W2: Anti-Predator Behavior Flashcards
Costs of Behavior
1) Time
2) Energy
3) Risk of Predation
4) Opportunity
Benefits of Behavior
1) Increased access to energy
2) Increased access to mates
3) Decreased risk of predation
What is the evolutionary arms race between predators and prey?
1) Prey are continually evolving defenses to avoid being eaten
2) Predators are continually evolving counter-defenses
What types of selection does predation exert on prey?
1) Life-dinner principle
2) Generation time effects
What evolved faster: prey defenses or predator attacks?
Prey defenses evolve faster than predator counter defenses
Life-diner Principle
Selection for defense may be stronger than selection for counter-defense.
Generation time effects
Prey usally have shorter generation times than their predators
Net Profitability Equation
E/T(t)
unit: energy per unit time
E = energy content per prey item
T(t) = time required to find and consume prey
Find/Consume Prey Equation
T(t) = T(s) + T(h) T(s) = search time T(h) = handling time (subdue, ingest, digest)
How do prey defenses affect the Find/Consume Equation?
Prey defenses increase T(s) or T(h) and reduce the profitability of the prey. (slight change in profitability can make it advantageous to switch to a different prey)
Great tit anti-predator experiment
Test food selection preference of great tits as food passed through their cage on a conveyor belt. Food choices: 1) inedible twigs (brown string in opaque straw) (2) Large, cryptic prey (mealworm in opaque straw) (3) small, conspicuous prey (1/2 mealworm in clear straw)
Result: Great its specialized on small, conspicuous prey when the abundance of twigs made it difficult for them to find large, cryptic prey.
What are the variables related to the food options for the great tit experiment?
E = energy value T(h) = handling time i(t) = encounter rate (items/sec)
How does this experiment capture the essence of a predator searching for a profitable but cryptic prey?
E(1)/T(h1) > E(2)/T(h2)
Anti-predator adaptations work by increasing what factors of the generalist equation?
1) Search time
2) Handling time
Search Time
Time spend prior to pursuit
=crypsis, mimicry, background selection, removing evidence
Handing Time
Time spent pursuing, subduing, eating, digesting prey
=protective spines, behavior, mis-directing an attack, startling displays
Batesian Mimicry
When edible species look like a protected species.
(Predators learn to avoid ‘model’ and the ‘mimic’ benefits from this learning. Problem: if the predators must learn to repsond to the model, too many mimics may ‘break’ the system.
Frequency dependent: only works when there are relatively few mimics
i.e.
mexican milk snake, tephridid flies, swasp fly, burrowing owls, octopus
Mullerian Mimicry
Toxic species converge on similar (often bright) colors.
Aposomatic Coloration
Warning coloration
What are three different types of mimicry?
1) Batesian mimicry
2) Mullerian mimicry
3) Chemical warefare
How do search images work?
The assist in finding cryptic prey (animals learn to focus on a specific salient feature)
They illustrate counter-adaptations predators have against cryptic prey.
Evidence: animals increase foraging rate or efficiency with experience.
What are some examples of group defense?
1) Dilution
2) Selfish herding
3) Predator confusion
4) Vigilance
5) Mobbing
6) Alarm calling
7) Sentinel behavior
Dilution
simple safety in number (reduced per capita predation risk) aka aggregation
Selfish Herding
prey jockeying for protected positions
