The Everglades' eclectic alligators are surprisingly diverse builders, bodyguards, commuters, and health-bringing engineers.

From the edge of the Miccosukee Indian Reservation, in the north of the Florida Everglades, it is a short fan-boat ride through grassy swamp to get to an island that 18-year-old Hector Tigertail's family visit each year. For decades, this family "hammock" – as the tree-covered islands that poke out from the Everglades are known – has been their retreat; a place where the family can camp, cook and hunt. But they share this particular island with at least one permanent resident: an American alligator that, at around 7ft (2.1m) from nose to tail, is the largest female he's ever seen.

Tigertail's family, members of the Miccosukee Tribe of Indians of Florida, and this powerful reptile, which locals refer to as Mama Gator, have lived side by side for much of the 60-year-old animal's life, he explains. This intimate coexistence provides a chance to observe how alligators meticulously shape their surroundings. Through the dry season between December and May, she excavates a "gator pond" with her snout, claws and tail, a depression where water pools and she can wallow, keep cool and mate. At the start of the rainy season (from June to November), she builds a raised nest for her clutch of eggs, from mud, grass and twigs – a time when the humans know to keep a respectful distance from the protective mother. In return, for the next few years, they are often rewarded with the sight of Mama and her baby gators in tow.

"We like to call her Mama Gator because she's everybody's grandma," says Tigertail.

In recent years, scientific research is adding support to something Florida's Miccosukee Tribe have long known: alligators like Mama play vital roles as "guardians of the Everglades" and engineer their environment in ways that protect freshwater ecosystems. Alligators carry around nutrients that feed ecosystem webs, and their ponds and nests provide refuges where plants, fish and frogs live. New data hints that that alligators may also benefit us.

"Apex predator or not, alligators are actually very helpful and they can change the ecosystem significantly," says Tigertail, who researches alligators for the Miccosukee Tribe's Fish and Wildlife Department. "During the dry season, a lot of animals – deer, fish, otters, turtles, birds – follow the alligators."

For those like biologist Christopher Murray who has spent decades closely studying alligators, it's high time to move past their reputation as cold-hearted killers and recognise the varied roles they're playing as caring and constructive ecosystem engineers. While the cute, herbivorous beaver is widely celebrated for stewarding temperate wetlands, it is the "gnarly swamp monsters" who deserve plaudits in the southeastern United States and many other places, says Murray, associate professor at Southeastern Louisiana University. "I think we're just beginning to understand that crocodilians, in general, and specifically alligators, do a lot more good than we think."

Alligators are often called "living fossils", relatively untouched by major evolutionary changes for at least eight million years, with remarkably similar ancestors already hunting swamps alongside the dinosaurs. Yet, beginning in the 1850s, the arrival of rifle-wielding European settlers into the wetlands of Florida and Louisiana drove this evolutionary line to the verge of extinction.

More than 10 million alligators were killed by commercial hunting up to the 1960s, driven by the popularity of their hides for bags, belts and boots, with others shot for sport or "just for fun" according to historical accounts. In 1967, American alligators were placed on endangered species lists, leading to nationwide hunting bans that allowed populations to recover. Today, the species is recognised as a standout conservation success story, as the population has rebounded to more than three million alligators estimated to live in the wild in the states of Florida and Louisiana, and thousands more spread across the south-eastern United States.

Just as conservationists began fighting to save the species from extinction in the 1960s and 1970s, researchers began documenting their important ecological roles. In the wet season, the raised ridges around the edge of these nests are relatively dry land where some plants can escape flooding and provide platforms where........

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