In December of 2018, the first North Atlantic right whale calves in nearly two years were spotted off the coast of Florida and Georgia, frolicking with their mothers in the warm waters of the Atlantic before heading back north.

That’s when Vineyard documentarians Liz Witham and Ken Wentworth got the call. Stationed in St. Augustine, Fla., they drove an hour north and hopped on a boat with the Georgia Department of Natural Resources. A biplane overhead patched down the coordinates, saying there was a mother-calf pair of the critically endangered species seven miles off the coast. They zoomed over to the spot. It was the first calf to get biopsied in nearly two years.

With only 400 of the animals left, and only 100 breeding females, probably the only thing more rare than a North Atlantic right whale calf is getting the chance to see one in person. Ms. Witham and Mr. Wentworth made sure their camera never stopped rolling.

“We were in the perfect place at the perfect time to be able to witness it,” Mr. Wentworth said.

“We got to spend a couple of hours near to them, and hear them breathe, and understand them as living, breathing animals, and not just a conceptual idea,” Ms. Witham added. “As soon as I saw that, I was totally hooked on this animal.”

A right whale calf swimming alongside its mother. — Courtesy NOAA; permit # 18786-04

For their newest project, Ms. Witham and Mr. Wentworth are working on a documentary that follows the journey of right whale calves over the course of a year, from the moment they are born in the waters of Florida and Georgia, to their journey 1,000 miles back north, to the April and May feeding season in Cape Cod Bay, to the return of the mothers back south in late fall. And they are following the calves’ journey through the eyes of the myriad conservationists, scientists, mammalogists, marine biologists, boaters and pilots who have dedicated their lives to the species’ conservation.

“We’re using the journey of the babies that were born as the basic narrative structure,” Mr. Wentworth said. “And as we do, we are weaving with that topic-based and historical flashbacks on the history of the whales.”

The idea arose out of work that Ms. Witham and Mr. Wentworth did on their previous documentary, Keepers of the Light, which followed the dramatic effort to move the Gay Head Light 150 feet away from the rapidly eroding face of the Gay Head Cliffs. During that project, the two spoke with Wampanoag Tribal members about the significance of the whale in native culture ­— focusing on the relationship between the ocean and the Island maritime community.

When they started to delve into the right whale’s story — a story that spanned centuries and continents — it seemed like the perfect opportunity for their next project.

“One of the things that we’ve been working on is humanity’s connection to nature,” Mr. Wentworth said. “Are we part of nature? Do we have dominion over it? And how does that play out? With the right whale in particular, it was the right whale to kill for the whaling industry because it has the most oil, and floated after you killed it. But now, it’s become the right whale to save.”

Once common around Vineyard waters and Cape Cod Bay, the large, docile baleen had been hunted to the point of extinction over the course of two centuries. It wasn’t until the New England Aquarium conducted a marine mammal impact study for an oil refinery project in the Bay of Fundi that scientists saw 20 or so right whales and realized that the species not only still existed, but may have had a breeding population.

That was 1980.

In the years since, a massive, multinational conservation effort has mobilized to conserve the right whale. For their project, Ms. Witham and Mr. Wentworth have spent the entire past year on the front lines, following every step of that complicated effort from the shores of St. Augustine to research labs on Prince Edward Island, using their camera to capture an inside look at a species on the brink of extinction.

“It’s a very coordinated, remarkable process,” Ms. Witham said.

Ms. Witham and Mr. Wentworth began by gaining access to NOAA, and from there networking with the dozens of agencies responsible for right whale surveying and research. By the end of the year, they had filmed from the cockpit of airplanes and the hull of boats, from the microscopes of research labs to the podia of conservation consortiums. It’s involved learning about telemetry buoys, entanglements, gear markings and whale markings, and navigating the complex relationship between industry and conservation.

“We’re with the leading experts in the world, getting two, three hours worth of one-on-one consultations on any question we ask,” Mr. Wentworth said. “I’m humbled to get to do this.”

Part of the filming process has also been documenting right whale deaths — 10 of which occurred in 2019. When the pair heard that Wolverine, a nine-year-old male named for three propeller scars on his back, had died off the coast of Canada, they drove 17-hours overnight from the Vineyard to document the animal’s necropsy in Shippagan, New Brunswick. They arrived within 30 minutes of scientists cutting the whale open in an attempt to determine its cause of death.

“This is a rare species. It’s not everyday that one washes up on the beach,” Ms. Witham said. “That makes every moment a research opportunity as they break down the whale.”

The scientists use massive hooks to strip the 30-ton whale on the shore, removing its eyeballs, analyzing its scar tissue, measuring its thickness, checking its lungs and using its baleen to determine with pinpoint accuracy its former locations. They look for bruising on the blubber and sores on the mouth. It’s literally the largest forensic crime scene in the world. It’s also the smelliest.

“They’re basically knee-deep in blubber,” Mr. Wentworth said.

Mr. Wentworth added that the necropsy is difficult for both the noses and the hearts of the scientists.

“The first one, they’re like, okay, we’ve got a dead whale, we’ve got a job to do. Then the second one, they’re like shoot, another one. But the seventh one?” Mr. Wentworth said. “They may need therapy. It’s emotional.”

Despite the large number of deaths, their experience over the past year has also been one of hope. The same mother that Mr. Wentworth and Ms. Witham saw in Florida was also spotted back in Cape Cod Bay. When they went out on a boat in April, they were surrounded by over 130 whales — nearly one third of the species. They’ve memorized the names of their favorite mothers, and met dozens of scientists who are now on a first-name basis with them. And last winter, over 100 right whales were spotted south of the Vineyard, many of which were mating. With a 12-month gestation period, that means they may be giving birth soon.

“That was the first time they had ever spotted a mass of whales this time of year,” Mr. Wentworth said. “But it was also the first time they had looked. So I am excited.”

The pair are also excited about getting their film to audiences, which is now mainly in the editing process. They hope to have it distributed by early winter of next year. Of course, part of that excitement comes from the thrill of presenting the story to the public. But they feel it’s about more than that. They’re part of the story now, too.

“We actually feel a deep obligation to bring this film forward, and do the most we can,” Mr. Wentworth said. “So many people have given us their time and their effort. They all know. One of their leading goals now is to get the word out. But they can’t just do it for everybody, and they chose us.”

Donations to support production of the film can be made to Ms. Witham and Mr. Wentworth’s nonprofit, Film Truth, through their website