predator-prey strategies

PREDATOR-PREY STRATEGIESBiological Science 3

2011

Strategies for Avoiding Predators• Poisons• Mimicry• Visual deception• Chemical defenses• Offensive weapons• Camouflage• Size

Poisons

•Poisonous organisms often have bright colours to warn predators away.•Examples: frogs, some butterflies, some plants.

Mimicry

•Batesian mimicry- a harmless species which resembles a poisonous or unpalatable species.•Mullerian mimicry- two unpalatable species which resemble each other.

Visual Deception

•Markings deceive predators, allowing the prey to escape.

•‘Eye’ markings on fish encourage predators to strike at the wrong end of the fish.•The ‘eye’ markings on this moth resemble an owl.

Chemical Defenses

•Noxious smelling chemicals discourage predators.•Example: skunks.

Offensive Weapons

•Offensive weapons allow prey to actively fight off predators.

•Antlers•Teeth•Claws

Camouflage

•Camouflage (cryptic colouring) allows prey to hide from predators.

Size•Very large organisms are generally too large to be vulnerable to predators

Strategies for Catching Prey

•Concealment•Filter feeding•Tool use•Stealth•Lures•Traps

Concealment•Some predators use camouflage to conceal them while they stalk the prey.

Filter Feeding

•Filter feeders take in a large volume of water and strain it out, retaining small organisms in the water.•Examples: flamingoes, Baleen whales.

Tool Use

•Some species use tools to access their prey.•Examples: primates using sticks to reach ants.

Stealth

•Snakes use their ability to sense infrared to hunt at night.

Lures

•Angler fish use lures to attract prey within striking range.•Examples: angler fish, some spiders.

Traps•Spiders create webs which trap prey (typically insects).

Relationships between Predators and Prey•The numbers of prey and predators are linked.•Following an increase in prey numbers, there is a corresponding increase in predator numbers.

Questions1. What is the difference between passive and active

predator avoidance strategies?

2. Only the males of most deer species have antlers. Explain why.

3. How could the large fake eyes seen on some butterflies evolve?

4. Explain how Batesian mimicry benefits the mimic.

5. Mature fur seals are a dark colour, while the pups are white. Explain the reason for these different colours.

6. Explain the cyclic dip in snowshoe hare & lynx numbers.