Abstract
The reproductive organs of 14 female Yezo brown bears (Ursus arctos yesoensis), mauled to death in a bear park, were studied morphologically with respect to thier configuration and seasonal variation.
The ovaries were completely covered with ovarian bursa, and their size and shape were similar to those of a broad bean. The medium sized follicles (size: 0.5-0.7 cm) were observed in bears ob-tained during June and early July, and the corpora lutea (size: 0.7-1.5 cm) were observed in those obtained in and after July. Invaginations of the surface epithelium known as a cortical cords were observed in all ovaries.
The oviducts, uniformly looped and encircling the walls of the ovarian bursae, entered the ovarian bursae through the small orifices. The length and thickness of oviducts were 5.0-7.0 cm and 0.1-O. 3 cm. In each individual case most of the fimbria was enclosed in a bursa, but a part of it pro-truded outwards.
Uteri were bipartite, and the length of the uterine horns ranged between 6.0 cm and 18.0 cm. The proliferation of uterine tissue and the appearence of PAS positive granules in the uterine glands were observed in bears obtained during June and July. The length of uterine bodies and cervices varied from 3.0 cm to 6.0 cm and 3.0 cm to 8.0 cm, respectively. Three annular folds were observed in an uterine cervix.
The length of vaginae and vulvae varied from 9.0 cm to 13.5 cm and 5.0 cm to 6.0 cm, respec-tively.
From these morphological observations, it is suggested that the breeding season of the female Yezo brown bear is a period from June to early July.
