Practice question

Inverse density dependence, or positive density dependence, means performance improves as density increases over the relevant range. One expression is mortality declining with density, perhaps because groups dilute predation risk or defend themselves cooperatively. Birth rate increasing with density can also express the same general phenomenon, so the keyed mortality statement is an example rather than a complete definition. Population regulation concerns feedback, not mere limitation. A drought may sharply reduce numbers yet fail to push the population toward a repeatable equilibrium. Competition, disease, territoriality, and some predator responses can strengthen with crowding, changing births or deaths in a direction that opposes the density change and thereby producing regulation. The example should therefore be understood as an application of a general model, with its assumptions kept explicit. Ecological predictions remain conditional on the stated environment, because changing resources, mortality, or interactions can alter the observed demographic pattern. This interpretation connects individual-level processes with measurable changes in survival, reproduction, recruitment, or abundance across the population.