Unit 1 Making a Living in the Wild

Chapter 7Predators and Prey

Predators and Prey

• Predators are organisms that survive by eating others (includes some plants and fungi)

• Prey is what they eat• Coevolution- changes in

both pred and prey due to their interactions

Predator Behaviors

• Prey selection- use experience to choose what to hunt

• Locating prey by vision, hear, smell

• One sense dominates the others

Examples

• Dolphins and bats use echolocation- sound waves

• Some animals use vibrations in ground or water or body heat

• Some use electrical fields in the water (sharks) called ampullae of Lorenzini

Capturing prey

• 1. Stalk and ambush- cats

• 2. Consistent pursuit- chimp hunt

• 3. Lure in prey- angler fish, less common

Hunting in groups

• Social carnivores• Can hunt larger prey• Then must share• Can use group as

defense as well

Group predation in other species

• Not just large carnivores

• Hawks• Humpback whales• Killer whales• Spiders• Ants

Handling prey

• Immobilize (stun)• Kill immediately and

take somewhere else and eat right away

• Store kill for later (cache)

Defense against predation

• Primary vs. secondary• Primary- built into body• Ex: spines• Secondary- behavior

when faced with predator

• Ex: run away, spray toxins

Secondary defenses

• 1. Flight- get away quickly

• Flagging behavior-act hurt to distract predator from young

• 2. Fight- usually when cornered, toxins

• Mobbing- diving and chirping loud to distract predator from young

Secondary defense

• 3. Freeze- silent, odorless, even may lose consciousness (tonic immobility)

Evolutionary arms race

• The better prey is at surviving, the better the predator must be to catch it

• Population size fluctuates in cycles• Both pred and prey usually stay stable• Prey usually reproduce faster than pred• Predators invest more in their young b/c

have longer lifespan