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Predation Part 1
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Includes the effects of predation, tools to investigate it, and the snowshoe hare cycle as a case study. It also covers the effect of a keystone species.
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EcologyLecture 7 Predation 1 08/03/21
What is predation?
- Predation is the consumption of one organism, in whole or in part, by another, where the
consumed organism is alive when the consumer first attacks it.
- True predators kill and eat their prey.
- Grazers (usually herbivores) often eat part of the organism they are consuming – this is not
deadly.
- Parasites (a bit like grazers) obtain nutrients from one or a few individuals and are harmful
but rarely deadly – often symbiotic.
- Parasitoids – insects in which the larva develops inside a single host which is ultimately
killed.
What are the effects of predation on prey populations in nature?
- Predators can suppress populations of prey.
- Predators can have little influence on numbers of prey even though they may eat a large
proportion of the population – other factors may control the prey population.
- Predators and their prey show cyclic interactions of build up and decline and other complex
relationships.
- Predators actually increase prey population through
indirect interactions.
What tools do we have to investigate predation?
- Observations of natural phenomena.
- ‘Natural’ experiments.
- Carefully manipulated experiments in lab and field.
- In simple experimental systems predator and prey
rarely coexist – Huffaker ran many experiments to
investigate the conditions that allow coexistence.
- Huffaker (1958, 1963) created ‘universes’ of
increasing complexity.
- Only in spatial heterogenous and complex systems
could both species survive.
The snowshoe hare cycle – a classic study of predator-prey interactions
Snowshoe hare (Lepus americanus)
- Abundant all across boreal North America.
- It falls prey to various predators, including the lynx.
- It does not hibernate, and eats herbaceous vegetation in summer, and
trees in winter.
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