Federal authorities are investigating the death of a Mexican gray wolf as wildlife managers prepare for an annual survey of the endangered species along the Arizona-New Mexico border.

Officials with the wolf recovery effort announced Tuesday that a female wolf was found dead in December in Arizona. They declined to release more information, saying the case is still under investigation.

For 2017, there were a total of 12 documented wolf deaths and one removal of a wolf from the wild that resulted in its death.

According to the most recent count, there are at least 113 wolves in the wild in Arizona and New Mexico.

Officials with the U.S. Fish and Wildlife Service say a new survey of the population will begin next Monday. The effort will take two weeks.