Tortoises native to the Arizona desert rarely grow in excess of about 15 pounds, so officials with the Arizona Game and Fish Department were quite surprised when they recently came across a huge 100-pound tortoise living comfortably in the Sonoran Desert.

Probably kept as an exotic pet and released into the Arizona wild by its careless handler, the behemoth reptile was an African spurred tortoise, according to Wildlife Extra News.

"Finding an exotic tortoise this size inhabiting the Sonoran Desert is a reminder of how important it is not to release any exotic species into the wild," said Cristina Jones of the Arizona Game and Fish Department.

Because they are native to the southern edge of the Sahara desert, these giant tortoises are right at home in the similar environment of the Arizona desert. But like many invasive species, their introduction can pose a serious threat to native species.

"Due to their immense size, while defending its territory, an African spurred tortoise could easily injure a native desert tortoise," said Jones.

The African spurred tortoise can grow to 150 pounds, which makes it the largest mainland tortoise species in the world. By comparison, Arizona's principal native species only grows to about 15 pounds — the native species wouldn't stand a chance in a battle over territory. The African tortoise also can radically alter the landscape. This tortoise had already established itself long enough to build two burrows, including one that was 9 feet deep.

"When people purchase these tortoises, they are about the size of a silver dollar, yet they can grow to more than 150 pounds," Jones said. "These exotic tortoises are long-lived and because of their propensity to dig long, deep burrows, they can be extremely difficult to contain."

Finding just one African spurred tortoise in the Arizona wild might be strange enough, but this was the second one found this year. Officials urge that pet owners understand what they are getting themselves into when they purchase an exotic pet, and to always avoid releasing any exotic animal into a non-native habitat.