Endangered Animals: Facts & Causes

Instructor: Heather Pier

Heather has taught high school and college science courses, and has a master's degree in geography-climatology.

What causes an animal to become an endangered species? In this lesson, you will learn about the various ways in which a species can become endangered.

What is an Endangered Animal?

When we say an animal is endangered, that doesn't really mean that the animal is in danger of being hurt or neglected, like we might think based on the definition of human endangerment. Instead, it is a reference to all animals of the same species being in danger of going extinct. For this reason, we often use the terms endangered animal and endangered species interchangeably.

So what causes an animal species to be at risk for extinction? There are several possible reasons why that could happen.

Population Problems

Anything that can potentially lower the global or regional population of an animal species is a potential cause of endangerment and extinction. Sometimes, this is caused by problems within the population of that species, and is not due to any aspect of their ecosystem or because of humans.

For example, a species might become endangered because a particular bacteria or virus is killing off large numbers of animals. When there are fewer healthy animals in a population, it is harder for them to successfully breed and raise enough young to replace the sick and dying members of the population.

Tasmanian devils, Darwin's frogs, and other species have all become endangered as a result of diseases infecting their populations.

Tasmanian devils have become endangered as a result of a rare type of facial cancer.

Habitat Problems

The most common cause of animal endangerment in modern times is habitat destruction. A habitat is the location where an animal lives, and it is part of the larger regional ecosystem.

The level of habitat destruction could range from a total loss of habitat due to human development in the area to more limited losses of habitat because a single host or food plant is experiencing population problems.

When an animal loses part or all of its habitat, it is like you losing part or all of your house. You might not have a place to sleep at night, or you might not be able to eat all of your favorite foods, or you might have a hard time going to work or school because your usual path to get there might be damaged. This would create a great deal of both mental and physical stress, particularly the loss of a food source. Habitat loss impacts non-human animals in a similar way.

The large scale loss of the world's rainforest areas has created a marked increase in the number of animals (and plants) being added to endangered species lists each year. In North America, monarch butterflies are being impacted by habitat loss. The Mexican forests which these butterflies overwinter in are rapidly being logged, and their sole food supply - the milkweed plant - is being destroyed by urbanization and pesticide use in agriculture. The resulting lack of food and overwintering habitat has pushed the monarch population to the verge of endangerment.

Monarch butterflies are at risk for endangerment in the near future due to widespread habitat destruction.

Invasive Species

Sometimes it isn't a disease or a lack of habit that causes a species to become endangered. It can also occur as a result of new species moving into an otherwise healthy ecosystem and disrupting its ecological balance.

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