California Tiger Salamander
Written By Tara Johnson-Kelly & Geoff Cline
As you drive through central California, you may look out your window and see a beautiful landscape of rolling foothills and wide valleys blanketed by annual grassland and open oak woodlands. Within this landscape, you may see herds of grazing cattle and spy new ponds that filled after heavy winter rains. This idyllic scenery seems fitting for charismatic wildlife like the bobcat, coyote, and cougar, but what if we told you there was something just as special living underground?
What is a California Tiger Salamander?
California tiger salamander larvae with external gills. Photo By: Robert Shields
Deep within a burrow dug by a California ground squirrel lives an adult California tiger salamander (Ambystoma californiense). It is an amphibian, like a frog, that is found only in the Central Valley, bordering foothills, and coastal valleys and foothills of central California (Storer 1925). It is roughly eight inches long and shaped like a lizard, with a smooth, stout body and flattened tail, four legs that stick out to the sides, and a broad, flattened head with a wide mouth that looks like it is smiling. Small eyes poke out to the sides from the top of its head. It is mostly black and, unlike its tiger namesake, is not striped but rather spotted with white to yellow blotches on its back and sides. During the dry summer and autumn, it remains in the burrow for most of the time and feasts on whatever insect prey it can fit in its mouth (Loredo et al. 1996). When rain arrives in late autumn and winter, it emerges from the burrow at night and migrates up to around one mile across the grassland in search of a seasonal pool (Loredo and Van Vuren 1996). When it reaches the pool, it gathers with other salamanders, breeds, and lays its eggs on emerging wetland plants. Soon after breeding, the adult leaves the pond at night and travels across the grasslands again in search of another burrow to call home.
Two to four weeks later, the eggs laid in the pool begin to hatch into aquatic larvae, like frog tadpoles (Storer 1925, Twitty 1941). The larvae are yellowish gray, have a flattened head with feathery external gills, and a long tail-fin (Stebbins 1951). Like the adults, they eat what they can fit in their mouth, including algae, aquatic invertebrates, and other amphibian larvae, even each other (Anderson 1968). The larvae develop rapidly. They grow limbs, reabsorb their feathery gills and tail-fin, and metamorphose into their terrestrial form in late spring or summer, just before the seasonal pool dries up (Storer 1925, Holland et al. 1990). These metamorphosed larvae emerge from the pool and travel over the grasslands in search of burrows of their own.
California tiger salamanders are patient creatures. They can live for about eight years in the wild and are adapted to survive prolonged drought conditions. During drought years, the seasonal pools they rely on for breeding may not fill up at all, preventing local populations from reproducing. However, because this species is long-lived, the local population can survive through all but the longest droughts until favorable conditions return.
Are they legally protected?
Yes, depending on their location, regional populations of the California tiger salamander are listed as threatened or endangered under the federal Endangered Species Act (ESA), while all regional populations are listed as threatened under the California Endangered Species Act (CESA). This means that any activity that might harm the salamander or its habitat may require a permit and conservation actions.
You might ask yourself: “Why bother protecting a salamander? What does it do for me?” Well, the California tiger salamander can be viewed as a form of natural pest control and an indicator of ecosystem health. They eat invertebrates that feed on the roots of grassland plants. If these invertebrates did not have predators, they would overpopulate the grasslands and destroy the habitat for all the other organisms that live there. Salamanders, in turn, provide food for countless other organisms in the food chain. If salamanders are absent from their typical habitat, it tells us that something is wrong in the ecosystem. The water quality may be too poor, or the food chain may be in collapse due to the introduction of an insatiable invasive species. Scientific research on the California tiger salamander has shed light on exactly how it fits into the food web and how its presence benefits the greater ecosystem. Additionally, protecting the California tiger salamander and its habitat ensures that California retains vital areas of open space for the enjoyment of its citizens and the benefit of other native wildlife.
What threats do they face?
The California tiger salamander is in decline due to several compounding threats: habitat loss and fragmentation, predation by and hybridization with invasive species, and climate change.
The California tiger salamander’s range once extended throughout the grasslands and open oak woodlands of central California’s valleys and foothills (Storer 1925). This region was characterized by a Mediterranean climate of cool, wet winters and hot, dry summers. The grasslands here were composed mostly of native perennial grass species mixed with annual grasses and forbs, and scattered throughout the landscape were thousands of seasonal pools (Sims 1988). Today, California looks drastically different. Over the past 150 years, the California tiger salamander has lost roughly three-quarters of its former range to the conversion of grasslands to industrial agriculture and urban development. Seasonal pools and small mammal burrows are destroyed during such land development, killing untold numbers of salamanders (Barry and Shaffer 1994). This development not only destroys habitat but breaks up larger areas into much smaller and poorer quality fragments, which can break up populations.
Another reason for the California tiger salamander’s decline is predation by, and hybridization with, invasive species. California tiger salamanders evolved to breed in seasonal pools devoid of fish and other predators. In recent decades, humans have stocked many of these breeding pools with nonnative fish, bullfrogs, and salamanders for sport. Nonnative fish and bullfrogs are prolific predators of amphibian eggs and larvae, capable of wiping out entire generations of California tiger salamanders (Sorensen 1994). This inevitably leads to population extirpation, or localized extinction. Aside from increased predation, invasive species can also threaten native species through hybridization. Beginning around 1950, bass fishermen began introducing nonnative barred tiger salamander larvae (Ambystoma mavortium) into ponds within the range of the California tiger salamander (Riley et al. 2003) because barred tiger salamander larvae survive longer and are more active on a fish hook than California tiger salamander larvae. Despite being distantly related and a genetically distinct species, the two types of tiger salamanders began to successfully interbreed with each other, producing viable populations of hybrid salamanders (Riley et al. 2003). This hybridization may seem benign, but when combined with habitat loss and fragmentation, it can drive a native species towards extinction through gene loss.
Climate change is the final compounding threat to the persistence of the California tiger salamander. Over the past few decades, we have witnessed changes in the amount and frequency of annual precipitation in California. Autumn and winter rain events that trigger salamander reproduction have been less intense and less frequent in recent years. This means that some California tiger salamander populations may forego breeding entirely if there has not been enough rainfall (Barry and Shaffer 1994), or the pools that do fill with rain dry up long before the salamander larvae can metamorphose. Although this trend may be bleak, there is still hope. Adult salamanders can live for about eight years, so there is still a chance that when rainfall conditions are right, a new generation of California tiger salamanders will survive.
LOA biologist Robert Shields with numerous California tiger salamander in a seine. Photo by: Geoff Cline
What conservation efforts are being performed?
Research, permitting and mitigation, and holistic ranching practices have all contributed to the preservation and recovery of the California tiger salamander.
Scientific research on the life history, habitat requirements, current range, and threats to the species’ survival is one of the greatest tools for conservation available. Research informs legal policy and development of effective methods for mitigating impacts to the species.
When a developer decides to build in California, they are required to undergo California Environmental Quality Act (CEQA) review, which analyzes and identifies potentially significant impacts to air quality, biological resources, etc. If the CEQA process finds that a California tiger salamander or its habitat may be impacted by the project, the project must mitigate for these impacts and secure the necessary permits issued by the USFWS and CDFW. The CEQA document, CDFW Incidental Take Permit, and USFWS Biological Opinion or Habitat Conservation Plan may require measures such as completing avoidance, preconstruction surveys, burrow excavation and relocation of California tiger salamanders, construction and maintenance of exclusion fences, and preservation of habitat in perpetuity or purchase of mitigation credits. These regulatory tasks require time and additional costs for developers.
Another conservation effort includes guiding ranchers to utilize practices that benefit California tiger salamanders. Ranchers can help them by grazing or not grazing at certain times of the year and installing cattle ponds or other seasonal ponds that only hold water during their breeding season. Some landowners have even turned their lands into mitigation banks, which allows them to continue grazing cattle while managing their land in support of California tiger salamanders and by selling credits to developers to mitigate for project impacts to other California tiger salamander habitats.
Fun Facts
Adult California tiger salamander entering a California ground squirrel burrow. Photo By: Tara Johnson-Kelly
California tiger salamanders are part of a family of salamanders known as “mole salamanders” or Ambystomatidae. The term “mole salamander” is derived from the fact that these animals spend their days underground in small mammal burrows. Mole salamanders are only found in North America.
Scientists have discovered that local California tiger salamander populations impacted by nonnative species can be slowly recovered by either allowing breeding ponds to fully dry up at the end of each breeding season or by physically removing the invasive species from the pond.
California tiger salamanders have also been found breeding in atypical habitats such as seasonal cattle stock ponds, slow sections of seasonal and perennial creeks, and other man-made structures that capture water during the breeding season (Alvarez et al. 2021).
In captivity, California tiger salamanders can live up to 30 or more years.
California tiger salamanders have poisonous pores on their backs, which can sometimes prevent animals from eating them. Some animals have learned to skin them to avoid the poison.
When California tiger salamanders run out of food in their burrow, they will sometimes move to a different burrow, even if it is not raining.
You can age a California tiger salamander by looking at the number of rings on their toes.
California tiger salamanders and other amphibians and reptiles never stop growing. Once they become adults, their growth just slows down but does not stop.
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