On July 7, Becki Grady saw a moose on her way to work in Anchorage, Alaska.
Though it's common to see moose near Alaska's largest city, even in areas where humans roam, there was something unusual about this particular animal — its hooves were elongated and curved.
"I've lived in Alaska my entire life and have never seen a moose like this," she wrote to KTUU. "I thought it had been injured until I saw that all four of its hooves were curved like that.”
The deformity is caused by copper deficiency, state wildlife biologist David Battle explained. The result is called "sleigh hoof."
"We see them every so often here in Anchorage and I know sometimes on the Kenai Peninsula," Battle said. "We get reports of them in Anchorage about once or twice a year at best ... it's not very common.”
Battle explained that region of Alaska doesn’t naturally have a lot of copper in the soil or vegetation, which the moose eat.
Although copper deficiency is uncommon in other parts of the state, the phenomenon is well-documented. An article published in The Journal of Nutrition in 1977 indicated that copper deficiency in the region had serious ramifications for the animals’ health, including blood disorders, heart defects and growth issues, in addition to hoof deformities.
Battle said many of these moose don’t appear often due to natural selection.
"When you have a deficiency of a needed mineral in a particular area, some individuals will be more efficient at absorbing it than others," he said.
The hooves on their own can be a threat to survival.
"More often than not, the extended hoof will break off on its own and it won't bother the moose, but I would expect that if that moose was in a region where it was running into predators — bears, wolves, etc. — it would probably stand a higher chance of being taken down by a predator,” Battle said.