142. Animal identification is difficult on outdoor units. Ear tattoos and tags are often difficult to read due to dirt. For this reason ear notching was often used in the past. This represents an unnecessary mutilation. The advent of electronic ear buttons is therefore welcomed on welfare grounds. The ear button provides a unique electronic identity which can be read with a hand held transponder reader and data logger. The logger has the potential to store necessary management information and to record data in the field. The development of equipment which is suitable and sufficiently robust to be used on outdoor units will facilitate better recording of individuals and as a consequence contribute to their welfare.