These salamanders skydive from the world's tallest trees, new study finds
The wandering salamander uses its limbs to glide from treetop to treetop, says biologist Christian Brown
When biologist Christian Brown set out to study the wandering salamander, he faced an unusual problem: how do you best observe a creature that spends most of its time living in the canopy of the world's tallest trees?
By giving them a field trip of sorts to a special, miniature skydiving facility.
Unlike most amphibians who live in ponds, swamps and rivers, wandering salamanders can be found in the massive redwood forests of North America's west coast. They're native to California, but can also be found in British Columbia.
They navigate the habitat by leaping into the air, guiding their fall like a skilled skydiver.
The California treetops might seem an unusual home for the salamanders, who need to keep their skin moist in order to breathe. But according to Brown, a PhD candidate in integrative biology at the University of South Florida in Tampa, the giant redwoods actually provide a perfect microclimate for them.
"There's a pretty consistent supply of fog that comes in off the Pacific Coast, and it rolls through the redwood canopy", he said.
"Organic matter gets trapped in these spaces where the branches meet the trunk. They're called fern mats because they are mostly made of ferns and they soak up and and hold the moisture. The salamanders like to go within and throughout them."
WATCH | High-speed video reveals a big difference in how salamanders react to falling
Wind tunnel free fall
At first, Brown tried to study the salamanders in their natural habitat — and he had to learn how to use professional tree climbing equipment to do it.
Although he said being 40 to 80 metres up in the redwoods was exhilarating, it was difficult to see exactly how the salamanders were moving through the air when they took their treetop leaps.
The solution was to capture a few of the animals on the ground and study them in the vertical wind tunnel at the University of California, Berkeley.
The tunnel is a miniature version of the wind machines used for recreational indoor skydiving. Using high-speed video cameras to observe the animals in the wind tunnel, Brown saw them first preparing to leap by bending their bodies to generate power, much like the way a fish swims. Then they launched themselves with all four legs splayed out like a skydiver.
Once in the air, the wind tunnel simulated an endless fall for the salamander as it hovered in place, allowing Brown to capture every movement with his cameras.
"They never flipped upside down, and they had control over an upright posture, but not necessarily stable." he said.
"Flying squirrels are notoriously stable because they have skin flaps that stabilize their body in the air. Salamanders don't have anything like that, but they are manoeuvrable. They're constantly adjusting their feet, their toes and their tail to compensate."
In the forest, this agility allows the salamanders to guide their descent from the tree so they can land in a desired location.
He and his colleagues published their observations this week in a study in the journal Current Biology.
Taking the 'gravity elevator'
The wandering salamander's treetop habitat — in theory — presents a major transportation problem.
The small creatures — adults range in size from 75 to 120 mm long — are vulnerable when exposed to the less congenial parts of their environment. Moving between different fern mats in their trees, or from tree canopy to tree canopy could mean tough climbing during which they could dry out, or be attacked by predators like owls or squirrels.
That's the problem biologists like Brown suggest the salamanders have solved by developing their extraordinary skydiving skills, which allow them to take controlled leaps from branch to branch or tree to tree.
"You can imagine that climbing the world's tallest trees as a small five gram salamander, could be pretty difficult, time-consuming and energy-consuming. And it could be far more efficient and faster to just take the gravity elevator back down."
Can Vancouver Island salamanders fly?
The salamanders that live in California's redwood trees have slightly longer legs and larger feet than other salamanders. This may be an adaptation to help make such impressive gliding possible. It is an area of study Brown wants to pursue in the future.
"We can look at different populations of wandering salamander. For instance there's a ... population on Vancouver Island, but there's no redwood trees," he said.
"So I'd really be interested to compare their genomes ... the size of their feet, and the length of their legs. How well are these ones from Vancouver Island at parachuting, versus the ones that we collected from the world's tallest trees? I hope to do that very soon. That would. Be cool."
Produced and written by Mark Crawley.