When disturbed by a predator in the canopy of the world’s tallest trees, some salamanders face a seemingly daunting task: Sail through the air to safety at least dozens of feet below.
Biologist Christian Brown of the University of South Florida had long wondered how these aptly named wandering salamanders can survive such massive leaps among northern California’s coastal redwoods—particularly since they lack skin flaps or sails like other “flying” amphibians. (Read about a flying frog with special webbed feet for sailing from tree to tree.)
Now, new experiments using a miniature wind tunnel box reveals the daring, four-inch creatures rely on the same techniques as human skydivers. The animals slow their descent as a parachuter would, holding up their chests and stretching out their limbs in an exaggerated starfish pose, according to a new study published today in the journal Current Biology.
Around 200 species of salamanders worldwide are known to clamber around in trees, but aerial behavior in salamanders has never been described before, Brown says.
“This is a fearless, five-gram salamander that climbs the tallest trees on Earth and isn’t afraid to take a leap of faith,” says Brown. “I think that’s inspiring, and I hope other people do, too.”
Inspired by National Geographic
Brown first learned about wandering salamanders in the October 2009 issue of National Geographic about redwoods. He was immediately inspired by the redwood canopy and the distinctive—and often understudied—animals that live there. (Read more about threats to California's redwoods.)
They then collected five wandering salamanders from the forest floor in California, dropping them one by one into the wind tunnel. For each experiment, the team recorded the animal’s movements with slow-motion video. Then they repeated the experiment with five individuals from each of three other North American salamander species that spend varying amounts of time in trees.
In all 45 trials, the wandering salamanders immediately positioned themselves in the parachuting starfish position, which creates drag that slows the animal’s descent. The effect is similar to a person putting their hand out the car window and angling it against the wind.
In over half the trials, wandering salamanders also undulated their tails to make course corrections. Sometimes they banked their turns, tucking in one leg and pivoting around it mid-flight. These efforts gave wandering salamanders precise control over their descent and slowed their speed by around 10 percent.
The team found the other salamander species in their experiments also parachuted, but that the behavior was rarer in amphibians that spend less time in trees. The Monterey ensatina, which resides on the ground, parachuted in only three out of 45 trials. (Learn about the Wallace's flying frog, also known as the parachute frog.)
“It was a great study that combined natural history with experimental design,” says Gary Bucciarelli, an ecologist at the University of California, Los Angeles, who wasn’t involved in the work. “It opens up a lot of questions about what’s actually happening in the natural habitat.”
Built to soar—and climb
Wandering salamanders are also physically built for gliding: They have a relatively flat body, long legs, and feet that are larger in proportion to their bodies than those of most salamanders, says Brown. This unique physique makes them good climbers as well.
Such adaptations also suggest that their parachuting prowess is useful for other scenarios beyond accidental falls or fleeing from predators. The salamanders likely can drop down to new fern mats—the vegetation platforms that accumulate on tree branches—to look for mates, water, or shade, he says. Supporting this idea, a recent study found wandering salamanders tend to resist walking straight down tree trunks.
“It’s a mode of transportation,” says Brown, like “taking the gravity elevator.”
Such research is especially important, Brown says, since there’s still much ecologists don’t know about old-growth coastal redwood canopies. The tallest trees are difficult to access, requiring special gear and training.
At the same time, these habitats have dramatically shrunk. Only around five percent of California’s original old-growth redwoods remain after decades of commercial logging; wildfires continue to threaten the rest. Climate change is also likely to alter the delicate foggy environment in the canopies, which could possibly imperil its residents.
“We drastically need baseline data for the redwood canopy,” Brown says, “so that we can understand how it’s changing and protect it.”