Taricha granulosa


     Adult Rough-skinned Newts feed carnivorously mostly on soft-bellied, slow-moving prey and aquatic invertebrates at night. A list of a few of the kinds and types of creatures that adult newts prey on are as follows; small tadpoles, amphibian eggs and larvae, other salamander eggs and frog eggs, crustaceans, insects, arachnids, mollusks, annelids, freshwater sponges, and occasionally small fish (Amphibiaweb 2013). Larval newts prey mostly on protozoans which are scraped off of rocks and the occasional insect larvae or small crustacean. Large larval newts have also been known to eat smaller larval newts. Adults hunt their prey in a slow determined fashion before quickly snapping at it and causing a suction to pull and swallow the prey, larger prey are sometimes grasped in its jaws (Amphibiaweb 2013). Algae and plant matter have also been found in the stomachs of newts although in small quantities thought to be accidentally ingested with other foods (Amphibiaweb 2013).

    Due to the Rough-skinned Newts high levels of tetrodotoxin it has very few natural predators. Thamnophis sirtalis, the Common Garter Snake, has developed, through coevolution, strong resistance to the effects of tetrodotoxin therefore the newt can be eaten with little to no side effects (Ridenhour et al. 2007). This is known as a predator-prey arms race, where the prey evolves higherAn adult Rough-skinned Newt being eaten by an adult Garter Snake. Used with permission from Edmund D. Brodie III. concentrations of toxin and the predator evolves higher resistance (Brodie III and Brodie Jr. 1999). Over time this brings about species of extremely high toxicity, many times more so than is necessary, as one newt is toxic enough to kill an estimated 25,000 mice (California Herps 2013). Levels of toxicity and toxicity resistance in both species vary with geography, with some populations of newts being less toxic and thus the Garter Snakes of that area being less resistant to the tetrodotoxin (Ridenhour et al. 2007).  A picture of a newt being eaten by a Gartner Snake, despite its high toxicity, can be seen on the right side of the page. According to Gall et al. (2011), Rough-skinned Newts can pick up on chemosensory cues from common garter snakes and other Rough-skinned Newts. These cues can let the newt know if there was a newt that was injured near it or if there is a garter snake that has eaten a newt nearby. The newt will avoid the Garter Snakes that have previously successfully eaten a newt but will not avoid Garter Snakes that haven’t eaten a newt or other newts giving off cues of injury (Gall et al. 2011). Other animals have been found to attempt to eat Rough-skinned Newts but are usually found dead, such as Bullfrogs and birds (Amphibiaweb 2013).

    Rough-skinned newts have been found coexisting with other newt and salamander species such as Ambystoma gracile the Northwestern Salamander, T. torosa- California Newt, and T. rivularis the Red-bellied Rewt. Rough-skinned Newts tend to exclude the California Newt from their habitat more than the other species of newt (Amphibiaweb 2013). When the rough-skinned newt shares a habitat with the Northwestern Salamander the adult newt is smaller in size compared to populations of newts that exist without the salamanders (Amphibiaweb 2013). This is probably because of competition for food, resources and breeding grounds.

    The Rough-skinned Newt is often sold as a pet under the name “Oregon-newt” or “Orange-bellied Newt”. Calling it an Oregon-newt, however geographically accurate, would not be an accurate description because it is illegal to commercially collect newts from Oregon for the pet trade, so one would likely be getting a Rough-skinned Newt from California (Caudata 2002). They are not an endangered or threatened species and the only conservation issue is deforestation of their breeding grounds which doesn’t represent a huge impact (California Herps 2013). The Rough-skinned Newt is safe to handle as long as it is not ingested, although one should wash their hands after handling the newt. There is some evidence that UV-B light has a negative effect on the newt, but not a lot of research has been done in that area (California Herps 2013). Other animals that have tetrodotoxin in their skin are the Pufferfish and the Blue-ringed Octopus as well as other newts of the genus Taricha (TTX 2001). For more information on Tetrodotoxin see Tetrodotoxin.

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