Still frame image showing the hindfoot of a live Wandering Salamander (Aneides vagrans) from a ventral perspective just before the salamander takes a step forward. This image shows the large digital blood sinuses and the points at which they connect near the distal-most joint. (Credit:
Photo by William P. Goldenberg)
PULLMAN, Wash. — High in the misty canopies of California’s coastal redwoods, a tiny salamander performs a feat that would make most rock climbers nervous: it lets go. But rather than plummeting 290 feet to the forest floor, the wandering salamander glides gracefully to another branch, sticking its landing with remarkable precision. Now, scientists from Washington State have discovered the surprising secret behind these amphibians’ impressive climbing abilities. Their transparent toe tips fill with blood in precise patterns as they move to help adjust grip and detachment.
The study, published in the Journal of Morphology, focuses on wandering salamanders. These little creatures live their entire lives high up in the canopy of the world’s tallest trees, never needing to come down to the forest floor. They make their homes up to 88 meters (about 290 feet) above ground in California’s coastal redwood forests.
Scientists have long been fascinated by the square-shaped toe tips of climbing salamanders, particularly those belonging to the genus Aneides. For over 100 years, researchers have observed bright red “lakes of blood” within these expanded digit tips, but the exact function of these blood-filled chambers remained a mystery until now.
What makes this discovery particularly fascinating is how it came about through an unexpected observation during a documentary film shoot. While working as a salamander expert on NBC’s “The Americas” documentary, lead researcher Christian Brown noticed something strange through the production team’s high-powered camera lenses: blood was rushing into the salamanders’ translucent toe tips just before they took steps.
Photo by Christian Brown)
“We looked at each other like, ‘Did you see that?’” recalled Brown of the moment he and camera assistant William Goldenberg first observed this phenomenon, in a statement.
Though the documentary crew moved on, the observation sparked a scientific investigation that would ultimately reveal a previously unknown physiological mechanism. Inside each toe tip is a remarkable system of expandable blood-filled chambers, similar to tiny water balloons that can fill up or deflate quickly. By studying preserved salamander toes under powerful microscopes and watching live salamanders in action, the researchers discovered these amphibians can actively control how much blood flows into these chambers, potentially allowing them to fine-tune their grip as needed.
Under the microscope, each toe tip revealed a large blood-filled pocket that divides into two connected chambers. Around these chambers, the researchers found special glands that produce mucus, likely helping keep the toes from drying out. The toe bone itself has a curved shape, possibly helping the salamander get a better grip on rough surfaces, like tree bark.
The research team’s findings challenge historical assumptions about these unique toe tips. While scientists once thought the blood-filled chambers might help with oxygenation, similar to how gills work, no evidence supported this claim. Instead, the blood appears to serve a much more mechanical purpose.
Photo by Christian Brown)
Through their detailed observations, the researchers discovered something unexpected: the blood rushing into the toe tips before “toe off” actually helps salamanders detach rather than attach. It works like a tiny hydraulic system. By slightly inflating the toe tip with blood, the salamander reduces the surface area touching the tree bark or branch, making it easier to lift its foot.
“If you’re climbing a redwood and have 18 toes gripping bark, being able to detach efficiently without damaging your toe tips makes a huge difference,” explains Brown.
This blood-powered system appears particularly valuable for wandering salamanders’ treetop lifestyle. The ability to quickly adjust grip strength by controlling blood flow to each side of their toe tips helps them navigate the uneven and often slippery surfaces of redwood bark. It also likely helps them stick their landings after gliding between branches, a remarkable feat for these small amphibians.
The implications of this research extend beyond just one species. Similar vascularized structures appear in other salamander species, including those living in water, suggesting this blood-powered mechanism might be a universal feature that serves different purposes depending on the salamander’s habitat.
“Gecko-inspired adhesives already allow surfaces to be reused without losing stickiness,” says Brown. “Understanding salamander toes could lead to similar breakthroughs in attachment technologies.”
These insights could inform the development of new adhesives, prosthetics, and even robotic appendages that might one day help machines navigate challenging terrain as effectively as these remarkable amphibians.
Paper Summary
Methodology
The research combined high-tech filming with traditional microscopic analysis. Using professional film equipment from the documentary shoot, researchers built a custom viewing platform with a clear surface that could be positioned both horizontally and vertically. They recorded salamanders walking across this platform using high-powered cameras that could capture blood flow in the translucent toe tips. Additionally, they examined preserved toe specimens under microscopes at Washington State University’s Franceschi Microscopy & Imaging Center, creating extremely thin tissue slices to study internal structures.
Results
The study revealed that salamanders can finely control blood flow to each side of their toe tips, allowing for asymmetrical pressure adjustments that improve grip on irregular surfaces. Surprisingly, increased blood flow before toe lift-off appears to assist in detachment rather than attachment by reducing surface contact area. The research team observed this pattern consistently across multiple trials with both horizontal and vertical orientations.
Limitations
The research was conducted with a relatively small sample size of three salamanders for the live observations and three preserved specimens for the anatomical study. The researchers note they limited their sample size to minimize impact on wild populations. While they could observe blood flow changes, they couldn’t directly measure how these changes affected grip strength or determine the exact mechanism controlling the blood flow.
Discussion and Takeaways
The findings suggest a novel mechanism for how salamanders navigate their arboreal environment. The blood-powered toe system appears to be particularly important for efficient attachment and detachment while climbing, potentially contributing to their remarkable ability to move through the redwood canopy. Moving forward, the research team plans to expand their investigation to examine how this mechanism works in other salamander species and habitats, which could provide broader insights into amphibian locomotion.
Funding and Disclosures
While the authors received no specific funding for this work, the research utilized equipment and facilities from various institutions, including Washington State University’s microscopy center and professional film equipment from the documentary production.
Publication Information
This research was published in the Journal of Morphology in 2025, authored by Christian E. Brown, William P. Goldenberg, Olivia M. Hinds, Mary Kate O’Donnell, and Nancy L. Staub. The study represents a collaboration between Washington State University, Goldenberg Film, Gonzaga University, and Lycoming College.
