Aggregations of Sharptail Snakes (Contia tenuis) on the East Slope of the Cascade Range in Washington State

Abstract

formed in some boxes over pools (30% of boxes in December, 30% in January, 0 in February) and riffles (50% of boxes in December, 20% in January, 20% in February). In all cases, water was flowing under the surface ice, and no anchor ice had formed on the bottom of the streams. No A. truei were found in the boxes. However, using a dip net we found A. truei in 4 of 4 streams searched: in 1 stream in November, 2 streams in December, 1 stream in January, and 4 streams in February. We found 9 adults and 12 larvae under rocks (< 35-cm diameter) in riffles. These had not burrowed into the stream bed. There may be geographic variation in overwintering locations, as A. truei in western Washington appear to burrow into the stream substrate (H. A. Brown, pers. comm.). The presence of anchor ice in some streams may preclude their use by this species. In the 10 streams observed, the water flowed all winter under deep layers of snow, and we suspect that the snow protected the streams from freezing and allowed the frogs to overwinter in the water. If anchor ice had formed in the study streams, the frogs probably would have been frozen. Because A. truei remain in the streams in winter, it is imperative that management activities near these 1Stand 2nd-order streams preserve the integrity of the stream structure and adjacent habitat. In particular, management activities that affect winter stream flow and icing conditions may adversely affect A. truei. Additional research is warranted on distribution of A. truei relative to winter stream conditions, winter survivorship, and to determine if A. truei also are buried in the substrate