Photographer Frank Liu was in Kenya's Masai Mara National Reserve in search of rhinos when he came across a rare sight.

Liu noticed a zebra foal with dark fur mixed with white polka dots. Because a zebra's stripes are typically unique, this was a first time this reserve had ever seen this sort of coloration.

The zebra was given the name Tira by Antony Tira, a Maasai guide who first spotted the foal and who served as Liu's guide. The zebra foal has a rare condition called pseudomelanism, which causes this stripe abnormality.

Tira is a plains zebra, but he doesn't like everyone else. Frank Liu

Other zebras in Botswana and Tanzania have also been photographed with similar pattern abnormalities.

A National Geographic article explored the causes of Tira's condition and other theories about zebras with different stripes. Cells called melanocytes produce the pigments that give zebras and other animals their distinct colors, but in the case of Tira, the melanin in those cells didn't manifest correctly.

Tira has abnormal stripes. Frank Liu

The article also notes that these animals don't normally survive as long because they're easier for predators to target. That said, other zebras with abnormal coats have been accepted into their packs and survived to adulthood.

Regardless, this was a special opportunity for Liu, who has photographed animals in over 30 countries around the world.

Underneath its hair, a zebra is black. Considering that fact when you look at Tira makes his pseudomelanism easier to understand. Frank Liu

The 28-year old's work, including travel across six continents, has been featured in major publications.

You can follow Liu's work on Instagram and his website, where you can see his best photos from previous trips to Patagonia, Switzerland, Namibia, and many other places.

In fact, you can follow along on his next tour, when he'll visit India to study Bengal tigers in the wild in 2020.