High speed video of a tree salamander in a vertical wind tunnel.
The salamanders that live all their lives on the crowns of the tallest trees in the world, the redwoods off the coast of California, have developed a behavior well adapted to the dangers of falling from great heights: the ability to parachute, glide and maneuver in the air.
Flying squirrels, as well as numerous species of glider frogs, geckos and ants and other insects, are known to use similar aerial stunts when they jump from tree to tree or when they fall, to stay in the trees and avoid landing on the ground. .
Similarly, researchers believe that the salamander’s parachuting skills are a way to return to a tree from which it has fallen or jumped, to better evade terrestrial predators.
“While they’re parachuting, they have an exquisite amount of maneuverable control,” said Christian Brown, a doctoral candidate at the University of South Florida (USF) in Tampa and the first author of an article on these behaviors. “It simply came to our notice then. They are able to turn around if they go upside down. They are able to maintain this parachuting posture and pump their tail up and down to make horizontal maneuvers. The level of control is impressive. “
The aerial dexterity of the so-called wandering salamander (Aneides vagrans) was revealed by high-speed video footage captured in a wind tunnel at the University of California, Berkeley, where the salamanders were pushed from a pole to a upward moving air column. , which simulates free fall.
The wandering salamander, Aneides vagrans, is about 4 inches (10 centimeters) long and lives all its life on the tops of redwood trees more than 150 feet above the ground. The researchers found that he has adapted to his high-altitude lifestyle by developing the ability to parachute and glide when he falls. Credit: Christian Brown
“What surprised me when I first saw the videos is that (the salamanders) are so smooth: there’s no discontinuity or noise in their movements, they’re just totally airborne,” said Robert Dudley. professor of integration at UC Berkeley. biology and animal flight expert. “This, to me, implies that this behavior is something deeply embedded in your motor response, which (fall) has to happen at reasonably high frequencies in order to affect the selection of this behavior. And it’s not just about of a passive parachute, not only are they parachuting downwards, they are also clearly doing lateral movement, which is what we call gliding. “
The behavior is even more surprising because salamanders, apart from having slightly larger pads, do not look different from other salamanders that are not maneuverable aerially. They don’t have leather flaps, for example, that reveal their ability to parachute.
The high-speed video reveals a big difference in how salamanders react to the fall. While terrestrial (non-tree) salamanders appear helpless during free fall in a vertical wind tunnel, tree salamanders maneuver with confidence. This suggests that tree dwellers have adapted to routine falls and perhaps use the fall as a way to move quickly through the treetops of the tallest trees in the world. White spots are paper disks joined with water to track the movement of the head, body, and tail. Credit: Video produced by Roxanne Makasdjian with images courtesy of Christian Brown
“Wandering salamanders have big feet, long legs, active tails. All of these things lend themselves to aerial behaviors. But everyone assumed it was for climbing, because that’s why they use those functions when we look at 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 parachute out and glide. “
Among the questions researchers hope to answer in future research are how salamanders get parachutes and maneuvers without obvious anatomical adaptations to planning and whether many other animals with similar air skills have never been noticed before.
“Salamanders are slow, don’t think they have especially fast reflexes. It’s life in the slow lane. And flight control is a quick response to dynamic visual cues and being able to orient, orient, and change body position, “Dudley said.” So it’s a little weird. How often can this happen, anyway, and how did 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 parachuting behavior of A. vagrants (adults are about 4 inches (10 cm) from snout to tail tip) with the skills of three other species of salamanders native to Northern California, each with varying degrees of arboreality. that is, 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 skilled parachutist. A related species, the so-called tree salamander, A. lugubris, which lives in shorter trees, such as oaks, was almost as effective for parachuting and gliding.
Two of the less arboreal salamanders: Ensatina eschscholtzii, a salamander that inhabits forest floor, and A. flavipunctatus, the spotted black salamander, which occasionally climbs trees, essentially fought ineffectively during the few according to which they were in the wind tunnel. All four species are pletodontid or lungless salamanders, the largest family of salamanders and are found mainly in the western hemisphere.
Wandering ducklings in a vertical wind tunnel at an air speed approximately corresponding to the terminal speed of the animal. Credit: Christian Brown
“The two less tree species move a lot. We call it inefficient, undulating motion because they don’t slide, they don’t move horizontally, they just glide in the wind tunnel and become ghosts,” Brown said. “The two most arboreal species never really fought.”
Brown encountered these salamanders while working in Humboldt and Northern California counties with nonprofit and college conservation groups that mark and track animals that live in the redwood canopy, mostly in the old forest about 150 feet from the land. With ropes and ascents, biologists regularly climb the redwoods, the highest of which rises to a height of 380 feet, to catch and mark stray salamanders. For the past 20 years, as part of a project led by James Campbell-Spickler, now director of the Eureka Sequoia Park Zoo, researchers have discovered that most of its tagged salamanders could be found in the same tree year round. year after year, albeit at different heights. They live mainly on mats of ferns that grow on duff, the decaying plant matter that accumulates at the junctions of large branches. Brown said a few stray salamanders marked from the redwood canopy were found on the ground, and most of them were found dead.
Brown noticed, as he picked them up to mark them, that the salamanders quickly got out of his hands. Even a light touch on a nearby branch or shade was enough to make them jump from the redwood cup. Given its location well above the forest floor, its carefree jumps into the air were amazing.
A. vagrans jumping. Credit: Christian Brown
“They jump in and even before they’re done walking, they have their front limbs open and they’re ready to go,” he said. “Therefore, the jump and the parachute are closely linked. They take office immediately. “
When he approached Dudley, who has studied this behavior in other animals, he invited Brown to bring some of the salamanders to his wind tunnel to record their behavior. With a high-speed video camera firing at 400 frames per second, Brown and Sathe filmed the salamanders as they floated in the air column, sometimes up to 10 seconds.
They then analyzed the pictures to determine the airborne posture of the animals and to deduce how they used their legs, body and tail to maneuver. They usually fall at a sharp angle, only 5 degrees from the vertical, but depending on the distances between the branches at the tops of the redwoods, this would usually be enough for them to reach a branch or trunk before they hit the ground. The parachute reduced its free fall speed by 10%.
Brown suspects that his aerial skills evolved to cope with falls, but have become part of his repertoire of behavior and perhaps his default method of descent. He and USF undergraduate Jessalyn Aretz found, for example, that walking downhill was much more difficult for the salamander than walking on a horizontal branch or a trunk.
“This suggests that when they roam, they probably walk on flat surfaces or walk upwards. And when they run out of habitat, as the upper canopy becomes drier and drier, and there’s nothing else for them up there, they could go back down to these better habitats, “he said. “Why go down again? You’re probably exhausted. You’ve burned all your energy, you’re a small 5 gram salamander and you’ve just climbed the tallest tree on Earth. You won’t turn around and go down, you’ll catch the gravity lift.
Brown sees A. vagrans as another child of the ancient forest poster that is similar to the spotted owl because it is found mainly in the crowns of the tallest and oldest redwoods, but also in Douglas fir and spruce Sitka.
“This salamander is a poster boy for the part of the redwoods that was almost completely lost due to logging: the canopy world. It’s not in these new-growth forests created by timber companies,” he said. to say. “It simply came to our notice then.