Arboreal Salamander

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 Unpublished genetic analyses (allozymes and mitochondrial DNA sequences) show that the chromosomal units do not correlate with patterns of genetic variation (Jackman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 (http://www.californiaherps.com/salamanders/pages/a.lugubris.html).

Two subspecies are recognized. A. lugubris lugubris is limited to California and northern regions of the Baja California peninsula. Disjunct populations of A. l. lugubris also occur in the foothills of the Sierra Nevada. A. lugubris farallonensis is found only on South Farallon Island, California (Stebbins 1985). Historical versus Current Distribution: Arboreal salamanders (Aneides lugubris) occur in coastal oak woodlands from northern California (Humboldt County) to approximately Valle Santo Tomás, Baja California del Norte, Mexico. Their range includes South Farallon, Santa Catalina, Los Coronados, and Año Neuvo Islands (Lynch and Wake, 1974; McPeak, 2000). In the foothills of the Sierra Nevada, a geographically isolated cluster of populations occurs in black oak and yellow pine forests (Lynch and Wake 1974). This group of populations is genetically distinct from coastal populations (Jackman 1993). The range of the arboreal salamander is similar to the range of the oaks, Quercus agrifolia and Q. wislizenii, presumably a consequence of shared moisture and soil requirements (Rosenthal 1957). However, in southern California, the species is frequently associated with sycamores (Platanus racemosa), bordering seasonal streams. Populations have certainly been eliminated as coastal California habitats have been developed, but the species survives in many urbanized regions where adequate cover is present. Adult Habitat Requirements: Arboreal salamanders are found in a variety of terrestrial and arboreal habitats, including under rocks and woody surface cover, in decaying stumps and logs, in decay holes in trees, and in rock crevices (Ritter and Miller 1899; Ritter 1903; Storer 1925; Miller 1944; Stebbins 1951; Rosenthal 1957; Anderson 1960). Climbing is facilitated by expanded tips of terminal phalanges and large subdigital pads, as well as by the prehensile tail of the arboreal salamander (Ritter and Miller 1899). Individuals have been found over 18m above ground in trees (Ritter and Miller 1899; Ritter 1903; Stebbins 1951). Arboreal salamanders can be found in microhabitats that are drier than those of sympatric salamanders (Storer 1925; Cohen 1952; Ray 1958; Anderson 1960). This species is generally absent from regions receiving < 25 cm of precipitation/yr (Rosenthal 1957).

Aneides lugubris is completely terrestrial and is nocturnal. Courtship Behavior: A courting male places his mental gland on the female’s dorsum and, in a succession of quick strokes, draws the mental gland across the female’s back (Arnold 1977). During this behavior, the male’s large and monocuspid premaxillary teeth may scratch the female’s skin and enable efficient delivery of mental gland pheromones to the female’s circulation. Brood Sites: Reported oviposition sites include in decay holes of live oak trees (most common), under rocks set deeply in the ground, in logs, under surface cover objects (e.g., stone slabs, flower box) and beneath the ground surface (Ritter and Miller, 1899; Ritter, 1903; Storer, 1925). Egg clutches have been found up to 9m in live oak trees (Ritter, 1903). The eggs are white and encapsulated in two jelly envelopes. Clusters are generally suspended from an overhead support by an 8-20 mm pedicel, although solitary eggs are also found associated with egg masses (Petranka 1998). The number of eggs in a clutch varies from 5 - 24 (Ritter 1903; Storer 1925; Stebbins 1951) with larger females producing more eggs (Anderson 1960). Ovarian counts range from 5-26 maturing oocytes (Anderson 1960). Females on densely populated islands tend to produce fewer eggs than females in less dense mainland populations (Anderson 1960). Eggs are large, 7 - 9.5 mm in diameter. Most females oviposit in late spring or early summer (Stebbins 1951; Anderson 1960). After an approximately 3-4 month developmental period, embryos hatch in August or September at between 26 and 32 mm TL (Storer 1925; Stebbins 1951). Parental Care: Females are often found coiled around the eggs; males are often in attendance as well (Ritter and Miller 1899; Ritter 1903; Stebbins 1951). Presumed family groups may stay associated after hatching (Ritter 1903). Age/Size at Reproductive Maturity: Arboreal salamanders are the largest species of Aneides; mature individuals range in size from 65-100mm SVL (Lynch and Wake 1974). Age-size relationships suggest that >= 3 years are required to reach maturity (Anderson 1960). Anderson (1960) reported that the minimum size of sexual maturity was 34mm SVL for females, though this size seems small for typical females reaching sexual maturity. Behavior: The arboreal salamander may utter a mouselike squeak by forcing air through the jaws or nasal passages (Stebbins 1985). The arboreal salamander is well known for its aggressive tendencies and weaponry. This species has a suite of morphological features that enable a strong, wound inflicting bite. The jaw muscles are hypertrophied, the skull is heavily ossified with especially strong jaws, and juveniles as well as adults possess enlarged and flattened, blade-like, monocuspid teeth (other plethodontids possess weaker bicuspid teeth as juveniles) (Wake 1966; Wake et al. 1983). In his description of the arboreal salamander, Cope (1899) writes that "On the whole, the physiognomy is not unlike that of a snapping tortoise." Scarred individuals are often found in the field (Miller 1944; N.L. Staub, personal observation) and Myers (1930) observed that salamanders housed in the same container bite each others’ tails. In a study of museum specimens, Staub (1993) found that 15% of the examined individuals were scarred, presumably from conspecific attacks. The frequency of scarring did not differ significantly between males and females (Staub 1993). Feeding Behavior: Arboreal salamanders are nocturnal and feed most actively under moist/wet conditions. Adults tend to feed on larger prey than juveniles, although Wake et al. (1983) point out that arboreal salamanders of all sizes take a range of prey items. The diet of arboreal salamanders includes millipedes, annelids, snails, and especially colepterans, hymenopterans (ants), isopterans (termites), isopods (sowbugs), chilopods (centipedes), and lepidopterans (Miller 1944; Zweifel 1949; Bury and Martin 1973; Lynch 1985). Miller (1944) suggests that fungus is an important component of the diet, but other authors have not confirmed this observation. Relative to syntopic species, the arboreal salamander consumes disproportionately larger prey items than expected for individuals of a given body size (Lynch 1985), and comparative data suggest that arboreal salamanders consume numerous large-sized prey that other species are unable to capture (Bury and Martin 1973). The structural components of the feeding apparatus are well-developed (e.g., well ossified skull) (Wake et al. 1983). Despite the large jaws and teeth, prey are typically captured by the tongue and brought fully into the mouth, usually without contacting the marginal dentition (personal observation). Predators: The Pacific rattlesnake (Crotulus viridis helleri) is a known predator of the arboreal salamander (Mahrdt and Banta 1997) and a California scrub jay (Aphelocoma coerulescens) has been observed trying to eat a juvenile arboreal salamander (Rubinoff 1996). Anti-Predator Mechanisms: Several anti-predatory behaviors have been observed when individuals are startled or attacked: a defensive posture (raising the body stiffly off the ground; Cohen, 1952; Stebbins, 1951), squeaking (Ritter and Miller 1899; Storer 1925), rapid movement and jumping (Ritter and Miller 1899), and biting (Ritter 1903; Storer 1925; Stebbins 1951; Lynch 1981). The arboreal salamander will bite terrestrial garter snakes (Thamnophis elegans) and in some cases the snakes can die from the inflicted wounds (Lynch 1981). Micturition, the act of voiding the bladder when startled, is a novel putative antipredatory behavior that has been documented for the arboreal salamander (Staub and Anderson in press). Parasites: Two species of nematode (Batracholandros salamandrae, Oswaldocruzia pipiens) have been found in the arboreal salamander (Schad 1960; Goldberg et al. 1998). Aestivation: Arboreal salamanders are more tolerant of dry conditions than are many species of salamanders and are often among the last salamanders to retreat underground or into tree holes to avoid dessication (Miller 1944; Cohen 1952; Ray 1958; Petranka 1998). This species has relatively low rates of water loss compared to other salamanders, possibly due to postural adaptations (curled body and tightly coiled tail), and a rapid rate of water uptake (Cohen 1952; Ray 1958). Historical versus Current Abundance: Arboreal salamanders remain common in many areas, however in some areas populations have declined in the past 20 years (D.B. Wake, in Petranka, 1998). Petranka (1998) suggests that large oaks used for nesting and aestivation should be preserved. The current decline of live oaks in California will have negative effects on arboreal salamander populations.

Although Aneides lugubris is not presently on any endangered species lists, population numbers appear to be declining (D. Wake pers. comm. 1999).

Observations: Very little is known about the longevity of these animals, but one specimen lived 5.3 years in captivity (Andrew Snider and J. Bowler 1992).

Some sources label A. lugubris as being a sensitive species as well as being relatively rare. The IUCN, CITES, and the U.S. Endangered Species Act does not label them this way. As with many animals, A. lugubris's primary threat is habitat fragmentation due to human development. As a lungless salamander (Plethodontidae) they breathe through their skin and membranes in the mouth and throat (Harding 1997 ) which makes them particularly sensitive to the effects of pollution.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Development - Life Cycle: metamorphosis

The arboreal salamander is more active at night and eats insects such as small crickets and termites, as well as other invertebrates found underneath leaf litter on the ground at night (Prairie 1999, Behler and King 1998).

Aneides lugubris, commonly known as the arboreal salamander, ranges all along the California coastline edges from Humboldt County to Baja, California and a small part of the north western area of Mexico. It is also found in the Sierra Nevada foothills, Santa Catalina, Los Coronados islands, and South Farallon (Behler and King 1998). Its original range was from Griffith Park to Decter Canyon (Resource Conservation 1999).

Biogeographic Regions: nearctic (Native )

The arboreal salamander likes moist places in leaf litter where it can hide during the day and forage food at night. It likes to live in oak woodlands along the coast of California and can be found in yellow pine and black oak forests in the Sierra Nevada foothills (Behler and King 1998).

Average lifespan
Status: captivity: 5.3 years.

The arboreal salamander's length ranges from four to seven and a quarter inches. It has fifteen to sixteen costal grooves and like all plethodontids has naso-labial grooves that possibly aid in smelling by funneling odors toward the nose. Their dorsal coloration is dark brown to gray with yellowish or white spotting. This spotting varies between populations and in some cases is absent. Underneath, A. lugubris is a solid cream color. The head of A. lugubris is large relative to the body. Its toe tips are expanded, digits elongated, and it has a moderately prehensile tail, all of which make it a most excellent tree climber among salamanders (Prairie 1999, Behler and King 1998).

Other Physical Features: ectothermic ; bilateral symmetry

Aneides lugubris breeds in late spring or early summer. The female lays twelve to twenty-four eggs in a moist hollowed area such as a rotten log or tree hollow. The female broods her eggs and they hatch within three or four months (Behler and King 1998).

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)

The arboreal salamander (Aneides lugubris) is a species of climbing salamander. An insectivore, it is native to California and Baja California, where it is primarily associated with oak and sycamore woodlands, and thick chaparral.