Why are there no frogs in Great Basin National Park? Great Basin National Park seems like a perfect refuge for frogs, with plenty of water--ten perennial streams, hundreds of springs, and six alpine lakes, but apparently there are no amphibians.

During 2002, an amphibian inventory was conducted within Great Basin National Park. Crews surveyed perennial streams, springs, and alpine lakes, but did not observe any adult amphibians, tadpoles, or egg masses. The reasons for this are unclear, but apparently frog distribution depends on more than just abundant water.

Lack of suitable breeding habitat is a major limiting factor in amphibian distribution. Most amphibians require still or extremely slow moving water to lay their eggs in. High gradient streams in the Park do not provide appropriate breeding habitat. The hundreds of springs in the Park may provide this habitat, however, no amphibians were found at the dozens of springs surveyed this year.

Isolation from source populations is another limiting factor. Streams leave the Park and then quickly disappear underground. Amphibian populations near the Park are not directly connected to these streams. Thus no corridors exist between the Park and nearby amphibian populations.

One amphibian species that does not require aquatic corridors for migration is the Great Basin Spadefoot (Spea intermontana), commonly referred to as a "toad." Spadefoots are distinguished from "true toads" (members of the family Bufonidae) by a black wedge shaped spade on their hind feet, used for burrowing. Spadefoots move considerable distances over land during spring and summer rains, travelling to breeding sites. They mate and lay their eggs in ephemeral pools and ponds, then burrow underground with their "spadefeet" to await the next rain. Spadefoots can remain underground for up to two years. The eggs of spadefoots mature very quickly; two weeks after laying eggs, the tadpoles have metamorphosed from tadpoles to adults, and have left the breeding ponds. The ability of spadefoots to aestivate during drought and quickly metamorphose from egg to adult allows them to take advantage of infrequent periods of moisture and rapidly shrinking breeding habitat. Spadefoots are superbly well adapted to the desert habitat.

Woodhouse's Toad (Bufo woodhousei) a "true toad" looks very similar to spadefoots, but is larger with wartier skin, and lacks the black wedge shaped spade on their hind feet. Woodhouse's Toad was collected several times in the 1930's from Warm Creek in Snake Valley, Utah. Woodhouse's toad is thought to have entered the Great Basin from the southwest after the Pleistocene.

After the Pleistocene, Great Basin climates rapidly became warmer and drier. Aquatic frogs such as Northern Leopard frogs and Spotted frogs became isolated in shrinking desert streams, marshes, and springs. Why frog species did not move upstream into the Park during this time, like Bonneville cutthroat trout and Great Basin spring snails, is unclear.

Northern Leopard frogs (Rana pipiens) are found in marshes and large valley springs. Northern Leopard Frogs are known from Shoshone and Cleveland ranches in Spring Valley and Bishop Springs and Gandy Salt Marsh in Snake Valley. Leopard Frogs have undergone dramatic declines throughout their range due to habitat loss, fungal infections, and competition with non-native fish and amphibians.

Bullfrogs (Rana catesbeiana) are non-native frogs that have been widely introduced into the Great Basin. Bullfrogs are found in Bishop Springs and Lower Strawberry Creek. Bullfrogs are large frogs, up to 8 inches long, and capable of swallowing leopard and spotted frogs whole. The introduction of non-native bullfrogs is a major concern in maintaining native frog populations. To protect native frog populations, DO NOT MOVE FROGS BETWEEN BODIES OF WATER.

Although no amphibians have been found in the park, we are still optimistic. Great Basin Spadefoots will likely be found in the Park's lower elevations and there is a small chance of finding Western Toads in the alpine lakes. The mystery of the missing frogs continues…

Caption: The Columbia Spotted Frog (Rana luteiventris) is found in two wetlands in Snake Valley, Utah.