Practice question

The simplest two-sample Lincoln–Petersen mark–recapture model assumes demographic and geographic closure between sampling occasions. No births, deaths, immigration, or emigration should change the population or alter the proportion of marked individuals. Under closure, the marked fraction after thorough mixing remains interpretable, allowing M/N ≈ R/C and N ≈ MC/R. Quadrat and transect methods sample spatial units and do not inherently require a closed population in the same formal sense, although movement during counting can still create error. Satellite methods track individuals and may explicitly measure movement rather than assume its absence. Closure is an approximation whose plausibility depends on study duration and boundary design; investigators can shorten intervals or choose natural boundaries to improve it. Open-population capture–recapture models, such as Cormack–Jolly–Seber approaches, relax closure and estimate survival or recruitment from multiple occasions. Other assumptions remain important even in a closed study: marks must persist, capture probabilities should be comparable, marking must not affect organisms, and individuals must mix before recapture.