Abstract
Recently the damages to young reforested trees by hares particularly to cryptomeria (Cryptomeria japonica D. DON), red pine (Pinus densiflora SIEB. et ZUCC.) and larch (Larix leptorepis MURRAY) have become serious in Yamagata Prefecture. The so-called Tohoku hare, Lepus brachyurus angustidens HOLLISTER, is very common in this district and wanders actively in the forest at night biting the growing top, branch and bark of the stem of the sapling.
The ecological study of the hare is fundamental for the control but so far little has been done. This paper is a part of the study dealing with the gestation period and the growth rate after the birth of the hare. Observations and measurements were done with 102 specimens. The results are as follows: The gestation period is 32-34 days as observed in 8 pregnant females. From the observation on gestation period it was suggested that the ovulation of this hare occurred after the copulation. The gestation period of this hare is longer than the domestic rabbit (Oryctolagus cuniculus var. domesticus (GMELIN)). The increase of body length of new born young continued for about 200 days after the birth until it reached about 49cm. The augmentation of body weight is continued for 260 days and reached about 2, 600g. The ear length and cranium length attained maximum of 8cm and 9.2cm respectively when the body weight increased to 2, 300g. The hind-limb length obtained maximum 15cm when the body weight became 2, 100g. The cranium width increased to its maximum much earlier becoming 4.5cm in the individual weighing 1, 800g.
