Publication Date

Fall 2013

Degree Type


Degree Name

Master of Science (MS)


Environmental Studies


Lynne Trulio


Ambystoma macrodactylum croceum, Amphibians, Endangered, Mortality, Roads, Salamanders

Subject Areas

Environmental science; Ecology; Biology


Amphibian populations have been declining at higher rates than bird and mammal populations. Agriculture, urbanization, including roads, and resource extraction continue to put pressure on all species. Roads in particular, are major sources of mortality. The Santa Cruz long-toed salamander (Ambystoma macrodactylum croceum), one of the most critically endangered species in the US, is one amphibian that is declining as a result of anthropogenic impacts, especially habitat loss and fragmentation due to urban development. Migration across roads puts these salamanders at risk from road-related death. This thesis quantified the rate of road mortality to these salamanders and other common amphibians during two A. m. croceum breeding-migration seasons in 2011-13 in a portion of the subspecies' range. Vehicular traffic was a major source of mortality to the salamander. Through traffic doubled the overall vehicle load on roads where the A. m. croceum migrated to and from breeding ponds. The Pacific chorus frog was also killed on the roads. This common species can be used as an indicator of road mortality risk for rarer amphibians. This study indicated that measures to reduce road mortality to the Santa Cruz long-toed salamander could include restricting vehicular traffic on roads adjacent to salamander ponds by limiting traffic to residential use only during breeding migrations, installing structures to protect A. m. croceum while crossing roads, and potentially assisting animals crossing roads at nighttime during the breeding migrations.