Population Cycles in Small Mammals
CHARLES J. KREBS and JUDITH H. MYERS
Institute of Animal Resource Ecology, University of British Columbia,
Vancouver, C a d
I. Introduction
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11. Historical Perspective
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111. Definition of the Problem .
A. What Prevents Unlimited Increase?
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B. What Causes the Cyclic Periodicity?
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c. What Produces Synchrony? .
D. What determines the Amplitude of the Cycle? .
IV. Population-Density Changes
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A. Techniques of Estimating Density .
B. Do Population Cycles Really Occur?
C. Structure of Population Fluctuations in Microtines
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1. Increase Phase .
2. Peak Phase
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3. Decline Phase .
4. Phsse of Low Numbers
V. Demographic Machinery
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A. Reproduction
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1. Litter Size
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2. Pregnancy Rate
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3. Length of Breeding Season .
4. Age a t Sexual Maturity
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5. Sex Ratio
6. Summary . .
1. Adult Mortality
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2. Juvenile Mortality
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3. Prenatal Mortality
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4. Summary . .
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B. Mortality
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C. Dispersal
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D. Growth.
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A. Food .
VI. Hypotheses to Explain Microtine Cycles
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1. Selectivity of Microtine Food Habits and Habitats
2. The Effect of Microtine Grazing on the Food Supply
3. The Influence of Food Quality and Quantity on Microtine Numbem
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B. Predation
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C. Weather and Synchrony
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D. Stress Hypothesis .
E. Behavior
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F. Genetics
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