Louisiana’s coastal wetlands were eroding rapidly, and an invasive rodent species was making the damage significantly worse. By the mid-20th century, the state was losing a football field of marshland every hour, in part because nutria, large semi-aquatic rodents imported from South America, were destroying the root systems that held the soil together. The solution that eventually stabilized the coast involved an unlikely partner: the American alligator, which had been hunted to the edge of extinction but was then bred commercially and returned to the marsh in large numbers.
The nutria was introduced to Louisiana by Edward Avery McIlhenny, an heir to the Tabasco sauce fortune, who saw the animal’s fur as a potential new commodity. In the 1930s, he imported the rodents to his Avery Island estate, bred them, and deliberately released them into the wild despite warnings from federal biologists about the risk of invasion. For years, a claim circulated that the animals had escaped during a hurricane, but McIlhenny’s business records indicated the release was intentional.
Nutria reproduced rapidly. They reached sexual maturity at six months, bred year-round, and produced several litters each year. Their feeding habits were particularly destructive: rather than grazing the tops of marsh plants like native muskrats, they dug down and consumed the dense root mats that physically held wetland soil in place. Once those roots were gone, the soil disintegrated, tides washed it away, and saltwater flooded in, converting vegetated marsh into open water permanently. By the late 1950s, Louisiana was losing between 25 and 35 square miles of coastline annually.
During the 1960s and 1970s, the international fur trade provided an accidental check on the nutria population, with trappers harvesting more than a million animals each year. When the global fur market collapsed in the 1980s, the harvest dropped sharply and the nutria population rebounded. More than 100,000 acres of marsh were denuded.
At the same time, the American alligator, the region’s primary natural predator of nutria, had been severely depleted by decades of unregulated hunting for its hide. Population estimates had fallen below 100,000. The marsh had lost both its structural anchor and one of its key predators.
In 1962, the Louisiana Department of Wildlife and Fisheries closed all alligator hunting in the state. The moratorium was designed by two field biologists, Ted Joanen and Larry McNease, who spent years tracking alligators in the marshes of the Rockefeller Wildlife Refuge. Their research showed that female alligators, the core of the breeding population, retreated deep into interior marshes to nest, while males and juveniles concentrated in open canals and waterways. They realized that a carefully timed hunting season, restricted to September and limited to accessible waterways, would target mostly males while leaving breeding females undisturbed.
An experimental season in 1972 confirmed the model. More than 80 percent of the animals harvested were male, and the breeding population remained effectively intact.
The next major step came in 1986 with an egg ranching program. In the wild, most alligator hatchlings died before reaching four feet in length, due to predators, flooding, and cannibalism. The new program allowed licensed farmers to collect eggs from wild nests, incubate them in controlled facilities, and raise the hatchlings in captivity, where survival rates were significantly higher. Researchers also discovered that incubation temperature determined the sex of the hatchlings, giving farmers precise control over their stock.
A central condition of the program required farmers to return a percentage of healthy juveniles to the marsh where the eggs were collected, initially 17 percent and later 12 percent. Every returned animal was measured, sexed, tagged, and tracked.
The commercial value of alligators changed the incentives of private landowners. Previously, many viewed the reptiles as dangerous pests and tolerated poaching. Once alligators became a reliable source of income through legal skin and meat sales, landowners had a financial reason to protect the animals and the wetland habitat they required.
The American alligator was removed from the endangered species list in 1987, just 25 years after the hunting ban was imposed.
As the alligator population recovered, its effect on nutria became measurable. Adult alligators, particularly those larger than five feet, shifted their diet to include significant amounts of mammalian prey. Stomach content analysis showed that nutria made up a large portion of the diet of big alligators in southeastern Louisiana. The predation was density-dependent: when nutria were abundant, alligators targeted them more heavily.
The state also launched a bounty program in 2002, paying trappers for nutria tails. Annual nutria removal reached roughly 400,000 per season, and documented marsh damage dropped from more than 100,000 denuded acres to about 16,000 by 2018.
Alligators also contributed to the landscape in other ways. Using their snouts, claws, and tails, they excavated depressions in the marsh known as alligator holes. These ponds retained water during dry seasons and provided refuge for fish, amphibians, turtles, and wading birds. Research in 2024, based on soil core samples analyzed by the Smithsonian’s Coastal Carbon Network, suggested that wetlands with alligators present stored more carbon, in part because the predators suppressed herbivores and allowed vegetation to grow more densely.
Over the course of the program, more than 11 million wild alligator eggs were collected, and more than 7 million farm-raised alligators entered commerce. Cumulative revenues exceeded $988 million. The program also provided indirect benefits, including storm surge protection, nursery habitat for commercial fisheries, and carbon storage.
Efforts to replicate the model elsewhere have had mixed results. Louisiana’s earlier attempts at bounties failed when they were never funded. In the United Kingdom, authorities removed tens of thousands of feral nutria from the Norfolk Broads, but without a native predator to maintain pressure, the effort required continuous human intervention that proved difficult to sustain.
The Florida Everglades offered a different warning. Burmese pythons, released through the exotic pet trade, severely reduced populations of raccoons, opossums, rabbits, and foxes. Pythons and alligators can prey on each other, but neither species can fully suppress the other. The Everglades’ invasive species problem remained locked in a persistent balance that neither predator could resolve on its own.
Louisiana’s program now faces a new threat from feral hogs, introduced illegally by sport hunters. Hogs have discovered that alligator nests contain a high-protein food source, and they have caused significant nest destruction. A 2011 survey found that more than half of the state’s alligator farmers had suffered nest losses to feral swine, and the damage appeared to be increasing.
The alligator program continues to provide revenue while supporting coastal marsh stability. The commercial killing of an endangered species, paired with habitat protection, became the mechanism that allowed the species to recover and helped stabilize the coastline it inhabits. Whether commercial harvesting can be applied more broadly to conservation remains an open question.
