The relationship between prey densities and predators is a complex one, governed by various mechanisms that shape their interactions. One important concept in this context is the Lotka-Volterra Predator-Prey Model, which describes how changes in prey densities affect predator growth rates.

According to the model, an increase in prey density (V) leads to an increase in the predator's growth rate (dP/dt). This is because predators are able to assimilate more energy from their prey as V increases, allowing them to reproduce and grow at a faster rate. The efficiency of this process is measured by the conversion efficiency (c), which represents the fraction of prey energy that is converted into new predator biomass.

However, changes in prey densities also have a demographic impact on predators. As V increases, predators may experience a scarcity of resources, leading to changes in their reproduction and survival rates. This demographic response is distinct from an increase in energy intake due to increased foraging efficiency, which is known as the functional response.

The numerical response of predators to changes in prey densities is also important. This refers to the change in predator density (P) as a function of change in prey density (V). The numerical response has two mechanisms: the demographic response and the aggregational response. The demographic response involves changes in predator reproduction or survival rates, while the aggregational response involves changes in predator aggregation patterns.

As noted by ecologist C.S. Holling, total predation can be viewed as a combination of functional and numerical responses. The functional response represents the change in predator's rate of prey consumption with changes in prey density, while the numerical response refers to the change in predator density itself.

In conclusion, the relationship between prey densities and predators is complex and influenced by various mechanisms. Understanding these mechanisms is important for understanding how predators respond to changes in their prey populations, and how this affects ecosystem dynamics as a whole.

Prey densities vs predators