Researcher ORCID Identifier

0009-0005-1026-0329

Graduation Year

2026

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Environmental Analysis

Reader 1

Dr. Robert Brodman

Reader 2

Veronica Vriesman

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© 2025 Ainsley K Murphy

Abstract

Understanding which environmental and biological factors support California newt (Taricha torosa) breeding is essential for conserving their declining populations in southern California. This study examined how key environmental conditions, such as water quality, hydrological characteristics, and habitat structure, alongside the presence of invasive species, shape newt distributions across two streams in the San Gabriel Mountains: Big Dalton Wilderness Area and Marshall Canyon Regional Park. Over two breeding seasons (March 2024-July 2025), repeated surveys documented newt abundance, egg masses, and habitat conditions including temperature, depth, pH, flow, conductivity, and dissolved oxygen. A principal component analysis identified temperature, conductivity, and depth as the strongest environmental gradients across sites. Subsequent statistical tests demonstrated that newts were more likely to occur in cooler and deeper pools, which highlights the importance of stable hydrological conditions for successful reproduction. The presence of invasive red swamp crayfish (Procambarus clarkii) significantly reduced newt occurrence, which is consistent with their known impacts on amphibian eggs and larvae. Newt abundance was substantially higher at Marshall Canyon than at Big Dalton, likely due to deeper pools, cooler temperatures, and the absence of crayfish. These findings underscore the need to protect stable aquatic habitats and reduce invasive species to support long-term persistence of T. torosa in southern California, while also highlighting the importance of continued research to track future changes.

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