In the Florida Everglades, the alligators are in trouble.

The reptiles are scrawny, weighing 80 percent of what they should. The alligators grow more slowly, reproduce less and die younger. Researchers are trying to figure out why this iconic species is in decline — and what it means for the Everglades.

"We've seen some alligators in some years that have been basically skin and bones," says Laura Brandt, a wildlife biologist at the Arthur R. Marshall Loxahatchee National Wildlife Refuge in south Florida. "And when we get concerned is when we see multiple alligators like that."

The situation is concerning because the reptiles are an indicator species of the Everglades, a watershed that supports dozens of federally threatened and endangered animals and provides drinking water for more than a third of Floridians. The alligators are responsive to environmental changes and influential as top predators and ecosystem engineers — which means that their well-being is an indicator of the health of the ecosystem.

Human interference with the Everglades, or the so-called River of Grass, has changed the historic flow of water and subsequently disrupted the animals' food supply.

"The Everglades food machine is broken," says Frank Mazzotti, a professor of wildlife ecology at University of Florida. "We've screwed up that pattern that produced and concentrated food, meaning alligators are getting skinnier."

Brandt and Mazzotti are part of a 15-member team of state and federal researchers. Their research is part of the world's largest environmental restoration, a $17 billion effort that spans a region twice the size of New Jersey.

For more than a decade, they've ventured into the wilderness of the Everglades to catch and study alligators to see whether the restoration is working.

Researchers like Mazzotti say as the Everglades' 30-year restoration reaches its midpoint, the watershed still needs help.

"There would be no fat. [The tail] would all be sunken in, and you would be able to see the tailbone with ... just the skin hanging on it and sunken in on the sides," Mazzotti says, describing the appearance of an alligator in bad condition.

The Everglades watershed once spanned nearly all of South Florida. Today it is half of its former self, sustained by a complex human-made system of canals, dams, water control points and pump stations.

Mazzotti says draining the Everglades upset the hydrology that alligators depend on, and that's why the restoration aims to resurrect a more natural flow.

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