Determining the Functional Form of Density Dependence: Deductive Approaches for Consumer‐Resource Systems Having a Single Resource

Consumer‐resource models are used to deduce the functional form of density dependence in the consumer population. A general approach to determining the form of consumer density dependence is proposed; this involves determining the equilibrium (or average) population size for a series of different harvest rates. The relationship between a consumer’s mortality and its equilibrium population size is explored for several one‐consumer/one‐resource models. The shape of density dependence in the resource and the shape of the numerical and functional responses all tend to be “inherited” by the consumer’s density dependence. Consumer‐resource models suggest that density dependence will very often have both concave and convex segments, something that is impossible under the commonly used θ‐logistic model. A range of consumer‐resource models predicts that consumer population size often declines at a decelerating rate with mortality at low mortality rates, is insensitive to or increases with mortality over a wide range of intermediate mortalities, and declines at a rapidly accelerating rate with increased mortality when mortality is high. This has important implications for management and conservation of natural populations.