The RAINBOW TROUT is another nonnative trout of the park waters. Its original range was on the Pacific slope of the Sierras and the Cascades, but it has been transplanted widely. It is bluish-olive above the lateral line, changing to silvery-green on the sides. Its name is derived from a broad, reddish stripe on the sides. It eats insects, worms, and smaller fishes, and is a favorite of the angler for its fighting ability and tendency to break water when hooked. Spawning occurs from autumn to spring, depending on the altitude. [Illustration: Cutthroat trout.] The most common amphibian in the park is the bright-green to tan LEOPARD FROG. Restricted to damp areas near ponds or creeks, it is most likely to be seen in spring and early summer when the gelatinous egg masses are being laid. The tadpoles develop into mature frogs in about 3 years. Until then, it lives on plant food; after maturity, it eats insects and worms. It is found in Moraine Park, Horseshoe Park, and other moist grassland valleys. The THREE-LINED TREEFROG, our smallest amphibian—about an inch long—is often mistaken for a young leopard frog. Although it is a treefrog, possessing disks on its toes, it is seldom seen in trees; it prefers small ponds or swampy grassland. It is sometimes found under rockpiles or pieces of damp wood. Despite its small size, its loud chirps in spring and summer can be heard a half mile away. During its singing, a vocal sac beneath the lower jaw inflates to a size larger than the creatures head. It is easily recognized by the three stripes down its back. Look for this diminutive amphibian at Gem Lake. The insectivorous MOUNTAIN TOAD, a nondescript denizen of marshy lake habitats, is common in Cub Lake Valley, Hallowell Park, and in the Ouzel Lake area in Wild Basin. In late spring, large numbers congregate in ponds to lay strings of eggs. The small tadpoles become adults by the end of summer. [Illustration: View of Mount Ypsilon from near Bear Meadows approach to Trail Ridge Road.]