Juveniles live on land for four or five years after metamorphosis. Adults are amphibious, and live in water and on land. Eggs are laid in water. They can be found especially after there has been a lot of rain.
Many newts make toxin in their skin to avoid predation, but the rough-skinned newt is especially poisonous. Toxicity is generally experienced only if the newt feels threatened, although sometimes skin irritation can be experienced after touching it.
Throughout much of the newt’s range, the common garter snake (Thamnophis sirtalis) is resistant to the newt's toxin. In several populations, these snakes successfully prey upon the newts. Toxin resistant garter snakes are the only known animals today that can eat a T. granulosa newt and survive.
This is an example of co-evolution. The snake’s resistance to the toxin has resulted in a selective pressure that favours newts which produce more potent levels of toxin. Increases in newt toxicity then apply a selective pressure favouring snakes with mutations conferring even greater resistance.
This cycle of a predator and prey co-evolving is sometimes called an evolutionary arms race. In this case it results in the newts producing levels of toxin far in excess of what is needed to kill any other conceivable predator.
Toxic animals usually warn predators that they are not good food. There's no point in being toxic unless it helps survival and reproduction. The underside of these newts is vividly coloured a yellow-orange. When a threat appears, the newt curls up its tail and lifts its head to show the warning colour. This can be seen in photographs.
- Photos of newts "Taricha granulosa granulosa – Rough-Skinned Newt". California Herps. Retrieved 2006-12-10.
- American Book Company, Liz Thompson (2006). Passing the New Jersey High School Proficiency Assessment in Science. American Book Company. p. 106. ISBN 1598071033.
- Geffeney, Shana L. et al. 2005. Evolutionary diversification of TTX-resistant sodium channels in a predator-prey interaction. Nature 434: 759–763.
- "Rough-skinned Newt". mbgnet.net. Retrieved 7 April 2011.