Louisiana residents vs. 20-pound swamp rats in ‘Rodents of an Unusual Size’

The Louisiana shoreline is under a dire environmental siege.

No, it has nothing to do with offshore drilling, climate change or hurricanes. We’re talking millions of 20-pound swamp rats eating away at wetlands, swamplands and forests, eroding shorelines and making them vulnerable to those other threats.

It’s become such a problem that the state of Louisiana is paying private citizens to kill these rats, called nutria, in an attempt to win the battle for the shore.

The documentary “Rodents of an Unusual Size,” by Bay Area filmmakers Chris Metzler, Quinn Costello and Jeff Springer, lays out the problem nutria pose but also takes us into the bizarre Louisiana subculture built around the critters that include a rodent-style Cajun cuisine and a local fur industry.

“There’s a continuity of a kind of full sensory experience of being there, between the food, music, the ungodly heat — it all blends together,” Costello said during a lunch with the three directors in San Francisco. (The restaurant did not serve nutria, thank goodness.)

Nutria are not native to Louisiana. They were brought there from Argentina sometime in the 1930s to be bred for their fur. Coats, shawls and hats from nutria fur were an international thing once — movie stars such as Greta Garbo and Sophia Loren wore them.

But there was a problem. These rodents escaped during storms and multiplied like rabbits. During the 1970s and ’80s, anti-fur and animal rights activists helped kill the industry. That left nutria out in the wild. They are vegetarians that eat and eat and eat. Shorelines were endangered, and the Louisiana government approved a program to hunt nutria.

The filmmakers spent four years in and around the Louisiana swamps making “Rodents of an Unusual Size,” and what they came back with is not only mind-blowingly informative, but also one of the most entertaining documentaries of the year.

We meet bounty hunters such as Thomas Gonzalez, a cagey veteran of the swamps; noted jazz musician Kermit Ruffins, who often plays the Bay Area but has a side gig promoting nutria cuisine; New Orleans reality TV chef Susan Spicer, who has a whole mess o’ nutria recipes; and many others.

“It’s as much about the culture of Louisiana,” Metzler said. “The culture is really what’s threatened. We talk about coastal erosion, etc., and the land is important. But really it’s what’s lost when this place disappears. The erosion and the nutria are going to win. This way of life is gonna have to change.

“So it’s about capturing this moment in time before it disappears or evolves and hopefully we find the value in it and experience it.”

And experience it they did. The three filmmakers spent a lot of time in boats on the swamps in all kinds of weather conditions. Thankfully, they didn’t get what the folks in those parts call the “nutria itch,” which Costello described as “a legendary ailment where if you’re around nutria long enough you’ll probably get this parasite that causes severe rash and miserable itching.”

Yuck, especially when most of the hunters in the documentary handle dead nutria without gloves.

On top of all this, the directors had to get creative about filming nutria, which are notoriously hard to capture on camera, as they are fast-moving and understandably wary of people.

Springer, who was also the cinematographer of “Rodents,” said they had to become like hunters themselves.

“This golf course in the movie was one of the best places to capture them visually,” Springer said. “They were still really skittish, and even with a really long lens it was hard to get shots of them. So we set up a hunting blind — a little camouflaged tent — with the help of one of our subjects. He would bait the area several days ahead of time. We’d go in there before the sun came up and wait.”

As much as nutria have become a threat to a way of life, the creatures have also become ingrained in Louisiana culture. A minor-league baseball team has a nutria mascot. There is a nutria fur beauty contest and “guilt-free” fashion show.

And there’s the cuisine. You can get nutria sausages, nutria jambalaya, nutria jerky — you name it.

“We had Kermit Ruffins cook us some nutria, and he did it in an open pan on a barbecue and marination was a six-pack of beer, and that turned out very well,” Springer said. “We also had Susan Spicer prepare nutria, and she did an Asian stir fry.”

So what does nutria taste like?

They all agreed at once: “Rabbit.”

“Not like chicken,” Springer laughed.

Of course, Metzler added, it depends who’s cooking it.

“When Susan Spicer cooked it, I thought it tasted like pork tenderloin. When we cooked it, it tasted like death.”

G. Allen Johnson is a San Francisco Chronicle staff writer. Email: ajohnson@sfchronicle.com Twitter: @BRfilmsAllen