Editing Mark and recapture (section)

== Field work related to mark-recapture ==
[[File:Novisuccinea chittenangoensis 5.png|thumb|Biologist is marking a [[Chittenango ovate amber snail]] to monitor the population.]]
Typically a [[researcher]] visits a study area and uses traps to capture a group of individuals alive. Each of these individuals is marked with a unique identifier (e.g., a numbered tag or band), and then is released unharmed back into the environment.  A mark-recapture method was first used for ecological study in 1896 by [[C.G. Johannes Petersen]] to estimate plaice, ''[[Pleuronectes platessa]]'', populations.<ref name="Southwood">{{cite book |last1=Southwood |first1=T. R. E. |last2=Henderson |first2=P. |year=2000 |title=Ecological Methods |edition=3rd |publisher=Blackwell Science |location=Oxford }}</ref>

Sufficient time should be allowed to pass for the marked individuals to redistribute themselves among the unmarked population.<ref name="Southwood"/>

Next, the researcher returns and captures another [[Sample (statistics)|sample]] of individuals. Some individuals in this second sample will have been marked during the initial visit and are now known as recaptures.<ref>{{cite web| url = https://www.merriam-webster.com/dictionary/recapture| title = Recapture Definition & Meaning - Merriam-Webster| date = 21 August 2023}} </ref> Other organisms captured during the second visit, will not have been captured during the first visit to the study area. These unmarked animals are usually given a tag or band during the second visit and then are released.<ref name="Southwood"/>

Population size can be estimated from as few as two visits to the study area. Commonly, more than two visits are made, particularly if estimates of survival or movement are desired.  Regardless of the total number of visits, the researcher simply records the date of each capture of each individual.  The "capture histories" generated are analyzed mathematically to estimate population size, survival, or movement.<ref name="Southwood"/>

When capturing and marking organisms, ecologists need to consider the welfare of the organisms. If the chosen identifier harms the organism, then its behavior might become irregular.

{{Gallery
|title=Different methods of "mark and recapture" 
|width=150 |height=100
|align=center
|footer=
|File:Collar tagged Rock Hyrax.JPG
 |Collar-tagged [[rock hyrax]]
 |alt1=Collar tagged [[rock hyrax]]
|File:Jackdaw with a ring.JPG
 |Ring-tagged [[Jackdaw]] 
 |alt2=[[Jackdaw]] with a numbered aluminum ring on its left tarsus
|File:Novisuccinea chittenangoensis 4.png
 |Marked Chittenango ovate amber snail
 |alt3=right side view of a snail with a number 87 on its shell
|File:Coenonympha tullia CMR, Drugeon - img 47288.jpg
 |Tagged Common Ringlet
 |alt4= An adult of Common Ringlet tagged by a number for a study using mark and recapture in order to evaluate the populations of this butterfly in the Drugeon valley (Doubs, France).
}}