Hellbenders can grow to more than two feet in length, making them the largest salamanders in North America. They live in clean, swift-running rivers across the eastern United States, from southern New York to northern Alabama. A separate subspecies, the Ozark hellbender, can be found crawling around a small part of southeast Missouri and northeast Arkansas.

Some people call them snot otters because they’re covered in a layer of slippery mucus. Others use the nickname “lasagna lizards” because the crinkly flap of skin on their sides, which helps them absorb oxygen, resembles a lasagna noodle.

Regardless of what to call them, hellbenders are in trouble. The International Union for Conservation of Nature classifies the hellbender as “near threatened,” while the Ozark hellbender was listed as endangered under the Endangered Species Act in 2011.

Hellbenders need cool, clear streams, and so climate change and pollution pose major threats to the species’ survival. In a recent study published in the journal Conservation Physiology, many hellbenders stopped eating and lost weight when water temperatures in the Allegheny River increased by 1.5 degrees Celsius (2.7 Fahrenheit). Scientists speculated that some salamanders were so hungry that they ate their own eggs during their critical breeding season.

“Hellbenders are definitely one of the indicators of a healthy environment,” said Brian Gratwicke, a co-author of the study who leads the amphibian conservation programs at the Smithsonian’s National Zoo and Conservation Biology Institute. “If you’re making the stream too warm or otherwise impacting that habitat, there are going to be consequences for these animals.”

The wood turtle spends much of its life in cool, meandering rivers, venturing upland to eat slugs and lay its eggs. But with roads carving up so much of its range from Maine to Virginia, this reptile cannot easily dodge tires.

“They're just slow-moving species,” said John Kanter, a senior wildlife biologist with the National Wildlife Federation, making them vulnerable to “getting squished.”

There is a relatively simple solution to the “turtle crossing the road” riddle: Add fencing to funnel the wayward reptiles away from dangerous thoroughfares. But state wildlife departments often lack the resources to put up that infrastructure, leading Kanter and others to call on Congress to dole out more wildlife money to states.

“I was licking envelopes and doing direct-mail appeal for my budget,” said Kanter, who spent much of his career with the New Hampshire Fish and Game Department.

“It’s gratifying when you get a bunch of people making donations. But the survival of these species and the habitats they depend on is too important to leave to that kind of bake-sale approach.”

The rivers of the Southeast once teemed with freshwater mussels, including the Texas heelsplitter, purportedly named for the pain they caused when humans accidentally stepped on them. People also harvested their shells to make buttons before the era of plastic.

But the United States has lost 35 species of freshwater mussels to extinction. And pollution, dam construction and rising water temperatures — tied to climate change — threaten 70 percent of the remaining species.

The U.S. Fish and Wildlife Service last month proposed protections for two especially imperiled species — the Texas heelsplitter and the Louisiana pigtoe — and designated about 1,860 river miles as critical habitat. The Texas heelsplitter can be found on river bottoms in East Texas and western Louisiana. There are only five remaining populations, all of which are on the brink of extinction.

Rare mussel species, nearly wiped out, gets rebirth in Virginia river

Freshwater mussels may be small, but they have a big impact on their ecosystems. They filter water and store contaminants in their flesh, significantly improving water quality, and their shells provide housing for crayfish and other smaller organisms.

Despite their critically important role in ecosystems, freshwater mussels have historically gotten a fraction of the investment that flows to more charismatic species, said Tierra Curry, a senior scientist at the Center for Biological Diversity, an environmental group.

“The monarch butterfly has gotten billions of dollars in funding, and it’s not even listed yet, because it’s beautiful and people can relate to that,” Curry said. “That’s more than freshwater mussels have ever gotten. It puts me on the verge of tears.”

These slender, playful predators once romped across the Great Plains. Then black-footed ferrets underwent their own Black Death.

Plague — along with a decline in numbers of its favorite meal, the prairie dog — nearly drove America’s only native ferret species to extinction before a captive-breeding program restored a wild population in the 1990s.

Now to sustain that precarious population, wildlife managers regularly spread insecticide to kill plague-carrying fleas, lay bait with flea-control medication for prairie dogs and even capture ferrets for vaccination against the infectious disease.

Fighting an ongoing plague across a vast swath of grasslands is a lot of work. And wildlife managers say they need more money for it.

“It’s extremely labor-intensive,” said Shaun Grassel, a member and former wildlife biologist of the Lower Brule Sioux Tribe. “And of course, when we talk about labor in anything, it’s extremely expensive.”

Wind sweeps fertile soil from the Missouri River Valley onto Iowa’s Loess Hills, making the formation one of the state’s best tallgrass prairies.

Lush with wildflowers, the hills attract a bounty of butterflies — everything from the iconic monarch to lesser-known (but equally beautiful) species, such as the regal fritillary.

With so much of Iowa converted to farmland, this sort of ecosystem is rare. Less than 0.01 percent of the state’s original tallgrass prairie remains. Now, what’s left is threatened by invasive cedar trees that shade out the native flowering plants.

Cutting down the invasive trees along the steep hills is both labor-intensive and expensive. Advocates for protecting Loess Hills hope the proposed federal law helps pay for the removal efforts.

This bulky shorebird goes on an epic journey every year, nesting above the Arctic Circle before migrating as far south as Australia and Argentina for the winter.

To make that approximately 18,000-mile round-trip journey, the red knot needs pit stops. One of the most important refueling stations is Delaware Bay, where the bird feasts on a smorgasburg of fatty eggs laid by the horseshoe crab.

But humans, too, exploit the crabs. Their bright blue blood contains a chemical used by doctors to test needles and other medical devices to make sure they are free of contaminants.

As this important food source for the red knot and other migratory birds has declined, calls for restoring more of the bay’s beaches — for both the bird and the crab — have grown.

A crustacean resembling a miniature lobster, the crayfish goes by many names in Appalachia: crawdad, crawdaddy and, in some cases, mudbug.

In 2016, the Fish and Wildlife Service placed two species of crayfish — the Guyandotte River and Big Sandy, named for the rivers they inhabit — on the federal endangered species list. The agency said that logging and coal mining threaten this species by depositing sediment and chemical runoff into streams.

Crayfish use their two large claws to burrow under rocks and build extensive tunnels, which other animals use as habitat. Their burrowing also releases critical nutrients, such as nitrogen and phosphorous, used by aquatic plants at the base of the food web.

How the West Virginia coal industry changed federal endangered species policy

“We know that when you eliminate crayfish from a watershed … you can see the beginnings of ecosystem collapse,” said Zachary Loughman, a biology professor at West Liberty University, a college in northern West Virginia.

Loughman’s work to survey crayfish in West Virginia ultimately led to the federal protections for the Guyandotte River crayfish. But he struggled to secure funding from the state Department of Natural Resources, and he had to compete with proposals to study more charismatic species.

Had the Recovering America’s Wildlife Act been law at the time, he said, “it would have been a miracle.”