PREDATION. READINGS: FREEMAN Chapter 53 Students who wish to observe their religious holidays in lieu of attending class must notify Dr. Molumby ([email protected]). CONSUMPTION. The consuming of one living thing by another. A basic eating relationship between populations of different species.
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Is thought to be ecologically important, but its impact is still debated. Suggested positive impacts include:
where N = number of prey
t = time
r1 = reproductive capacity of prey (births exceed deaths)
where P = number of predators
t = time
- r2 = reproductive capacity of predators (deaths exceed births)
This graph shows a limit cycle of predators and prey.
Similar data is provided in Figure 53.10 (Freeman, 2005).
*Reported in SCIENCE 8-25-95
1. Food addition (rabbit chow)
2. Predator exclusion (mammals only, not birds)
3. Food addition and predator exclusion
4. Fertilizer (NPK plant nutrients) addition
5. Control areas (nothing was done in these areas)
The 5 different management areas were selected as random from a larger area that had a relatively uniform community structure.
Snowshoe hare density was monitored at various periods throughout the 8 year study.
1. Food addition tripled (3x) hare density.
2. Predator exclusion doubled (2X) hare density.
3. Food addition and predator exclusion increased hare
density eleven-fold (11X).
4. Fertilizer addition had hare density equivalent to
control areas (no effect).
FOOD - HARE - LYNX INTERACTION
Test 1. Twig consumption increases as hare density increases, but 60-80% of available food is not consumed.
Test 2. Unlimited added rabbit chow does not stop cycle.
Test 3. Added natural food does not stop hare decline.
* Bioscience 1/01** HYPOTHESIS REJECTED
Test 1. 95% of radio-collared hare deaths were due to predation.
Test 2. There were few deaths of radio-collared hare where predators were excluded.
Test 3. Predator exclusion nearly eliminated the decline phase of the snowshoe hare cycle.
* Bioscience 1/01** HYPOTHESIS ACCEPTED