Life History of the Southern Torrent Salamander (Rhyacotriton variegatus) in Coastal Northern California

Abstract

Southern Torrent Salamanders (Rhyacotriton variegatus) range widely from north coastal Oregon to northern California but are a patchily distributed inhabitant of forested seeps and headwater springs. We collected bimonthly samples of this species from managed forest sites in the Mad River watershed, Humboldt County. Larvae were measured, marked, and released, but a limited number of transformed individuals were preserved for laboratory analyses. North coastal R. variegatus breeds annually and has an extended courtship and egg-laying period. Cloacal spermatophores were present in gravid females from February through June, and oviposition likely occurs spring through fall. A prolonged larval period (hatching to metamorphosis) lasts 2–2.5 yr; transformed females require another 1.5–2 yr until first breeding, and clutch size averages 7.5 eggs. Adult sizes, size at metamorphosis, and developmental times were comparable to north coastal Oregon R. variegatus, suggesting that a simple north-south, harsh-mild environmental cline does not influence developmental time for coastal populations. Unexpectedly, clutch size and size-fecundity relationships for the California population of R. variegatus were more similar to Rhyacotriton cascadae, an inland, northern species with longer larval periods and larger sizes at metamorphosis, than to R. variegatus in north coastal Oregon. Rhyacotriton variegatus has limited rates of population increase because of long generation times and low fecundities and could be highly sensitive to frequent disturbances that impact numbers.