16: Predation & Defense

disadvantages of herbivory for plants?

1) decreased biomass/growth

2) delayed maturity

3) decreased fecundity

4) death

advantages of herbivory for plants

seed dispersal & pollination

advantage & disadvantage of herbivory for animals?

advantage→food is abundant

disadvantage→low food quality, especially protein

What amt of plant biomass is consumed by herbivores? Why do animals eat younger leaves rather than older ones?

usually 6-10% in forests & 30-50% in grasslands

-younger leaves richer in nutrients

Advantage & disadvantage of carnivory?

advantage→high food quality(protein)

disadvantage→food is scarce & harder to obtain

what kind of environments do carnivorous plants typically occupy?

low in nitrogen, such as bogs & tropical savannas

Explain the “Search Image” Foraging strategy.

scanning for specific cues associated w/ a species

How does the abundance of prey affect a “search image?”

useful only when the favored species is common

Explain the “information transfer” foraging strategy. Example?

obtain info from others abt the location of good foraging areas

ex// vultures watching each other’s elevation

Why is social behavior important in foraging food?

hungry individual can watch where others go to get food

Example of prey deception.

alligator snapping turtle opens its mouth & wiggles a red tongue that attracts deceived fish

What is the optimal size of food that a predator should take?

neither too small(too few calories) nor too large(too difficult to handle)

Advantage of group foraging? How does dispersion of prey affect group foraging?

-more time spent searching for food rather than being vigilant for predators

-group foraging is more likely if prey are clumped

What is the major problem w/ group foraging? How can this be minimized?

increased intraspecific comp. which can be minimized by forming mixed species group

Define Kleptoparasitism. What is this common in?

when an individual steals/attempts to steal food from another

-common in birds

Is cannibalism a form of density-independent or density-dependent regulation?

density-dependent

Advantage & disadvantage of cannibalism?

advantage→increases own fitness & decrease fitness of competitors

disadvantage→an organism’s own offspring are sometimes killed

Explain the Type I Predator Response

Prey are taken at a constant rate until Predator is satisfied (limited # of prey can be taken)

Explain the Type II Predator Response

1) Time is spent pursuing, eating, & digesting prey

2)less time spent to find additional prey

3) number of prey taken rises at decreasing rate

Explain the Type III Predator Response

1) requires at least 2 species of prey

2) predatory pressure depends on density of prey(e.g. eat less if less prey & eat more if more prey)

3) sigmoidal curve

What is a point of switching?

prey density below which a predator switches its search image to an alternate prey & above which it switches from an alternate prey

ex// too little rabbits→fox preys on mice

too many rabbits→fox preys only on rabbits

What is a threshold of security?

prey density below which predators no longer find it profitable to hunt prey

-palatable(tasty) species are still gonna be sought after even though it may be rare

ex// rabbits become so rare that its not worth it for foxes to hunt for it

If prey population increases, predator population usually _______

increases too

Cryptic (camouflage) coloration examples?

-this is mimicking background objects

1) Counter shading- fish are dark above & light on belly

2) walking sticks

3) striped patterns

How can prey “misdirect” predators?

1) fake head

2) eyespot marking

What is aposematic(warning) coloration?

bright colors or bold patterns tell predators they are unpalatable(not yummy)

Batesian(Cryptic) mimicry

Model is unpalatable

but mimic is palatable

Mullerian(warning) mimicry

both Model & mimic are unpalatable

How is Predator Satiation a behavioral defense for prey? Explain.

Impalas can produce a bunch of offspring all at 1 time, so predators cannot eat all of them so more offspring survive

Examples of a predator employing crypsis?

-sharks also have countershading

-camouflaged polar bears

Example of Predator employing mimicry?

Zone-tailed Hawk mimics Turkey vulture(which only feeds on dead animals)