Skydiving salamanders live in the tallest trees in the world

Image: The wandering salamander, Aneides vagrans, is about 10 inches long and lives its entire life in the crowns of redwoods, more than 50 feet above the ground. Researchers found that it has adapted to its high-rise lifestyle by developing the ability to skydive and glide while falling.
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Credit: Christian Brown

Salamanders that live their entire lives in the canopy of the world’s tallest trees, the California coast redwoods, have evolved a behavior well adapted to the dangers of falling from high places: the ability to parachute, glide and maneuver in the air.

Flying squirrels, not to mention countless species of gliding frogs, geckos and ants and other insects, have been known to use similar aerial maneuvers when jumping or falling from tree to tree, to stay in the trees and prevent them from falling. landing on the ground.

Likewise, the researchers suspect that this salamander’s skydiving abilities may be a way to bounce back to a tree it fell or jumped from, to better avoid terrestrial predators.

“While skydiving, they have an outstanding amount of maneuverable control,” said Christian Brown, a doctoral student at the University of South Florida (USF) in Tampa and lead author of a paper on this behavior. “They can turn. They can turn themselves when they go upside down. They can maintain that skydiving stance and pump their tails up and down to perform horizontal maneuvers. The level of control is just impressive.”

The aerial prowess of the so-called wandering salamander (Aneides vagrans) was revealed by high-speed video footage taken in a wind tunnel at the University of California, Berkeley, where a perch’s salamanders were pushed into an upward-moving column of air that simulated free fall.

“What struck me when I first saw the videos is that they (the salamanders) are so smooth — there’s no interruption or noise in their movements, they just surf all the way up in the air,” said Robert Dudley, UC Berkeley professor of integrative biology and an expert on animal flight. “To me that means that this behavior is something that is deeply embedded in their motor response, that it (falling) has to happen at fairly high frequencies in order to effect selection for this behavior. And it’s not just passive skydiving, they’re not just skydiving down. They also clearly do the sideways movement, which we would call gliding.”

The behavior is all the more surprising because, apart from having slightly larger soles of the feet, the salamanders don’t look any different from other salamanders that are not maneuverable from the air. For example, they don’t have skin flaps that could alert you to their skydiving.

“Wandering salamanders have big feet, they have long legs, they have active tails. All these things lend themselves to aerial behavior. But everyone just assumed this was for climbing because that’s what they use those features for when we look to them,” said Brown. “So it’s not really a specific aerodynamic control surface, but it functions as both. It helps them climb, and it also seems to help them skydive and glide.”

One of the questions the researchers hope to answer in future research is how salamanders manage to parachute and maneuver without apparent anatomical adaptations to gliding and whether many other animals with similar air skills have never been spotted before.

“Salamanders are slow, you don’t think they have particularly fast reflexes. It’s life in the slow lane. And flight control is all about reacting quickly to dynamic visual cues and being able to aim and orient and change your body position, Dudley said. “So, it’s just a little strange. How often can this actually happen, and how can we know?”

A paper detailing the behavior will be published in the journal May 23 current biology

Life in the canopy

Using the wind tunnel, Brown and UC Berkeley graduate student Erik Sathe compared the gliding and parachuting of a. bums – adults are about 4 inches (10 centimeters) from snout to tail tip – with the abilities of three other salamander species native to Northern California, each with varying degrees of arboreal growth – that is, a tendency to climb or live in trees . The wandering salamander, which probably spends its entire life in a single tree, moving up and down but never touching the ground, was the most proficient skydiver. A related species, the so-called tree salamander, A. lugubriswhich lives in shorter trees, such as oaks, was almost as effective at skydiving and gliding.

Two of the least arboreal salamanders – Ensatina eschscholtziia salamander that lives on the forest floor, and A. flavipunctatus, the speckled black salamander, which occasionally climbs trees – essentially waved ineffectively for the few seconds they were airborne in the wind tunnel. All four species are plethodontid or lungless salamanders, the largest family of salamanders and are mostly found in the Western Hemisphere.

“The two least tree species flutter around a lot. We call it an ineffective, undulating motion because they don’t slide, they don’t move horizontally, they just float in the wind tunnel and flip,” Brown said. “The two most arboreal species never really fluttered.”

Brown encountered these salamanders while working in California’s Humboldt and Del Norte counties with nonprofit and university conservation groups that mark and track the animals that live in the redwood canopy, primarily in old-growth forest about 50 feet above the ground. . Using ropes and scaffolding, the biologists regularly climb the redwoods — the tallest of which rise to 380 feet — to capture and mark roaming salamanders. Over the past 20 years, as part of a project led by James Campbell-Spickler, now director of the Sequoia Park Zoo in Eureka, the researchers found that most of their marked salamanders can be found on the same tree year after year, although different heights. They mainly live in fern mats growing in the duff, the decaying plant material that collects in the junctions of large branches. Brown said few marked wandering salamanders have been found from the redwood canopy on the ground, and most of these were found dead.

Brown noticed, as he picked them up to mark them, that the salamanders quickly jumped out of his hands. Even a light tap on a branch or a shadow passing nearby was enough to make them jump off the redwood canopy. Given their location high above the forest floor, their casual leaps into thin air were surprising.

“They’re jumping, and before they’re even done toe-toeing, they’ve got their front legs spread and they’re ready to go,” he said. “So the jump and the parachute are very closely linked. They take the position immediately.”

When he approached Dudley, who has studied such behavior in other animals, he invited Brown to bring some salamanders into his wind tunnel to record their behavior. Using a high-speed video camera that shot at 400 frames per second, Brown and Sathe filmed the salamanders as long as they hovered on the air column, sometimes for up to 10 seconds.

They then analyzed the frames to determine the animals’ attitudes in the air and to infer how they used their legs, bodies and tails for maneuvering. They usually fell at a steep angle, only 5 degrees from vertical, but based on the distances between branches in the crowns of redwoods, this would usually be enough to reach a branch or trunk before they hit the ground. Skydiving reduced their free fall speed by about 10%.

Brown suspects that their aerial skills evolved to deal with traps, but became part of their behavioral repertoire and perhaps their standard method of descent. For example, he and USF student Jessalyn Aretz found that walking downhill was much more difficult for the salamander than on a horizontal branch or on a trunk.

“That suggests that when they roam, they’re probably walking on flat surfaces, or they’re walking uphill. And when they’re out of habitat, because the top canopy gets drier and drier, and there’s nothing else for them there they’d just go back.” can fall to those better habitats,” he said. “Why would you walk back down? You’re probably exhausted already. You’ve burned off all your energy, you’re a 5 gram little salamander and you’ve just climbed the tallest tree on Earth. You’re not going to turn around and walk over to down – you’re going to take the gravity lift.”

brown looks a. bums as another old-growth poster child related to the spotted owl, as it is mainly found in the crowns of the tallest and oldest redwoods, although also Douglas fir and Sitka fir.

“This salamander is an example of the part of the redwoods that has been almost completely lost to logging – the foliage world. It’s not there in these new forests created by logging companies,” he said. preserving redwoods, but also restoring redwoods so that we could actually have canopy ecosystems. Restoring redwoods to the point of fern mats, to the point of salamanders in the canopy — that would set a new bar for conservation.”

In the meantime, this inhabitant of old-growth forests has a lot to tell us about evolution and perhaps the origins of flies, Dudley said.

“It (sliding) is a novelty, something unexpected in an otherwise well-studied group of animals, but it illustrates the urgency with which animals living in trees need to develop air capacity, even if they don’t have wings,” Dudley said. “Flight, in the sense of controlled air behavior, is very common. They control their body position and they move sideways. This predisposes many, many things that live in trees to eventually develop flapping flight, which is probably difficult to evolve and why it has only appeared on the planet three times today.”

Co-authors of the paper with Brown and Dudley are Sathe and Stephen Deban, professor of integrative biology at the University of South Florida.


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