Wednesday, December 22, 2010

The Salamander and the Rockslide

 Photo Credit: Arie van der Meijden.
Charles Camp described the Mount Lyell Salamander, Spelerpes platycephalus, in 1916 from specimens he collected at the head of Lyell Canyon, about 10,800 ft above sea level in Yosemite National Park. He described the habitat as at the upper edge of the Hudsonian life-zone. Two specimens were taken in a patch of heather among the rocks where water was flowing beneath the surrounding snowbanks. Today the Mount Lyell Salamander is know to have a wide distribution in the Sierra Nevada's from elevations of 1220 to 3660 meters above sea level. Stejneger and Barbour (1917) considered it to be in the genus Eurycea, but in 1923 Dunn placed it in Hydromantes, a genus erected by Gistel in 1848. Today Hydromantes contains three species, all are endemic to California. H. platycephalus inhabits exposed granitic rock outcrops, talus, and rock fissures, near seepages from streams or melting snow, and it has also been found in the spray zone of waterfalls. Eggs are thought to be deposited in terrestrial situations such as cracks and crevices below the surface in moist or wet limestone talus or in other subterranean cavities - they remain undiscovered. Eggs are also thought to undergo direct development because its close relatives undergo direct development. This is a cold-tolerant species, with body temperatures reported to be as low as -2.0 ˚C to 11.5 ˚C, but laboratory specimens preferred 13–14 ˚C (Brattstrom, 1963).

Today, a Yosemite National Park population of Hydromates platycephalus is part of a battle of conflicting interests involving traffic, ecotourists, and a landslide. There is a one-lane bridge over the Merced River with traffic lights on each end which alternate in a cycle that lasts several minutes, the westbound traffic is allowed through, then eastbound. It's a slow process that results in lengthy delays, and could be vulnerable to floods. The reason for the traffic bottleneck is a landslide that occurred five years ago on Highway 140. An estimated 800 million tons of rocks and debris blocked the road and forced tourists from the San Francisco Bay area to take hours-long detours to reach the valley. Engineers responded quickly and installed a temporary solution. But a longer-term fix has proven more difficult. One solution involves installing a cement bridge, but that's clearly inappropriate for a national park since it would spoil the natural surroundings. Another possibility is to build  two viaducts, but that would destroy a wildflower area. A third solution would be to tunnel under the landslide, but the Mt. Lyell Salamander inhabits the rockslide and construction could destroy it. Finally, the current situation could be kept as is as long as the existing road does not wash out in a flood (Baume, 2010; Burke, 2010).

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