Northwestern Salamander (Ambystoma gracile) Oviposition Sites and Hatching Success in the Cascade Mountains of Southern Washington.

. Reproductive success of amphibians is influenced by choice of oviposition sites, including NorthwesternSalamanders (Ambystoma gracile) whose egg masses are fixed to vegetation. During summers of 1999-2002, I surveyed 33permanent ponds in a 26 ha wetland (935 m elevation) for Northwestern Salamander egg masses, quantified oviposition sitecharacteristics, and tracked embryonic development and survival. The number of egg masses found ranged from 141-235annually, and the active oviposition period was 4-8 weeks. An average (+ SE) of 63.4 ± 3.7% of egg masses were attached tostems of Sitka Sedge (Carex sitchensis), 23.3 ± 3.4% to overhanging shrub stems or completely submerged sticks, and 8.3 ±4.9% were unattached. On average, 62.0 ± 6.1% of egg masses were in deep water, 25.7 ± 4.9% in shallow water, and 12.3 ±2.6% along the edge of deep and shallow areas. Egg masses were deposited at an average depth of 24.4 ± 0.5 cm. A mean of53.1 ± 3.5% of egg masses had at least one embryo hatch, which on average took 9.0 ± 0.5 weeks. Rough-skinned Newts(Taricha granulosa) were observed feeding on embryos. Regression tree models indicated that use of ponds for oviposition wasnegatively influenced by the relative abundance of Rough-skinned Newts, and positively related to the relative abundance oflarval Northwestern Salamanders. Hatching success was greatest in intermediate sized ponds where the number ofoverhanging shrubs was greatest. These results suggest that Northwestern Salamanders avoided ponds where potentialpredators were most abundant (including Brook Trout, Salvelinus fontinalis) and that the presence of larval conspecifics wasindicative of favorable oviposition and rearing habitats.