Predator-Prey Dynamics Notes

Definition: A species interaction where one organism (predator, $+$ ) consumes another organism (prey, $-$ ).
Types of Predation: Includes carnivory, herbivory, and parasitism.
Ecological Niches: Involves the specific interrelationship of a species with biotic and abiotic variables, defining its functional role in the ecosystem.

Interactions between two species categorized by outcome

Predator Tasks: Predators must successfully detect, locate, approach, capture, and handle prey.
Dietary Specialization:
- Specialists: Focus on specific prey, highly adapted for efficient exploitation.
- Generalists: Flexible diets, able to switch between prey types based on availability.
Hunting Strategies:

Diagram illustrating ambush, ballistic interception, and pursuit hunting strategies

Ambush Predation: "Sit-and-wait" strategy relying on heightened visual, chemical, or tactile senses and rapid movement. Lures may be used in low-density prey conditions (e.g., bird poo spider).
Ballistic Interception: Predators predict future prey location based on initial observations. Escapes depend on local habitat and prey reaction timing (e.g., frogs waiting until a snake strikes before leaping to exploit the close quarters effect).
Pursuit Predation: High-speed locomotion involving visual or auditory camouflage. Predators are typically larger and faster than prey, though capture success rates can be low (e.g., Cheetah success rate is $40\text{--}58\%$ ).
Turning Gambit (Howland 1974): Smaller prey can execute sharper, faster turns than larger predators to escape.
- Cooperative Hunting: Used by social carnivores (e.g., wolves, African wild dogs, lions, dolphins, orcas).
Benefits: Higher attack success, energy efficiency, capability to hunt larger prey, territory defence, social learning, and shared cub care.
Costs: Shared rations, social conflict, increased visibility to prey, and free-riding by group members.

Avoiding Detection: Camouflage matching the environment, disruptive coloration breaking up body outline, and remaining motionless.
Avoiding Capture: Locomotor capabilities including speed, agility, erratic movements, flight, burrowing, and swimming.
Physical Defences: Armor, shells, and sharp spines (e.g., echidnas, hedgehogs, porcupines).
Chemical Defences: Toxins, venom, and noxious tastes (e.g., Dendrobates reticulatus, skunks).
Warning Signals (Aposematism): Bright warning coloration, sounds, or odors signaling toxicity or unpalatability to predators.
Mimicry Systems:
- Batesian Mimicry: A harmless species mimics the appearance of a harmful or unpalatable species (e.g., the harmless blenny Petroscirtes breviceps resembling the venomous Meiacanthus grammistes).
- Müllerian Mimicry: Two or more unpalatable or harmful species evolve similar warning signals to reinforce predator avoidance.

Comparison of the harmless blenny Petroscirtes breviceps and the venomous species Meiacanthus grammistes

Behavioural Mechanisms:
- Group Living: Provides "more eyes" for early predator detection, confusion of predators, and collective defence.
- Dilution Effect: Individual risk of mortality decreases as group size increases.
- Selfish Herd: Individuals move toward the center of a group to reduce exposure to edge attacks.

Graph demonstrating how larger pigeon flock sizes decrease hawk attack success

Alarm Signals: Visual or vocal warnings given to group members (e.g., Urocitellus beldingi alarm calls, white-tailed deer tail flagging).

Predator Naivety and Learning: Unexposed ("naïve") prey populations lack evolved antipredator responses (e.g., island Northern Quolls lost predator avoidance behaviors within $13$ generations in the absence of predators, as shown by Jolly et al. 2018).
Trade-Offs of Defence: Antipredator behaviors carry fitness costs, such as reduced time spent foraging or lost mating opportunities (e.g., Fiddler crabs hiding in burrows).