Columbia Spotted Frog. Rana luteiventris

Description: Adult: A medium-sized frog with a head and body length of 45-100 mm. Its body form is similar to that of Rana pipiens, but it is slightly more robust. The eyes are large and are oriented somewhat dorsally. The tympanum is prominent and smaller than the eye. Dorsolateral folds are present but they are rather indistinct. The toes of the hind feet are fully webbed. The hindlimbs are relatively shorter than those of R. pipiens. The skin is textured with scattered small bumps.

Generally dark brown above with many small, irregular spots of even darker colour. A dark mask running from the nostril to the tympanum may be discernible. A light jaw stripe is present from the snout to the insertion of the forelimb. In Alberta, the venter is salmon to red in colour, especially in the region of the hind limbs. This colour is very vivid and appears to be very superficial. The throat and other parts of the venter may be spotted or mottled with grey.

Larvae: Tadpoles are dark dorsally, flecked with gold. The venter is iridescent bronze. The anus is dextral and the spiracle sinistral. Newly transformed froglets have a total length of about 25 mm.

Variation: In very young specimens, the bright ventral colour may be faint or absent. Males have nuptial pads in the breeding season. Females are considerably larger than the males.

Natural history: The spotted frog is highly aquatic and is usually found associated with permanent water, particularly in regions of mixed coniferous forest and subalpine forest from 995 to above 2,150 m. It is rather slow in its movements and appears to be generally unwary. Its fright response is to swim to the bottom and then remain motionless, often hidden under submerged vegetation. It sometimes forages away from the water and is chiefly nocturnal in its activity patterns.

The adults eat worms, insects, arachnids, molluscs and crustaceans and they feed both above and below the water. Tadpoles may be eaten by passerine birds or aquatic insect larvae. Adults may be taken by hawks, ravens, gulls, owls, garter snakes, mustelids, and coyotes. Extralimitally cannibalistic predation of adults on larvae has been observed, and it has been suggested that such behavior may be particularly important in resource-limited high elevation (and high latitude) regions.

Reproduction: Pre-reproductive life span may be as long as four to six years. The spotted frog breeds as early as winter thaws will permit. Males call from the water near shore. There is no distinctive mating call, but the males make short grunting noises. The males are not territorial during the breeding period. Amplexus is pectoral. The breeding period lasts only a few weeks. Large eggs (5-12 mm in diameter) are laid in communal masses. 700-1,500 eggs are laid in a clutch. Time from laying to hatching appears to be very variable - four days to three weeks. The larvae normally metamorphose during the summer of the year of their hatching, but in more northerly locations they may overwinter as tadpoles and metamorphose the following year.

Voice: A series of rapid, low-pitched clicks, building in intensity. The duration of individual calls is highly variable, but they usually last less than ten seconds.

Distribution: In Alberta, the Columbia spotted frog is limited to sub- alpine and alpine regions and occurs at elevations of about 2,000 m. It occurs from Waterton Lakes National Park north through Jasper to perhaps as far as 55° N. Extralimitally, it occurs from the extreme southern Yukon through most of B .C, Washington, Oregon, Idaho, Montana and Wyoming, with isolated populations in Nevada and Utah. Its range in the United States is highly fragmented. It is absent from Vancouver Island.

Conservation status: Some populations, especially in areas of human disturbance, have disappeared. The status of remaining populations is uncertain, although some declines have been proposed.

Remarks: Rana luteiventris has recently been separated from Rana pretiosa, within which it was formerly included, on the basis of genetic differences. No morphological characters to distinguish these two species have yet been identified, but all spotted frogs in Canada, except extreme southwestern B.C., are referrable to R. luteiventris.

Significant references: Black 1969; Green 1985; Green et al. 1996, 1997; Hovingh 1993; James 1998b; Logier 1932; Moore and Strickland 1955; Pilliod 1999; Roberts 1992; Rodgers and Jellison 1942; Ross et al. 1999; Salt 1979; Svilha 1935; Turner 1958,1959,1960; Turner and Dumas 1972.