Skydive from the salamanders and glide from the tallest trees [High Speed Video]

Salamanders that live their entire lives in the crowns of the world’s tallest trees, California’s coastal redwoods, have evolved behavior well suited to the dangers of falling from great heights: the ability to parachute, glide, and maneuver in the airs.

Flying squirrels, along with many species of gliding frogs, geckos, ants and other insects, are known to use similar aerial acrobatics by leaping from tree to tree or falling, in order to stay in trees and to avoid landing on the ground. .

Similarly, researchers believe that this salamander’s parachute jumping skills are a way to navigate itself to a tree it fell or jumped from, to better escape terrestrial predators.

“While they’re skydiving, they have an exquisite amount of maneuverable control,” said Christian Brown, a doctoral student at the University of South Florida (USF) in Tampa and first author of a paper on these behaviors. “They are able to turn. They are able to turn over if they get upside down. They are able to maintain this skydiving posture and pump their tail up and down to perform horizontal maneuvers. The level of control is simply impressive.

The aerial dexterity of the so-called wandering salamander (Vagrans aneids) was revealed by high-speed video footage captured in a wind tunnel at the[{” attribute=””>University of California, Berkeley, where the salamanders were nudged off a perch into an upward moving column of air, which simulates free fall.

“What struck me when I first saw the videos is that they (the salamanders) are so smooth — there’s no discontinuity or noise in their motions, they’re just totally surfing in the air,” said Robert Dudley, UC Berkeley professor of integrative biology and an expert on animal flight. “That, to me, implies that this behavior is something deeply embedded in their motor response, that it (falling) must happen at reasonably high frequencies so as to effect selection on this behavior. And it’s not just passive parachuting, they’re not just skydiving downwards. They’re also clearly doing the lateral motion, as well, which is what we would call gliding.”

The behavior is all the more surprising because the salamanders, aside from having slightly larger foot pads, look no different from other salamanders that aren’t aerially maneuverable. They have no skin flaps, for example, that would tip you off to their parachuting ability.

The high-speed video reveals a big difference in how the salamanders react to the fall. While terrestrial (non-arboreal) salamanders seem helpless during a free fall in a vertical wind tunnel, arboreal salamanders maneuver with confidence. This suggests that tree dwellers have adapted to routine falls and may be using falling as a way to move quickly through the canopy of the world’s tallest trees. The white spots are paper discs attached with water to track the movement of the head, body and tail. Credit: video produced by Roxanne Makasdjian courtesy of Christian Brown

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

Among the questions the researchers hope to answer in future research are how salamanders manage to parachute and maneuver without obvious anatomical adaptations to gliding and whether many other animals with similar aerial skills have never been noticed before.

“Salamanders are slow, you wouldn’t think they have particularly quick reflexes. That’s life in the slow lane. And flight control is about reacting quickly to dynamic visual cues and being able to target, steer and modify your body position,” Dudley said. “So it’s just kind of weird. How often can this happen, anyway, and how would we know? »

An article describing the behavior was published on May 23, 2022 in the journal Current biology.

life in the canopy

Using the wind tunnel, Brown and UC Berkeley graduate student Erik Sathe compared the gliding and skydiving behavior of A.vagrans – adults measure about 4 inches (10 centimeters) from snout to tip of tail – with the abilities of three other salamander species native to Northern California, each with varying degrees of treeiness – i.e. the propensity 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 capable skydiver. A related species, the so-called arboreal salamander, A. lugubriswhich lives in shorter trees, such as oaks, was nearly as effective at skydiving and gliding.

Two of the least arboreal salamanders — Ensatina eschscholtziia forest floor salamander, and A. flavipunctatus, the occasional tree-climbing black spotted salamander – essentially fluttered about inefficiently for the few seconds it was airborne in the wind tunnel. All four species are plethodontid or lungless salamanders, the largest family of salamanders and are found primarily in the Western Hemisphere.

Vagrans aneides parachuting into a vertical wind tunnel at a speed corresponding approximately to the terminal velocity of the animal. 1 credit

“The two less arboreal species are very fidgety. We call it inefficient, rippling motion because they don’t slide, they don’t move horizontally, they just hover in the wind tunnel in a panic,” Brown said. “The two most arboreal species never actually fought.”

Brown encountered these salamanders while working in Humboldt and Del Norte counties in California with nonprofit and university conservation groups that mark and track animals that live in the canopy of redwood trees, mostly in old-growth forest. about 150 feet above the ground. Using ropes and ascenders, biologists routinely scale the redwoods — the tallest of which is 380 feet — to capture and tag wandering salamanders. Over the past 20 years, in a project led by James Campbell-Spickler, now director of the Sequoia Park Zoo in Eureka, researchers found that most of their tagged salamanders could be found in the same tree. year after year, although at different heights. They live mainly in mats of ferns growing in humus, the decaying plant matter that accumulates at the junctions of large branches. Brown said few marked wandering redwood canopy salamanders have been found on the ground, and most of them have been found dead.

Brown noticed, while picking them up to mark them, that the salamanders quickly jumped out of his hands. Even a light tap on a branch or a passing shadow was enough to make them jump out of the redwood canopy. Given their location above the forest floor, their nonchalant leaps through the air were surprising.

“They jump, and before they’re even done jumping, they have their forelimbs spread and they’re ready to go,” he said. “Thus, the jump and the parachute are very closely linked. They assume the position immediately.

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

They then analyzed the frames to determine the animals’ posture in the air and infer how they used their legs, body and tail to maneuver. They usually fell at a steep angle, only 5 degrees from the vertical, but depending on the distances between the branches in the treetops of the redwoods, that would usually be enough for them to reach a branch or trunk before hitting the ground. Skydiving reduced their free fall speed by about 10%.

Brown suspects that their aerial skills have evolved to deal with falls, but are now part of their behavioral repertoire and perhaps their default method of descent. He and USF undergraduate student Jessalyn Aretz found, for example, that walking downhill was much more difficult for the salamander than walking on a horizontal branch or trunk.

“This suggests that when they roam, they’re probably walking on flat surfaces, or they’re walking uphill. And when they run out of habitat, as the upper canopy becomes increasingly drier, and it doesn’t there’s nothing else for them up there, they could just come down to those better habitats,” he said. “Why come down? You’re probably already exhausted. You’ve burned all your energy, you’re a little 5 gram salamander and you’ve just climbed the tallest tree on Earth. You’re not going to turn around and go down – you’re going to take the gravity lift.

Brown sees A.vagrans as another poster child for old growth forests that is akin to the spotted owl as it is found primarily in the tops of the tallest and oldest redwoods, but also in Douglas fir and Sitka spruce .

“This salamander is a poster child for the part of the redwoods that has been almost completely lost to logging – the canopy world. There are none in these new forests being created by the corporations. logging,” he said. “Maybe it would help not only redwood conservation efforts, but also redwood restoration efforts, so we can actually get canopy ecosystems. Restore the redwoods to the point of carpet ferns, to the point of salamanders in the canopy – that would be a new bar for conservation.

In the meantime, this ancient forest dweller has a lot to tell us about evolution and possibly the origin of flight, Dudley said.

“It’s (gliding) a novelty, something unexpected in an otherwise well-studied group of animals, but it illustrates the urgency with which tree-dwelling animals must develop their aerial ability, even though they don’t have wings,” Dudley mentioned. “Theft, in the sense of controlled aerial behavior, is very common. They control their body posture and move laterally. This predisposes many, many things that live in trees to eventually evolve flapping flight, which is probably hard to evolve and why it’s only appeared three times on the planet today.

Reference: “Gliding and parachuting by arboreal salamanders” by Christian E. Brown, Erik A. Sathe, Robert Dudley and Stephen M. Deban, May 23, 2022, Current biology.
DOI: 10.1016/j.cub.2022.04.033

The paper’s co-authors with Brown and Dudley are Sathe and Stephen Deban, a professor of integrative biology at the University of South Florida.