Avoid detection

Birds - set up feeder

• 1 meter away or 4 meters away- Close to cover or away

• Behind cover was fake hawk

• Took down cover and expose hawk to birds and wanted to see

• further from hawk - longer time to resume feeding and dropped feeding - risky to be out in open

• close to hawk - safer - used cover took more time

1. Avoid Detection: Crypsis

• Blending with background via evolutionary modification of coloration, marking, morphology and behaviour

• 2 methods to achieve crypsis

  • change appearance to match background

    • Physiological colour change

    • distort pattern/color with motion

    • Cuttlefish - on screen that looks like checkerboard - change to checkerboard

  • Chose background that matches your appearance

    • Via color,

    • Via orientation/positioning to match patterning

    • Moths - large moth has verticle lines, small maoths have horizontal lines - place on trees (naturally vertical) but also horizsontal. Put them on trees - when larger moth put on verticle - took long time for predator to detect them, but put verticle on horizontal predator found them fast and vice versa

1. Avoid Detection: Time spent moving

Movement of prey (foragin, travel), influences the risk of being killed by a predator

Activity level of prey will be lower when predators are present

1. Avoid Detection: Feed in areas of low risk

• some build their own safe food locations

• American pika - feed amongst boulders and rocks and even make runs of rocks to forage out into meadow

2. Avoid Capture - Increase vigilance

• Predators rely on surprise to capture prey, once detected their success is diminished

• Vigilance - when animals scan their surrounding for potential predators

• Vigilance decreases probability of predation but also decreases short term energy gain (animals eat with face down)

• Long term benefit of trade offs is access to additional food patches

2. Avoid Capture - Initiate flee

• Flight Initiation distance is the distance at which an animal moves away from an approaching threat - but if foraging and you notice do you flee? Depends on distance

  • further - stay bc can eat more and save energy

  • Factors that affect FID

    • Energetic state

    • more conspecifics - shorter (wait)

    • predator speed - longer (ASAP)

    • distance to cover

    • prey hungry or not

    • Dont mistake this for habituation

• Protean flee behaviours - animals enhance escape by moving in an erratic unpredictable way making it hard for predator to follow target (butterfly, mice)

2. Avoid Capture - Aposematism

• dangerous/unpleasent attributes

  • Visual signals, acoustic signals (rattle), chemical signals (smell)

  • Behaviour enhances aposematism

    • Aposematic individuals are usually:

      • Diurnal - active during the day

        • Likely to be detected by visual predatory, flaunt their displays and little eed for speed

      • Aggregative

        • associate with other aposematic individuals - necessary for reinforced learning for predator - mullerian mimicry - look like venemous species thus predators learn to avoid (monarch butterfly)

2. Avoid Capture - Mimicry

• Batesean mimicry - members of a harmless species that have evolved morphology / behaviour that mimics dangerous

  • ant mimicking spiders (legs mimic antennae)

  • Cost - fitness of mimics is negativley frequency dependent - spiders too common then wont work

2. Avoid Capture - Pronouncment of vigilance

• predators reply on remaining undetected, once detected predator will often not attack

• Pronouncement of vigilance displays show predator that it has been detected

  • jumping up and down i have energy, or deer white tail

3. Deflecting attack - display false structures

3. Deflecting attack - (3)

1. Distraction - pretend to be injured

2. Autonomy - drop tail

3. Feigning injury or death - play dead snake and stink

3. Deflecting attack - Startle or imitation displays

• Intimidate predator at moment of attack

• May serve to deter attack or distract predator long enough to allow escape

• False eye spots on caterpillar to look like snake

3. Deflecting attack - fight back

• spines, teeth

• Alarm call - visual, auditory, chemical (shrek), mechanical - to broadcast presence of predator and trigger escape or call in other predators to increase confusion or get support

Predation risks affects prey decision making

• trade offs

  • Behavioural - sacrificing one behaviour for another

  • Risk effects arise when prey alter behaviout in response to predators and these responses carry costs

• Vigilance - foraging tradeoff

  • scaning environment for predators, many cat feed and be vigilant at same time - thus adjust tradeoff according to local threat (more cautius in tall grass)

• Predation senstitive foraging

  • areas of low risk can sometimes come at the cost os reduced forace intake (elk moving to areas with more protection but then less food) e

• State dependent foraging

  • animals consider variability in food abundance in deciding where to forage - these habitats all carry some form of predation risk

  • Risk senstitivity depends on state of satiation and need of forager

  • Willingness to endure risk reduces probability of starvation

Predator strategies for hunting prey

• like prey, predators also evolved strategies

Predator prey interactions- predator hunting mode

• hunting mode - set of behavioural strategies that a predator employs while searching for prey

1. sit and wait or ambush - motionless until catching distance

2. sit and pursue - motionless until chasing distance

3. active hunting - predator continuously moves through environment to find follow and chase down prey

Active vs Passive strategies

• Passive

  • save energy but relies on prey coming to you

  • risky to wait for prey but dont spend energy looking

  • small home

  • active mobile prey

• Active

  • Expends mor eenrgy but encounter rate is higher

  • can be eaten by sit and wait

  • range widley

  • feed on sedentary and mobile prey

Predator prey interactions - Non-consumptive effects

1. consumptive interactions - predators kill and consume prey

2. non- consumptive interactions - the threat od predation generates behvioural, morph, of phys anti predator responses in prey (ecology of fear)

   1. physiological stress response

   2. Stress alters prey physiology (dcreased survival), behaviour (movement), morphology (escape)

      1. behavioural modification

         1. sound of predator in song sparrows fed their young few times per hours

         2. can also alter trophic cascades - wolves scare elk to towns, humans scare wolves and cottonwood started to grow and beavers increased

Predator prey interactions - Behavioural Game Theory

• Ideal free distribution predicts resource matching to that intake rates are equalized

• - The oucome od this assumption is high degree of overlap in patch use by predator and prey

• But predators can move in search of patchy prey and prey can move to resources or hide to avoid predators

• Most predator -prey interactions insist of 2 player game in which a responsive prey is trying to avoid being killed by equally responsivr predator (track each others behaviour)

  • Game example: fear management under time contraints

    • Seabirds eat worms when tide is out (time sensitive) and predator watches this - a predator must choose when to attack after foragers settle into patch - individual prey must choose how to allocate their limited time bt anti-predator viilance and feeding - solution involves unpredictability in BOTH predator attack time and gradual decrease in responsiveness for prey

  • Game example - fear managment

    • attacking after predictable time (10 min laways) not good or being vigilant all the time not good thus, predator should do non predictable early attacks but not all the time and decreasing prey vigilance overtime wil detect early attacks and reduce wasteful vigilance should predator is absent - keeping each other on their toes

Predator prey interactions - Long time frame

2 criteria tells us this

1. escalation -coevolving species in an arms race continually develop adaptations and counter adaptations against each other

2. local co-adaptation - co-adaptations become increasingly powerful (weapons) yet species are not any better off/adapted

   Results in geographic mosaic pattern where both species have roughly matched abilities across their shared range - where species dont overlap there is no escalation

Example of arms race - antlion sit and wait for ant arrival - ants tha tlive in viscinity of antloins posess ability to rescue nestmates from antlion home and learn from their own experiences

• Escilation in this example — antlion firther associates vibrations when rescuer has arrived - ands capable of forming generalizable memeory of home/pit when they or nest mate are trapped to avoid future encounters

• Local coadaptation in this example - many ant species have the potential to perform rescue behaviour but those tha tlive in same ecological niche as antlions are capable of performing highly integrated precise rescue behaviour patterns

Summary