How do long-toed salamander populations (and by extension, other amphibian species) persist in the middle of urban spaces in the Salish Sea region?

 
While most of Seattle prepares for bed, listening passively to the drizzle upon their roofs, Julianna Hallza embraces the crunch of gravel underfoot as she walks a dark pathway through the Union Bay Natural Area in Seattle. It is February 2021; the sky is a sheet of heavy clouds, punctuated by the tops of cottonwoods outlining a nearby pond and a row of willows delineating a small sliver of forest.

Ruler, camera, and notebook in hand, Hallza turns toward the willows. Her gaze is not aimed up at their crowns — rather, her headlamp concentrates a bright circle upon the ground. A few steps off the path, downed branches and trunks appear among the tall grasses and blackberries. Hallza kneels down, grabs a log with both hands, and rolls it gently toward her. Underneath, it is warm enough that a faint wisp of steam emerges into the cold air. Nestled in the black soil is the animal she came here for: a long-toed salamander (Ambystoma macrodactylum).

The hand holding this long-toed salamander illustrates the size of the salamander.  photo by Julianna Hallza

a tale of two habitats

Long-toed salamanders are “biphasic,” meaning that their life cycle requires two distinct habitats: one for eggs to mature, and one for adults to persist. As adults, the salamanders spend the non-breeding season burrowed underground in forests to avoid cold temperatures in winter and drought in late summer. Long-toed salamanders are considered “fossorial,” or burrowing, because of their tendency to spend time underground, but they don’t typically dig the burrows themselves. Instead, they use existing dens created by mice, moles, or other animals, and they occasionally dig along tree roots where the soil is easier to move.

Wetland at the Union Bay Natural Area. photo by Thomas Noland

Screenshot of Google Earth showing a region around Seattle.

Long-toed salamanders lay eggs singly or in small clusters enveloped in a jelly-like protective layer. This layer allows the eggs to absorb oxygen from the water. Eggs develop over the course of a few weeks, and tiny embryos are visible wiggling their tails before the eggs even hatch. Initially, hatchling salamanders are very small, about a centimeter (half-inch) or less, and only have tiny “balancers” extending from where their front legs will eventually grow. The tadpole-like larvae are distinguishable from frogs and toads because of their external gills, which allow them to breathe underwater.

Over the next weeks or even months, the larvae develop front and then back legs, and their tails become more defined. As water levels drop in late summer, their gills reabsorb into their bodies, and they metamorphose into their terrestrial adult form. From there, the salamanders migrate to upland forests, and the cycle begins again.

A long-toed salamander poses on a leaf showing its namesake appendages and characteristic golden stripe. Every individual’s stripe is different, like a fingerprint. photo by Dominick Leskiw

As urban amphibians attempt to migrate between habitats, they are sometimes forced to cross busy roads. Salamanders in particular (but frogs, too) move very slowly on land. Roads are exposed surfaces with nowhere to hide from traffic. Drivers are unlikely to see amphibians because they are so small, and many people don’t even notice when they run one over.

To help amphibians cross roads, restoration practitioners sometimes install underpasses or overpasses encouraging safe travel. These structures allow amphibians to escape traffic by crawling through tunnels specially designed to facilitate movement, or over bridges with natural habitat. Fences funnel amphibians toward these structures and away from exposed sections of road. In places where these structures have not been built, volunteer groups may gather at popular crossing sites on rainy spring evenings to carry amphibians across the road. This kind of support reduces amphibian mortality and contributes to increased habitat connectivity, even in highly urbanized spaces.

help from a furry friend

Humans aren’t the only ones who create and connect amphibian habitat, though. Another ecosystem engineer, the beaver, also modifies landscapes in ways that benefit amphibians. Beavers dam streams to create ponds, and they dig canals that connect these ponds to forests. These spaces between ponds and forests are where beavers harvest additional wood and where salamanders spend the non-breeding season.

Beaver canals link wetlands to upland habitat by creating pathways with plenty of woody debris as cover along the way. Some amphibians follow beaver trails away from their natal (birth) ponds as they disperse because of the increased moisture and easier movement these trails allow. While the use of beaver canals has not been studied in long-toed salamanders, other amphibians such as the endangered Oregon spotted frog are known to use them.

Beaver ponds are also critical for many amphibians because they retain water late into the summer months when other ponds are dry, provide habitat for multiple species to coexist, and increase wetland connectivity at the landscape scale by creating a patchwork of stream and pond habitats across a watershed.

The trees that beavers harvest play a role, too. Holding another downed log in her hands, Hallza notices a riot of animacy — bugs, fungi, mice, salamanders, and more — below its decaying bark. Here on the ground, and even after death, a part of this tree has found new life.

the amphibian corridor

Urban amphibian habitats are not always separated by roads, but amphibians can still face other challenges to migration and breeding in urban greenspaces that are fragmented by pollution, non-native species, or poor habitat quality. Within the Union Bay Natural Area, there are no cars to threaten amphibian populations, but some parts of the park may be more hospitable for salamanders than others.

The park is plagued with invasive Himalayan blackberries and other non-native species. To control the blackberries, some parts of the space are mowed into grassy fields, but these spaces do not provide optimal cover for salamanders, which prefer moist, shady habitat with shrub or tree cover. To make matters worse, one of these large, grassy spaces cuts between a pond that long-toed salamanders use to breed and a forested stretch that could act as an overwintering site. A gravel path also separates the pond from the forest.

With these impediments in mind, in 2015, master’s student Kathleen Walter created a restoration site to provide a connection between the pond and forested area. This restoration site, named the Amphibian Corridor, was constructed by digging a trench between the pond and the forested area to increase soil moisture, planting native vegetation to provide shade and leaf litter, and placing large woody debris down for shelter. Additionally, Walter installed a culvert under the gravel path that separates the pond and forest, hoping that amphibians could crawl through the tunnel to complete their migration.

Salamander under woody debris. photo by Julianna Hallza

Through her study, Hallza also got to know several of the salamanders, in a way. Another beautiful facet of these animals is that the bright yellow spots and blotches running along their heads, backs, and tails are unique to each individual, like a fingerprint. Hallza recalls finding one salamander twelve times over the course of twelve weeks — under the same log every time, no less! This salamander was completely missing a foot the first time she found it. Yet, as the weeks progressed, Hallza noticed that it slowly regained use of its leg and eventually began to regrow toes, too. She sees this salamander’s story as a testament to the resilience of the species, and a reminder that even seemingly small things, like a single piece of wood, can make a big impact.

Amphibians & Reptiles of Washington | Burke Museum

Long-toed Salamander | Washington Department of Fish & Wildlife

Assessing the efficacy of wildlife underpasses in mitigating amphibian road mortality: A case study from the northeastern United States | Marcelino, M., S. Parren, B. Mosher. 2025 in Journal for Nature Conservation 86:126901.

Use of Restored Urban Habitat by Long-toed Salamanders (Ambystoma macrodactylum) in Seattle, Washington, USA | Hoza, J. and J. Bakker. 2023 in Herpetological Conservation and Biology 18(1):84-93.

Occupancy of Stream-Associated Amphibians within the Interstate 90 Snoqualmie Pass Corridor | Gustafson, A. 2018 in All Master’s Theses. 884.

Long-toed Salamanders: Microhabitat Preference and Movement in the Union Bay Natural Area | Hoza, J. 2021.

Late-Season Movement and Habitat Use by Oregon Spotted Frog (Rana pretiosa) in Oregon, USA | Christopher A. Pearl, Brome McCreary, Jennifer C. Rowe, Michael J. Adams, 2018

Julianna Hallza surveying boreal toads (Anaxyrus boreas boreas) for a monitoring project. photo by Stephen Bunnell

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