Predator vs. Prey: Predation and Fear for your life!
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Predator vs. Prey: Predation and Fear for your life!
Marine Predators
Top predatorsUpper level mesopredators
Lower Level Mesopredators
Predation in Marine Communities
• Predation contributes to the structure of many marine communities through trophic cascades
Predator
Resource
Prey
Indirect
Effect
Direct Effect
Direct Effect
• Otters, Urchins, and Kelp Forests
Estes,1978
Predation in Marine Communities
• Blue crabs, Periwinkle Snails, Cordgrass
Silliman and Bertness, 2002
Predation in Marine Communities
SillimanSalt Marshes
Loss of Top Predators
Predator-Prey Arms Race• Natural selection will– Favor predators that are efficient– And select for improvement in prey defenses to
overcome predators• A cycle and escalation of adaptations and counter-
adaptations– an arms race!
Predator-Prey Arms Races• Red Queen Evolution– “it takes all the running you can do to keep in the
same place”– Without constant evolution, you would be eaten!
• Why is it that the arms race is always slightly in favor of the prey? – Life dinner principle- the rabbit is running for his
life while the fox is only running for his dinner’• Dawkins 1979• It’s a lots more important to avoid being eaten than it is
to miss a meal!
Predator-Prey Arms Races
Temporal trends in bite mark frequencies on Mesozoic motile and sessile crinoids (A).
Predator-Prey Arms Races
Don’t eat me!
• Prey have developed multiple adaptations to avoid being eaten– 1) Camouflage• Used by many marine organisms
– The master of camouflage
Don’t eat me!
• Prey have developed multiple adaptations to avoid being eaten– 1) Camouflage• Can be visual
Don’t eat me!
• Prey have developed multiple adaptations to avoid being eaten– 1) Camouflage• Often visual
Camouflage
• Polymorphic cryptic coloration– Different color morphs exist within a population• May prevent predators from developing a search image
• Search Image
Camouflage
• Palma and Steneck , 2001– Polychromatic variations
enhance survival in polychromatic habitats
Don’t eat me!
• Prey have developed multiple adaptations to avoid being eaten– 1) Camouflage• Or chemical
– Decorator crabs
• Prey have developed multiple adaptations to avoid being eaten– 1) Camouflage– 2) Warning Coloration-Aposematism• Bright colors become associated with defended animals
– Has evolved independently multiple times
Don’t eat me!
Aposematism
• Common in marine nudibranchs
Aposematism
• Conspicuous colors help predators to learn to avoid unpalatable prey and may help to reduce recognition errors
Aposematism
• Fish learn to avoid distasteful chemicals!– In order to examine chemical defenses, and identify the
compounds responsible, scientists often extract and separate chemical from the organism• Bioassay guided fractionation
– Extracted chemicals are then applied to a food and compared to the same food sans chemical
Aposematism
• Different strategies to avoid nasty chemicals– Blennies regurgitate
treated food and then refuse to accept anything that looks like it
– Killifish just learned to avoid the noxious chemical
Mimicry• Batesian mimicry- a relatively scarce, palatable, and
unprotected species resembles an abundant, relatively unpalatable, or well-protected species, and so becomes disguised.
Batfish
Advantageous when mimics are scarce relative to model
Disadvantageous when mimics are abundant
Although there is still lots of debate about this in the literature
Mimicry
• Mullerian mimicry- when two unpalatable species grow to resemble each other– Predators who learn to avoid one, learn to avoid
the other
The two invertebrates on the left are different species
of sea slugs, while the one on the right is a marine
flatworm. All three secrete noxious substances and
are unpalatable.
• Prey have developed multiple adaptations to avoid being eaten– 1) Camouflage– 2) Warning Coloration– 3) Defense- toxins and other physical protection• Constitutive defenses• Induced defenses
Don’t eat me!
• Bryozoans, barnacles, and many gastropods produce spines, thickened shells, or growth asymmetries in response to waterborne predator chemical cues
Induced Defenses
Induced Defenses
• Marine Bryozoans
Harvell 1986
Induced Defenses
• Chemical defenses can also be up-regulated (especially in algae)
Constitutive Defenses
• Less common than induced defenses in marine communities
• In marine environments, these are mostly chemical defense s
• Species or genera can differ on const. vs induced
Constitutive Defenses
• Why might induced defenses be more common than constitutive defenses?– Allocation costs- defenses require energy to
produce– Opportunity costs- resources allocated to defenses
cant be allocated elsewhere
Chemical Defenses
• Do chemical defenses actually reduce fitness or do they just taste bad?– Didemnins in tunicates
• Prey have developed multiple adaptations to avoid being eaten– 1) Camouflage– 2) Warning Coloration– 3) Defense- toxins and other physical protection– 4) Autotomy
Don’t eat me!
Autotomy
• Common in crab species– Porcelain crabs in
particular have a hair trigger on shedding limbsMantis shrimp vs crabDoesnt always work....
• Prey have developed multiple adaptations to avoid being eaten– 1) Camouflage– 2) Warning Coloration– 3) Defense- toxins and other physical protection– 4) Autotomy– 5) Behavioral Escape- Antipredator behaviors• In space or in time!
Don’t eat me!
Behavioral Escape• Plankton and Small Nekton Vertical migrations– Occur in pelagic environments with no structure• Forage at the surface at night and migrate to the
depths during the day– More pronounced in pigmented species that are more
conspicuous to visual predators (Hays et al. 1994)• Migrations strength is often seasonally coordinated with predatory fish abundance
• Demersal fish are thought to inhabit shallow water during the day to avoid larger fish predators and migrate to deeper depths to forage at night
– But this theory has been called into question by a few studies
Behavioral Escape
Behavioral Escape
• Predators also induce prey to seek refuges and/or reduce their activity to reduce their chance of being eaten –anti-predator behavior
Anti-predator Behaviors
• These antipredator behaviors also result in prey feeding reductions
Anti-predator Behaviors• These antipredator behaviors also result in prey feeding
reductions– Consumptive effects
• Or Density Mediated Interactions• Changes in prey and resource abundance due to lethal interactions with predators
– Non-consumptive effects • Or Trait Mediated Interactions• Changes in prey habitat or resource use in response to predator risk
Predator
Prey
Resource
Non-Consumptive effects
• Toadfish, mud crabs, oysters
Grabowski, 2004
Non-consumptive effects
• Toadfish, mud crabs, oysters
Grabowski, 2004
Non-Consumptive Effects
• Spiders, grasshoppers, and grass– Consuming vs scaring
Non-consumptive Effects• Which drives
the majority of indirect interactions?
• On average, TMI’s are responsible for 85% indirect effects
Preisser et al. 2005
Behavioral Escape and NCEs
• Behavioral escapes are often initiated once a predator has been perceived– Usually by chemical detection (although other sensory
modalities are possible-they are less studied)
Behavioral Escape
• Experimenting with predator chemical cues
Determining prey response to cues• Prey use information about cues and their
environment to determine if, when, and how much they will respond
• Threat sensitive predator avoidance (Helfman, 1989)
What predator traits do you think affect the magnitude of anti-predator behaviors and non-consumptive effects?
Risk is context-dependent
• Threat sensitive predator avoidance (Helfman, 1989)
– Predator Identity (Turner, 1999)
Risk is context-dependent
• Threat sensitive predator avoidance (Helfman, 1989)
– Predator Identity (Turner, 1999)
Risk is context-dependent
• Threat sensitive predator avoidance (Helfman, 1989)
– Predator Identity (Turner, 1999)
– Predator Diet (Schoeppner and Relyea, 2005)
Diet Specific Responses
• The magnitude of behavioral response to diet is due to the phylogenetic relatedness of the prey (Schoeppner and Relyea, 2005)
Diet Specific Responses
• Predator Diet
Risk is context-dependent
• Threat sensitive predator avoidance (Helfman, 1989)
– Predator Identity (Turner, 1999)
– Predator Diet (Schoeppner and Relyea, 2005)
– Predator Size (Hill and Weissburg, 2013)
NCEs and the Perception of Predator Size
• Examined mud crab behavior and predation on oysters in the presence of differing size caged predators
Small CrabMultiple Small
CrabsLarge Crab
40-60mm CW>100mm CW Control
Zero Crab Control
40-60mm CW
Predator Size is Perceptible in Chemical Cues
• Large blue crabs and multiple small blue crabs suppress mud crab foraging activity
• Small (non-risky) crabs do not affect foragingPredation on Oysters
B
N=18 ANOVA P<0.0001
B
AA
SmallMultiple SmallLargeControl
80
70
60
50
40
30
20
10
0
% o
f Oys
ters
Eat
en
A
B B
A
N=18, P<0.001
Hill and Weissburg, Oecologia, 2013
Learning to run from predators
• How are chemical cues of predators learned?
Predation Risk Allocation Hypothesis (Lima and Bednekoff 1999)
• Prey behavior should depend on the duration or high risk vs. low risk situations and the level of risk associated with them
• Predictions– 1) As duration of predator exposure increases, prey
vigilance should decrease since long periods of prey vigilance may result in an unnecessary loss in energy intake
– 2) Animals exposed to lots of risk, should forage during brief safety periods, when compared to prey with infrequent risk
Predation Risk Allocation Hypothesis (Lima and Bednekoff 1999)
Predation Risk Allocation Hypothesis (Lima and Bednekoff 1999)
• Prey behavior should depend on the duration or high risk vs. low risk situations and the level of risk associated with them
• Predictions– 3) As risk associated with high risk situations
increases, prey should increase their antipredator response, but then will increase their foraging effort in low-risk situations
• But the risk allocation hypothesis is a bit paradoxical– Typical dogma is that prey exposed to higher
predation risk should reduce their activity and increase vigilance• For instance, animals from populations with predators
often have stronger responses to predation threats than prey from predator-free populations
Predation Risk Allocation Hypothesis (Lima and Bednekoff 1999)
• However, so far the risk allocation theory has met with mixed support– 13 studies have investigated the prediction• 6 studies found no support • 4 found partial support• 3 fully supported model
Predation Risk Allocation Hypothesis (Lima and Bednekoff 1999)