California Tiger Salamander

The Biogeography of the California Tiger Salamander (Ambystoma californiense)
by Elizabeth Kanner, student in Geography 316 Fall 2003

Thank you for visiting our site. This web page was written by a student in Geography 316: Biogeography and edited by the instructor, Barbara Holzman, PhD. All photos and maps are posted with specific copyright permission for the express use of education on these web pages. The students have tried to be as accurate as possible with the information provided and sources and references are cited at the end of each page.

Description
California Tiger Salamanders are considerably large for today’s amphibians. The male can reach 8.5 inches long and the females 7 inches (NPWRC 2002, FWS 2003). Males differ from females in their overall size as well as their enlarged cloacae during breeding season (FWS 2003). The adults are stocky with round heads, protruding black eyes and long tails that curl around their body. They are slick, glistening black with yellowish spots and stripes on their back, sides and tail. These markings slightly resemble those of a tiger and earn the species their name. This yellowish color also outlines their wide mouth, which gives the appearance of broad painted smile. Like other salamanders, its body is low to the ground and its four legs protrude sideways from its body as though it were ready to run (figure 2).

Figure 2: California Tiger Salamander
(Gerald and Buff Corsi © 1999 California Academy of Sciences)

Ecology and Nesting Habitat
The California Tiger Salamander is found in annual grasslands and open woodlands (FWS 2003). Here, the Mediterranean climate creates hot dry summers and cool rainy winters. The mean annual precipitation is 20 to 40 inches per year with mean annual temperatures of 50 to 58 degrees Fahrenheit (USFS 2003). Ecological characteristics of this area include dry soils, needlegrass grasslands, valley oaks, coast live oaks and ephemerally flooded claypan depressions called vernal pools (USFS 2003).

Like most of their relatives, the adult California Tiger Salamander is terrestrial. For six to nine months out of their year, they live in their nesting habitat in the grassy highlands. Since they are poor burrowers themselves, the California Tiger Salamanders take advantage of the abandoned refuges of small mammals such as ground squirrels and gophers (Nickles 2003). In the driest months, they enter a dormant state called estivation (FWS 2003).

Breeding Behavior
In early winter, just after sufficient rains have fallen for the ground to be moist and for temporary pools to begin to form, these salamanders begin their nocturnal breeding migration (NPWRC 2002). On rainy nights, the adults emerge from their underground burrows and roam, often more than a mile, to lay their eggs in these newly replenished vernal pools (CBD 2003). Males typically outnumber females and often precede females to the ponds (LaMonte 2002).

After the eggs are fertilized internally, a single female can lay up to 1300 eggs and deposit them individually or in small batches (CBD 2003). Shortly after breeding, adults will return to their terrestrial habitat (LaMonte 2002). Ten to 14 days later, larvae hatch from the eggs (CBD 2003). The pool in which they hatch is their home for the next 2 to 3 months (NPWRC 2002). For the first 6 weeks, the larvae are only able to eat small crustaceans, algae, and mosquito larvae. When they are large enough, they begin to take advantage of aquatic insects, invertebrates and tadpoles of Pacific treefrogs, California red-legged frogs, western toads, and spadefoot toads (CBD 2003). Once they reach metamorphosis, which is usually by late spring or early summer, juveniles are ready to roam to their terrestrial nesting habitat (Loredo 1996). These juveniles are known to disperse up to two miles from their natal ponds (CBD 2003).

Distribution
The California Tiger Salamander is endemic to California (Loredo 1996). Their range is not only geographically restricted to the state but isolated from any other salamander species (Loredo 1996). Historically, the California Tiger Salamander’s distribution was throughout California’s Sacramento and San Joaquin River Valleys, surrounding foothills and westward in the lower elevations of California’s central Coast (Barry 1994). The grasslands and woodlands areas of the central valleys and foothills are relatively xeric and are characterized by hot and dry summers followed by cool and wet winters. The California Tiger Salamanders are a stenotopic species. Their summer estivation and winter breeding habitat needs limit them to Mediterranean climate conditions and to areas where both winter ephemeral pools form and burrowing squirrels and gophers can be found. California’s central valleys, foothills below 1500 feet, and central coastal valleys meet these habitat conditions (Barry 1994, FWS 2003).
As is illustrated in the map below, the two coastal ranges of the Sonoma and Santa Barbara County populations are discontinuous from each other and from several populations in the valley and foothills (see figure 3) (Miller 2003). Today, California Tiger Salamander distribution is concentrated in the northern part of their historical range and their populations exist in disjunct vernal pool complexes (Miller 2003, FWS 2003). The limited distribution is due primarily to human induced habitat loss (Nickles 2003).

Figure 3: Distribution map of the

California Tiger Salamanders

populations (map courtesy of the ARMI

National Atlas for Amphibian Distributions,

 www.pwrc.usgs.gov/armiatlas.)

Figure 5: Fish and primitive tetrapod from the late Devonian period
(Carroll 1997)

Tracing the evolution of salamanders from their primitive amphibian ancestors has proven difficult for biologists. First, there is a lack of amphibian fossil records from the late Permian to the Jurassic period (Carroll 1988). There is also a significant difference in the morphology of Paleozoic/ early Mesozoic amphibians and today’s living frogs, salamanders, and caecilians (Colbert 1980). For this reason, the modern amphibians along with their late Mesozoic and Cenozoic ancestors are grouped in the subclass Lissamphibia which means ‘living amphibian’ (Carroll 1988). Secondly, there is continued debate over the true evolutionary relationships of the salamander (Larson 1993). In 1993, Larson published two possible cladograms for Caudata (Figure 6). In the first, Duellman and Trueb design a cladogram based on morphological differences in salamander families. In the second, Larson uses molecular differences to develop the evolutionary tree (Larson 1993).

Pleistocene fossil records indicate the North American Lissamphibia reacted to glacial advances and retreats by corresponding pattern of dispersal out and back from glacial areas (Carroll 1997). In California, a high percentage of amphibians are phylogenenetically distinctive (Shaffer 2001). Originally, biologists recognized the California Tiger Salamander as a subspecies of the geographically widespread tiger salamander (Ambystoma tigrinum). More recently, genetic comparisons indicate that the California Tiger Salamander is a genetically distinct species that is endemic to the state (Larson 1996, Shaffer 1994).

Conservation Challenges
The Sonoma population of the California Tiger Salamander is the northern most coastal population (Nickles 2003, FWS 2003). Genetically distinct and geographically isolated from other populations by nearly 50 miles, the Sonoma population lives on the Santa Rosa Plain, which stretches from the Santa Rosa to Cotati in Sonoma County (CBD 2003, Lanzendorfer 2002).This population is unstable and prone to extinction for a number of reasons, primarily the significant loss of breeding habitat. The species requires access to contiguous areas of ephemeral ponds, vernal pools or swales during their short breeding season (CBD 2003, FWS 2003). The distinguishing characteristic of this ecosystem is combination of standing water in winter with full evaporation in summer. This combination creates an ecosystem free of predatory fish, which is a critical condition for the survival of salamander larvae (NPWRC 2002). The Center for Biological Diversity suggests that a breeding pond complex surrounded by approximately 1000 acres provides the minimum acceptable habitat (CBD 2003). Much of the Santa Rosa Plain is already lost to agricultural production and urban/ suburban built environment. “Historically, vernal pools have occurred in the Santa Rosa Plain,” says research biologist Dave Cook, “Now their habitat has been restricted to one slim strip of land,” (Lanzendorfer 2002). Any remaining open 1000-acre segment of land in Sonoma County is undoubtedly under intense economic pressure to develop.

Introduced species also present conservation challenges for the California Tiger Salamander. Nonnative tiger salamanders have been introduced to the area as fish bait. One concern is possible out competing for resources or interbreeding with introduced species (FWS 2003). Studies find that, since no reproductive isolation between the endemic California Tiger Salamander and introduced tiger salamanders from the Great Plains has evolved, there is the potential for hybridization (Shaffer 2001). In addition, predatory fish introduced for mosquito abatement purposes pose a threat to the salamander larvae (LeMonte 2002).

Barry, Sean J., H. Bradley Shaffer. 1994. “The Status of the California Tiger Salamander (Ambystoma californiense) at Lagunita: A 50-year Update.” Journal of Herpetology 28(2): 159-164.

Carroll, Robert L. 1997. Patterns and Processes of Vertebrate Evolution. Cambridge: Cambridge University Press.

----------------. 1988. Vertebrate Paleontology and Evolution. New York: W.H. Freeman and Company.

Center for Biological Diversity (CBD). Center Moves to Protect Vanishing Amphibian under both Federal and California Endangered Species Acts. [Online]. Available: http://www.biologicaldiversity.org/swcbd/species/ctigersal/ [Sept. 22, 2003]

Colbert, Edwin H. 1980. Evolution of the Vertebrates: A History of the Backboned Animals Through Time. 3^rd ed. New York: John Wiley & Sons.

LaMonte, Greg. (2002, 02, 8). AmphibiaWeb: Information on amphibian biology and conservation. [Online]. Available: http://amphibiaweb.org [Oct. 13, 2003]

---------------- (1993). “Phylogenetic Relationships of the Salamander Families: An Analysis of Congruence Among Morphological and Molecular Characteristics.” Herpetological Monographs. 7:77-93.

Loredo, Ivette, Dirk Van Vuren, and Michael L. Morrison. 1996. “Habitat Use and Migration Behavior of the California Tiger Salamander.” Journal of Herpetology 30(2): 282-285.

United States Department of Agriculture – Forest Service (USFS). Subsection 263Aj: Coastal Hills – Santa Rosa Plain. [Online]. Available: http://fs.fed.us/r5/projects/ecoregions/263aj.htm [Oct. 10, 2003]

Species Name: Ambystoma californiense Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Amphibia Subclass: Lissamphibia Order: Caudata Family: Ambystomatidae Genus: Ambystoma Species: Ambystoma californiense
	Figure 1: California Tiger Salamander (© 2000 Joyce Gross)