Bombina orientalis (Boulenger)
Bombinator orientalis Boulenger, Ann. Mag. Nat. Hist., ser. 6, 5:143, pl. IX, fig. 2, February, 1890 (type locality restricted to Chefoo, China, by Pope, Bull. Amer. Mus. Nat. Hist., 61:435, August 29, 1931).
Bombina orientalis, Stejneger, Bull. U. S. Nat. Mus., 58:51, figs. 30-43, pl. VII (reproduction from Boulenger, supra), July 22, 1907.
Specimens examined (87).—2 mi. N Chip´o-ri, 8 (KU), 5 (UMMZ); 1 mi. SW Inje, 1 (KU); 15 mi. NE Mosulp´o, Cheju Do, 6 (KU); Sangdaehwa, 2 (KU); Taehoesan-ni, 1 (KU); 1 mi. W Tangjonggok, 32 (KU), 17 (UMMZ); Tangnim-ni, 2 (KU); 3 mi. SW Yanggu, 1 (KU); 2 mi. N Yongdae-ri, 8 (KU), 4 (UMMZ).
Remarks.—Most of our specimens were taken from breeding congresses after heavy rains in rice fields and other shallow temporary waters. Thirteen individuals from Chip´o-ri were collected from foxholes around the edge of a military compound (two pairs in amplexus; no egg masses seen), and represent a small sample of frogs that were everywhere following a heavy rain on the night of May 13-14. On April 23, 32 Bombina orientalis and three Rana temporaria dybowskii were trapped in the water-filled bottom of an unused grease pit near Tangjonggok. Many tadpoles and two kinds of egg masses (small clusters and beadlike strings) were present; the small clusters of Bombina were commonest. On June 13 at the same locality, thousands of these toads were observed (hundreds in axillary amplexus) in foxholes, temporary rain pools, and backwashes along the Puk-ch´on [river]. On June 12 near
Yongdae-ri many individuals were seen (several pairs in amplexus), along Route 24 paralleling the Puk-ch´on, in rain pools and in ditches and backwashes from the river; almost all available water contained small (approximately 10 × 10 mm.) egg masses. Numbers of eggs per mass, selected at random, were 5, 2, 2, 5, 2, 8, 8, 2 and 5. Some that were saved subsequently hatched on June 15-17.
The call is a quiet low trill or series of staccato whistles rising slightly at the beginning; a short peeplike note also was heard. The specimens from Cheju Do, which are generally smaller than those collected on the mainland in spring, were taken on September 6 in a small stream that had large volcanic rocks in many places and that was flanked by thick brush and small trees. The earliest and latest dates on which B. orientalis was collected were April 21 and September 6, respectively.
In the breeding season, males are distinguished from females by the large blackish (probably brownish earlier in season) areas on the anteroventral surface of the antebrachium, the metacarpal tubercle, and the inner surface of the first finger (sometimes also the second and third). Also, males have conspicuous black-tipped tubercles on the back (usually absent in females) that extend onto the limbs (usually smooth in females, at least laterally). Field observations by one of us (Byers) suggested that the dorsal pattern of males had greater contrast than that of females and that the venter was brighter reddish. Eight females from Tangjonggok averaged 47.9 (43-51) in snout-vent length, whereas 24 males from there averaged 50.0 (46-55), indicating little, if any, size difference between the sexes.
Okada (1931:29) recorded variation in color of live Korean individuals (green or brown dorsally and pale yellow or red ventrally) and variation in extent of black markings on the belly (op. cit.:fig. 12). The specimens from Cheju Do (28, 32, 32, 32, 37 and 46 in snout-vent length) have less black ventrally than specimens from the mainland.
Bufo bufo gargarizans Cantor