Description The California Tiger Salamander is a stocky salamander with a broad, rounded snout. Its eyes are relatively small but protruding, with black irises. The base dorsal color is black, and the dorsal side is commonly marked with bold patches of lemon-yellow spots that are concentrated along the sides of the animal. The belly is generally gray in color, and may display a few small spots of white or yellow color. Adults generally have 12 costal grooves.
Distribution is restricted to the Central Valley of California and lower elevations to the west. The range includes areas around Sonoma, Petaluma, and the Colusa-Yolo county line, south to the vernal pools in Tulare County, and amongst the coast ranges south to the ponds and vernal pools in the Santa Ynez Drainage (Santa Barbara County).
The habitat of this salamander is restricted to grassland and low foothills, where the long-lasting vernal pools it uses for breeding exist. Permanent aquatic sites can be used for breeding, but use of such sites is only common in the absence of predatory fish. Dry season habitat sites are within reasonable distance of breeding sites, and generally consist of small mammal burrows as well as man-made enclosures.
Life History, Abundance, Activity, and Special Behaviors The California Tiger Salamander engages in nocturnal breeding migrations. Movement occurs from dry season refuge sites to the breeding ponds from November to April, thought most commonly from December to March. These migrations don't occur until the ground has become moist, because the breeding pools do not form until the soil below them becomes saturated from the autumn rains. Males precede females to the breeding sites, and males often outnumber females at these sites. Shortly after breeding, the adults vacate the ponds. Eggs are deposited singly or in small groups of 2-4, submerged in the relatively shallow depths of the temporary pools. A minimum of 10 weeks is required for complete development (including metamorphosis).
Trends and Threats Like many other amphibians in central California, this species has suffered from habitat lost due to the conversion of land for agricultural and urban uses (Fisher and Shaffer 1996). In Sonoma County, 95% of the salamander's preferred vernal pool and grassland/oakland habitat has been lost. Another threat comes from the introduction of predatory fishes such as the mosquitofish, which is still used as a method of mosquito control. California Tiger Salamanders also have been adversely affected by the 1986-1990 California drought, which led to a decrease in suitable breeding habitat. This will likely be exacerbated with climate change.
As of 2005, both the Sonoma and Santa Barbara populations (formally as Distinct Vertebrate Population Segments) are classified as Federally Endangered, originally listed as Endangered in 2003 and 2000, respectively but downgraded subsequently. US District courts reversed the downgrade in 2005.
Relation to Humans
Despite the petition to list the California Tiger Salamander as State Endangered (in 2009), the California Department of Fish and Game continues to list this species as Threatened.
Intensified agriculture or grazing Urbanization Disturbance or death from vehicular traffic Prolonged drought Habitat fragmentation Predators (natural or introduced) Loss of genetic diversity from small population phenomena
Comments Recent molecular research has supported full species status for A. californiense, in contrast to its previous status as a subspecies of Ambystoma tigrinum (Shaffer and McKnight 1996). Full species status for A. californiense is also supported by its geographical isolation plus differences in coloration and natural history seen in A. californiense, as compared to other members of the A. tigrinum complex (Petranka 1998).
This species was featured as News of the Week on 18 March 2013:
Johnson et al. (2013) highlights the intersection of evolutionary history, restoration ecology, and conservation biology by testing three Tiger Salamander species found in California - Ambystoma californiense, Ambystoma tigrinum mavortium, and their hybrids - in experimental pools with different drying schedules. Illustrating the adaptive differences in the three clades of Ambystoma, they found that non-natives and hybrids did the best in pools that dried more slowly, like man-made ponds in the highly modified California landscape, while the native California Tiger Salamander did the best in pools that dried out more quickly and which simulated more naturalistic ponds found in California.
This species was featured as News of the Week on 15 July 2024:
Hybridization is a significant threat to at-risk species, especially when the hybrid offspring perform better than the parents (i.e., hybrid vigor); however, investigation into the mechanisms underlying hybrid vigor is limited. Populations of the vulnerable California Tiger Salamander (Ambystoma californiense) in Salinas Valley, California, are currently at risk of being eradicated by their hybrid offspring, and Burger et al. (2024) measured physiological traits and the interactions of these traits to better understand the success of these hybrids. They analyzed how changes in water loss affect metabolic rate using a new performance metric– the water-gas exchange ratio – that measures how well an organism can breathe while minimizing water loss, referred to as respiration efficiency. The physiological mechanisms that allow for cutaneous gas exchange (thin and highly vascularized skin) also result in high rates of water loss; therefore, organisms that physiologically reduce their water loss rates will also experience reductions in metabolic rates (a trade-off), which may limit their ability to conduct energetically demanding activities. For respiration efficiency, individuals that are more efficient (higher ratio) would be able to sustain longer bouts of energetically demanding activities while minimizing the risk of dehydration. They found that hybrids exhibited the highest respiration efficiency, potentially an explanation for their continued success. Ambystoma californiense exhibited the lowest respiration efficiency and the weakest trade-off between metabolic rate and water loss, indicating that these two traits may be decoupled in this species. By decoupling these traits, A. californiense would be able to regulate each trait separately, which may result in reduced sensitivity to environmental change. However, the increased respiration efficiency of hybrids may allow them to continue outcompeting native A. californiense. This study provides key insights into these hybrids, highlighting the potential need for management actions to maintain non-hybridized A. californiense populations while also emphasizing the importance of incorporating integrated, multitrait analyses into our investigations of species differences. (Written by Isabella Burger)
Fisher, R. N., and Shaffer, H. B. (1996). "The decline of amphibians in California's Great Central Valley." Conservation Biology, 10(5), 1387-1397.
Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C. and London.
Shaffer, H. B., and McKnight, M. L. (1996). ''The polytypic species revisited: differentiation and molecular phylogenetics of the Tiger Salamander Ambystoma tigrinum (Amphibia: Caudata) complex.'' Evolution, 50, 417-433.
Species Account Citation: AmphibiaWeb 2024 Ambystoma californiense: California Tiger Salamander <https://amphibiaweb.org/species/3829> University of California, Berkeley, CA, USA. Accessed Dec 25, 2024.
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