After a deer's ribs were pierced by an arrow, bone grew over the shaft and arrowhead.

Deer aren't usually considered especially badass, but one white-tailed deer in North Carolina turned out to be a lot more metal than expected.

A close encounter with a hunter left the deer with several broken ribs and part of an arrow embedded in its body. Remarkably, the animal survived, and bone grew around the shaft and arrowhead lodged in the creature's side.

The deer lived with the arrow inside its body until years later, when another hunter killed the animal, cut the deer open, and discovered its amazing secret. The man later mounted the skeletal oddity, and in February 2017, the Utah Conservation Officers Association (UCOA) shared a photo on Facebook. [27 Oddest Medical Case Reports]

In the image, the arrow lies diagonally across five of the animal's ribs, encased almost entirely in layers of bone. As the tough tissue formed over the arrow, it acted as a splint for the damaged rib cage, strengthening the deer's injured body, UCOA representatives reported in the post.

Prior to its demise, the deer looked "natural and healthy," Robert Stegall, current owner of the mounted ribs, told the outdoor-lifestyle website Wide Open Spaces. Stegall's father shot the deer — a four-point buck — in Anson County, North Carolina, about 30 years ago, Wide Open Spaces reported.

Stegall recounted that his father didn't suspect that there was anything unusual about the deer until he removed its hide and noticed the bone-wrapped arrow in the animal's ribs. Stegall's father eventually mounted and framed the rib cage portion, and in 2017, he presented the piece to his son as a birthday present, Stegall said.

While the sight of a rib cage bolstered by a bone-encased weapon is unnerving, it's not unusual for bone to grow around structures that invade a body, Yara Haridy, a doctoral student at the Natural History Museum in Berlin, told Live Science in an email.

"I have seen bone grow over a variety of foreign objects, usually teeth," Haridy said. For example, if a predator bites an animal and a tooth becomes lodged in a bone, that bone can cover the embedded tooth as it heals.

When the deer was injured, several of its ribs were probably fractured; this likely caused massive bleeding, so a large blood clot formed not only over the broken bones, but also over the arrow, Haridy explained.

"The blood clot then becomes the outline for a 'soft callus' to form, made of cartilage. Later, this cartilage is replaced by bone, making a hard callus," she said.

Another way that bone can wrap around a foreign body is through metaplastic ossification, a pathological process that can occur after trauma. In this case, other types of tissue transform into bone. It's hard to say for sure which of these processes took place inside the deer without cutting into the bone tissue and analyzing it, "but both are good candidates," said Haridy, who recently tweeted the image of the deer's ribs.

Original article on Live Science.