A stocky, large-bodied salamander. Dorsal coloration varies from light brown to blackish brown. The venter is light yellow to orangish red. Upper and lower eyelids are dark. The iris is yellow and the eyes are relatively small. This species has a dry, warty skin, except in mating season when adult males develop a smooth, even slimy, skin. The skin of both males and females is lighter colored during the mating season. Adults are 5.6-8.7 cm snout to vent length (12.5-22 cm total length). Some populations have adults which retain gills (Stebbins 1985; Petranka 1998). Hatchlings are 8-12 mm total length (Stebbins 1951; Riemer 1958). Larvae are pond type with busy gills ande a tail fin which extends foward to the shoulder area. Young larvae have a weak dorsal stripe which becomes diffuse a few weeks after hatching. The color pattern of older larvae is a mottled or reticulate pattern of pigmentation, usually with two rows of light spots on the sides of the body. A dark stripe extends from the nostril to the eye. Populations of T. granulosa in and around Crater Lake, Oregon, are sometimes treated as a distinct subspecies (T. g. mazamae) based on the presence of dark blotching on the venter (Nussbaum and Brodie 1981; Stebbins 1985; Petranka 1998).
Taricha granulosa may be distinguished from T. torosa by the V-shaped pattern of the palatine teeth (compared to Y-shaped), dark lower eyelid, and less protruberant eyes. These species also differ in their defensive posture (see below) (Stebbins 1985).
This species was featured as News of the Week on 28 September 2020:
Dangerously poisonous newts (Taricha granulosa), which sequester the toxin tetrodotoxin (TTX), and predatory garter snakes (Thamnophis sirtalis), which can evolve TTX resistance, are engaged in a classic coevolutionary arms race. While generally roughly matched, in western Oregon and Washington other factors are important. While local adaptation dominates, a study (Hague et al. 2020) of geographic variation found that toxin levels are clearly predicted by the phylogeographic population genetic structure of newts and by factors in local environments. Still, predators have higher levels of resistance than the toxins of co-existing newts, suggesting intense selection. What at first seems to be intense arm race coevolution is shown to be a landscape level pattern-- a geographic mosaic of coevolution based on a mixture of often intense natural selection as well as demographic and environmental effects. This study enriches our understanding of this fascinating phenomenon, which is taking place over a large expanse of time and space (Written by David B. Wake).
This species was featured in the News of the Week, 11 May 2020:
Many salamandrids possess tetrodotoxin (TTX), the same neurotoxin found in pufferfish. Although TTX in marine animals derives from symbiotic bacteria or diet, the source in amphibians has been controversial. Populations of rough-skinned newts (Taricha granulosa) possess different amounts of TTX due to the evolution of TTX resistance in populations of predatory garter snakes. Vaelli et al. (2020) examined the skin microbiome in high- and low-TTX populations of newts and found that bacterial diversity was lower in the highly toxic population, suggesting their skin microbiota is tightly regulated. Several strains of bacteria, particularly Pseudomonas, cultured from the skin of toxic newts were shown to produce TTX in the lab, and Pseudomonas were significantly more abundant in toxic than non-toxic newts. The ability of rough-skinned newts to resist TTX appears to derive from mutations in the target of the toxin, voltage-gated sodium channels (NaVs); all six NaV genes possess mutations in the TTX-binding region of the channel, and electrophysiological experiments with the most widely expressed channel (NaV1.6) verify the mutations confer resistance to almost infinite concentrations of TTX. They show an important role that symbiotic microbes play in the physiology and evolution of their multicellular hosts. (Heather Eisthen and Patric Vaelli)
This species was featured in the News of the Week, 4 April 2016:
The Rough-skinned Newt, Taricha granulosa, is engaged in an evolutionary arms race with its only known significant predator, the Common Garter Snake, Thamnophis sirtalis. In regions where snakes are absent (such as some islands near Vancouver Island, Canada), newt toxicity is low to absent, whereas in sites where toxicity-resistant snakes are common (various sites in California and Oregon), newt toxicity is high to very high. The authors of a new paper (Hague et al. 2016) studied newts in southeast Alaska, where snakes are absent, and as expected, toxicity levels were low at most sites examined. However, puzzling variation was found. In one lake on Wrangell Island, no toxicity was found, but newts from another lake on the same island displayed surprisingly high levels, rivaling those in some areas where snake predators have high toxin resistance. Various explanations are offered, but reciprocal selection does not fully explain the toxicity variation in newts (David B. Wake).
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This species ranges from southwestern Alaska, along the coast of North America through British Columbia, Canada, Washington, Oregon, and California to the San Francisco Bay area. Terrestrial habitat is forests in hilly or mountainous areas, occasionally grasslands or pastures. Aquatic habitat includes seasonally ephemeral ponds, as well as lakes and sluggish areas of streams. Rarely found in fast-flowing water (Riemer 1958; Stebbins 1985; Petranka 1998).
Populations in Idaho are considered introduced by the Idaho State Department of Fish and Game (https://idfg.idaho.gov/species/taxa/15503).
Rough-skinned newts migrate annually to and from their aquatic breeding sites. Migration occurs primarily in rainy weather when the temperature is >5º. Breeding season varies with latitude, and has been recorded over most months of the year with a peak from March to early May. Courtship includes a period of amplexus of the female by the male. During amplexus, the male rubs his head over the females. Fertilization is internal by means of a spermatophore, deposited by the male on the substrate and picked up by the female in her cloaca. Oviposition takes place shortly after mating. Eggs are layed singly, attached to submerged vegetation, rootlets, or detritus. (Nussbaum and Brodie 1981; Petranka 1998). Development time and length of the larval period vary geographically. Larvae eat small aquatic invertebrates. Prey of adults includes aquatic and terrestrial invertebrates, and also amphibian larvae and eggs (Petranka 1998).
While T. granulosa is the most toxic newt in North America, all species of Taricha possess the potent neurotoxin known as tetrodotoxin. This serves the newt as an antipredator defense, and is also harmful to humans (Brodie et al. 1974; Petranka 1998). Despite their toxicity, newts are subject to predation by racoons and garter snakes (Thamnophis.) Thamnophis sirtalis is a specialist predator on newts and has evolved resistance to the tetrodotoxin (Brodie and Brodie 1990; Petranka 1998; Motychak et al. 1999). When harassed, Taricha assume the “unken reflex” where the head is raised, the tail is turned up and held straight over the body, the limbs are extended, and the eyes are closed (Riemer 1958; Brodie 1977). This action exposes the bright aposomatic coloration found on the newt's belly. The exact pattern of this reflex is a species-specific character, distinguishable from sympatric T. torosa, which holds the tail straight, while T. granulosa curls the tip (Stebbins 1985; Petranka 1998).
Regional differences exist in the preferred habitat of T. granulosa. Populations in the Cascades and Coast Range of Washington are most dense in mature and old-growth forests (Aubry and Hall 1991; Corn and Bury 1991), while popuations in the Oregon Cascades are relatively dense in younger stands. These differences should be considered for species management. Logging has a negative impact on the terrestrial habitat and migration corridors of this species and this should be investigated in detail (Petranka 1998).
The most toxic newt, Taricha granulosa has been responsible for severe illness and even death of people who have eaten it (e. g., Petranka 1998). Care should be taken when handling these animals. Wash hands after holding newts and do not touch eyes or mouth area.