BETHEL, Alaska (AP) — The Alaska Department of Fish and Game announced an early closure of the hunting season for the Mulchatna caribou herd.

The closure will take effect at 11:59 p.m. Friday, KYUK-AM reported Tuesday.

The hunt was originally scheduled to close in March, but officials said the restriction is a conservation measure following the herd’s population drop to half the size it was three years ago.

The state reduced the number of caribou that hunters could kill from two to one in August. Federal managers followed suit and restricted caribou hunting kills to bulls on federal lands in western game units. Federal officials closed the hunt entirely in their jurisdiction in December.

“If we harvest too many bulls, or too many animals in general, there won’t be any growth in the herd, any minimal growth in the herd,” said Todd Rinaldi, regional management coordinator for the state’s Division of Wildlife Conservation for Central Southwest Alaska.

State officials said they do not know why the population dropped and are working to understanding why it happened.

Wildlife managers plan to launch a plan to communicate Mulchatna herd conditions and state decisions to communities, including publishing a magazine called Caribou Trails.

“That communication plan is going to involve not only emails to previous and current permit holders, but it’ll have direct postal mailings to all current box holders in the region,” Rinaldi said.