Courtesy of Arizona State University
Tiger salamanders like this young, healthy specimen show few symptoms of infection until they are dying.
It’s no secret that amphibians have been having a hard time of it lately. They are declining worldwide, but exactly what’s killing them—is it ultraviolet light from an eroded ozone layer? pesticides run amok? a deadly fungus?—is unclear. A new study adds another, unexpected possible culprit: Fishermen toting store-bought salamanders as bait for largemouth bass may be unwittingly transporting a lethal disease from pond to pond.
When scores of tiger salamanders started going belly up in cattle watering holes statewide, ecologist Jim Collins of Arizona State University teamed with doctoral student James Jancovitch to investigate. They identified the cause of death as an iridovirus, similar to a virus that afflicts frogs. The surprise came when the scientists performed a genetic analysis of the iridoviruses from similar die-offs all around the Rocky Mountains. Some closely related viruses turned up at far-flung sites in Arizona and Canada, while distantly related viruses appeared among dead salamanders recovered from within a single pond.
The pattern was so strange, it seemed as though the animals could fly. And maybe in a sense they did—in the bait buckets of fishermen. Collins and Jancovitch examined salamanders from a Phoenix bait shop and found viral strains similar to those killing salamanders in Colorado. “Salamanders being moved around as bait are functioning like Typhoid Mary,” Collins says. If his theory proves true, Collins has a good solution: Do not transport a bait salamander any farther than the creature can walk.