Predation and Herbivory II Flashcards
Animal strategies to avoid being eaten
- behavioural
- signalling to deter predators
- physical features
Behavioural strategies
- staying out of sight
- seeking refuge - costs energy and hampers foraging opportunities but fitness benefits outweigh costs
- nocturnality
communal defense - forming a defensive circle - mobbing
- alarm vocalizations
- fighting back - attacking/mobbing via chemical and mechanical means
Signalling to deter predators
- aposematic coloration (learning to not eat certain organisms with toxins
- Batesian mimicry - a non toxic species resembling a toxic one
- Mullerian mimicry - a toxic species resembling other toxic ones
- bluffing - a pattern displayed by an animal that lacks strong defenses
example of bluffing
mayflies posture themselves to make them seem larger
Physical Features
- body size
- safety-in-numbers
- rapid movement
- body armour
- autonomy
Pros and Cons of body size
pro: not dying, from predators
con: takes a lot of energy to maintain large body size
How do species that coexist with predators avoid being eaten if they do actively signal to /deter the predators
refuge
- the existence of refugia has been used as one explanation for why predators do not drive their prey to extinction
Gause’s Predation experiment
- three different treatments
- putting predator and prey in a water solution did nnot result in th eoscillations predicted by the Lotka-Volterra predator- pret model
- prey and predator both went extinct
- given refugia for prey, they are able to hide so effectively that predator died
Critique of Gause’s Predation experiment
immigration created artificially restocking population
What did Gause’s Predation experiment show?
that immigration might be one reason why predator and prey population dynamics show oscillations and why avoid extinction
Types of Refuge
- spatial
- metapopulaiton rescue
Plant defences
- make them less likely to be eaten (resistance)
- reduce the harm while being eaten (tolerance)
Structural defensive strategies for plants
- pointy stuff (thorns, spines)
- trichomes (extension of epidermis that inhibit insect movement)
- can also make hard, rigid leaves that are difficult to eat
Crypsis
- “hiding”
- ex. Mimosa pudica “wilt” when something comes into contact with them
ex. stone plant, a type of succulent, avoid being eaten by blending in with their environment
Chemical Defensive Strategies - plants
- secondary metabolites: compounds not involved in PSN nor are necessary for respiration, growth or development
- alkaloids: noxious odors, repellent taste, excessive stimulation, lethargy
Indirect Plant defensive strategies
sometimes plants call on animals to defend them
Constitutive defences (define, pros and cons)
- permanent defenses
- produced continuously, regardless of what happens to the plant
- pro: no need to worry about sudden attacks
- con: cost heaps of energy to maintain
Induced Defences (define, pros and cons)
- phenotypic plasticity
- concentrations of a defensive chemical (or morphological defence trait) increase rapidly in response to herbivore damage
- pro: no constant maintenance cost
- con: sudden attacks can be more damaging
Example of constitutive defence
toxins
- tobacco contains nicotine, an alkaloid compound that is toxic to some herbivores
Example of induced chemical defence
tomato plants increase volatile compound production after infestation by spider mites
Why are toxic alkaloids more common in tropical plants?
- tropical areas have more diverse communities of herbivores
- greater variety of herbivores, greater variety of defences needed
Why do plants not have warning coloration?
- plants are generally green because of the interaction between light and chlorophyll
- color other than green = less light absorbed= less photosynthesis
Why are some fruits toxic?
- they are not ripe yet
- to reduce risk of seeds being digested
- to facilitate seed dispersal by frugivores
Why is the planet green?
- because predators limit their plant-eating prey
Top-Down control of herbivores by predators
- top-down trophic cascade of effects from carnivore to plant
- carnivores tend to compete with each other for food, and plants also compete strongly
- herbivores tend to compete less - because they are controlled by predators)
