Ecology Lecture 11 Predation Herbivory

Predation

Predators obtain energy and nutrients by killing and eating prey

Some plants can consume animals to obtain nutrients an example is

The venus fly trap

Herbivores consume

producers such as plants and/or algae

Generalist:

Select and eat a wide variety of food items

Specialist:

Feeding upon a single species or a restricted range of closely related species

What are examples of specialist?

Ant eaters, pandas, koalas

Predators and herbivores can limit

the abundance (population size) of species

Explain what’s happening?

Spider densities on the Caribbean islands with and without lizards

The synchrony of population cycles between predators and prey suggests that

these oscillations are the result of interactions between them

Decline of predators causes

Increase of prey

Increase of prey causes

More food for predators and causes an increase of predators

Decline of prey causes

lower survival and reproduction of the predator

Predator population sizes

lags behind prey abundance

What other factors can cause fluctuations?

Resources, disease, and more

Active hunting strategies:

Predator spends most of the time moving around looking for prey

Ambush hunting strategies:

Wait for a potential prey to pass by

Behavior defenses:

Alarm calling, spatial avoidance, reduction of activity, and mobbing

Alarm calling:

Warning relatives by saying predators are approaching

Spatial avoidance:

Potential prey moves away from a predator

Reduction of activity:

Avoid being detected by predator by reducing movement

Mobbing:

Distraction of predator

Crypsis:

Camouflage that either allows an individual to match its environment or breaks up the outline of an individual to blend in better with the background

Chemical defenses:

Often more effective at deterring predators if the prey can convey the defense before an attack occurs

Warning coloration (aposematism):

Distastefulness evolves in association with very conspicuous colors and patterns

Batesian mimicry:

Palatable species evolve warning coloration that resembles unpalatable species

Mullerian mimicry:

Several unpalatable species evolve a similar pattern of warning coloration

What is going on?

A beetle has eliminated 99% of the Klamath weed population in North America

Long-term fencing to prevent deer herbivory caused

much greater amount of plant growth in a Canadian national park

Removal of sea urchins from a rocky shore habitat caused

Biomass of different algae to increase

Pressure from herbivores allows

evolution of plant defenses (phenotypically plastic defenses induced by attack or fixed defenses

Structural defenses:

Sharp spines, “hairs”

Chemical defenses:

Sticky resins and latex compounds and alkaloids with a wide range of toxic effects

What is a parasitoid?

An organism whose larvae develop inside or on a single host feeding on it and eventually killing it

Are parasitoids predators or parasites?

Both could be considered