Unit 2 Making a Living in the Wild Chapter 7 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

Primary defenses 1. Camouflage 2. Warning displays (aposematism)- coloration Mimicry (2 types) Mertensian- resemble something dangerous Batesian- resemble something unpalatable Mullerian mimicry- two unpalatable animals resemble each other

Primary defense cont 4. Lifestyle- avoidance, live in large numbers, etc

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