Predation and Herbivory

Types of Species Interactions

  • Interspecific Competition: Interaction where different species compete for the same resources.

  • Predation: One species (predator) captures and kills another (prey). This interaction is shown as ( - +).

  • Parasitism: One species benefits while the other is harmed ( - +).

  • Mutualism: Both species benefit from the interaction ( + +).

  • Commensalism: One species benefits while the other is unaffected ( + 0).

Predation Overview

  • Objectives of studying predation:

    • Understand how predators regulate prey populations.

    • Assess how prey populations influence predator populations.

    • Explore the coevolution of predator and prey.

Forms of Predation

  • Predators are classified as heterotrophs.

  • Types of Predators:

    • Carnivores: Consume animal tissue.

    • Herbivores: Consume plant or algal tissue.

    • Omnivores: Consume both plant and animal tissue.

  • Predation interaction is direct and complex: the predator consumes multiple prey, acting as a mortality agent.

True Predators vs. Other Consumers

  • A true predator kills its prey immediately upon capture.

  • Scavengers: Organisms that consume carcasses of animals that died from other causes.

  • Herbivores and Frugivores often do not kill whole plants; however, seed predators and plankitvores can act as true predators.

Predator-Prey Population Dynamics

  • Prey Mortality \left(CN_{prey}\right): Influenced by predation rate defined by:

    • Rate of predation: \left(\left(cN_{prey}\right)N_{pred}\right)

    • c = capture efficiency of the predator

    • N_{prey} = size of the prey population

    • cN_{prey}= prey consumption rate (the number of prey consumed per predator per unit time)

  • Population Changes:

    • For prey, population growth rate is decreased by predation.

    • Predator population increases in response to increases in prey population.

Graphical Representation of Population Dynamics

  • Predator-prey interactions can be graphed.

  • X-axis: Size of prey population (N_{prey})

  • Y-axis: Size of predator population (N_{pred})

  • Critical point at which net growth for prey is zero is defined by:

\left(cN_{prey}N_{pred=}\left.rN_{prey}\right)\right.

Density of predators labs behind of prey: a delayed population response of predators to increase in prey numbers

  • Reproductive rates: predators have slower reproductive rate compared to prey

  • Populations response: takes time for predators to respond to changes in prey availability due to breeding cycles.

  • Resource availability: increase in prey population, takes time for predators to increase population based on new prey.

  • Ecological interactions: predator-prey dynamics grows together, prey increase then does predators.

Functional Responses in Predation

  • Type I Functional Response:

    • Prey capture rate increases linearly with prey density.

    • Predators are assumed to be never satiated.

  • Type II Functional Response:

    • Predation increases at a decreasing rate to a maximum level.

  • Type III Functional Response:

    • Low predation at low prey densities, increasing sigmoidally with higher prey densities.

Behavioral and Physical Defenses of Prey

  • Prey have evolved various defenses against predation, illustrating co-evolution:

    • Chemical Defenses: Such as alarm pheromones and toxins.

    • Cryptic Coloration: Blending into the environment.

    • Object Resemblance: Mimicking non-living objects.

    • Flashing Coloration: Displaying colors when disturbed to confuse predators.

    • Warning Coloration (Aposematism): Bright colors signaling toxicity to potential predators.

    • Mimicry (Batesian and Müllerian): Resembling toxic species to avoid predation.

Hunting Tactics of Predators

  • Strategies include:

    • Ambush Hunting: Waiting for prey to come close.

    • Stalking: Approach and quick attack with minimized pursuit.

    • Pursuit Hunting: Chasing prey over longer distances.

  • Predators may use techniques like cryptic coloration to hide from prey.

Impact of Predators on Prey Behavior

  • Predators influence prey beyond direct mortality:

    • Reduced feeding opportunities in high-risk areas.

    • Altered growth and reproductive patterns due to predator presence.

  • Empirical Studies:

    • Investigate effects of predator presence on prey species like mayflies and aphids.

    • These studies reveal important insights into how predation can shape community dynamics and influence the life cycles of these organisms.

New section

Types of Species Interactions

  • Interspecific Competition: Different species fighting for the same resources.

  • Predation: One species (predator) catches and kills another (prey).

  • Parasitism: One species gets benefits at the expense of another.

  • Mutualism: Both species gain benefits from their interaction.

  • Commensalism: One species benefits while the other is not affected.

Predation Overview

  • Key goals in studying predation:

    • Understand how predators control the number of prey.

    • See how prey numbers affect predators.

    • Look at how predators and prey evolve together.

Forms of Predation

  • Predators are organisms that eat others.

  • Types of Predators:

    • Carnivores: Eat meat.

    • Herbivores: Eat plants.

    • Omnivores: Eat both plants and meat.

  • Predators eat multiple prey, which influences their survival.

True Predators vs. Other Consumers

  • A true predator kills its prey right away.

  • Scavengers: Eat the remains of animals that died from other reasons.

  • Herbivores might not kill the plants they eat, but some like seed eaters can act more aggressively.

Predator-Prey Population Dynamics

  • Prey Mortality \left(CN_{prey}\right) How often prey die as a result of predation.

    • Rate of predation: \left(\left(cN_{prey}\right)N_{pred}\right)

    • c = capture efficiency of the predator

    • N_{prey} = size of the prey population

    • cN_{prey}= prey consumption rate (the number of prey consumed per predator per unit time) This determines how many prey are eaten per predator.

  • Population Changes: Prey numbers decrease due to being eaten, while predator numbers can grow as there are more prey available.

Graphical Representation of Population Dynamics

  • Predator-prey relationships can be shown on a graph:

    • X-axis: Prey population size (N_{prey}).

    • Y-axis: Predator population size (N_{pred}).

    • There is a critical point where prey numbers stabilize: \left(cN_{prey}N_{pred=}\left.rN_{prey}\right)\right.below this line, prey populations grow; above it, they decline).

    Density of predators labs behind of prey: a delayed population response of predators to increase in prey numbers

    • Reproductive rates: predators have slower reproductive rate compared to prey

    • Populations response: takes time for predators to respond to changes in prey availability due to breeding cycles.

    • Resource availability: increase in prey population, takes time for predators to increase population based on new prey.

    • Ecological interactions: predator-prey dynamics grows together, prey increase then does predators.

Functional Responses in Predation

The higher the amount of prey available, the more the predator will eat.

Number of prey consumed v. prey population size:

  • Type I Response: Capture rate goes up with prey numbers in a straight line.

  • Type II Response: Capture rate increases, but not as fast and levels off.

  • Type III Response: Low capture rates at low prey numbers, but they increase dramatically as prey numbers rise.

Proportion of prey population consumed v. prey population size:

  • Type I Response: capture rate is constant, independent prey population size.

  • Type II Response: capture rate of predation declines when prey population grows.

  • Type III Response: low capture rate at low prey numbers, but rises to maximum before declining as predation reached maximum.

Type I Response assumes that predators are never full and will never stop feeding.

Type II Response results display the energy that predators give to search and handle prey that are being consumed.

Type III Response results can be caused by several different factors due to the availability of places were prey can be sheltered and can escape from predators. (e.g. if there were no places to hide then protected preys would be low and consumed preys will be high)

Numerical Response

The more prey predators eat will increase the predators reproduction.

Foraging

Animals must distribute time for

  • avoiding predators

  • defense

  • searching mates

  • caring for young

Behavioral and Physical Defenses of Prey

Prey have developed ways to defend themselves against being eaten:

  • Chemical Defenses: Things like poisons or warning scents.

  • Cryptic Coloration: Blending into the background.

  • Object Resemblance: Looking like inanimate objects.

  • Flashing Coloration: Bright colors shown when startled to confuse predators.

  • Warning Coloration (aposematism): Bright colors indicating they are dangerous to eat.

  • Batesian Mimicry: Living in the same habitat with inedible species while resembling them to deter predators.

    • model- inedible species

    • mimic- edible species that look like model

  • Mullerian Mimicry: Unpalatable, venomous or toxic with similar color pattern (e.g. both animals look the same and are both dangerous)

Protective Amor

Many animals use protective armor to defend against predators, including:

  • Hard Shells: Turtles and armadillos have shells for defense.

  • Exoskeletons: Insects and crustaceans possess hard outer layers made of chitin.

  • Thorns and Spines: Porcupines use sharp quills to deter attacks.

  • Scales and Bony Plates: Fish and reptiles have tough outer coverings for protection.

Behavioral Defense

tactics prey utilize to escape predators, including: - Fleeing: Rapidly evading threats.

  • Hiding: Finding cover to prevent detection.

  • Mobbing: Collective actions to frighten away predators.

  • Distraction Displays: Actions that mislead a predator's focus.

  • Changing Activity Patterns: Modifying behaviors to steer clear of high-risk times for predation.

Induced Defense

responses prey exhibit when faced with predators to improve survival.

  • Chemical Defenses: Producing toxins or deterrents in response to threats.

  • Morphological Changes: Developing thicker shells or spines when at risk.

  • Behavioral Adaptations: Altering feeding or habitat preferences to avoid predators. These defenses are activated specifically when a threat is present.

Hunting Tactics of Predators

  • Predators use various hunting methods:

    • Ambush Hunting: Waiting for prey to come nearby.

    • Stalking: Sneaking up and quickly attacking.

    • Pursuit Hunting: Chasing prey over long distances.

  • Some predators use camouflage to approach their prey stealthily.

Lethal and Nonlethal Effects

  • Lethal effects lead to the death of an organism due to predation.

  • Nonlethal effects do not cause death but change behavior, physiology, or reproductive success.

  • (e.g. predator presence may alter prey foraging patterns, reduce activity levels, or increase stress, impacting overall health and fitness)

Impact of Predators on Prey Behavior

  • Predators affect prey behavior beyond just killing:

    • They can reduce feeding in areas where they're at risk.

    • They can change growth and reproduction patterns due to their presence.