Normally, it's a rhino's pointy horns that stand out as the animal's most distinctive feature. But the Denver Zoo's resident rhinoceros has another noticeable adornment that's been catching the eye of curious visitors.

Rudy, the 29-year-old black rhinoceros, whose full name is Rudisha, has been seen sporting a thick ankle bracelet on his front left leg.

Much like a Fitbit or Apple Watch for humans, the anklet acts as an activity tracker for the rhinoceros. The device monitors Rudy's movements, behaviors, health, and physical fitness.

The anklet is part of a wider research project, organized by the American Institute of Rhinoceros Science. The goal is to improve rhino wellbeing and also to help save a critically endangered species. Several other rhinos in zoos accredited by the Association of Zoos and Aquariums are also taking part in the science-based project.

The world's wild black rhino population faces threats due to habitat loss and illegal poaching. The Denver Zoo explains that while conservation efforts have allowed the species to recover from an estimated 2,000 individuals in 1993, to about 5,000, they are still considered highly endangered. Currently black rhinos are found only in scattered pockets of Africa from the Cape to Somalia, typically in protected areas or reserves.

Rhinos are also very slow to reproduce, which makes it even harder for the population to regrow.

According to 9News, Rudy arrived at the Denver Zoo in 2016. He came to Colorado from the Oklahoma City Zoo, but was born on August 16, 1993 at Sedgwick County Zoo in Wichita, Kansas. The massive mammal is extremely food-motivated, and especially enjoys apples and fresh plants.

Visitors can find Rudy just to the right of the main entrance near the Gates Center.

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