PREDATOR – PREY RELATIONSHIPS Chapter 20

PREDATION a biological interaction where a predator (an organism) kills and eats its prey (another organism)= represented by +/ -

- = one species is harmed +/ - + = one species benefits - = one species is harmed

Predators are Important part of a healthy Ecosystem Predators kill vulnerable prey, (sick, young, injured) leaving more food for the survival and prosperity of healthy prey animals. They control the size of prey populations, which helps slow down the spread of disease. Predators will catch the least capable animals, leaving only the best to survive and reproduce.

Predation is a straight-forward interspecies community interaction Predation is a straight-forward interspecies community interaction. One species uses another as a food resource. Predators play an important role in controlling prey population numbers in some systems. In simple systems, the predator-prey relationship results in a pattern.

Classic example of predator-prey dynamics: Canadian Lynx and Snowshie Hare

prey numbers increase, predator numbers increase…to a point where the predation causes population decline in the prey item..

Idealized predator-prey coupled dynamics. It is important to note that in most systems the food web- is far more complex than just a single predator and single prey item. Figure 14.2c

Predator-prey relationships often have ramifications for other parts of the ecosystem. The hare-lynx relationship is an example. Hares eat twigs, more hares = more damage to trees. More lynx = fewer hares and less damage to trees. Figure 14.26

Tactics of the Predator 1) Camouflage and disguise Figure 14.1

Tactics of the Predator 2) Patience is a Virtue (Hide and Wait) Figure 14.1

Tactics of the Predator 3) Death by Poisoning (Venoms) Figure 14.1

Tactics of the Predator 4) “Right this Way Please”: trap-doors, nets, webs Figure 14.1

Tactics of the Predator 5) Bigger, Badder, Faster 200 mph Figure 14.1 700 lbs & built to kill 17,000 lbs, and perhaps as smart as you http://www.youtube.com/watch?v=DWsN63PRCW8

Responses of the Prey 1) Camouflage or disguise Figure 14.17b

Responses of the Prey 2) FLEEING Figure 14.17b

Responses of the Prey 3) Eat me and die (poisonous bodies) Figure 14.17b

Responses of the Prey 4) “Shields up”: (armor): Spines or Shells! Figure 14.17b

Responses of the Prey 5) Playing dead!!! Figure 14.17b

Responses of the Prey 6) Mimicry- a prey defense where one organism resembles another dangerous creature to avoid being eaten Figure 14.17b

Responses of the Prey 6) Strength in Numbers: Figure 14.17b

Herbivory, a special case of predation… Not really- herbivory involves the taking of plant material by an animal herbivore- is almost always non-fatal, and can sometimes be an advantage for the plant- or at least stimulate growth and promote community diversity... Herbivory generally becomes a problem when the ecological system is out of balance. Figure 14.16

Predator-prey relationships