Transcript Predator vs prey Lec UPDATED

Predator vs. Prey: Predation and
Fear for your life!
Marine Predators
Upper level
mesopredators
Top predators
Lower Level Mesopredators
Predation in Marine Communities
Predator
Direct
Effect
Prey
Direct
Effect
Resource
• Predation
contributes to the
structure of many
marine
communities
through trophic
cascades
Predation in Marine Communities
• Otters, Urchins, and Kelp Forests
Estes,1978
Predation in Marine Communities
• Blue crabs, Periwinkle Snails, Cordgrass
Salt Marshes
Silliman
Silliman and Bertness, 2002
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 counteradaptations– 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!
Predator-Prey Arms Races
• 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).
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
Don’t eat me!
• 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
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.
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
Batfish
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.
Don’t eat me!
• 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
Induced Defenses
• Bryozoans, barnacles, and many gastropods
produce spines, thickened shells, or growth
asymmetries in response to waterborne
predator chemical cues
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
Don’t eat me!
• Prey have developed multiple adaptations to
avoid being eaten
– 1) Camouflage
– 2) Warning Coloration
– 3) Defense- toxins and other physical protection
– 4) Autotomy
Autotomy
• Common in crab species
– Porcelain crabs in
particular
have a hair trigger on
shedding limbs
Mantis shrimp vs crab
Doesnt always work....
Don’t eat me!
• 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!
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
Behavioral Escape
• 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
• 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
Predator
Prey
• Or Trait Mediated Interactions
• Changes in prey habitat or
resource use in response
to predator risk
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
>100mm CW
Large Crab
40-60mm CW
Small Crab
40-60mm CW
Multiple Small
Crabs
Control
Zero Crab
Control
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 foraging
Predation on Oysters
80
% of Oysters Eaten
70
N=18 ANOVA P<0.0001
A
A
A
60
B
50
A
B
B
B
Large
Multiple Small
40
30
20
10
0
Hill and Weissburg, Oecologia, 2013
N=18, P<0.001
Control
Small
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
Predation Risk Allocation Hypothesis
(Lima and Bednekoff 1999)
• 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