When it comes to the Endangered Species List, some animals stand out as celebrities: polar bears, giant pandas, and snow leopards. But sadly, the list is so extensive that there are many species you may never have suspected are endangered. Some are on their way out through natural selection, but others are being forced out by factors brought on by humans. Here are 20 that might surprise you.

1 of 20 Zebras Brad / Flickr / CC BY-ND 2.0 An icon of the African plains and a necessity in any wildlife documentary, the zebra is actually in trouble. Specifically, it's the Grevy's zebra that is endangered. There are several species of zebras in Africa, including the plains zebra, the mountain zebra, and the grevy's zebra. Among them, the mountain zebra is considered vulnerable and the plains zebra is near threatened, but the grevy's zebra is in dire straits — fewer than 2,000 individuals are left in the wild.

2 of 20 Peacocks George Edward Lodge / Wikimedia Commons / Public Domain We wouldn't think of peacocks as endangered, considering you can find them in any wildlife park, petting zoo, and even the occasional farm. But there are subspecies of this flamboyant bird that are in danger of disappearing, including the Bornean peacock-pheasant (pictured in the monograph above) and the Hainan peacock-pheasant from the island of Hainan, China. For both species, habitat loss is a major factor in their decline. Only about 600 to 1,700 Bornean peacock-pheasants and between 250 and 1,000 Hainan peacock-pheasants are left in the world.

3 of 20 Giraffes Charlotte Bleijenberg / Getty Images Giraffes are practically part of the landscape of Africa, standing tree-like in the grasslands. Most giraffe species are not a huge concern to conservationists, yet the nominate subspecies of the Northern giraffe, the nubian giraffe, is critically endangered. It has experienced a 95% population decline over 30 years. The total population is estimated to be at 650, primarily in Ethiopia and South Sudan.

4 of 20 Hummingbirds Jerry Oldenettel / Wikimedia Commons / CC BY-SA 2.0 Though you may see a flock around that sugar-water feeder you set out, quite a few hummingbird species are actually listed as endangered by IUCN. Some of these species include the oaxaca hummingbird pictured above, with around 600 to 1,700 mature individuals remaining; the mangrove hummingbird, which was discovered in 2005 and lives along the Pacific coast of Costa Rica; and the chestnut-bellied hummingbird, a near-threatened species found in Colombia with an estimated 10,000 to 20,000 individuals left.

5 of 20 Horses Aloxe / Wikimedia Commons / CC BY-SA 3.0 It may come as a surprise that horses are endangered — specifically, the Przewalski's Horse. Closely related to but genetically unique from its domestic cousins, this wild horse is endangered. It was listed as extinct in the wild from the 1960s to 1996 when one surviving individual was found in the wild and other individuals were reintroduced. Currently, there are about 178 mature horses living in the wild with more individuals in captive breeding programs and zoos. A major threat to the species is a loss of genetic diversity and, as a result, disease.

6 of 20 Howler Monkeys Ruestz / Wikimedia Commons / CC BY-SA 3.0 Howler monkeys are so common to Central and South America that it's hard to think there is any risk for them. But with habitat loss and capture or predation by humans, there is indeed a problem for several species. The Yucatan black howler monkey is endangered and is expected to decline by up to 60% over the next 30 years. Meanwhile, the Maranhao red-handed howler monkey is also endangered, with approximately 250 to 2,500 mature individuals remaining in the wild.

7 of 20 Fruit Bats 79Photography / Getty Images Some bat species are having trouble with white nose syndrome, including fruit bats. Turns out, a whole slew of species of fruit bat are endangered, including the golden-capped fruit bat (also known as the giant golden-crowned flying fox), with an estimated 10,000 individuals remaining; the Salim Ali's fruit bat, with possibly fewer than 400 left; and the Sao Tomé collared fruit bat, which is rare and has an unknown population. Most of the decrease in fruit bat population is due to hunting, habitat loss, and disturbances to roost sites.

8 of 20 Ground Squirrels Greg Schechter / Wikimedia Commons / CC BY 2.0 Rodents are usually a surprise for the Endangered Species List since they tend to be great at adapting and especially skilled at reproducing. But if they don't have a place to live, they're out of luck. Thanks to agricultural development, urbanization, and a whole lot of rodenticide, California's San Joaquin antelope ground squirrel (also known as the Nelson’s antelope squirrel), with only 20% of its former range, has an unknown but decreasing population.

9 of 20 Dolphins Alatom / Getty Images Even the most charismatic of animals isn't off the chopping block. The South Asian river dolphin has two subspecies based on the river systems in which they are found, the Ganges River dolphin and the Indus River dolphin. Though a strong effort has been made to research and conserve the species, there is still relatively little known about them. Of the Ganges River dolphins, there are about 3,500 left, while there are an estimated 1,200 to 1,800 Indus River Dolphins remaining.

10 of 20 Galapagos Penguins Gareth Codd / Getty Images The Galapagos penguin is the smallest penguin in the world, and it is also the one that lives the farthest north. This aquatic bird is endangered, with a population of 1,200 and decreasing. The Galapagos penguin lives 20 years on average and mates for life. Contamination from oil spills, hunting, fishing, and non-native predators are all threats to it.

11 of 20 Mice abrahambio / Wikimedia Commons / CC BY-SA 4.0 Even mice are on the Endangered Species List. Quite a few have the dubious honor, including Nelson’s spiny pocket mouse (pictured) and the salt-marsh harvest mouse. The Nelson’s spiny pocket mouse is endangered due to loss of habitat in Mexico and Guatemala, where the mouse is also impacted by floods and landslides. Found in the salt marshes bordering San Francisco Bay, the salt-marsh harvest mouse is impacted by habitat loss as a result of residential and commercial development, dam and water management systems, and invasive plant species.

12 of 20 Parakeets Mark Newman / Getty Images Several gorgeous species of this popular house pet are on the brink of extinction in no small part because of their popularity as house pets. Populations of the sun parakeet, estimated to be between 1,000 and 2,500 individuals, have declined due to trapping for the cage-bird trade as well the diminishing quality of their habitat. Though the total population is not known, the reasons for population decline are similar for the grey-cheeked parakeet of Ecuador and Peru.

13 of 20 Crayfish Mike Powles / Getty Images Usually we think of crayfish as a common Southern food pulled from rivers. However, a surprising number of crayfish species are on the decline. Those on the Endangered Species list include the white-clawed crayfish (pictured above), the phantom cave crayfish, the slenderclaw crayfish, the giant freshwater crayfish, and the aptly named Sweet Home Alabama crayfish of Marshall county, Alabama. This native Alabama crayfish is threatened by pollution of the freshwater aquifer and its close proximity to roads and urban development.

14 of 20 Deer outcast85 / Getty Images Many species of tiny musk deer are so diminutive they look like the prehistoric animals that were the first mammals to arrive on the planet. The species includes the Himalayan musk deer (pictured above), the black musk deer, the Kashmir musk deer, and the Chinese forest musk deer, among others. These deer are hunted primarily for their musk glands, which are used in traditional East Asian medicines and cosmetics.

15 of 20 Water Buffalo Steve Garvie / Wikimedia Commons / CC BY-SA 2.0 The water buffalo is a surprise for this list as we think of it as a domesticated animal, but like horses, it's the wild cousins of the domesticated beasts that are at risk. There are as few as 2,500 mature individuals left and researchers estimate the species has experienced a population decline of at least 50% over the last three generations. The major threats include interbreeding with feral and domestic buffalo as well as habitat loss, hunting, and disease from domestic livestock.

16 of 20 Vultures J.M. Garg / Wikimedia Commons / CC BY-SA 3.0 Vultures aren't usually considered the most attractive of birds, but the Egyptian vulture is a notable exception. The striking bird is found in Europe, Africa, and India, but rapid and severe declines in the Indian populations as well as a long-term decline in the European populations put the population at around 12,000 to 38,000 mature individuals. One of the threats to Egyptian vultures is the drug diclofenac, which is used as a painkiller for livestock. The vultures, who feed on animal carcasses, are killed from consuming animals that were treated with the drug. As a result, some countries have banned the use of diclofenac.

17 of 20 Hippos Raimond Spekking / Wikimedia Commons / CC BY-SA 4.0 Pygmy hippopotamus are the diminutive relatives of the Hippopotamus amphibius. The two do not share a habitat, however, as the pygmy hippo is only found in Liberia, Ivory Coast, Sierra Leone, and the Guinea regions of West Africa. While the pygmy hippopotamus population in the wild is unknown, the total number of mature individuals is estimated to be between 2,000 and 2,500. Deforestation is the greatest threat to the pygmy hippo, but this animal is also hunted for meat.

18 of 20 Sea Lions Yummifruitbat / Wikimedia Commons / CC BY-SA 2.5 Pinnipeds are geniuses in the marine world, but sadly their smarts can't keep them off the Endangered Species list. The Steller sea lion, the fourth largest pinniped behind walruses and two types of elephant seals, has a global population of around 81,300 animals. An improvement in population for the two subspecies considered together, the western Steller sea lion and the Loughlin’s Steller sea lion, has improved the Steller sea lion's status from endangered to near threatened. The western Steller sea lion population has continued to decrease due to disease and killing by fishermen, while the Loughlin’s Steller sea lion population is trending upward.

19 of 20 Gazelle Sanjay Acharya / Wikimedia Commons / CC BY-SA 3.0 As with zebras, no documentary about the African savanna is complete without a few gazelles being caught by lions or cheetahs. But feline predators are not the only threat to a number of gazelle species. The cuvier's gazelle of northwest Africa is considered vulnerable with an estimated population of 2,300 to 4,500 individuals, while the slender-horned gazelle of the Sahara has only around 300 to 600 mature individuals remaining. The speke's gazelle (pictured above) from the Horn of Africa is considered possibly extinct in Ethiopia, while remaining populations in Somalia, thought to be in the tens of thousands, face severe pressure from hunting and habitat loss.