The Outer Banks have a strange geometry. They seem to operate in two dimensions. Flat land, flat water. Dolphin backs move like pinwheels on the sea’s surface, rising higher than the island soil. I have never seen a shore so flat. My companions are Chelsea, a photographer, and Sue Stuska, wildlife biologist for CLNS. As our boat’s nose bumps the dock, we see bubbles of washed-up jellyfish on the yellow beach. We have arrived on Shackleford Island, a part of North Carolina’s Cape Lookout National Seashore, and home to 118 wild horses. These horses are likely descendants of those that escaped shipwrecks in the 1500s. In 1974, Dan Rubenstein, then a Duke Ph.D. student of zoology, began a study of their social lives. At the time, many Duke researchers were studying the societies of primates and other animals that live with their kin.

“One of the key questions that we wanted to understand better was why animals cooperate and live socially,” said Rubenstein, now chair of the Department of Ecology and Evolutionary Biology at Princeton University. “I thought if we really wanted to understand why animals would come together, we needed to look at a species where there wasn’t kinship.” Horses form groups with non-relatives, he explained. Such a system provided an excellent opportunity to learn why individuals formed groups. In horse society, both males and females leave the group they are born into for a new one. These groups, called harems, typically consist of one male and several females with offspring. Younger males form bachelor herds.

In the early years of his research, Rubenstein saw that Shackleford horses strayed from a typical social pattern. Usually horse groups have home ranges that they share with other groups. “But on Shackleford, because of the structure of the island, they defended territories,” Rubenstein said. Keeping a territory allowed harems to feed more “wisely,” and to ensure that food remained in winter months. If you do not finish all the grass in a patch, someone else will come and eat it, Rubenstein explained. “If you control it, you can let it recover and rotate.”

Stallions fought to maintain territories and to guard mares from other males. Rubenstein said research has shown, however, that these are not male-dominated groups. “If females don’t like the males they can vote with their feet. They can leave the group.”

The island has undergone a transformation since Rubenstein first began his research—and so has horse behavior. In 1974, only a small patch of maritime forest stood on the island. The horses shared Shackleford with feral cows, sheep and goats. In 1986, the Park Service moved to restore Shackleford to its natural state, forested, without any hoofed herbivores, Rubenstein said. They removed all sheep, goats and cows. Horses remained, as they were considered part of the region’s history.

“Over time, the territoriality has been eroded on the island,” Rubenstein said, “because the physical structure of the island has changed.” As trees spread in the absence of browsers, like goats, grassland reduced. Food for horses decreased and with woodlands, males had less visual access to their territories. Over time the horses became less territorial, though males still guard their females from other stallions. After the other feral animals were removed, the horse population lived relatively unmanaged for a decade. By 1996, more than 200 horses lived on the island, and the Park Service worried that the hurricane-plagued habitat was too fragile to support such large animals.

The Park Service removed around 80 horses from Shackleford, but many tested positive for equineinfectious anemia which by North Carolina law requires them to be euthanized or live quarantined from other horses. Quarantine placement proved difficult to find, however, and the animals were put down. Stuska, who began working for the Park Service in 1999, three years after the removal, described the situation as very emotional. The action caused a public outcry from Outer Banks residents and horse lovers. “They didn’t look sick,” Stuska said of the horses. “There was a lot of distress.” As a result of the incident, the state of North Carolina passed legislation in 1998 to created a partnership: the Cape Lookout National Seashore would manage the horses jointly with the Foundation for Shackleford Horses, a nonprofit organization run entirely by volunteers.

Rubenstein, whose students continue to study the herd, said the co-management seems to be working well. The Foundation, founded in 1996, works to “To preserve and protect the Shackleford Horses and to ensure that their place in history is continued into the future.”

Its president and chairperson, Carolyn Mason, said she grew up in the Outer Banks knowing wild horses lived nearby.

“When I was a little girl—I’m 68 years old—there were horses on Core Banks,” Mason said. “I just felt like they belonged there.” Mason said while leading the Foundation she has learned to be a “parrot,” soliciting and communicating the advice of Rubenstein and other scientists to best manage the herd. “Without fail, the experts would say, ‘How can I help you?’” she said. “I feel like I’ve been in graduate school for the last 15 years.”

Currently, the horse management plan calls for a population between 110 and 130 horses. The Park Service and Foundation maintain this range by two mechanisms: removing horses for adoption, and administering contraception to mares. At the start, a number of horses were removed in a series of “roundups,” the last of which occurred in 2005. The most recent plan calls for removal of two to four foals each year by darting.

Porcine Zonae Pellucidae vaccine, or PZP, is delivered by dart to selected mares as birth control. The vaccine has been administered to zoo residents as well as other wild populations living in restricted space, such as elephants in South African game parks. When injected into the muscle of a mare, PZP alters sperm receptors on the membrane of her eggs, preventing fertilization. Mares must have booster shots annually. After five to seven consecutive years of injections, mares typically become infertile. This differs by individual horse, however. Stuska noted that one mare, Sabrina, foaled after seven years on PZP.

Cassandra Nuñez, associate research scholar at Princeton, who began researching the horses as Rubenstein’s Ph.D. student in the mid 1990s, began a study, supported by the Park Service and Foundation in 2005 to examine what effects contraception was having on horses’ behavior. After this initial project, she continued her own research on the subject. Nuñez found that mares who had received PZP were more promiscuous and left their harem groups more frequently for new ones. This dispersal disrupted group stability, Nuñez said, as mares usually stay in one harem for many years. She added that switching groups can be stressful for mares. PZP also seemed to alter female cycling. Contracepted mares were more likely to give birth later in the year, indicating that they were ovulating during what was the non-breeding season.

“We definitely think that [immuno-contraception] is the most humane method out there, but if you can use it in a way that mimics the natural biology at all that would be best,” Nuñez said.

On Shackleford Island with Stuska, we hope to collect dung samples to check mares for pregnancy. This knowledge will drive decisions such as how many mares and which mares to contracept.

Earlier that morning, in Stuska’s office, we saw Shackleford lineages listed on a Velcro board. The Park Service adheres to a naming system initiated by Rubenstein.

“Youngsters have the first letter of their mother’s name,” Stuska said. The Park Service later began to choose names from a theme for foals born in the same year. This way, a name can tell you the age and family of a horse, she said. Dance, was one such theme, and resulted in Swing, Jitterbug and Cha-Cha. Harems on the Velcro are organized by home range, with the mid-island harems at the middle of the board. Relationships are determined by DNA analysis through blood samples during roundups and by dung samples for all new foals. Stuska tallies the numbers for each family line. This helps to determine which horses can come off the island. Less well-represented lines get to stay. In a small population, genetic diversity is extremely important. Stuska meets with the Foundation on all horse removal decisions. She spends two to three days a week out with the horses.

Stuska has a history with horses. Before working for the Park Service, she taught horse science or horse technology at community and private colleges, worked as a groom for competition animals and was a wrangler at a guest ranch in Colorado.

“Wild horses take care of themselves,” Stuska said, contrasting her current charges with her previous, domestic ones. She added that visitors sometimes seem to not understand that the Shacklefords are wild, that they should not be bothered and that they can be dangerous. “They are wild animals and feral animals and that’s the whole reason they’re here,” Stuska said. “For us to do anything that would make them less wild, that’s not the reason that they are there.” She added,

“Here, you see horse society as it really is.”

We climb into an ATV, stored in a Park Service shed near the dock. Chelsea and I ride in a cart attached to the back of Stuska’s vehicle. The wheels press into the wet sand. Foam bubbles from the sea. The landscape parallel to us turns to marsh. Driftwood stalks rise in places and sometimes pools of marsh water reach the sea. It is unlike any marsh I have seen. A flat and dry jungle at the sea. The trees grow shorter than most, but seem tall on the flat land, and birds are above them, black triangles of cormorants. An egret flies from dark marsh reeds to forest behind.

Maritime forests are defined as live oak trees at least 15 feet high, Stuska said. And they are rare. Here was a mix of forest and marsh. We entered a marsh playground, its driftwood structures and water pools, thin as plates over the sand. Off the beach and into the grasses, we saw him, our first horse.

“Judd,” said Stuska. His back is to the dunes. Judd gives a snort, a flutter of his nostrils, as he brings his mouth to the grass. He has a white spot on his forehead and, like most Shacklefords, long fur above his hooves. He, and a nearby horse, Zim, are bachelors who have traveled together for several years. Their anatomy shows evidence of Spanish ancestry. They are built like A-frames, with their front legs close at the top. Stuska tells us we are in a maritime shrub and brackish marsh habitat. Judd is eating cordgrass and Zim is eating centipede grass. Stuska says that in island exclosures, plots of land fenced off for research purposes, you can see the impact horses have on their landscape. Plant density, height and species composition are all different.

We ride through the dunes and meet white-maned Clapton and his dark-maned mares. We need dung samples from mares in Clapton’s harem for pregnancy tests, as well as one from a new foal. The foal is white and tan like Clapton. His name is Havana and his mother is called Hercules and her older daughter, Hip-Hop. Havana is resting in the sand now, his legs bent underneath him.

“When he gets up, he’ll poop,” Stuska tells us. And she is correct.

We move forward slowly. They turn their heads to us and pause, then walk, bowing as they push their knees forward. Havana puts his nose under his mother’s chin and keeps close to her as we approach.

Stuska notes that we are too near the horses. Visitors to the island, she reminds us, should not interfere with the animals. “Once they move away, it’s too late. They are already bothered.” She tells us the best way to watch horses is when you can see them all in one glance.

After Stuska collects the dung, we go on and suddenly the dunes are so high that there is no sea, only sky and in it flocks of birds. Their colors and shadows pierce the monocolored dunes.

We come across three more mares: Gray and white Dusty, tall, chestnut Zelda and Helena. Stuska says Zelda is scared of her—she darted her once. She tells me to watch for Zelda’s dung and for Chelsea to watch for Dusty’s. We, then, see Toro, a stallion. He is shorter, broader than the mares—younger than them too—with a black mane and brown fur. We stay near the harem when they disappear for a time in the marsh. When they come out of it, we follow them to a sand floor, where they stop. Helena begins to brush her front hooves on the ground.

“Helena’s gonna lay down and roll—see how she’s pawing!” Stuska says. And then the mare drops, her knees, then back on the sand, rolling like a beetle, dust clouding to the top of her raised hooves. Toro goes down too, then snorts out the sand in his nostrils, shakes grains off his cheeks.

The mares begin to walk west, and suddenly Toro wishes to change their direction. He quickens the switch in his front legs, nose down, ears back, herds them eastward. Like a parade caravan, they move over a dune. They stop to feed and we stay with them for nearly two hours, finding separate waiting places atop the dunes, seeing the sea in two directions, careful not to come between Toro and a mare when we collect their dung. From the top of a dune, they seem too large for their landscape. Giants in a land where they mow grasses to beneath ankle height. Small trees, bare hills. In November, their coats are the richest colors in the landscape.

“They’re charismatic megafauna,” Stuska said earlier of the Shacklefords. “I think people just like wild horses whether it’s here or out west or wild burros in the Grand Canyon or manatees.” Not all species are treated with such concern. “If we set out to decrease raccoons there would probably not be an interest group made to save the raccoons,” she said.

We sailed back to Harkers Island Visitor Center later that afternoon and went to meet Mason at her home, which also serves as an adoption farm for the foals brought off Shackleford. It is nearing dusk when we arrive. A gravel road winds through fenced enclosures up to the house. Cats climb on fenceposts. Mason and her young granddaughter meet us.

The ranch has 13 horses now. Eleven are Shacklefords, though not all of them are up for adoption. Sophia, for example, is a mare Mason decided to keep when she became attached to her, and Dima, a young male, has angular limb displacement, likely from premature birth.

“When we first get them, we’re dodging feet and teeth. Even the little ones will try to kick us,” Mason says. A team containing two veterinarians sets out to dart foals on the island. “They go down in the sand like ballerinas,” Mason describes. She goes with vets to meet the horses. When they are awake, they bring them to the adoption farm, give them clean hay and water and leave them alone for some time. Later, they hold them down and squirt feed in their mouths—a mixture of pellets, white Karo syrup, mineral salt and a few grains of de-wormer.

“They spit all over you,” Mason says. “On the third day, they open their mouths.”

Once the horses are eating properly, they begin work with a trainer. After they can be hooked up and lead, they are ready for adoption.

“Until the past year or so, if we had five horses, we had 48 applications,” Mason said. Since the economy crashed, the Foundation has had few requests and is trying fostering. Since adoptions began, Mason said about 70 horses have been placed in homes, as far north as New Hampshire and south as Florida. Foundation members typically visit a farm before sending a horse to it. Most Shacklefords are pets, but some are ridden. Owners of adopted horses say the Shacklefords are exceptionally smart.

Mason walks toward a pen and the horses in it come forward before we even reach the fence. She kisses their noses. “With horses, you move your hands like you’re underwater,” Mason says. I cannot recall ever seeing horses so tame. It is hard to believe they were born feral. The two nearest us are both male, Soprano, Mason’s “blondie,” and Adagio.

It grew darker and mosquitoes began to bite. Mason got repellent for us and for the horses. She says she had little experience with horses before she started the ranch. “When I was little someone put me on a Shetland pony. He tried to bite me.”

Mason, who was a teacher and librarian, now applies for equine-related grants, or grants for non-profits to operate the farm and further research on the herd. She has some volunteers, but during the week, it is usually just her with the horses.

“It’s a lot of work. Once I get out here and get the work done, they’re very funny. They have a sense of humor.” She tells us about the dynamics of her ranch residents. The hierarchy in the young males has shifted. Belaro is the youngest, so he had a hard time at first. Soprano and Adagio are the most dominant. Diego was dominant but now he’s laid back.

As she speaks, I’m sandwiched between Soprano and Diego who are both nuzzling my shoulders. I move to avoid having my feet stepped on, as Mason warns, but both horses want to be close.

Chelsea and I tell Mason about the horses we saw that day, especially Toro’s harem. She tells us Dusty has changed colors. “When Dusty was a baby she was almost white with gold stripes on her legs. When she shed, she had a black face with a white star.”

As affectionate as her Shacklefords are, Mason maintains the wildness of horses still on the island. “They can kick your knee-caps off before you can blink. The adult horses can take the muscle out of your arm,” she says.