Rana amurensis coreana Okada
Rana temporaria coreana Okada, Annot. Zool. Japon., 11:140 (footnote), July 25, 1927, nomen nudum.
Rana temporaria coreana Okada, Jour. Chosen Nat. Hist. Soc, 6:19, pl. 1, fig. 7, 1928 (type locality, Keijo [= Seoul], Korea).
Rana amurensis coreana, Shannon, Herpetologica, 12:38, March 6, 1956.
Specimens examined (9).—Central National Forest, near Pup´yong-ni, 1 (KU); 2 mi. S Ch´orwon, 1 (KU); 4 mi. W Ch´ungju, 1 (KU); 1 mi. N Oho-ri, 1 (KU); 5 mi. ESE Seoul, 3 (KU); Yongp´yong, 2 (KU).
Remarks.—One individual of R. a. coreana (KU 38698) and one of Rana temporaria dybowskii (KU 38715) were collected on May 29 along a stream in the Central National Forest in association with R. rugosa and R. nigromaculata. Specimens of coreana from the vicinity of Seoul were found in rice fields. The earliest date of collection was April 13 at Yongp´yong. Our largest specimen of coreana measured 47 in snout-vent length.
Because R. a. coreana and Rana temporaria dybowskii are sympatric in central Korea and closely resemble one another, the two species were not distinguished in the field and the following observations may pertain to either (or both) species. Wood frogs were observed 2 mi. E Songdong-ni on July 12 in paddies (rice fields) along with individuals of Hyla arborea, Rana rugosa, and Rana nigromaculata. At Chip´o-ri on April 6, individuals (probably R. t. dybowskii) were seen in a seepage pool from an abandoned rice field; R. nigromaculata also was seen there. Six or seven egg masses (some having small tadpoles) were observed in the shallow water, but it was not certain to which species the eggs belonged. Completely metamorphosed young (probably R. a. coreana) were first seen 1 mi. N Oho-ri on June 9. At Taehoesan-ni on November 12, several sluggish frogs were seen in a small pool that was covered by a thin layer of ice.
On September 26 in the Central National Forest, many wood frogs of various sizes were observed. R. amurensis and R. temporaria probably have extended breeding seasons that correspond to those of R. rugosa and R. nigromaculata. Judging from our observations, amurensis prefers the proximity of water, whereas temporaria may occur some distance from permanent water.
In our specimens, R. amurensis coreana differs from R. temporaria dybowskii in having (1) smaller maximal size, (2) more slender body, (3) shorter legs, (4) incompletely webbed toes, (5) no mottling or barring on lips, (6) no contrasting barred pattern on hind legs, (7) dark brown stripes (usually) between dorsolateral folds, (8) a dark brown, linear mark below canthus, and (9) an immaculate ventral surface. Two additional distinguishing characters, which we found difficult to evaluate, are the nearly straight, dorsolateral folds, and lack of vocal sacs or ostia in males of R. a. coreana (Shannon, 1956:38). Some of the differences between the two species were illustrated by Okada, 1931:107, fig. 48, R. temporaria temporaria [=R. t. dybowskii] and 123, fig. 54, R. temporaria coreana [=R. amurensis coreana].
Rana temporaria dybowskii Günther