. The Canadian field-naturalist. Natural history. 2001 Adams and Frissell: Habitat Use and Migration by Tailed Frogs 253 The lakeshore, one inlet stream, and the uppermost Moore Creek reach were again searched during the night (and Moore Creek also during day) of 7-8 October 1998. Hobo-Temp® data loggers recorded stream tem- peratures from 31 July 1997 to 8 October 1998 (with several gaps) at three locations each in Moore (Figure 1) and Twelvemile creeks. Using a digital thermometer, we took a longitudinal temperature profile in Moore Creek downstream of the lake out- let on 28 July 1998 and t
. The Canadian field-naturalist. Natural history. 2001 Adams and Frissell: Habitat Use and Migration by Tailed Frogs 253 The lakeshore, one inlet stream, and the uppermost Moore Creek reach were again searched during the night (and Moore Creek also during day) of 7-8 October 1998. Hobo-Temp® data loggers recorded stream tem- peratures from 31 July 1997 to 8 October 1998 (with several gaps) at three locations each in Moore (Figure 1) and Twelvemile creeks. Using a digital thermometer, we took a longitudinal temperature profile in Moore Creek downstream of the lake out- let on 28 July 1998 and took focal point tempera- tures at some Ascaphus locations. Results and Discussion Adult movements At the lake weir in Moore Creek, we trapped 32 frogs moving downstream and one moving up- stream. As the trapping period progressed, the num- ber of adult Ascaphus moving downstream into the trap increased from no frogs for the period of 7 August through 3 September 1997 to nine frogs on 6 October, three days before the weir was removed (Figure 2). The sex ratio of captured frogs was male biased (chi square = , p = ). The timing of frog captures coincided with a drop in water temperature (Figure 2). The frogs began moving downstream into the trap when average daily stream temperatures dropped below 16°C, and most were captured when average temperatures fell below 14°C (Figure 2). Whenever frogs were recorded in the trap, the maximum daily temperature had not exceeded °C during at least one day of the two- to-three-day trapping interval. The pattern of frog captures suggests that a direct- ed, seasonal migration was occurring in upper Moore Creek. The seasonality of the movement is clear from the complete absence of any frogs in the down- stream trap for at least the first month of operation. Although there was unquestionable directionality of capture in the traps, concluding that a downstream migration was actually occurring depends on two assumptions: (1) that
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