Both genetic mark-recapture and physical mark-recapture are similar in basic study design, involving pursuit by a helicopter, and relying on the unique marking of individuals. However, in contrast to physical mark-recapture, genetic mark-recapture does not rely on chemical immobilization and handling of polar bears. Instead, DNA is extracted from a small sample of skin and hair collected via a biopsy dart fired from a helicopter. The tissues contain a DNA code unique to the each individual (i.e. the mark). Gender can also be determined via genetic analysis. The recapture event occurs when either the bear is biopsy darted on a later occasion or when a genetic sample is recovered from a polar bear killed during a subsistence harvest.