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How do predation and disease help limit population growth?

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Common wildebeest — 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, predation and disease act as density-dependent factors, meaning their influence on a population intensifies as the number of individuals per unit area increases. These forces serve as regulating mechanisms that help maintain population density within a specific range.12

Disease

Diseases spread more rapidly in high-density populations because individuals live in closer proximity, facilitating transmission. As the population size decreases—due to mortality or other factors—the frequency of contact between individuals drops, which in turn reduces the transmission rate of the disease.12

Predation

Predation limits population growth by directly reducing the number of individuals in a prey population. Ecologists often model these interactions using the Lotka-Volterra equations, which calculate how the growth rate of a prey species is reduced by the presence and activity of predators. The impact of predation is influenced by the size of both the predator and prey populations, as well as the availability of spatial refugia where prey can escape predation.34