Rough-skinned newts – surprisingly toxic 

click to enlarge A rough-skinned newt.
  • A rough-skinned newt.

Whistler Naturalists

Participating in the BioBlitz was a great experience. It gave a plant person like me a chance to get to know some of the critters in our valley. On display at Lost Lake (to name a few) were a deer mouse, a shrew, a garter snake, a northwestern salamander, western toads, sticklebacks, and some of the coolest bugs, slugs and worms I’ve ever seen. One creature that I saw for the first time in Whistler, shown to me by local expert Conner McGillion, was the Rough-skinned newt. Apparently this little creature carries one of the most toxic substances in nature.

The Rough-skinned newt is a type of salamander known as Taricha granulosa in the science world. Taricha is Greek for preserved mummy, possibly referring to the rough skinned appearance and granulose is Latin for full of small grains, referring to the rough skin of terrestrial adults. Like other amphibians it breathes through its skin and is highly sensitive to the environment it is in. It is a good rule of thumb to never handle amphibians since any cream/sun screen/bug spray from a hand can be harmful, and even the temperature of a hand can feel like a burn to the little creatures.

The Rough-skinned newt is found along the coast from California to Alaska, and the newt I saw during BioBlitz was found in Lost Lake. Eggs are laid on submerged vegetation and hatched larvae have bushy gills, a large tail fin and balancers (a pair of appendages projecting from the side of the head and arising before the forelimbs develop). They will undergo metamorphosis into land dwelling adults 4-5 months to a year after hatching, and after spending some time on land will mate in quiet water habitats — where the cycle begins once again.

Adults are 10 to 20 cm in length and from above they are brown, but from below they are a bright yellow or orange colour. This bright colouring is a warning to potential predators that it is toxic. When threatened the Rough-skinned newt will display a body posture called the unken reflex, a rigid U-shaped posture that reveals the bright orange ventral coloration, and release toxic skin secretions.

If this anti-predator mechanism doesn’t work, this is when the Rough-skinned newt relies on its chemical defenses — a potentially fatal toxic substance when ingested. This toxic substance is called tetrodotoxin and is a potent neurotoxin that is concentrated in the skin, ovaries, muscles, and blood of adults. There is a story that a group of campers were once mysteriously found dead. After investigation, the reason for their deaths was discovered to be from drinking toxic tea caused by a Rough-skinned newt that had unknowingly crawled into their tea kettle.

Because of their toxicity the newt has few predators, with the exception of the Garter snake. Garter snakes and Rough-skinned newts have a great co-evolutionary tale. Through time as the Garter snake evolved a resistance to the Rough-skinned newt’s chemical defenses, the newt would develop defenses with greater and greater toxicity. Even today, highly toxic-resistant Garter snakes are found in areas with highly toxic Rough-skinned newts, whereas Garter snakes that are not as toxic-resistant are found in areas with Rough-skinned newts that are not as toxic.

It was great to see all those who participated in BioBlitz. If you didn’t get a chance to check it out, there’s always next year.


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