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 O

yste

rs E

ate

n

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)