The growth of the Japanese harvest mouse, Micromys japonicus (Thomas)
I. The change in the external characters of the suckling young
1959 Volume 1 Issue 6 Pages 121-127
Details
1959 Volume 1 Issue 6 Pages 121-127
In our laboratory we have been breeding many harvest mice, Micromys japonicus (Thomas) for these three years. Three litters were born in last autumn and nineteen litters in this spring. We have observed the changes in the external characters from the time of birth up to the time of weaning. The results obtained are summarized as follows:
1) The average litter size is 2.27 in captivity, while it is 5.32 under natural conditions.
2) The average body weight at birth is 1.15±0.09 grams. The sex ratio (_??_/ _??_) is 1.24, but there is no significant difference in statistical point of view.
3) The first body hair is noticed on the fourth day. Ear-holes open on the seventh day. Each pair of incisors of upper and lower jaws erupts on the eighth to the tenth day. This mouse seems to stop nursing on about the fifteenth day.
