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The California newt or orange-bellied newt ( Taricha torosa), is a species of newt endemic to California, in the Western United States. Its adult length can range from . Its skin produces the potent toxin tetrodotoxin.
The egg mass released by the female contains between seven and 30 eggs, and is roughly the consistency of a thick gelatin dessert. Typically, the egg masses are attached to stream plant roots or to rocky crevices in small pools of slow-moving water, but they have also been known to be attached to underwater rocks or leaf debris. While shallow in a wide sense, these pools are rather deep relative to the average depth of a Southern California stream, varying in depth from about .
Adult newts typically leave the pools shortly after breeding has concluded, however, some adults may remain in the pools for an additional few months to feed. Larvae hatch sometime in early to midsummer, depending on local water temperature. Larvae are difficult to find in streams, as they blend in well with the sandy bottom, to which they usually stay close.
The size of maternal eggs influence the sizes of larvae. The larvae from larger eggs will not only experience shorter time period on Metamorphosis than larvae from smaller eggs, but also grow larger.
In terms of asserting territoriality, California newts tend to exhibit aggressive behavior in order to mark their territory. This is especially the case between males, as California newts tend to be more gregarious and assertive in breeding season. Shortly after breeding season, the California newt tends to revert back to more solitary behavior in both the aquatic and terrestrial phases of its life cycle. This pattern applies to both their aquatic and terrestrial phases, with individuals becoming less social outside of mating contexts.
In addition to its bright coloration, the California newt has developed the ability to secrete a foamy substance when exposed to high temperatures. This adaptation is particularly useful in fire-prone environments such as the coastal regions of California. The foam acts as a barrier as it forms a protective layer that helps the newt retain moisture and shield itself from burns during wildfire events.
The vocalizations of California newts are functional and are usually related to defense and sexual behaviors. They have three primary vocalizations: clicks, squeaks, and whistles. Clicks are most frequently produced, usually occurring in response to unfamiliar environments or confrontations. Squeaks are associated with defense behavior and may serve to startle predators, potentially reinforcing the recognition of the species as toxic. Whistles appear to be related to sex recognition or hierarchical interactions.
Due to their toxicity, California newts have few natural predators. Garter snakes are the most common, and some species have developed a genetic resistance to tetrodotoxin. The mutations in the snake's genes that conferred resistance to the toxin have resulted in a selective pressure that favors newts that produce more potent levels of toxin. Increases in newt toxicity then apply a selective pressure favoring snakes with mutations conferring even greater resistance. This evolutionary arms race has resulted in the newts producing levels of toxin far in excess of what is needed to kill any other conceivable predator.
Taricha torosa has also been known to utilize the "unken reflex" in response to threats from predators. In this posture the California Newt stretches out flexes the dorsal side of their body shooting their head and tail into the air, and exposing their brightly colored underbelly. This variation of the unken reflex seems to be species-specific and differs from Taricha granulosa due to the tail remaining straight instead of curling.
Introduced as fish bait and stock pond prey, red swamp crayfish are an incredibly aggressive, prolific, and stalwart species that will prey upon newt larvae and egg masses. The crayfish will also disrupt newt breeding via competition for space during the summer mating season and physically antagonizing adults. Crayfish will typically maul the adult newts with their claws, and subsequent infection can lead to death. Taricha torosa that are present in streams with introduced crayfish often sport tails with several notches removed.
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