Explain density-dependent regulation and provide an example in mammals.

• A. Population growth accelerates when density increases because individuals help each other.
• B. Population growth slows as density increases due to resource limits, disease, or social stress; e.g., hare populations surge and crash due to resource limits and predator pressure.
• C. Population size is constant regardless of density.
• D. Regulation that acts only through abiotic factors.

Answer: (B)

Density-dependent regulation is the idea that a population’s growth slows as it becomes more crowded, because limited resources, increased disease transmission, and social stress make more individuals die or reproduce less. This creates a check on growth and often guides populations toward a carrying capacity.

A mammal example is hare populations. When resources are plentiful, hares can increase rapidly, but as numbers rise, food becomes scarce, survival of young declines, parasites and diseases spread more easily, and predators can have more success catching prey. The together‑moving pressures from resource limits and predation tend to push the population back down, producing the characteristic boom-and-bust cycles seen in many mammal populations.