Population bottleneck

A population bottleneck occurs when a large population suddenly shrinks to a much smaller size, like when a species nearly goes extinct and only a handful of individuals survive. This dramatic reduction means the surviving animals carry only a fraction of the genetic diversity that existed before, which can lead to genetic problems and reduced ability to adapt to changes in their environment. Classic examples include cheetahs, whose populations crashed so severely that all living cheetahs today are extremely similar genetically, making them vulnerable to disease and environmental stress.