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In 1973, the Endangered Species Act (ESA) was passed, as concern had been expressed over the nation’s native animals becoming extinct.

The ESA was bought in to protect and recover species.  The ESA is administered by the U.S. Fish and Wildlife Service (Service) for land mammals.  The Commerce Department’s National Marine Fisheries Service (NMFS) is in charge of marine mammals. 

Under the act of 1973, individual species may be listed as endangered or threatened.

The U.S. Fish and Wildlife Service defines ‘Endangered’ as a species in danger of extinction throughout all or a significant portion of its range.

They define ‘threatened’ as a species likely to become endangered within the foreseeable future.

I have listed ten of North America’s mammals on the U.S. Fish and Wildlife Sevice endangered list.  

Please note that the service list varies from the list from the International Union for Conservation of Nature (IUCN) red list, which deals with species worldwide.

Mexican Wolf

The Mexican wolf was hunted to almost extinction.  By the 1970s, the Mexican wolf was almost wiped out in North America.  Only a few were left in the wild and a small amount in captivity.  The Mexican wolf has a gray coat with yellow hints and usually white fur around the bottom of its legs and muzzle.

The Mexican wolf is the smallest gray wolf subspecies, measuring about the same size as a German Shepherd.  Compared to most wolves, they are slender, partly due to their prey.  Mexican wolves will feed on deer, which they can outrun to catch.

The Mexican wolf is still highly endangered, although they were once abundant throughout North America.  Their decline began when the livestock industry moved into the Southwest.  With their habitat lost to humans, the wolves lost a massive chunk of their food source.  To combat this, they started to kill the settler’s livestock.

The U.S. Biological Survey began hunting and killing Mexican wolves to protect their livestock and livelihood.  

The Mexican wolf was added to the endangered species list in 1976, and the United States and Mexico governments captured the remaining wolves in the wild alive.  The government only captured five Mexican wolves but started a breeding program soon after.

The Mexican wolf can now be found in New Mexico and Arizona.  In the most recent study in 2017, there were 240 Mexican wolves in breeding programs, estimated to be 143 in the wild, but it is still on the endangered list. 

Key Largo Woodrat

Once the Key Largo woodrat roamed throughout most of Key Largo, the woodrat is now limited to the Northwest Regions, reducing its habitat dramatically.  Gray-brown or described as sepia; they have a cinnamon color on their sides.  Their large ears, hairy tail, and bulging eyes depend on their tropical hardwood habitat to build their large stick houses.

Most known for their house building, the Key Largo woodrat built these from sticks and twigs.  Woodrats build their nests against fallen trees, boulders, rock piles, sheds, outbuildings, and tree stumps.   The woodrats live in these houses alone but can be used by several generations, with the ability to make the homes larger if they need to.

The Key Largo woodrat has adapted to its move north of Key Largo.  In the north, the woodrat generally does not build their house out of sticks and twigs but will live in the rocks’ crevices.  They will put a few twigs propped up against the rock outside.  They also nest in holes in the roots of large trees.

The woodrat was listed as endangered in 1983 through an emergency listing action to provide the species’ welfare.  In the 1980s, there were thought to be 6500 wood rats in north Key Largo, but by the 1990s, their habitat had shrunk to three square miles.  

After 1500 nights of trying to trap the Key Largo woodrat, only seven animals were trapped, showing how low the numbers had dropped.  

The Key Largo woodrat is now possibly below a minimum population threshold to survive extinction.

Over 40% of all mammals are rodents.  Find out more about this varied order of mammals

Carolina Northern Flying Squirrel

The federal government lists the Carolina northern flying squirrel as an endangered species.  They can be found in western North Carolina, eastern Tennessee, and southwest Virginia.  

The Carolina northern flying squirrel is one of two flying squirrels in the area, with the smaller southern flying squirrel being widespread and not endangered.  The flying squirrels have skin flaps that extend between the wrists and the ankles, and they use their tail, which is flattened, to steer themselves when gliding from tree to tree.  

The flying squirrels can glide a distance of approximately 65 feet and speed to eight miles per hour.  They can grow up to eleven inches long and are tan or brown, with belly hair that is white at the tip, leading to a dark grey by the skin.  

Northern squirrels live in conifer and mixed forests, which have drastically reduced in the past few decades.  Northern flying squirrels rely on specific fungi to survive, and these fungi are dependent on spruce and hemlock trees.  Due to the hemlock forests being reduced by an invasive insect called the hemlock woolly adelgid, their natural habitat has been decimated.  

Another reason for their decline is the smaller southern flying squirrel.  Not only are they more aggressive when finding food and shelter, but they also carry a parasite that can be lethal to the northern flying squirrel.

The Carolina northern flying squirrel lives in the high mountains of North Carolina and Tennessee.  The decline of the squirrel was one of the first warnings to scientists that the high-elevation forests’ health was at risk.

If you or someone you know loves squirrels, then check out these great squirrel gifts on Amazon by clicking here

Gulf Coast Jaguarundi

The Gulf Coast jaguarundi has been on the endangered list since 1977.  Although part of the Felinae (cat) family, their appearance resembles an otter or weasel.  With flat tails and short legs, they also have a flat head with a long slender body.  Although much smaller at roughly a tenth of the cougar’s size, they are closely related.

Although not confirmed in the U.S. since 1986, people still say that they have seen these in south Texas, particularly in Laguna Atascosa National Wildlife Refuge.  They can also be found in the north of Mexico.

In 2014, the U.S. Fish and Wildlife Service developed a recovery plan for the species. They have planted shrubs and plants found in the jaguarundi’s natural environment in the Rio Grande Valley in Texas.

The building of the Mexico-U.S border fence may be the biggest threat to their population as it would hinder migration.

Many mammals are classed as near threatened.  Find out more here


Another animal where the IUCN red list and the U.S. Fish and Wildlife Service differ is the ocelot.  Listed as least concern by the IUCN, the ocelot is listed as endangered by the official U.S. service.

The ocelot has one of the most beautiful furs, with a background color that can be gray, reddish-gray, yellowish, brownish, or cream with solid black markings.  These markings are not uniform and can be spots, dots, smudges, and stripes.  

Although rare in North America, Ocelots can still be found in Mexico and every country South, except Chile.  The North American range of the ocelot once included Arizona, Arkansas, Louisiana, and Texas, although they are not thought to be in Arkansas or Louisiana anymore.

There have been five sightings in five years of an ocelot in Arizona, although researchers say there is unlikely to be a breeding population.

There are approximately fifty ocelots living in Texas at the moment.  Vehicles are the primary cause of ocelot deaths in Texas, and the Texas Department of Transportation has recognized this.  They have plans to install the first highway wildlife crossing tunnels in Texas.  These wildlife crossings have successfully kept the Florida Panther’s population alive and increasing.

The evolution of the cougar is fascinating.  Find out more here

False Killer Whale

The False killer whale gets its name in more than one way.  The false killer whale is not a killer whale at all but a dolphin.  Their name comes from their look, which includes a similarly shaped skull to that of killer whales.

Reaching sizes up to 6m (20 ft) long, the false killer whale is dark gray or black.  In captivity, they have been known to reach the age of 62.  The main diet of the false killer whale is fish and squid, with tuna and mahi-mahi being their favorite due to their large size.  

They will also attack smaller dolphins, and there have been attacks on sperm whales and smaller sharks.  Several false killer whales can group up to take on larger prey.

False killer whales are distributed worldwide in warm and tropical temperate waters. In North America, a population of false killer whales can be found in the Hawaiian Islands.  

The false killer whales in North America have been listed as endangered since 2012, and there are an estimated 150 – 200 living in the Hawaii area, a number that has been declining recently.

Want to know which mammals have become extinct in the last 100 years. Find out in an article I have written.

Woodland Caribou

Woodland caribou are the only members of the deer family where both the male and the female have antlers.  Covered in brown fur, they have patches of white on their belly, neck, and tail.  

Caribou live in some of the coldest climates in Canada.  From boreal forests to the open tundra, caribou could be seen almost everywhere at one time, but this has changed.  With the loss of habitat, caribou are having a hard time surviving.  

Due to logging companies, Caribou are constantly forced to move by the loss of their habitat.  Once a forest has been logged, it can take decades to return to normal.  The habitat change needed by the caribou also adds another problem for them.  

By moving into different areas, predators such as wolves, which were not in the previous area, will prey on the deer.  If the area they live in gets smaller, the deer’s density increases, leading to more predation.  

Predators are not the only cause of concern for the woodland caribou.  The climate change is causing snow and ice to cover the tundra’s vegetation, and there are more frequent fires in the forests, killing off the lichen they desire.  

There is good news for the woodland caribou; however, the population in the Selkirk Mountains in Seattle is being proposed for a downlisting from endangered to threatened.

Watching wild deer is special.  Find out the best ways of watching deer without disturbing them here

Roy Prairie Pocket Gopher

Also known as the Mazama pocket gopher, this small animal is about the same length as a dollar bill.  They have pouches on their bodies, which they use to transport food and nesting materials.  

The gophers are excellent at digging and essential to the prairies they inhabit.  They can turn over up to seven tons of soil per acre per year, leading to higher regional plant diversity.  

Being subterranean rodents, they are very rarely seen above ground.  Their burrows include chambers for food caches and nesting.  Reptiles, amphibians, and invertebrates also use their holes.

The gophers are only found in one state in the United States, Washington.  There are believed to be up to five thousand Roy Prairie Pocket Gophers in Washington, but this could be as low as two thousand.  If this is correct, and the number of gophers keeps declining, this could severely affect their inhabited prairies.

Prairie dogs kiss each other when meeting.  Find out why in this article I wrote

Sperm Whale

The sperm whale has the largest brain of any creature, not only in North America but also in the world.  They are also the loudest creature on Earth, with their communication clicks measuring 230db.  This is louder than a space shuttle launch exhaust, an earthquake on the Richter scale of 5.0, and only a little quieter than the atomic bombs dropped on Japan.

The sperm whale gets its name from a substance called spermaceti that whalers once believed was sperm.  Scientists are still unable to explain the function of spermaceti.

The sperm whale is the largest toothed whale, measuring up to 20.5 meters (67 feet), and can weigh up to 57 tonnes.

There are an estimated 1,997 sperm whales in California, Oregon, Washington, and Hawaii, approximately 4,000.

The sperm whale is one of the largest whales in North America. If you would like to find out which whales make up the top ten, I have written an article you may find interesting. You can find the article here.

Sierra Nevada Bighorn Sheep

The Sierra Nevada bighorn sheep look very similar to other bighorn sheep from the desert.  Both the males and females have horns, with the males being larger.  The horns coil out from the base at different angles to most other bighorns.  

The Sierra Nevada bighorn is named after the range it inhabits, and it is still only found in this area.  The U.S. Fish and Wildlife Service has listed them as endangered since 1999.

The sheep’s terrain is rocky, rough, and steep, which they use to keep themselves away from predators.  Their split hooves allow them to venture up very steep inclines, and they can jump long distances.  They will range from an elevation up to 14,000 ft in winter to 9,000 ft in the summer months.

The Sierra Nevada bighorn sheep population reduced dramatically over the last century, from a population likely exceeding 1,000 individuals to 100 animals in 1995.  

Since the sheep were added to the Endangered Species Act in 1999,  numbers have increased to over 600 animals.

If you would like more information on the bighorn sheep, I have compiled a list of 101 facts. You can find the article here.