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How can seasonal changes cause a population to fluctuate?
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population ecology
A herd of common wildebeest (Connochaetes taurinus) migrating across a dusty savanna in Africa. The animal is a keystone species (i.e., a species with a disproportionately large effect on its biological community) in plains and acacia savanna ecosystems from southeastern Africa to central Kenya.
In population ecology, seasonal changes drive population fluctuations by altering the availability of life-sustaining resources, such as food, light, and temperature. These environmental shifts directly influence fertility, mortality, and migration patterns.12
Key mechanisms include:
- Resource Pulses: Seasonal variations, such as spring thaws or increased daylight, can trigger rapid bursts in primary productivity. For example, nutrient upwelling in lakes or oceans leads to plankton blooms, which subsequently support spikes in consumer populations.12
- Breeding and Life Cycles: Many species synchronize their reproduction with seasonal peaks in food abundance to ensure offspring survival. In temperate mountain regions, plants and animals undergo intense growth or breeding phases during short, favorable seasons, followed by periods of dormancy or migration.3
- Migration: To cope with seasonal scarcity, many species migrate to exploit fluctuating resources across different regions. By moving between areas of high productivity, these populations avoid the limitations of a single environment’s carrying capacity during harsh seasons.4
- Predator-Prey Dynamics: Seasonal changes can create oscillating patterns where predator populations track the abundance of their prey, which itself may be fluctuating due to seasonal food availability.51