. The Canadian field-naturalist. Natural history. 254 The Canadian Field-Naturalist Vol. 115 1 T C !E o (0 © 3 C I 0> a w CD 3 > C M 1 o_K2L CM 3 â 2 k£. â larvae E9 adults VI , oK3 , OCTTI CO *-' d) O I'll 3 Location and date, 1998 (0 558 3 Figure 3. Numbers of Ascaphus larvae and adults per minute spent searching by each team during night surveys. Numbers above bars are the total numbers of individuals observed during each survey. Inlet 3 was surveyed only in October, = upstream; = downstream. Butler Creek (Montana) and concluded that the frogs exhibited ex
. The Canadian field-naturalist. Natural history. 254 The Canadian Field-Naturalist Vol. 115 1 T C !E o (0 © 3 C I 0> a w CD 3 > C M 1 o_K2L CM 3 â 2 k£. â larvae E9 adults VI , oK3 , OCTTI CO *-' d) O I'll 3 Location and date, 1998 (0 558 3 Figure 3. Numbers of Ascaphus larvae and adults per minute spent searching by each team during night surveys. Numbers above bars are the total numbers of individuals observed during each survey. Inlet 3 was surveyed only in October, = upstream; = downstream. Butler Creek (Montana) and concluded that the frogs exhibited extreme philopatry; however, their annual summer sampling period may have ended too early to detect an autumn migration. By contrast, based on seasonal changes in densities of adult Ascaphus, Metter (1964a) hypothesized that adults moved from the Touchet River (Washington) into more shaded tributaries in the late summer. In the Palouse River (Idaho) and tributaries during the same time period, though, he found no seasonal differences in frog densities. Brown (1975) observed aggregations of up to 20 females in "small, shallow tributaries" of Razor Hone Creek, Washington, in late July and sug- gested that females may move into the warmer tribu- taries to lay eggs. However, evidence of actual upstream movements was lacking. Landreth and Ferguson (1967) suspected that frogs moved down- stream out of small, intermittent creeks to the Lostine River, Oregon, to mate, but again, had no direct evidence of migration. If Tailed Frogs migrate in response to local conditions, diverse movements among sites would be expected. Stream temperatures and Ascaphus distribution The average August stream temperature at the upper Moore Creek temperature recording location exceed- ed 16°C both summers (Table 1). Average daily tem- peratures exceeded 18°C for at least 5 days in 1997 and 20 days in 1998 (Figure 2), and we likely missed recording many of the warmest days both years. Wa
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