Past exam of the short options course of the University of Oxford / 2021 / 9 / a / i / Solution

The per-capita net growth rate is $r/(1+b{N}^2)-\delta$. Thus $r$ is the low-density per-capita birth or recruitment rate, $\delta$ is the constant per-capita death or removal rate, and $b$ controls density-dependent suppression of recruitment. Both $r$ and $\delta$ have units of inverse time; $b$ has units of inverse population squared. The population scale $b^{-1/2}$ halves the recruitment rate from its low-density value. Larger $b$ makes suppression important at smaller population sizes. These are interpretations of this phenomenological population dynamics model, rather than independently specified biological mechanisms.