For centuries, extermination was the law of the land for gray wolves in the United States. Driven by fear and ill-informed traditions, hunters, farmers, ranchers, and state and federal employees shot them. Trapped them. Poisoned them. They burned pups in their dens. In Minnesota, the last place in the contiguous U.S. where wolves hung on in significant numbers, the state dropped strychnine-laced meat from airplanes and, as late as 1965, offered a bounty of $35 per dead wolf. The number of wolves fell to 700 or fewer, all in the state’s remote northeast corner. The species, an estimated 2 million in North America at the time of European colonization, looked as if they might disappear from the lower 48 states. But in 1973, the Endangered Species Act passed with bipartisan support and was signed into law by President Richard Nixon, granting gray wolves protection.
Afterward, the country’s wolf population began to rebound. Now there are wolves across the Great Lakes states of Minnesota, Wisconsin and Michigan, in the Northern Rockies, in Oregon and Washington states, in California and, since December 2023, in Colorado. Today, there are nearly 8,000 in the contiguous U.S. (an equivalent number live in Alaska)—just a tiny fraction of their historic number, but a beginning.
“All we had to do was stop killing them,” says Jill Fritz, Humane World for Animals senior managing director of wildlife protection and a Minnesota resident. “They began to recover on their own.”
Over the last half century, the ESA has enabled many species to come back from the brink. Ninety-nine percent of the greater than 1,700 U.S. species listed as endangered have not gone extinct (though 21 species have disappeared, because they were listed too late or funding for their protection was inadequate).
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A law that saves
More than 100 listed species of animals and plants have either recovered or been reclassified from endangered to threatened, including the least tern, the brown pelican, the bald eagle, the peregrine falcon, the Steller sea lion and the American alligator.
The ESA is popular: Research presented in the June 2025 Conservation Letters (funded in part by Humane World) found that over the last 30 years, support for the law has held steady at 84 percent. “Most Americans believe the ESA should be more protective of species than is currently the case,” states the paper, written by Michigan Technological University wolf researcher John Vucetich and other wildlife biologists.
And yet, despite the law’s success and popularity, over the past five decades it has come under attack at the federal and state levels. Critics who want to exploit the animals protected or the land they live on have tried to weaken the ESA. They are trying to rush to delist species before researchers consider them recovered and able to survive without protection. In response, Humane World and other advocates have submitted scientific evidence to the U.S. Fish and Wildlife Service in support of continued and new protections and sued the agency to keep gray wolves and grizzly bears listed and to force action on other species. We’ve won again and again.
What we’re seeing now is an attempt to change the rules of the game by pulling the right to make decisions away from the experts.”
Nicholas Arrivo, attorney for Humane World for Animals
Today, though, the ESA and the species it protects are under attack as never before. Among the biggest threats are three bills introduced in Congress. Unlike Fish and Wildlife Service rules, these bills shield certain delisting decisions from being challenged in court using scientific evidence. Nicholas Arrivo, a Humane World attorney who has successfully argued for years to keep gray wolves and grizzly bears listed, says ESA opponents who failed to get species delisted by going through the Fish and Wildlife Service are trying to make an end run around science.
“What we’re seeing now is an attempt to change the rules of the game by pulling the right to make decisions away from the experts,” he says. For example, “even though wolves have been controversial, there’s been a willingness to let the system work. [Now,] there’s a huge new willingness to make political decisions.”
The ESA Amendments Act of 2025 (H.R. 1897) would make it easier to delist and harder to list species. It would also slash protections for critical habitat on which species depend. “This is like a love letter to any opponent of the ESA,” says Tiffany MendozaFarfan, Humane World Action Fund legislative program manager. Two other bills would delist species. The Grizzly Bear State Management Act (H.R. 281/S. 316) would delist grizzly bears in the Greater Yellowstone Ecosystem and block courts from reviewing that action. The Pet and Livestock Protection Act (H.R. 845) would delist gray wolves nationwide and also block judicial review. Despite what the name of the bill implies, it would do little to nothing to protect pets or cattle and sheep; wolf attacks on pets are rare, and wolves are responsible for just over 1% of farm animal losses. Instead, the bill puts a target on wolves to appease industry interests.
Trophy hunters and recreational trappers want to be able to kill grizzly bears and wolves. Ranchers, who are allowed to graze their cattle on public lands at subsidized rates, do too. There’s even a proposal to open a gold mine near Yellowstone National Park, home to the second largest population of grizzly bears in the lower 48 states.
The ESA forbids people from harming listed animals, and “harm” has long been defined to include actions that cause wildlife to die by damaging their habitat. The Trump administration, which has declared an energy emergency to allow oil and gas drilling in areas protected under the ESA, has proposed getting rid of that definition of harm.
But without that definition of harm and the protection of their habitats, animals such as bald eagles, spotted owls, American alligators and polar bears might have gone or would be going extinct, says Gillian Lyons, director of regulatory affairs at Humane World Action Fund.
“This is the scariest time for the ESA we have ever seen,” Lyons says.
Brian Nesvik, who was confirmed as the new director of the Fish and Wildlife Service in August, formerly served as head of the Wyoming Game and Fish Department. He has worked to delist grizzly bears and wolves and called for the ESA to be “pruned.”
Wolves have only begun to recover, yet in many places—Idaho, Montana and Wyoming and portions of Washington, Oregon and Utah— they are no longer listed under the ESA. (An August federal court ruling in response to a lawsuit by Humane World and other advocates could lead to their relisting). In Idaho, Wyoming and Montana, wolves are once more baited, snared and shot from planes and helicopters—all in the name of protecting cattle, sheep, deer and elk. In reality, bad weather and diseases account for most animal losses, and wolves keep deer and elk herds healthy by killing sick animals and helping prevent the spread of disease. In Yellowstone, where wolves were reintroduced in the mid-1990s, they have famously helped to restore an ecosystem by preying on deer and elk who ate trees and shrubs along riverbanks, leading to erosion and the disappearance of other animals.
Approximately 99%
of species listed under the ESA have avoided extinction.
More than 100 wolves now live in Yellowstone, and the park with its open vistas allows people to not only spot these shy creatures but witness their lives. Amanda Wight, who focuses on wolves as senior program manager of wildlife protection for Humane World, saw her first wild wolves at Yellowstone, through a borrowed spotting scope that she pointed at a distant den while standing in a group of excited observers. In a later visit, Wight watched 1048, a male who was not the alpha or breeding male in the pack but who had fathered the most pups. His secret? He cared for other members of the pack, raising their chances of survival. Wight saw him return to the den, with a belly full from feeding off of a carcass, and howl, calling pups so that he could regurgitate the meat and feed them.
“Wolf packs are families—I love how smart they are, how social,” Wight says. “The more I learn, the more I want to know.”
For hundreds of years, the emotions people felt about wolves were fear and hatred. Wight felt gratitude. She felt awe. That she had actually seen them in the wild. That the ESA has made those moments possible.
A half century of the ESA and its protections has shown that species are resilient. Animals can come back. But only if we continue to give them a chance.
What’s at stake
These are some of the species the ESA protects.
Grizzly bears in the lower 48 states
Status: Threatened, but there are efforts to delist
Estimated number: Less than 2,000
Locations: Northern Continental Divide Ecosystem of Glacier National Park, Greater Yellowstone Ecosystem, and four other areas in northern Montana, northern Idaho, northern Washington and southeast British Columbia
Source: Graphic adapted from C. L. Shafer, Conservation Genetics Resources, Springer Nature, 2022
Yellowstone Grizzly 399 was much beloved, but the forces threatening the survival of grizzlies in that ecosystem and other isolated populations eventually took her life. The celebrity bear, who gave birth to 18 cubs over 28 years, charmed crowds along park roads as she emerged year after year and navigated traffic to lead her young to food. In 2024, though, a car hit her. Even as grizzly numbers have nearly tripled since protection under the ESA, every year bears die after being struck by vehicles or shot by hunters or ranchers who view them as a threat. A record number of 90 bears died in 2024. In Yellowstone, mega droughts and extreme wildfires have shrunk natural food sources such as white bark pine (also listed as endangered), cutthroat trout and elk, causing grizzlies to move out of the protection of the park. At the same time, the grizzly bear population in the park is far too small to survive long-term because it lacks genetic diversity, says Wendy Keefover, senior strategist for native carnivore protection at Humane World. “They’re in great danger of extinction.”
Monarch butterflies
Yiming Chen/Getty Images
Status: Proposed to be listed as threatened
Estimated number: 233,000 counted, in 2023, along the California coast, Baja California, and inland in California and Arizona, down 81% during the past 25 years; a year later, 9,000 were counted, down an additional 96
Locations: Proposed critical habitat of 4,395 acres in coastal California where butterflies west of the Rockies spend the winter
Patches of milkweed that monarchs depend on for food have dwindled as more land is cleared for agriculture and as farmers apply herbicides. Global warming is raising temperatures for monarchs in the western U.S., changing where milkweed grows and affecting the timing of the two migrations monarchs make: one east of the Rockies, from Mexico to the Midwest and the East Coast of the United States; the other west of the Rockies, from coastal California inland. Humane World and other advocates encourage people to plant milkweed and other native plants in their backyards and not to use chemicals.
Humpback whales
Robert Smith/Getty Images
Status: Some populations remain endangered
Estimated number: 84,000 for all populations
Locations: Central America, Western North Pacific, Arabian Sea, Cape Verde Islands in Northwest Africa
The researcher who discovered that humpback whales sing, Roger Payne, worked with Humane World advocates to secure a moratorium on commercial whaling in 1985, saving humpbacks and other whales hunted to near extinction in the 20th century. Four of 14 populations remain listed as endangered, though. One (Mexico) is listed as threatened. Entanglements with fishing gear, ship strikes and pollution continue to kill whales.
Rufa red knots
Danita Delimont/Getty Images
Status: Threatened
Estimated number: 42,000
Location: Eastern United States
Rufa red knots migrate 9,000 miles each spring from where they breed in the Arctic to South America. The birds are kept alive along the way by the eggs of horseshoe crabs, but these are harder to find because biomedical companies gather over a million horseshoe crabs a year to harvest their blue blood, which clots in the presence of bacterial toxins. They pierce them through the heart, drain up to a third of their blood, then release them back into the wild, where many die. Humane World is urging companies to use non-animal tests and calling on governments to designate these as the preferred standard. We, alongside partners, have also petitioned the National Oceanic and Atmospheric Administration to list the horseshoe crab as endangered or threatened.
Horseshoe crabs
Chris Engel/Pixabay
Living fossils, horseshoe crabs resemble their ancestors, who appeared around 445 million years ago—long before the dinosaurs—in shallow bays. They mate in May and June up and down the East Coast, particularly in the Delaware and Chesapeake bays. Their eggs look like pale green marbles piled in the sand. Not only rufa red knots, but other shorebirds, fish and sea turtles eat the eggs. Horseshoe crabs have survived mass extinctions, the rise of mammals, ice ages and humans. Until now.
Florida panther
Carlton Ward Jr/Wildpath
Status: Endangered
Estimated number: 120 to 230
Location: Southwestern Florida
Listed in 1967 under a law that preceded the ESA, the Florida panther, the only mountain lion still found east of the Mississippi, was nearly hunted to extinction—to just 10 individuals. Now there are as many as 230 throughout Florida with the biggest concentration in the Southwest. Hunting stopped, but the population is threatened by urban sprawl that has reduced habitat and increased deaths from motor vehicles.
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