Large Aneides, 65-100mm in SVL (Lynch and Wake 1974). Dark brown dorsal color, with small, cream-colored spots on the head, trunk, tail, and limbs; cream-colored venter; yellow undersides of feet and tail. The head is large and triangular with heavy jaw musculature. Individuals of this species possess enlarged toe tips and prehensile tails (Stebbins 1985).
 

Interspecific Associations/Exclusions: Arboreal salamanders are syntopic with California slender salamanders (Batrachoseps attenuatus), the wandering salamander (A. vagrans), and the black salamander (A. flavipunctatus) in regions north of San Francisco Bay. Throughout most of the rest of its range A. lugubris occurs in sympatry with Ensatina and a number of species of Batrachoseps. Ecological interactions between these species are not well understood. Maiorana (1978) showed that there may be competition for food between California slender salamanders and arboreal salamanders when large prey are limited. When large prey items are not limiting however, Lynch (1985) found broad dietary differences between these two species-the arboreal salamander tends to eat a few, large bodied prey in addition to a diverse assortment of other prey items. Arboreal salamanders occasionally prey on Batrachoseps (Storer 1925; Miller 1944).

Chromosomal variation: There are two geographically segregated groups of chromosomally differentiated populations of the arboreal salamander (Sessions and Kezer 1987). These two karyotypes intergrade in south and east central Mendocino County (Sessions and Kezer 1987). Unpublished genetic analyses (allozymes and mitochondrial DNA sequences) show that the chromosomal units do not correlate with patterns of genetic variation (Jackman 1993). The Farallon Island population is genetically most similar to the nearest mainland population, not populations in the Gabilan mountains to the south as suggested by Morafka (1976) (Jackman 1993).

See another account at californiaherps.com.