AQUATIC PARAMETERS AND LIFE HISTORY OBSERVATIONS OF THE GREAT BASIN SPADEFOOT TOAD IN UTAH Peter Hovinuh', Boh Benton^'^, and Dave Bomholdt^'^ .\bstr.\ct.-The distrihution and lireeding hahitats of the Great Basin spadefoot toad {Scaphiopu.s intermontanus) were investigated in the Bonneville Basin of western Utah. The permanent springs and man-made reservoirs used for breeding were largely found below the 16()0 m elevation. The pH's ranged between 7.2 and 10.4 and the total dis-.solved solids between 170 and 4800 mg/i. The springs were less alkaline than the rain-filled reservoirs. The lack of aquatic vegetation was a common feature of the reservoirs and most of the springs. Observations of breeding without rain are noted as well as the lack of breeding with rain. The snout-vent lengths of adult spadefoots are greater in the Bonneville Basin than in other parts of the Great Basin. Utilization of permanent water sources and stimuli for emer-gence and breeding, as well as the larger adult size of S. intermontanus in the Bonneville Basin, are discussed in rela-tion to the diverse precipitation patterns, the sparseness of the water sources, and the Holocene history of the Great Basin. Spadefoot toads have been extensively studied in California, Arizona, New Mexico, Texas, and Oklahoma. Very little information is available for the Great Basin spadefoot toad {Scaphiopus intermontanus). Tanner (1931) found S. intermontanus widely dis-tributed in Utah. Most observations in Utah have been within the Colorado River drain-age (Tanner 1931, Hardy 1938, Wood 1935, Wright and Wright 1949). Observations of S. intermontanus in the Great Basin ecosystem are less frequent. Tanner (1931) found spade-foots common along the Wasatch Front and reported observations near Candy and Callao in Utah, near the Nevada border. Synder (1920), Linsdale (1938), and La Rivers (1942) reported the records for Nevada. Scaphiopus intermontanus has several unique features that are not found in other spadefoot species: (1) breeding is reported to occur without rainfall for stimulus (Lin.sdale 1938), (2) a large number of chorusing adults is not es.sen-tial for breeding (Wood 1935, Blair 1956), and (3) permanent water can be utilized for breeding (Bragg 1961). This study describes the breeding habitat of S. intermontanus in the Bonneville Basin of the Great Basin in western Utah, which is bounded by the ancient shoreline of Lake Bonneville, a lake that desiccated some 11,000 years ago (Currey 1980). Lake Bonne-ville filled the valleys in western Utah to a height of about 1552 m above sea level, with up to 350 m of water, and covered 5,000,000 hectares. The lake existed at the high level for about 3000 years and filled the valleys at lower levels for 10,000 years. We found that most breeding sites of S. intermontanus oc-curred in areas that were inundated by Lake Bonneville and that many of these sites were associated with permanent springs. This study extends some of the earlier observations that are unique to S. intermontanus, de-scribes the breeding habitat, and interprets these observations in terms of the Holocene hi.storv of the Bonneville Basin. Methods and Materials Chemical analysis was performed by the Uintex Corporation under contract to the Bu-reau of Land Management and reported in "Water Inventory for Tooele Range Environ-mental Statement" for the Salt Lake District Bureau of Land Management (March 1981). 'Department of Biochemistry. University of Utali. Salt Luke Citv. Utah 84 U2. Reprint requests should be sent to 721 Set end Av UtahH4ia3 •Sail Lake Dislncl Office, Bureau of Land Management, 2370 South 230() West, Salt Lake Citv. Utah 84119. 'Present address; U.S. Fish and Wildlife Service. 2078 Administration Building. 1745 West 1700 South, Salt Lake Cilv. Utah 84104. 'Present address: MmeraK \l.n.a,;.-,n.ni s,.rvice. Atlantic COS Region. 1951 Kidsvell Drive. Vienna. Virginia 22180. 22
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