How will the population of mice and voles change if fox numbers decline over several years? - briefly
A sustained decline in fox populations reduces predation on small rodents, causing mouse and vole numbers to increase sharply. Eventually, heightened competition and disease among the enlarged rodent populations may temper this growth.
How will the population of mice and voles change if fox numbers decline over several years? - in detail
If the number of foxes falls steadily over several years, the immediate ecological effect is a reduction in predation pressure on small mammals such as mice and voles. With fewer predators, survival rates of juvenile rodents rise, leading to an increase in the overall population size.
The growth of the rodent community proceeds through several stages:
- Release from predation: Adult mortality drops, allowing more individuals to reach reproductive age.
- Higher reproductive output: Larger cohorts of breeding females produce more litters per season.
- Density‑dependent regulation: As numbers climb, competition for seeds, roots, and insects intensifies, limiting further expansion.
- Disease transmission: Crowded conditions facilitate the spread of pathogens, which can cause periodic declines.
- Resource depletion: Over‑exploitation of vegetation may trigger a shortage of food, eventually curbing population growth.
Consequently, the rodent population is expected to rise sharply during the early years of fox decline, then stabilize at a higher equilibrium or exhibit cyclical fluctuations driven by the factors above. The exact magnitude of the increase depends on habitat quality, climate conditions, and the presence of alternative predators such as raptors or mustelids, which may partially offset the loss of foxes.