Paulson Ecology of Place Initiative Biodiversity Project's Journal

Walking around Wellesley as spring unfolds, showy trees bloom in brilliant floral displays and lively birds sing. But concealed on the forest floor are small red-backed salamanders (Plethodon cinereus), which crawl between soil and a thick layer of leaf litter. These amphibians often go unnoticed by the Wellesley community—yet it’s possible that they play a major role in Wellesley’s small forest ecosystems.


A red-backed salamander found near Lake Waban.

Small and unobtrusive, red-backed salamanders generally do not exceed 10 cm in length. Despite their terrestrial life, they have evolved to be lungless: they breathe through their thin skin in moist environments, constrained to the dark, damp forest floor. This seeming limitation—lunglessness—is hardly a barrier, as the salamanders take full advantage of the forest floor, consuming small invertebrates like worms, millipedes, fly larvae, and collembola.

Throughout the northeast United States, red-backed salamanders are one of the most abundant vertebrate species in forest ecosystems, occurring at densities of up to eight individuals per square meter! They are so abundant that their total biomass alone equals that of all small forest mammals combined, and is double that of passerine birds. Red-backed salamanders are common predators of invertebrate “detritivores”, tiny animals that feed on dead organic material like leaf litter and rotting logs. Because red-backs are so abundant, by consuming detritivores they slow down the decomposition of logs and leaf litter on the forest floor, and can shift the structure of entire food webs!

But while red-backed salamanders are abundant in northeastern forests, what about at Wellesley, where the suburban campus landscape is relatively fragmented? Roads, paths, buildings, and heavily managed green spaces slice through small forest patches, creating a disjointed matrix of red-backed salamander habitat. Red-backed salamanders are sensitive to environmental perturbations, including disturbance caused by humans. Can small forest patches in areas of high human impact still support red-backed salamander populations?

To understand this question better, in early April we deployed more than sixty small wooden boards, called coverboards, arranged in transects at several locations across campus. Coverboards create habitat for red-backed salamanders, which use them for shelter, similar to how they might use a fallen log. We can survey an area for salamanders by simply overturning the boards and noting when and how many salamanders we see. We’ll also be collecting data on the invertebrates we find in an effort to further document Wellesley’s biodiversity.

Map of coverboard locations at Wellesley. Coverboards are arranged in transects. Salamanders have been found under the coverboards by Lake Waban and in other areas on campus near the Science Center.



Coverboards are small 12”x12”x2” square boards that mimic red-backed salamander habitat.

Over time, we hope to discover the extent to which Wellesley’s matrix of forest habitat and built landscape can support red-backed salamanders. We’ll also be able to detect trends in the red-backed salamander population, which might help us understand overall changes in environmental quality, especially as it relates to biodiversity and human disturbance.

A red-backed salamander found in a small forest fragment by Wellesley’s Science Center.

We’re thankful to have these small amphibians contributing to biodiversity at Wellesley, and are excited for the discoveries ahead as we begin to monitor them more carefully. What kinds of creatures or plants are you seeing at Wellesley and beyond? Take some photos and upload them to iNaturalist, and direct message us on instagram (@wellesleypaulson), to show us what you’ve been spotting!

Walking through the woods on the path around Lake Waban in the early spring, you might hear a chorus of quacking. A little exploration might lead you to find the small amphibian responsible for this cacophony: the Wood Frog (Lithobates sylvaticus) which breeds in at least four wetlands across Wellesley’s campus.

Wood frog chorus at Wellesley’s Kettle Pool

Wood frogs emerge from the woods, where they spend the winter frozen underneath leaf litter, in early spring to begin their annual breeding cycle, migrating to small, temporary water bodies called vernal pools. Wood frogs, like many frogs and salamanders, have evolved breeding strategies to rely exclusively on these ephemeral pools, which don’t support fish populations because they fill with water for only part of the year before drying out, protecting the eggs from fish predation.

A male and a female frog in amplexus in Wellesley’s Kettle Pool. In this position, the female lays eggs which the male promptly fertilizes.

Wellesley College’s campus is home to this critical habitat. There are two certified vernal pools on the Wellesley landscape recognized by the Massachusetts Natural Heritage and Endangered Species Program, and we documented breeding wood frogs in these certified pools this spring. Records show that wood frogs have used these two pools for decades—in the early 1990s Marcy Thomas, Instructor in Biology, observed evidence of breeding wood frog populations and helped certify the vernal pools.

An adult wood frog observed at Wellesley in May 2018.

Wood frogs are also found in the “Kettle Pool,” an old concrete-lined Botanic Gardens water feature and the “Maple Swamp” which is a natural wetland, but is supplemented with water pumped from the college's maintenance tunnels. While these two pools are not officially certified due to the heavy influence of humans, earlier this March we found eggs in the pools, evidence that both host breeding wood frogs. These wetlands force us to think a little more broadly about how to conceptualize biodiversity in the built environment at Wellesley, a landscape highly influenced by human activities.

Wood frogs breed at four pools across Wellesley College’s campus: A) Lake Waban Pool, B) Maple Swamp C) Kettle Pool and D) Fuller Brook Pool

The wood frog’s annual breeding ritual occurs in careful consortium with the signals of spring at Wellesley, as warming temperatures trigger mass migrations to the vernal pools. The process begins with a loud chorus produced by adult males to attract females. This gathering of adult frogs continues for around three weeks, with females each leaving behind a mass of eggs before all adults retreat back into the woods and nearby meadows. Each egg mass contains 1000 to 3000 eggs, from which tadpoles emerge 9 to 30 days after the female frogs lay the eggs.

This early spring flurry of commotion and chorus is a crucial phase in the life history of the wood frog at Wellesley and beyond. Wellesley isn’t the only place where amphibians are emerging from their winter retreats, gathering in spring chorus, often to attract mates. Have you heard any frogs recently? Share an audio recording on iNaturalist. Happy observing!

Gray squirrels (Sciurus carolinensis) may be the most commonly recognized mammal on campus, skittering about snacking on fallen acorns or sheepishly nibbling an occasional tortilla chip or other human-derived treat. They seem to operate in a world of their own—while aware of surrounding humans, they are always busy as they scramble around, deftly moving from ground level to the tops of large trees. Their acrobatic movements in treetops impress onlookers, as they sometimes seem to barely avoid falling. Campus squirrels are so amusing and charismatic that they have inspired several instagram accounts including @wellesleycollegeboyz and @squirwelles.


Squirrel, recently spotted on iNaturalist, eating a tortilla chip found in nearby trashcan by the Lulu Chow Wang Campus Center.

But where do the squirrels go during frigid winter days like today, or during the night? Squirrels don’t hibernate, and can be seen foraging for seeds, berries, and nuts throughout the winter, but they do need refuge at night and when the weather gets particularly cold.

With Fall comes leaf senescence: leaves fall off trees, bringing to view the gray squirrel’s home: the drey, a large and cozy nest constructed in the crook of a branch at least 20 feet from the ground. Dreys look like a large haphazard sphere of leaves and sticks, yet they are in fact very complex, having central cavities of about 6-8 inches across to allow space for the squirrel. Rugged outer walls are lined with an inner layer of finer materials like pine needles and moss.


A squirrel drey by Simpson Hall.

To get ready for the winter’s bitter cold, squirrels begin to build and bolster their dreys in the summer or early fall, starting by gnawing small live branches, with leaves attached, off trees. Gathering the sticks before leaves begin to fall is key—the leaves simply dry on the sticks without falling, remaining intact to function as natural insulation for the squirrel’s winter refuge.

Many squirrels choose to make not just one drey, but two! They’ll use the second as a backup home, just in case their first is disturbed by a predator or parasites. It’s no wonder squirrels seem so busy. All the while, they are busy gathering mast—nuts like acorns and beechnuts—in large communal buried stores, which will help them survive the harsh winter.

Next time you go for a walk on campus, or even are simply walking from East Side to West Side, try to count how many dreys you spot. You might be surprised by just how many you see!

More squirrel dreys at Wellesley

Can you find any of these dreys? Let us know by direct messaging @wellesleypaulson on Instagram!

Wellesley College’s campus features alternating wooded areas and open spaces, making ideal habitat for the red-tailed hawk (Buteo jamaicensis), a striking raptor that many human members of the College community have spotted this Fall.

Red-tailed hawks are birds of prey, and hunt not by hovering and soaring in the air, but rather by perching on branches and swooping down to ground level to capture prey such as mice, voles, squirrels, and chipmunks. They are one of the largest hawks in North America, and also one of the most widespread and common. Here at Wellesley, red-tailed hawks enjoy perching in tall trees that surround open spaces, where they can easily spot prey even from 100 feet above ground level.

October 30th, 2019

Emma Andrews ‘23 was walking back to her dorm after a shift at the Wellesley College Botanic Gardens when she found herself approaching a young red-tailed hawk perched on a low tree branch right by the Silver Thread Brook - the small stream that feeds Paramecium Pond. She realized the hawk had just captured a small rodent, most likely a vole, and watched it as it munched on its morning catch. She managed to get a mere 4 meters from the hawk before it became wary and flew, with its meal, to a nearby tree.

Emma recounts her experience witnessing this striking wildlife interaction:

“it was unusual yet very cool to be in such close proximity to a hawk... I occasionally hear the distant screech of a hawk at Wellesley, but hadn’t ever been so close! Just a beautiful reminder of how much life this campus hosts.”

Emma Andrews '23 spotted a red-tailed hawk after it had recently captured a small rodent

November 8th, 2019

Midafternoon, two red-tailed hawks perched above the Science Center Meadow on horizontal branches of two trees that frame the meadow, most likely looking for prey. One, perched just some 10 feet from the ground, may have been slightly distracted by curious human onlookers, though it was surprisingly stoic and un-spooked. Red-tailed hawks’ relative tolerance for humans is one trait that makes the species so adaptable— so much so that the species’ population is actually increasing overall.

A red-tailed hawk perches on a tree branch by the Science Center Meadow

Red-tailed hawks are incredible predators that likely help keep Wellesley’s burgeoning small rodent population in check. Although there has been a sudden uptick in red-tailed hawk sightings at Wellesley on iNaturalist, this may have also coincided with the loss of leaves from deciduous trees making the perching hawks much more visible to passerbys. Red-tailed hawks can be spotted at Wellesley year-round. Whatever it may be, red-tailed hawks are welcome additions to Wellesley’s campus, bringing balance to the landscape’s ecosystems.

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Welcome to the Paulson Ecology of Place Initiative Biodiversity Project! This is our first news post, and we plan on continuing to feature diverse wildlife and plants, as well as interesting nature details, in the future!