There are various natural reasons why some species face extinction. While human interaction is one of the biggest contributors to it, there are also natural occurrences that force it to happen. This is in fact what we are going to discuss further in the next lines.
Climate change does pose real danger to terrestrial animals even though there’s no threat of comet impacts or major asteroids. You don’t have to look further. Just think of the last Ice Age which was roughly 11,000 years ago. This is when numerous megafauna mammals failed to quickly adapt to the warming temperatures.
While it is somewhat unusual for a single disease to clean a species, groundwork needs to be laid by the loss of habitat, lack of genetic diversity and/or starvation.
The introduction of bacterium or lethal virus at inopportune time could cause massive loss among animals.
Loss of Habitat
Majority of the animals are requiring certain land area for them to live. The given area must give them enough grounds to forage and hunt, raise their young, breed and when needed, expand their population. A single bird might be contented nesting in high branches of trees while large predators measure its dominance in square miles. Without having enough land area, these animals may have a hard time to live.