Nicholas School of the Environment Archives

Look at the nearest window. What did you see first—the glass itself or what was on the other side? For birds, that distinction is a matter of life and death.

A dead red-eyed vireo above the entrance to the Brodhead Center at Duke. Every year, millions of birds die after colliding with windows. Buildings with lots of glass are particularly dangerous.

Every year, up to one billion birds die from hitting windows. Windows kill more birds than almost any other cause of human-related bird mortality, second only to feral and domestic cats. Both the transparency and reflectiveness of glass can confuse flying birds. They either don’t see the glass at all and try to fly through it, or they’re fooled by reflections of safe habitat or open sky. And at night, birds may be disoriented by lit-up buildings and end up hitting windows by mistake. In all cases, the result is usually the same. The majority of window collision victims die on impact. Even the survivors may die soon after from internal bleeding, concussions, broken bones, or other injuries.

Madison Chudzik, a biology Ph.D. student in the Lipshutz Lab at Duke, studies bird-window collisions and migrating birds. “Purely the fact that we’ve built buildings is killing those birds,” she says.

Every spring and fall, billions of birds in the United States alone migrate to breeding and wintering grounds. Many travel hundreds or thousands of miles. During peak migration, tens of thousands of birds may fly across Durham County in a single night. Not all of them make it.

Chudzik’s research focuses on nocturnal flight calls, which migrating birds use to communicate while they fly. Many window collision victims are nocturnal migrants lured to their deaths by windows and lights. Chudzik wants to know “how we can use nocturnal flight calls as an indicator to examine collision risks in species.”

Chudzik (back) setting up one of her recording devices on the Museum of Science and Industry in Chicago. The devices record flight calls from birds migrating at night.
Image courtesy of Chudzik.

Previous research, Chudzik says, has identified a strong correlation between the number of flight calls recorded on a given night and the overall migration intensity that night. “If sparrows have a high number of detections, there is likely a high number migrating through the area,” Chudzik explains. But some species call more than others, and there is “taxonomic bias in collision risk,” with some species that call more colliding less and vice versa. Chudzik is exploring this relationship in her research.

Unlike bird songs, nocturnal flight calls are very short. The different calls are described with technical terms like “zeep” and “seep.” Chudzik is part of a small but passionate community of people with the impressive ability to identify species by the minute differences between their flight calls. “It’s a whole other world of… language, basically,” Chudzik says.

Chudzik can identify a species not only by hearing its flight call but also by seeing its spectrogram, a visual representation of sound. This spectrogram, from a recording on Adler Planetarium, has flight calls from four species. The x-axis represents time, while the y-axis shows frequency. The brightness or intensity indicates amplitude.
Image from Chudzik.

She began studying nocturnal flight calls for research she did as an undergraduate, but her current project no longer needs to rely on talented humans to identify every individual call. A deep learning model called Nighthawk, trained on a wealth of meticulous flight call data, can identify calls from their spectrograms with 95% accuracy. It is free and accessible to anyone, and much of the data it’s been trained on comes from non-scientists, such as submissions from a Facebook community devoted to nocturnal flight calls. Chudzik estimates that perhaps a quarter of the people on that Facebook page are researchers. “The rest,” she says, “are people who somehow stumbled upon it and… fell in love with nocturnal flight calling.”

In addition to studying nocturnal flight calls, Chudzik’s research will investigate how topography, like Lake Michigan by Chicago, affects migration routes and behavior and how weather affects flight calls. Birds seem to communicate more during inclement weather, and bad weather sometimes triggers major collision events. Last fall in Chicago, collisions with a single building killed hundreds of migratory birds in one night.

Chudzik had a recorder on that building. It had turned off before the peak of the collision event, but the flight call recordings from that night are still staggering. In one 40-second clip, there were 300 flight calls identified. Normally, Chudzik says, she might expect a maximum of about seven in that time period.

Nights like these, with enormous numbers of migrants navigating the skies, can be especially deadly. Fortunately, solutions exist. The problem often lies in convincing people to use them. There are misconceptions that extreme changes are required to protect birds from window collisions, but simple solutions can make a huge difference. “We’re not telling you to tear down that building,” Chudzik says. “There are so many tools to stop this from happening that… the argument of ‘well, it’s too expensive, I don’t want to do it…’ is just thrown out the window.”

A yellow-bellied sapsucker collision casualty in front of the French Family Science Center last year.

What can individuals and institutions do to prevent bird-window collisions?

Turn off lights at night.

For reasons not completely understood, birds flying at night are attracted to lit-up urban areas, and lights left on at night can become a death trap. Though window collisions are a year-round problem, migration nights can lead to high numbers of victims, and turning off non-essential lights can help significantly. One study on the same Chicago building where last year’s mass collision event occurred found that halving lighted windows during migration could reduce bird-window collisions by more than 50%.

Chudzik is struck by “the fact that this is such a big conservation issue, but it literally just takes a flip of a switch.” BirdCast and Audubon suggest taking actions like minimizing indoor and outdoor lights at night during spring and fall migration, keeping essential outdoor lights pointed down and adding motion sensors to reduce their use, and drawing blinds to help keep light from leaking out.

Use window decals and other bird-friendly glass treatments.

There are many products and DIY solutions intended to make windows safer for birds, like window decals, external screens, patterns of dots or lines, and strings hanging in front of a window at regular intervals. For window treatments to be most effective, they should be applied to the exterior of the glass, and any patterning should be no more than two inches apart vertically and horizontally. This helps protect even the smallest birds, like kinglets and hummingbirds.

It can be hard to see from a distance, but these windows on Duke’s Fitzpatrick Center have been retrofitted with tiny white dots, an effective strategy to reduce bird-window collisions.

A 2016 window collision study at Duke conducted by several scientists, including Duke Professor Nicolette Cagle, Ph.D., identified the Fitzpatrick Center as a window collision hotspot. As a result, Duke retrofitted some of the building’s most dangerous windows with bird-friendly dot patterning. Ongoing collision monitoring has revealed about a 70% reduction in collisions for that building since the dots were added.

One obstacle to widespread use of bird-friendly design practices and window treatments is concerns about aesthetics. But bird-friendly windows can be aesthetically pleasing, too, and “Dead birds hurt your aesthetic anyway.”

If nothing else, don’t clean your windows.

Bird-window collisions don’t just happen in cities and on university campuses. In fact, most fatal collisions involve houses and other buildings less than four stories tall. Window treatments like the dots on the Fitzpatrick building can be costly for homeowners, but anything you can put on the outside of a window will help.

“Don’t clean your windows,” Chudzik suggests—smudges may also help birds recognize the glass as a barrier.

Window collisions at Duke

The best thing Duke could do, Chudzik says, is to be open to treating more windows. Every spring, students in Cagle’s Wildlife Surveys class, which I am taking now, collect data on window collision victims found around several buildings on campus. Meanwhile, a citizen science iNaturalist project collects records of dead birds seen by anyone at campus. If you find a dead bird near a window at Duke, you can help by submitting it to the Bird-window collisions project on iNaturalist. Part of the goal is to identify window collision hotspots in order to advocate for more window treatments like the dots on the Fitzpatrick Center.

Spring migration is happening now. BirdCast’s modeling tools estimate that 260,000 birds crossed Durham County last night. They are all protected under the Migratory Bird Treaty Act. However, Chudzik says, “We haven’t thought to protect them while they’re actually migrating.” The law is intended to protect species that migrate, but “it’s not saying ‘while you are migrating you have more protections,’” Chudzik explains. Some have argued that it should, however, suggesting that the Migratory Bird Treaty Act should mandate safer windows to help protect migrants while they’re actually migrating.

“This whole world comes alive while we’re asleep, and… most people have no idea,” Chudzik says about nocturnal flight calls. She is shown here on Northwestern University, one of the Chicago buildings where she has placed recorders for her research.
Photo courtesy of Chudzik.

We can’t protect every bird that passes overhead at night, but by making our buildings safer, we can all help more birds get one step closer to where they need to go.

Post by Sophie Cox, Class of 2025

To get a fuller picture of a forest, sometimes research requires a team effort

By Robin Smith

On April 1, 2024

In Animals, Biology, Climate/Global Change, Environment/Sustainability, Field Research, Lemurs

Film by Riccardo Morrelas, Zahava Production

For some people, the word “rainforest” conjures up vague notions of teeming jungles. But Camille DeSisto sees something more specific: a complex interdependent web.

For the past few years, the Duke graduate student has been part of a community-driven study exploring the relationships between people, plants and lemurs in a rainforest in northern Madagascar, where the health of one species depends on the health of others.

Many lemurs, for example, eat the fruits of forest trees and deposit their seeds far and wide in their droppings, thus helping the plants spread. People, in turn, depend on the plants for things like food, shelter and medicines.

But increasingly, deforestation and other disturbances are throwing these interactions out of whack.

DeSisto and her colleagues have been working in a 750,000-acre forest corridor in northeast Madagascar known as the COMATSA that connects two national parks.

The area supports over 200 tree species and nine species of lemurs, and is home to numerous communities of people.

A red-bellied lemur (*Eulemur rubriventer*) in a rainforest in northeast Madagascar. Photo by Martin Braun.

“People live together with nature in this landscape,” said DeSisto, who is working toward her Ph.D. in ecology at the Nicholas School of the Environment.

But logging, hunting and other stressors such as poverty and food insecurity have taken their toll.

Over the last quarter century, the area has lost 14% of its forests, mostly to make way for vanilla and rice.

This loss of wild habitats risks setting off a series of changes. Fewer trees also means fewer fruit-eating lemurs, which could create a feedback loop in which the trees that remain have fewer opportunities to replace themselves and sprout up elsewhere — a critical ability if trees are going to track climate change.

DeSisto and her colleagues are trying to better understand this web of connections as part of a larger effort to maximize forest resilience into an uncertain future.

To do this work, she relies on a network of a different sort.

The research requires dozens of students and researchers from universities in Madagascar and the U.S., not to mention local botanists and lemur experts, the local forest management association, and consultants and guides from nearby national parks, all working together across time zones, cultures and languages.

Forest field team members at camp (not everyone present). Photo credit: Jane Slentz-Kesler.

Together, they’ve found that scientific approaches such as fecal sampling or transect surveys can only identify so much of nature’s interconnected web.

Many lemurs are small, and only active at night or during certain times of year, which can make them hard to spot — especially for researchers who may only be on the ground for a limited time.

To fill the gaps, they’re also conducting interviews with local community members who have accumulated knowledge from a lifetime of living on the land, such as which lemurs like to munch on certain plants, what parts they prefer, and whether people rely on them for food or other uses.

By integrating different kinds of skills and expertise, the team has been able to map hidden connections between species that more traditional scientific methods miss.

For example, learning from the expertise of local community members helped them understand that forest patches that are regenerating after clear-cutting attract nocturnal lemurs that may — depending on which fruits they like to eat — promote the forest’s regrowth.

Camille DeSisto after a successful morning collecting lemur fecal samples.

Research collaborations aren’t unusual in science. But DeSisto says that building collaborations with colleagues more than 9,000 miles away from where she lives poses unique challenges.

Just getting to her field site involves four flights, several bumpy car rides, climbing steep trails and crossing slippery logs.

“Language barriers are definitely a challenge too,” DeSisto said.

She’s been studying Malagasy for seven years, but the language’s 18 dialects can make it hard to follow every joke her colleagues tell around the campfire.

To keep her language skills sharp she goes to weekly tutoring sessions when she’s back in the U.S., and she even helped start the first formal class on the language for Duke students.

“I like to think of it as language opportunities, not just language barriers,” DeSisto said.”

“Certain topics I can talk about with much more ease than others,” she added. “But I think making efforts to learn the language is really important.”

When they can’t have face-to-face meetings the team checks in remotely, using videoconferencing and instant messaging to agree on each step of the research pipeline, from coming up with goals and questions and collecting data to publishing their findings.

“That’s hard to navigate when we’re so far away,” DeSisto said. But, she adds, the teamwork and knowledge sharing make it worth it. “It’s the best part of research.”

This research was supported by Duke Bass Connections (“Biocultural Sustainability in Madagascar,” co-led by James Herrera), Duke Global, The Explorers Club, Primate Conservation, Inc., Phipps Conservatory and Botanical Gardens, and the Garden Club of America.

“Biodiversity Is Essential, and It’s Not a Nice-to-Have”

By Sophie Cox

On March 27, 2024

In Animals, Environment/Sustainability, Policy, Science Communication & Education

Filmmaker Ashley Hillard and cinematographer Alan Dunkin in Yellowstone. Photo by Hillard.

“I have been interested in storytelling and the environment since my earliest memories,” says Ashley Hillard, a documentary filmmaker with an interest in wildlife management and conservation practices in the United States.

Hillard has a background in film, largely with production companies, talent agencies, and independent projects on the side, but she later shifted into climate tech recruitment. Now she is pursuing an environmental leadership Masters in Environmental Management degree at Duke while working on documentary projects. She is also a Communications Assistant Intern in the Duke Environmental Law and Policy Clinic.

She has been working on a film called “Coexistence,” a documentary that spotlights North American species and wildlife management practices. Hillard got the idea for the project when she noticed that U.S.-based researchers often choose to study species in other countries, perhaps “because it’s easier to go over and say ‘Why don’t you try this?’ rather than having to deal with issues in your backyard.”

“We need to pay attention to our own backyards,” Hillard emphasizes. “The hope,” she says, is “more laws and policies and values change along with behaviors as we become more informed and more aware.” She also believes that “local efforts can usually go further.” Part of her goal in creating films about conservation is to help viewers realize that “individuals can be part of change.” Films and other forms of storytelling can inform people about specific species and conservation efforts, but Hillard hopes her work can help shift perspectives more broadly as well. Effective conservation is often “a social attitudes and values issue,” Hillard says. “There needs to be a shift in how we view the environment.”

An American bison that Hillard saw while filming in Yellowstone.
Photo by Hillard.

Shifting baseline syndrome is the idea that people’s expectations of how nature should look reflect their own experiences rather than an accurate picture of the natural state of landscapes, flora, fauna, and wildlife abundance. Our understanding of what nature “normally” looks like changes over generations and is skewed by the societies and time periods we inhabit. The more we damage our environments, the less we collectively remember what they looked like before—and the less motivated we may be to restore them to a condition most of us can’t remember.

When humans and wildlife come into conflict, our perceptions of how nature “should” be can matter tremendously. Gray wolves were recently delisted from the Endangered Species list, then re-listed in most places—both were controversial decisions—but their numbers are far lower than they were historically. Still, some think there are too many wolves. In the Western U.S., gray wolf conservation efforts often clash with the desires of ranchers and and hunters, who may view higher wolf populations as a threat to livestock or game animals like deer and elk. But some of these hunters and ranchers, Hillard says, “are real conservationists doing amazing work,” and she thinks they should get more attention.

While creating the film, Hillard has tried to capture the complexities of wildlife conservation. It’s not as simple as “They’re bad, they’re good, and this is how we solve it,” Hillard says.

There are different ideas about how conservation efforts should be conducted and which animals should be protected in the first place. The dominant approach to wildlife management in the U.S., Hillard says, is rooted in the idea that there are “good” species that people can use and “bad” species that people don’t like to live with, such as wolves and other predators. “This perspective,” she says, “came over with colonists.” She mentions Little Red Riding Hood and the Big Bad Wolf; the stories we tell about animals can reflect societal attitudes toward them. Many indigenous peoples, meanwhile, have traditionally viewed all species as kin. This “cultural aspect” affects people’s willingness to coexist with species like wolves, which in turn affects our conservation practices.

A gray wolf at the Grizzly and Wolf Discovery Center in Yellowstone.
Photo by Alan Dunkin, provided by Hillard.

In this country, very few people are killed by wildlife—about 700 annually, according to one review that counted deaths from bites, wildlife-vehicle collisions, and zoonotic diseases. Car accidents, on the other hand, are more than 60 times more deadly, killing about 43,000 people in the U.S. per year. “We have a certain acceptance of how we die,” Hillard says. “There are a number of things that kill people with much higher percentages [than deaths from wildlife] that we… accept as day-to-day,” but we don’t tend to hear calls to eliminate cars from society, while an animal that harms a human is often given a death sentence. Hillard thinks media in general should be more careful about how they share stories about wildlife, especially negative encounters. If stories focus only on rare but tragic incidents, it can distort perceptions of species and “feed into that doom loop.”

Films, Hillard says, can inspire people “to look at things differently and see things from different perspectives.” Storytelling is also a way of communicating scientific information and encouraging action. Hillard feels that some stories about environmental issues are told in a one-sided, black-and-white way, but the nuances of these problems are important. “Finding those complexities and working through them… and then trying to craft stories around that to share with the public so they can make more informed decisions” is part of the goal of Hillard’s films.

“Coexistence” focuses on well-known, often controversial species like red wolves and mountain lions. “Familiarity and awareness of a species can contribute to interest in protecting them,” Hillard says. Such species are sometimes referred to as charismatic megafauna and can be viewed as ambassadors for conservation or umbrella species whose protection helps other wildlife as well. But Hillard has concerns about the term charismatic megafauna. “It diminishes a species’s value and reduces them to ‘cute’ so you no longer see them as an intrinsic part of an ecosystem,” she says. She believes it’s important to emphasize protection of entire ecosystems, not just specific species within them.

A Mexican gray wolf pup at the California Wolf Center. The Mexican gray wolf is a gray wolf subspecies.
Photo by Hillard.

Hillard hopes that her films inspire more awareness of and interest in environmental issues. “There’s a lot of pressure to get it right,” she says. And storytelling can have its own issues when it comes to presenting accurate information. “Information can be left out or shaped in a way to make it more compelling,” Hillard acknowledges. She feels that many wildlife films focus first on scenery and animals, then discuss conservation issues at the end. But “Coexistence” is “very much focused on the issues.” It is expected to be released by early 2025.

“I strive to tell impactful stories in creative ways that are more upbeat in tone,” Hillard says. She believes it’s important for people to be aware of the challenges facing wildlife, but she also wants to inspire hope and the belief that individual actions can matter. “To feel powerless can make you feel hopeless, and there is a lot to be hopeful for,” she says. “But there needs to be a shift in how we view the environment.”

One major problem she sees is our consumerist, materialistic society. “We’re kind of consuming ourselves off the planet,” Hillard says. “How do you change behaviors within a society that’s so hyper-consumptive?”

Films and other forms of storytelling can make scientific information more accessible. “Communicating is that bridge to getting people to care, to understand it, to learn about it,” Hillard says. “Without communication, science studies and research may be siloed in academia.” When we lack accurate and accessible information, we may rely on “‘I heard someone say something about that thing’” rather than science to inform our understanding of issues.

Along with providing accurate information, Hillard wants to encourage “a view of mutualism with other species” and raise questions like “How can we be better neighbors to nonhuman species?”

Ultimately, she wants viewers to recognize that “biodiversity is essential, and it’s not a nice-to-have.”

Hillard at Lands End Lookout in San Francisco.
Photo credit Alan Dunkin, provided by Hillard.

Post by Sophie Cox, Class of 2025

Reducing Food Insecurity and Creating Community at Durham’s Catawba Trail Farm

By Gabrielle Douglas

On February 27, 2024

In Anthropology, Environment/Sustainability, History

At Catawba Trail Farm in north Durham, the idea of community remains at the forefront of all that they do. A space dedicated to growing, learning, and diligent work, the farm invites all willing to become involved. Recently, students at Duke University had the opportunity to bear witness to these qualities, through a course taught by Dr. Brian McAdoo of Duke’s Nicholas School of the Environment.

*Picture of volunteers at Catawba Trail Farm (Credit: @UrbanCommunityAgrinomics on Instagram.)*

The Catawba Trail Farm was once known as Snowhill Plantation, yet despite this co-founder Delphine Sellars refers to it as “a place of healing.” This is because Sellars recognizes the importance of acknowledging the past when attempting to shape the future. Sellars’ focus is on taking land formerly used to abuse enslaved people and transforming it into a place of empowerment and healing. This is seen through the connection between the farm and McAdoo’s course here at Duke. The course, “Exploring Earth Sciences: Surviving Anthropocene in North Carolina,” explores a range of themes such as food insecurity, environmental justice, and global change through the context of environmental studies. Additionally, McAdoo’s course has what is referred to as the ‘Catawba Trail Mission’ where Duke students, in partnership with Catawba Trail Farm, seek to not only target this food insecurity within the community, but also uncover the history hidden within the roots of the farm.

*Picture of* Delphine Sellars (*Credit: @UrbanCommunityAgrinomics on Instagram.)*

The most recent progress of this mission can be seen through the class’s work with the gravesite of William Johnston, who established Snowhill Plantation in 1763. Through a geophysical survey, the class identified several unmarked graves of enslaved people buried with the Johnston family. Through this they have worked to trace their lineages to their loved ones and inform them of their findings. The class has also used this same technology to help identify and ensure that the traits and key aspects of the land are fully understood and respected.

Through the work between Duke and Catawba Trail Farm, students are granted the opportunity to take their learning beyond the textbook and truly begin to understand the depth behind the land outside of technological gadgets. Catawba Trail Farm helps in this journey while simultaneously learning more about the rich nature of the land and its inhabitants. This constant sense of learning and support is what makes students such as Duke master’s student, Roo Jackson, comfortable in saying Catawba Trail Farm “feels like home.”

Post by Gabrielle Douglas, Class of 2027

Glowing Waterdogs and Farting Rivers: A Duke Forest Research Tour

By Sophie Cox

On January 25, 2024

In Animals, Biology, Climate/Global Change, Environment/Sustainability, Field Research, Science Communication & Education

Jonny Behrens looks for aquatic macroinvertebrates with Duke Forest Research Tour participants.

“Who would be surprised if I told you that rivers fart?”

Nick Marzolf, Ph.D., went on to explain that streams release greenhouse gases from decaying matter and gas-producing bacteria. This revelation was one of several new facts I learned at the annual Duke Forest Research Tour in December.

“First and foremost,” says Duke Forest Senior Program Coordinator Maggie Heraty, “the Duke Forest is a teaching and research laboratory.” The Office of the Duke Forest hosts an annual Research Tour to showcase research activities and connect to the wider community. “Connecting people to science and nature, and demystifying scientific research, is a key part of our goals here,” Heraty says.

Duke Forest, which consists of over 7,000 acres in Durham, Orange, and Alamance Counties, lies within the Cape Fear and Neuse river basins, two of seventeen river basins in North Carolina. What exactly is a river basin? Heraty quoted a poetic definition from North Carolina Environmental Education:

“A river basin encompasses all the land surface drained by many finger-like streams and creeks flowing downhill into one another and eventually into one river, which forms its artery and backbone. As a bathtub catches all the water that falls within its sides and directs the water out its drain, a river basin sends all the water falling within its surrounding ridges into its system of creeks and streams to gurgle and splash downhill into its river and out to an estuary or the ocean.”

Located within the Cape Fear River Basin, the headwaters of New Hope Creek, which passes through the Korstian Division of Duke Forest, are fed by roughly 33,000 acres of land, over 5,000 of which are in the Duke Forest. Land outside of the Forest is of vital importance, too. Duke Forest is working in partnership with other local conservation organizations through the Triangle Connectivity Collaboration, an initiative to connect natural areas, create wildlife corridors, reduce habitat fragmentation, and protect biodiversity in the Triangle region.

New Hope Creek in the Korstian Division of the Duke Forest.

Dwarf waterdogs

We walked down a short trail by the creek, and the tour split into two groups. Our group walked farther along the stream to meet two herpetologists studying the elusive dwarf waterdog.

Bryan Stuart, Ph.D., Research Curator of Herpetology at the North Carolina Museum of Natural Sciences, and Ron Grunwald, Ph.D., Duke University Senior Lecturer Emeritus, are involved in a study looking for dwarf waterdog salamanders (Necturus punctatus) in New Hope Creek. Dwarf waterdogs are paedomorphic, Stuart said, meaning they retain larval characteristics like external gills and a flat tail throughout their lives. In fact, the genus name Necturus means “tail swimmer” in reference to the species’s flat tail.

According to Stuart, on October 3, 1954, Duke professor and herpetologist Joe Bailey collected a dwarf waterdog in New Hope Creek. It was the first record of the species in Orange County.

The Duke Forest is in the westernmost part of the species’ Piedmont range, though it extends farther west in parts of the sandhills. “To have a dwarf waterdog record in Orange County—that’s almost as interesting as it gets,” Stuart said.

Ron Grunwald and Bryan Stuart discuss dwarf waterdog research at New Hope Creek.
Photo provided by The Office of the Duke Forest.

In the late 1960s, Michael A. Fedak, Bailey’s graduate student, did a thesis on dwarf waterdogs in the area. His specimens are still stored in the collections of the North Carolina Museum of Natural Sciences.

No one had studied this population since—until now.

Dwarf waterdogs are very sensitive to pollution and habitat disturbance, Stuart said, on top of the fact that New Hope Creek is already at the edge of the species’s habitat. When Fedak studied them several decades ago, the salamanders were abundant. Are they still?

Stuart, Grunwald, and other researchers want to find out. “The challenge of salamander biology,” Grunwald said, “is that it always happens when it’s freezing.” Surveying salamander populations, he explains, isn’t like watching birds or counting trees. It requires you to go where the salamanders are, and for dwarf waterdog research, that means dark, cold streams on nights when the water temperature is below 55 degrees Fahrenheit.

Researchers bait funnel traps with chicken liver or cat food and set them underwater overnight. Sometimes they catch crayfish. Sometimes they catch nothing. And sometimes they catch exactly what they’re hoping to find: the elusive dwarf waterdog. After all this time, these slippery, nocturnal, chicken-liver-loving salamanders are still here.

Two dwarf waterdogs in a funnel trap before being released back into New Hope Creek.

Though the traps have been successful at capturing some individuals, they will never catch them all, so researchers calculate the recapture rate to estimate the total population. Imagine a bag of rice, Grunwald said. You could count each individual grain, but that would be challenging and time-consuming. Alternatively, you could pull out one grain of rice, color it, and put it back in the bag, then estimate the total number by calculating the probability of pulling out the same colored grain of rice again. In a very small bag, you might draw the same rice grain several times. But the more rice you have, the less likely you are to draw the same grain twice.

To figure out if any of the dwarf waterdogs they catch are recaptures, the researchers mark each individual with a visual implant elastomer, which is “just a fancy way of saying rubber that we can see,” Grunwald said. The material is injected under a salamander’s “armpit” with a small syringe, creating a pattern visible under ultraviolet light. With two colors (fluorescent yellow and red) and four possible injection locations (one behind each leg), there are plenty of distinct combinations. Grunwald showed us a waterdog that had already been marked. Under a UV flashlight, a spot just below its right foreleg glowed yellow.

Captured dwarf waterdogs are injected with a special rubber material that glows under a UV light. Each salamander is marked with a distinct pattern so researchers can recognize it if it’s ever recaptured.

Establishing a recapture rate is essential to predicting the total population in the area. The current recapture rate? Zero. The sample size so far is small—about a dozen individuals—and none of them have been caught twice. That’s an obstacle to statistical analysis of the population, but it’s good news for the salamanders. Every new individual is one more dwarf waterdog survivor in New Hope Creek.

Ron Grunwald with Research Tour participants looking at dwarf waterdogs in bags.
Photo provided by The Office of the Duke Forest.

Stream health

Next, at a different spot along the stream, we met Nick Marzolf, Ph.D., a postdoctoral scholar, and Jonny Behrens, a Ph.D. student, to learn more about New Hope Creek itself. Marzolf and Behrens have both been involved with aquaterrestrial biogeochemistry research in the lab of Emily Bernhardt, Ph.D., at Duke University.

Protecting New Hope Creek requires understanding individual organisms—like dwarf waterdogs—but also temperature, precipitation, oxygen levels, pesticide runoff, and biodiversity overall. When humans get stressed, Behrens said, different organs have different physiological reactions. Similarly, different organisms in a stream play different roles and respond to stress in different ways.

Jonny Behrens and Research Tour participants look at aquatic macroinvertebrate samples.
Photo provided by The Office of the Duke Forest.

Behrens passed around vials containing aquatic macroinvertebrates—specimens big enough to see with the naked eye—such as the larvae of mayflies, crane flies, stoneflies, and dragonflies. They are known for being good indicators of stream health because there are many species of macroinvertebrates, and they have different tolerances to stressors like pollution or changes in water temperature.

Aquatic macroinvertebrates can indicate the health of a stream through their species diversity and abundance.
Photo provided by The Office of the Duke Forest.

The water downstream of a nearby wastewater treatment plant is much warmer in winter than other waterways in the area, so researchers see more emergent adult midges and caddisflies there than they do here. Aside from temperature, organisms need to adapt to other changing conditions like oxygen levels and storms.

“Rain is really fun to watch in streams,” Behrens said. The water level rises, pulling up organic matter, and sand bars change. You can tell how high the water got in the last storm by looking for accumulated debris on trees along river banks.

Farting rivers and the peanut butter cracker hypothesis

Marzolf studies hydrology, or “how water moves through not only the landscape but also the river itself.”

Nick Marzolf demonstrates a technique to measure gasses in streams using a syringe.

Part of his research involves measuring gases in water. Streams, like cars and cows and people, release greenhouse gases, including carbon dioxide and methane. In fact, Marzolf and colleagues hypothesize that New Hope Creek contributes more CO₂ to the atmosphere per unit area than anywhere else in the Duke Forest.

Decaying matter produces CO₂, but that isn’t the only source of greenhouse gasses in the creek. Microscopic organisms, like methane-producing bacteria, produce gases as well.

The “peanut butter cracker hypothesis,” Marzolf said, compares organic matter such as leaves to a cracker, while the “peanut butter,” which makes the cracker more palatable, is the microbes. Scrumptious.

Disturbing the sediment at the bottom of New Hope Creek causes bubbles to rise to the surface due to the metabolic activities of gas-producing bacteria.

Marzolf turned to Behrens. “Do you want to walk around and see if you can stir up some methane bubbles?” Behrens waded into the stream, freeing bubbles from the pressure of the overlying water keeping them in leaf mats. We watched the bubbles rise to the surface, evidence of the activities of organisms too small to see.

Behrens walks around in New Hope Creek to stir up gas bubbles from aquatic bacteria.

Restoring a stream to protect its pigtoe

Finally, Sara Childs, Executive Director of the Duke Forest, discussed stream restoration projects. Though structures in the Duke Forest like remnants of old mills and dams can alter and damage ecosystems, they can also have historical and cultural significance. Duke Forest prioritizes restoration projects that have meaningful ecological, teaching, and research benefits while honoring the history of the land.

For instance, the Patterson Mill Dam was built in the late 1700s and probably remained in use for about 100 years. The stream has already adapted to the structure’s presence, and there isn’t necessarily ongoing degradation because of it. Duke Forest restoration projects, Childs said, don’t revolve around very old structures like the Patterson Mill Dam. Instead, they are planning to remove two more recent structures that are actively eroding banks, threatening wildlife habitat, and creating impounded, oxygen-poor areas in the stream.

One of the structures they are hoping to remove is a concrete bridge that’s endangering a threatened freshwater mussel species called the Atlantic pigtoe (Fusconaia masoni). Freshwater mussels, according to Childs, require a fish species to host the developing mussel larvae on their gills, and the Atlantic pigtoe favors the creek chub (Semotilus atromaculatus). The concrete bridge forms a barrier between the pigtoe and the chub, but removing it could reunite them.

Before starting construction, they will relocate as many mussels as possible to keep them out of harm’s way.

New Hope Creek, home to waterdogs and pigtoe and farting microbes, is precious to humans as well. Heraty describes it as “a really spectacular and beautiful waterway that we are lucky to have right in our backyards here in Durham.”

Post by Sophie Cox, Class of 2025

Following the people and events that make up the research community at Duke

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