As the ferry cuts through the choppy waters of Long Island Sound, 14 Yale undergraduates stand on the deck, outfitted with backpacks and sunblock. Within minutes their destination, a rugged piece of land known as Horse Island, comes into view.
When they arrive, the students, who are enrolled in Professor Casey Dunn’s “Invertebrates” course, scatter across the 17-acre island, carrying nets and buckets. And as they have each week during the fall semester, they begin exploring its rocky beaches and wading through tidal pools, collecting — and then analyzing — marine specimens.
The ferry ride takes only about 20 minutes, but it transports these students to a living classroom that feels a world away from campus.
Students ride the ferry to Horse Island 1 ½ miles offshore in Long Island Sound.
“Today you will focus on an organism for your final project,” Dunn, a professor of ecology and evolutionary biology in Yale’s Faculty of Arts and Sciences, tells the students before they disperse to collection points across the island, the largest of the Thimble Islands, an archipelago located in the Sound.
While many Yale courses feature field trips to Horse Island, Dunn’s class is the first to meet weekly and incorporate a lab on the uninhabited island, which sits 1 1/2 miles offshore and about 12 miles from the heart of the university’s New Haven campus. The island, which is managed by the Yale Peabody Museum, has its own research station, a minimalist, off-the-grid structure. Water for washing and research activities comes from a rain collection cistern system. Potable water must be carried in.
Experiencing these animals in their natural environment is very different from working with them in the lab. You see them as part of the larger ecosystem.
The course, which Dunn has taught since 2018, offers an overview of animal diversity focused on marine invertebrates. Students explore evolutionary patterns, organism structures, and the role of environment in this evolution.
“There are multiple themes we touch on, and one is ocean diversity,” says Dunn, who is also a curator in the Yale Peabody Museum’s Division of Invertebrate Zoology. “In order to understand the diversity of life on Earth, you really need to understand the animals that live in the ocean.”
Casey Dunn, a professor of ecology and evolutionary biology in Yale’s Faculty of Arts and Sciences, teaches “Invertebrates,” a course focused on marine invertebrates.
With its mix of intertidal pools and rocky beaches, Horse Island offers an ideal habitat for dozens of invertebrate marine species — and for people who want to study them.
“This is the first class where I’ve been able to go out in the field for hands-on learning,” says junior Madelyn McElroy, an ecology and evolutionary biology major from Georgia. “Experiencing these animals in their natural environment is very different from working with them in the lab. You see them as part of the larger ecosystem.”
It was this power of experiential, hands-on research that inspired Dunn to “radically rethink” the course. Previously held in lecture halls and classroom laboratories, the twice-weekly course now splits students’ time between the classroom and Horse Island.
“When I’m working with marine invertebrates in my own research, the first thing we have to do is find them, so we’re going out to the field and collecting them,” Dunn explains. “Next, we identify them, figure out what species they are, orient ourselves, and then begin working with them in the lab. That’s what my students are doing this fall.”
It was this hands-on opportunity that drew sophomore Anita Duncan to the class.
In the island’s open-air research station, students analyze and document marine organisms.
“The weekly trips have been an incredible opportunity,” says Duncan, an ecology and evolutionary biology major. “The range of organisms we’ve found on such a small island so close to Yale was a surprise, and exploring in the field lets me deeply internalize the concepts we learn in lecture. Catching a ctenophore [a jelly-like marine animal] has taught me much more than reviewing a flashcard about one.”
Duncan, who is from Alabama, has also been surprised by her classmates and the different perspectives they bring to the class. “I’m amazed by the diverse ways they engage with the work we’re doing,” she says. “Some have backgrounds and interests in areas that I wouldn’t have seen as related to marine invertebrates, and it’s really allowed for interesting connections and viewpoints.”
Indeed, the course has long attracted students with a wide range of interests.
“I get students from the humanities, some with arts backgrounds, who are interested in these animals from an aesthetic perspective, and others who are fascinated by the ocean,” Dunn says. “I learn to see the animals in new ways working with them.”
On the island, the tides dictate the day’s activities. “If there’s a low tide, we can go out in water shoes and wade and turn over rocks and look through the seaweed, and collect all kinds of things,” Dunn says. “If the tide is higher and there’s not much exposed habitat, we scoop animals out of the water at the dock or use the Peabody’s boat to go out deeper and with nets.”
Today the tide is low. In a sheltered tidal pool, three students wade waist-deep into the water and, peering through face masks, collect organisms. They gather algae, crab, and sponge species.
Intertidal pools, rocky beaches, plenty of vegetation make Horse Island an ideal habitat for invertebrate marine species.
“I consistently look forward to this day the most in my week,” says Celeste Giannoulias, a sophomore from New York who’s also an ecology and evolutionary biology major. “Being out here — it’s just beautiful — and the chance to do this work together is such a rare opportunity.”
On the other side of the island, two students climb among beachside boulders, collecting snail, oyster, and whelk species. They carry the specimens back to a staging area outside the research station, where the creatures are rinsed with fresh water and laid out on a table for an initial assessment.
“We make a first pass out here and then bring the animals into the station where we have the microscope tables, a photography area, and a small printer for students to print their work,” Dunn says.
Peering through a microscope, junior Samara Davis watches a drop of sea water come to life with dark flitting specks and an orange wormlike organism. “They are amazing,” she says.
An ecology and evolutionary biology major from New York, she sketches what she sees in a notebook on her lap.
All specimens are donated to the collections of the Peabody Museum, which purchased the island in 1971 for use as a research site. And on this day, two members of the museum staff — Andy Todd, the museum’s imaging and recording studio manager, and Patrick Sweeney, collections manager of its botany division — are on hand to help students as they examine, sketch, photograph, and even video record their specimens.
View of a magnified marine organism in the research station. Students collect, analyze, and photograph specimens.
“The studio on the island here has been designed to work with students,” Todd says. “My goal is to introduce them to photographing in the field, help walk them through the process and learn how much it has to offer.”
Help from the museum staff and other Yale offices has made this year’s move to the island possible, Dunn says.
“We’ve had incredible support from the Peabody and from the Department of Ecology and Evolutionary Biology to make all the pieces work,” he says. “Arranging transportation for the students, booking the ferries, making sure the facility is ready, and making sure we have great support in the teaching labs – they’ve just been phenomenal.”
A student studies a specimen on Horse Island.
As this day’s class winds down, students pack up the lab and secure the specimens for the ferry ride back to the mainland. Back in New Haven, they’ll return to the classroom. But in a week’s time, they’ll board the ferry again.
For Victor Nguyen, a neuroscience major, the open-air invertebrate study has been a real change of pace. Most of his coursework has focused on the human brain.
“I wanted to take a course that was fun and that let me look at biology through a different lens,” says Nguyen, who is a senior from Arkansas. “My other labs have been much more sterile and removed. Horse Island makes science feel alive.”
