Warren Pond in southern Connecticut, bordered by shady oaks and maples, is a lovely place to fish for bass or sunfish. Or, if the mood strikes you, to hunt the Eastern red-spotted newt. Why one would want to hunt newts is a valid question. But for Evan Grant, who was stalking the banks of Warren Pond this month, scanning the water through polarised sunglasses, the answer is that many species of salamander in the United States, including the newts he was seeking, may be on the brink of a deadly fungal assault, much like the one that has devastated some frog and toad populations worldwide.
In 2013, scientists discovered that a fungus called Batrachochytrium salamandrivorans, commonly known as Bsal, was attacking salamanders in Europe. Researchers later determined that species in the United States were vulnerable to the infection. And earlier this year, the US Fish and Wildlife Service temporarily banned the import of 201 species of salamanders that pose a danger of carrying the fungus into the United States. The wildlife service has proposed a permanent ban, and just finished a public comment period on that proposal. The service will make a final decision in the coming months.
In the meantime, the US Geological Survey (USGS) is monitoring vulnerable salamander populations to catch any early signs of infection. So far, researchers have not found evidence of Bsal. Evan, a research wildlife biologist with the agency’s Amphibian Research and Monitoring Initiative, has been up and down the East Coast, catching red-spotted newts, swabbing their skin to check for infections and sending samples to the National Wildlife Health Center in Wisconsin.
In mid-May, he put on rubber boots and shouldered a long-handled dip net to explore the pond, in Newtown, Connecticut, with Adrianne Brand, a wildlife biologist who is also with the initiative. Not that anyone really needs a reason. Newts, and salamanders in general, are just plain cool. They do not simply grow from egg to adult the way mammals or reptiles do. They have several stages, from egg to larva to adult, and in any given species, they may skip a stage, change whether they live in water or on land, grow lungs or stick with gills. Some absorb oxygen through their skin, and skip both lungs and gills. Newts, in particular, are like ecological utility infielders, switching habitats and physiology depending on what is needed for the game of staying alive.
The two researchers found no newts in the pond, so they moved on to a swampy patch in the woods of Paugussett State Forest, down a hillside from a suburban cul-de-sac. The water, about knee high, was dark with detritus, and surrounded by thickets. After a few minutes of swishing his net through the water, which ran over the top of his boots, Evan called out, “Yo! Newt!” The catch was about 3-inches-long, identifiable as a male because of the shape of its tail and rough patches on the inside of its hind legs, with a dark greenish brown colour and red spots that warn predators of toxins in the skin.He swabbed the skin and snipped off the ends of the swabs for testing.
The United States is considered a global treasure trove of salamander diversity, and the USGS study is concentrating on sampling a few areas that have species like the newt, known to be vulnerable to Bsal, and are close to ports where animals in the pet trade are imported, like New York and New Orleans. From 2004 to 2014, according to the Fish and Wildlife Service, about 2.5 million salamanders were imported into the United States for the pet trade, many from Asia, where the fungus seems to have originated.
Crossover
Scientists believe it was the importation of salamanders to Europe that led to the appearance of the fungus in the Netherlands, Belgium and the United Kingdom. Salamanders may serve as a kind of early warning system for environmental problems, and they are deeply embedded in forest ecosystems, so their reduction or disappearance could have unpredictable consequences. But scientists have always been fascinated by a kind of flexibility in their life histories that is not seen in most vertebrates.
The newt is a prime example. Sean Sterrett, a wildlife ecologist with Penn State and the USGS, who works with Evan, said the newt emerges from an egg laid in the water as a tadpole-like larva, metamorphosing into a tiny salamander shape with gills. Many salamanders have flexible courses of development. Some, like hell benders, keep their gills and never leave the water. And salamanders have other oddities — some of the giant ones in China can grow to nearly 6-feet-long and smell like stale urine.
Others can poke the ends of their ribs out of their skin as a defence. And some engage in a kind of cannibalism that makes the worst playground bully seem like the Dalai Lama. These are the larvae of the tiger salamander. In any given clutch of eggs a few grow particularly big heads. “The big heads are adapted to eating other larvae,” said Sean. The cannibals thrive on the nutritious sibling diet, and do not look any different as adults.
Of course, salamanders themselves suffer predation, even with their toxic skin. “Raccoons skin them,” Evan said. “You sometimes come to a pond and you find a pile of salamander skins.” But not the heads. The raccoons apparently like the brains. Evan and Adrianne caught only five newts at the suburban slough, so they planned to go back for more sampling. The survey of newt populations is about half-done, Evan said, and so far no Bsal has been detected. If it does appear, he hopes by then they will know more about which areas have thriving populations and how to protect them.