The results of live trapping of coypus in cage traps is described. Considerable turnover of populations probably amounting to a more or less continuous interchange of some animals between neighbouring populations is demonstrated and it appears that females probably move fairly short distances before littering whilst males move longer distances. The more immigrants move into an area, the more residents apparently move out. There is some evidence of synchrony of breeding and at peak littering times trapping may catch twice as many males as females, and possible explanations for this are discussed. It was found that coypus have a sense of orientation in that when animals were moved from their place of trapping they quickly moved back again. An area was trapped out and from this it was concluded that coypus can be eliminated from an area using cage traps if immigration can be prevented.