Giraffes are considered to be one of the world's most unique creatures, as they are also the tallest. In a new discovery, scientists reveal that giraffes apparently belong to four species as opposed to just one species.

These four species have not been observed to mate with each other, even if they all appear very similar to each other. Now, two of these four species are now considered to be endangered.

The species are now known as the southern, Masai, reticulated and the northern giraffes. However, in the past three decades, giraffe populations have already fallen to just around 100,000 individuals from more than 150,000.

According to Giraffe Conservation Foundation's Julian Fennessy, since there are now four distinct species, conservation status and efforts for each species will be better defined.

To date there are less than 4,750 northern giraffes and less than 8,700 reticulated giraffes in the wild, making them the most endangered large mammals in the world.

Geneticists figured out DNA differences among the giraffes which can be compared to polar bears being vastly different to brown bears.

According to Axel Janke of the Goethe University, the team has been extremely surprised since the coat and morphological pattern differences are very limited among the giraffes.

Prior to this study, it was thought that all giraffes have identical ecological needs, and since they are now divided into four species, this means that they all have diverse requirements. Janke adds, nobody really knows since this megafauna has been mostly overlooked by science.

By examining DNA from 190 individuals, researchers studied their genetic makeup based on nine known subspecies of giraffes in the African continent. Species is identified when a group of animals breed with one another however, cross breeding can also occur with other animals.

This new study is published in the journal Current Biology.