BIOLOGY OF APODEMUS-SYLVATICUS IN LEON PROVINCE, SPAIN

This paper deals with the biology of the field-mouse (Apodemus sylvaticus) in a central zone of the province of Leon, Spain. Three hundred and twelve individuals were caught in systematic trappings during a period of two consecutive years and were used in this experiment. The observation obtained during the sampling and the information obtained from the specimens reveal that there was a variable choice of habitat throughout the year, the winter activity taking place under groups of holm-oaks (Quercus ilex). The elevated proportion of males to females was constant. Reproduction takes place in summer, two litters being possible within the same reproduction period. There was a certain age variation between the two stages of moulting. These two stages occur with slight age variations between specimens and three different kinds of melanine distribution have been observed during these moulting periods. In general, the biology of Apodemus sylvaticus in this area of Leon has more similarities to that of their European counterparts than to that of field-mice from other parts of the Iberian Peninsula which have typically mediterranean climate.