It’s wet out there. It’s mud time, mushroom time, the Season of the Newt.
In Tilden Regional Park (where the annual road closure is in effect), in Briones, in a hundred secret places across the spongy landscape, the brown-and-orange amphibians have gathered to mate. They may trek for considerable distances, from the standpoint of a six-inch salamander, to get to their traditional meeting sites.
California newts appear to smell their way to their destination, following pheromone trails. They may also rely on some kind of poorly understood kinesthetic sense; laboratory subjects have been found to become disoriented after being whirled around in containers.
Once they’ve reached their goal, male newts wait at the shoreline for females. A male that has found a partner may be joined by other hopefuls, forming what is known as a newt knot. Newts are not at all shy about the process; mating can take place in broad daylight, in front of God and everybody.
You would think the preoccupied amphibians would be vulnerable to predators during this amatory frenzy. But they’re not, and they seem somehow to know that. They’re also not particularly secretive as they migrate.
Our local California newts, and their close relatives the red-bellied and rough-skinned newts, are loaded with a potent poison called tarichotoxin, essentially the same as the tetrodotoxin—TTX for short—that makes puffer fish a lethal meal. Think of newts as ambulatory fugu. The substance is also similar to saxitoxin, present in the microorganisms that cause “red tides.”
Whatever you call it, the newt’s secret weapon is the most poisonous nonprotein known to science. It’s a neurotoxin that kills by blocking sodium channels through which nerves activate muscles. With the chest muscles paralyzed, death by asphyxiation follows. Bits of newt skin have proven fatal to fish, frogs, reptiles, birds, and mammals. And we know that a single newt contains enough TTX to kill an adult male human.
That fatality took place in 1979, when a 29-year-old college student in Coos Bay, Oregon got newt-swallowing drunk and ingested a rough-skinned newt on a dare. (I have spent time in Coos Bay, a dismal little lumber town, and can understand how the place might be conducive to extreme behavior). Within 10 minutes the victim’s lips began to tingle; numbness and weakness followed, then cardiopulmonary arrest. In another incident, a scientist who got newt toxin into a puncture wound on his index finger survived, but the affected arm went numb up to the shoulder for half an hour.
Like many toxic creatures—insects, sea slugs, other amphibians like the tropical arrow-poison frogs, even one bird, the pitohui of New Guinea—western newts advertise their inedibility with bright colors. A perceived threat triggers what herpetologists call the “unken reflex”: The newt arches its body downward, throws its head back, and extends its tail over its back, showing off its orange or red undersurface. This seems to give would-be predators pause.
Newts are also similar to other distasteful animals—the monarch butterfly, for instance—in serving as models for edible (if you don’t object on principle to eating salamanders) mimics. There’s another California salamander called the ensatina, which, depending on location, can be blotched or mottled with black and yellow or black and orange. Where its range overlaps with the California newt, though, the ensatina matches its brown back and orange belly, and even its yellow eye color.
Monarch butterflies, of course, are protected by chemicals from the milkweed plants they fed on as caterpillars. Where does the newt’s defense come from? Good question.
Other toxic amphibians do acquire their protection from their food. Along with wallabies, chameleons, and other exotics, arrow poison frogs native to Panama and Costa Rica have gone feral in Hawaii. The Central American populations contain a formidable brew of alkaloids; their descendants on Oahu, though, lacked most of those compounds, while some contained chemicals not found in the ancestral group. With insufficient time for radical evolutionary changes, the different diet of the Hawaiian frogs seems the most likely explanation. Recent research demonstrates that the frogs do acquire a toxic alkaloid from their insect prey, then modify it to make it 5 times more potent.
So newts may also be appropriating the chemical defenses of the insects they eat. But other lines of research implicate bacteria in the toxicity of the fugu fish, whose poison, TTX, is similar to the newt’s. TTX-producing bacteria have been found in algae, which are eaten by fish, crabs, and other sea creatures; some, including the notorious blue-ringed octopus of Australia, concentrate enough of the substance to inflict lethal bites. Something similar may be going on in the freshwater food chains that culminate in the newts, although the specifics are unclear.
No defense is perfect, though. A newt may be a fatal mouthful for most predators, but the common garter snake has evolved immunity to its toxin. (Some common garter snakes are more common than others: The endangered San Francisco garter snake, arguably North America’s most beautiful serpent, is a form of this species). Garter snakes and newts appear to be locked in a chemical arms race, ratcheting up to higher and higher levels of toxicity and resistance.
Newts aren’t out to get people; they have entirely different things on their minds. They’re harmless enough if not taken internally. So admire them from a distance, and contemplate their role in the work of the late Frank Zappa (remember the recurring newt motif in 400 Motels?) And if you do happen to pick one up, wash your hands!