Postnatal Growth and Development of the Formosan Wood Mouse Apodemus semotus

Abstract

Abstract. Postnatal growth and development of Apodemus semotus were investigated from birth, to day 90, in the laboratory. Morphometric measure-ments a t birth, of both sexes combined, revealed body weight to be 2.09f 0.17 g, mean head and body length to be 35.51f 2.94 mm, mean tail length as 13.59k0.76 mm and mean hind foot length as 6.52f 0.47 rnm. Body weight was found to increase steadily until day 50, whereas the instantaneous growth rates of other measurements declined earlier. Head and body length increases declined to a minimum a f t 4 day 40, that of tail length after day 45, of hind foot length after day 32, and of ear length after day 28. Although tail to body length ratio reached more than 100 % on day 36 for males and on day 28 for females, no sexual differences were found in the growth rate of body weight (using the Gompertz equation), or of linear dimensions (using the logistic equation). Pinnae unfolded on days 2-3, the auditory meatus opened on days 12-14, and the eyes opened on days 14-16. Growth and development were divided into four periods: 1) neonate, days 0-6; 2) transition, days 7-14; 3) socialization, days 15-24; and 4) juvenile, day 25 to sexual maturity. In the field, the spring generation of juveniles grew quickly, whereas the autumn generation grew more slowly. Comparisons of the developmental pattern of A. semotus with those of other Apodemus species and of other species of related genera, revealed that the developmental pattern of A. semotus was broadly similar to that of Mus species and to those of some Rattus species. Key words: Postnatal growth; Developmental pattern; Growth equations; Instantaneous growth rate; Apodemus semotus. Growth patterns during development have been widely considered a potential and valuable tool for understanding the ecological status of a given species, and are thought to reflect phylogenetic relationships among related speci'es