Yellowstone National Park Amphibians

General

Cool, dry conditions limit Yellowstone's amphibians to four species. Population numbers for these species are not known. Amphibians: boreal toad, chorus frog, spotted frog, tiger salamander.

Status

The spotted frog may be declining in the West. Some researchers suspect that there are more amphibians in Yellowstone than are currently known, but this has not been documented yet.

Yellowstone is home for a small variety of amphibians. Glacial activity and current cool and dry conditions are likely responsible for their relatively low numbers in Yellowstone. In 1991 park staff began cooperating with researchers from Idaho State University to sample additional park habitats for reptiles and amphibians. This led to establishment of long-term monitoring sites in the park (map, page 119). The relatively undisturbed nature of the park and the baseline data may prove useful in testing hypotheses concerning the apparent declines of several species of toads and frogs in the western United States. Reptile and amphibian population declines may be caused by such factors as drought, pollution, disease, predation, habitat loss and fragmentation, introduced fish and other non-native species. Although no Yellowstone reptile or amphibian species are currently listed as threatened or endangered, several-including the boreal toad-are thought to be declining in the West. Surveys and monitoring are underway to try to determine if amphibian populations are declining in Yellowstone National Park

BLOTCHED TIGER SALAMANDER

Identification

The only salamander in Yellowstone. Adults range up to about 9 inches, including the tail. Head is broad, with a wide mouth. Color ranges from light olive or brown to nearly black, often with yellows blotches or streaks on back and sides; belly is dull lemon yellow with irregular black spots. Larvae, which are aquatic, have a uniform color and large feathery gills behind the head; they can reach sizes comparable to adults but are considerably heavier. Habitat Breeds in ponds and fishless lakes. Widespread in Yellowstone in a great variety of habitats, with sizable populations in the Lamar Valley. Behavior Adult salamanders come out from hibernation in late April to June, depending on elevation, and migrate to breeding ponds where they lay their eggs. Mass migrations of salamanders crossing roads are sometimes encountered, particularly during or after rain. After migration, return to their moist homes under rocks and logs and in burrows. Feed on adult insects, insect nymphs and larvae, small aquatic invertebrates, frogs, tadpoles, and even small vertebrates. Preyed upon by a wide variety of animals, including mammals, fish, snakes, and birds such as sandhill cranes and great blue herons.

Bufo boreas boreas

Identification

Yellowstone's only toad. Adults range up to about 4 inches, juveniles just metamorphosed from tadpoles are only one inch long. Stocky body and blunt nose. Brown, gray, or olive green with irregular black spots, lots of warts, and usually a white or cream colored stripe down the back. Tadpoles are usually black and often congregate in large groups. Habitat Once common throughout the park, now appears to be much rarer than spotted frogs and chorus frogs; scientists fear this species has experienced a decline in the Greater Yellowstone Ecosystem. Adults can range far from wetlands because of their ability to soak up water from tiny puddles or moist areas. Lay eggs in shallow, sun-warmed water, such as ponds, lake edges, slow streams, and river backwaters. Behavior Tadpoles eat aquatic plants; adults eat insects, especially ants and beetles, worms and other small invertebrates. Sometimes active at night. Defends itself against predators by secreting an irritating fluid from numerous glands on its back and behind the eyes. Eaten by snakes, mammals, ravens, and large wading birds.

Rana petiosa

Identification

Abundant and best known amphibian in Yellowstone. Maximum length is 3.2 inches, newly metamorphosed juveniles less than one inch long. Upper surface of the adult is gray-brown to dark olive or even green, with irregular black spots; skin is bumpy; underside is white splashed with brilliant orange on the thighs and arms on many but not all individuals. Tadpoles have long tails and may grow to 3 inches long. Habitat Found all summer along or in rivers, streams, smaller lakes, marshes, ponds, and rain pools. Lay eggs in stagnant or quiet water, in globular masses surrounded by jelly. Behavior Breeds in May or early June, depending on temperatures. Tadpoles mature and change into adults between July and September. Tadpoles eat aquatic plants, adults mostly eat insects but are highly opportunistic in their food habits (like many other adult amphibians).

Pseudacris triseriata maculata

Identification

Adults reach 1 to 1 1/2 inches in length, and females are usually larger than males; newly metamorphosed froglets are less than one inch long. Brown, olive, tan, or green (sometimes bi-colored) with a prominent black stripe on each side from the nostril through the eye and down the sides to the groin; three dark stripes down the back, often incomplete or broken into blotches. Habitat Common, but seldom seen due to its small size and secretive habits. Live in moist meadows and forests near wetlands. Lays eggs in loose irregular clusters attached to submerged vegetation in quiet water. Behavior Breeds in shallow temporary pools or ponds during the late spring. Calls are very conspicuous, resembles the sound of a thumb running along the teeth of a comb. Males call and respond, producing a loud and continuous chorus at good breeding sites, from April to early July, depending on elevation and weather. Usually call in late afternoon and evening. Tadpoles eat aquatic plants; adults mostly eat insects. Eaten by fish, predacious aquatic insect larvae, other amphibians, garter snakes, mammals, and birds.

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