Research overview: the geographic and demographic closure assumption in capture-recapture

Closed-population capture-recapture models assume the population neither gains nor loses individuals during the survey, through births, deaths, immigration, or emigration, an assumption central to estimating abundance from photographic recaptures. This overview explains why closure matters, how violations bias estimates, and how researchers design surveys to approximate it, typically by keeping survey duration short relative to the animals' demographic and movement timescales. It distinguishes geographic closure (no movement in or out of the sampled area) from demographic closure (no births or deaths) and describes tests and consequences of failure. For wide-ranging cats, balancing closure against the need for enough captures is a core design challenge. Understanding closure clarifies why camera surveys for tigers or jaguars run for weeks, not years, at a given site.