Trap Avoidance By Marked Nutria: A Problem In Population Estimation

Data from the use of live traps in marking and recapturing nutria (Myocastor coypus) for an estimate of the population size showed a disproportionate level of recapture in adults and subadults. The use of radio transmitters to determine movement and the use of steel traps and shooting to obtain recaptures demonstrated that the adult and subadult nutria were avoiding the live traps. Population estimates by the Schnabel method and the Lincoln Index illustrated the error introduced by trap avoidance. The use of a different recapture technique eliminated this source of error.