Life History of Postmetamorphic Coastal Tailed Frogs (Ascaphus Truei) in Northwestern California

Abstract

We conducted nocturnal surveys of postmetamorphic Ascaphus truei on six streams in north coastal California from 2002–04, using mark-recapture techniques to determine sizes of age classes, growth rates, site fidelity, reproductive chronology, and seasonal activity within the stream channel and riparian zone. Ascaphus truei grew year-round, but grew faster during the summer (1.47 ± 0.06 mm/month) than winter (0.89 ± 0.04 mm/month). Growth curves indicate that following metamorphosis, females likely reached sexual maturity in three years, whereas males became reproductive in two years. Tailed frogs in these coastal streams exhibited limited within-channel longitudinal movement (x¯ = 13.6 m), although movements were highly variable (range = 0–112 m). Significantly more frogs were captured in summer than fall, and very few frogs were captured in winter. Significantly more reproductive adults were captured in spring than summer, suggesting that breeding occurred primarily in spring. Recapture data indicated that females deposited eggs in the stream mostly during July and August and may have a biennial reproductive cycle. This study has quantified life history traits for A. truei populations in coastal northwestern California that contrast to results for inland and northern Ascaphus populations. Comparative geographic variation studies throughout the range of Ascaphus are needed to aid in understanding life-history and ecological differences both within and among regions.