Science, Tech, Math › Animals & Nature Reasons Animals Become Endangered Share Flipboard Email Print Freder / Getty Images Animals & Nature Wildlife Conservation Amphibians Birds Habitat Profiles Mammals Reptiles Insects Marine Life Forestry Dinosaurs Evolution View More By Jennifer Bove Wildlife Expert B.S., Biology, University of Missouri in Columbia Jennifer Bove is a contributing writer for the National Wildlife Foundation. She is the author of a series of children's non-fiction books about animals, published by HarperCollins. our editorial process Jennifer Bove Updated July 07, 2019 When an animal species is considered endangered, it means that the International Union for Conservation of Nature (IUCN) has evaluated it as nearly extinct, which means that a significant portion of its range has already died off and the rate of birth is lower than the species' death rate. Today, more and more animal and plant species are on the verge of extinction because of a variety of major factors that cause a species to become endangered, and as you might expect, humans play a role in quite a few of them. In fact, the biggest threat to endangered animals is human encroachment on their habitats. Fortunately, conservation efforts around the world are bent on helping these endangered animals revitalize their dwindling populations through a variety of humanitarian efforts, including curtailing illegal poaching, halting pollution, and habitat destruction, and curtailing the introduction of exotic species into new habitats. Habitat Destruction and Pollution Every living organism needs a place to live, but a habitat is not just a residence, it is also where an animal finds food, raises its young and allows the next generation to take over. Unfortunately, humans destroy animal habitats in a number of different ways: building houses, clearing forests to get lumber and plant crops, draining rivers to bring water to those crops, and paving over meadows to make streets and parking lots. In addition to physical encroachment, human development of animals' habitats pollutes the natural landscape with petroleum products, pesticides, and other chemicals, which destroys food sources and viable shelters for the creatures and plants of that area. As a result, some species die outright while others are pushed into areas where they can't find food and shelter. Worse yet, when one animal population suffers it affects many other species in its food web so more than one species' population is likely to decline. Habitat destruction is the number one reason for animal endangerment, which is why conservation groups work diligently to reverse the effects of human developments. Many non-profit groups like the Nature Conservancy clean up coastlines and establish nature preserves to prevent further harm to native environments and species around the world. Introduction of Exotic Species Destroys Delicate Food Systems An exotic species is an animal, plant, or insect that is introduced into a place where it did not evolve naturally. Exotic species often have a predatory or competitive advantage over native species, which have been a part of a particular biological environment for centuries, because even though native species are well adapted to their surroundings, they may not be able to deal with species that closely compete with them for food. Basically, native species haven't developed natural defenses for an exotic species and vice versa. One example of endangerment due to both competition and predation is the Galapagos tortoise. Non-native goats were introduced to the Galapagos Islands during the 20th century. These goats fed on the tortoises' food supply, causing the number of tortoises to decline rapidly. Because the tortoises could not defend themselves or stop the overpopulation of goats on the island, they were forced to abandon their native feeding grounds. Many countries have passed laws banning specific exotic species known to endanger native habitats from entering the country. Exotic species are sometimes referred to as invasive species, especially in cases of banning them. For instance, the United Kingdom has placed raccoons, mongooses, and cabbages on their invasive species list, all of which are barred from entering the country. Illegal Hunting Can Endanger Species When hunters ignore rules that regulate the number of animals that should be hunted (a practice known as poaching), they can reduce populations to the point that species become endangered. Unfortunately, poachers are often hard to catch because they are deliberately trying to evade authorities, and they operate in areas where enforcement is weak. Furthermore, poachers have developed sophisticated techniques for smuggling animals. Baby bears, leopards, and monkeys have been sedated and stuffed into suitcases for transport. Live animals have been sold to people who want exotic pets or medical research subjects. And, animal pelts and other body parts are also secretly smuggled across borders and sold through black market networks of buyers who pay high prices for illegal animal products. Even legal hunting, fishing, and gathering of wild species can lead to population reductions that cause species to become endangered. A lack of restriction on the whaling industry in the 20th century is one example. It wasn't until several whale species were nearing extinction that countries agreed to abide by an international moratorium. Some whale species have rebounded thanks to this moratorium but others remain at risk. International laws forbid these practices, and there are a number of government and nongovernment organizations (NGOs) whose sole purpose is to stop illegal poaching, especially of animals like elephants and rhinoceroses. Thanks to the efforts of groups like the International Anti-Poaching Foundation and local conservation groups like the PAMS Foundation in Tanzania, these endangered species have human advocates fighting to protect them from outright extinction. How Are Animals Endangered? Of course, species endangerment and extinction can happen without human interference. Extinction is a natural part of evolution. Fossil records show that long before people came along, factors such as overpopulation, competition, sudden climatic change, and catastrophic events like volcanic eruptions and earthquakes drove the decline of numerous species. There are a few warning signs that a species could become extinct. If a species has some economic importance, such as the Atlantic salmon, it may be at risk. Surprisingly, large predators, who we might expect to have an advantage over other species, are often at risk as well. This list includes grizzly bears, bald eagles, and gray wolves. A species whose gestational period is lengthy, or who have small numbers of offspring at each birth has the potential to become endangered more readily. The mountain gorilla and California condor are two examples. And species with weak genetic makeup, like manatees or giant pandas, have more risk of extinction with each generation.