Annual weight variation and reproductive cycle of the wood mouse (Apodemus sylvaticus) in a Mediterranean environment

Abstract

This paper describes the weight variation and reproductive seasonal patterns of the wood mouse in a Mediterranean scrubland in southern Portugal. A total of 156 individuals were marked and followed up to 242 days. Summer corresponded to the non-breeding period in the study area, instead of winter, such as in other areas of central and northern Europe. As a consequence, a displacement of the annual density and weight cycles were observed. The higher densities, usually recorded before the non-reproductive period, were recorded during spring instead of summer. In addition, the typical weight depression of the non-reproductive period was reported in summer. Reproductive individuals were consistently heavier than non-reproductive, except in summer when a significant weight decrease was observed and in autumn when there were few subadults in the population. Juvenile males grew faster than juvenile females. However, there was little evidence of differences on growth of juveniles born at different times of the year.