Montana wildlife managers say a spring survey of bighorn sheep shows that past actions of killing sick bighorns in an effort to prevent a pneumonia outbreak from killing even more bighorns appears to have resulted in a higher survival rate for lambs.

Mike Thompson of Montana Fish, Wildlife and Parks tells the Missoulian that in two herds where sick sheep were killed and removed the survival rate for lambs is about 30 percent.

He says in two herds where culling efforts were halted because of the difficult terrain, there was a 96 percent decrease in normal lamb survival.

Thompson says the culling also likely prevented three other bighorn herds from becoming infected.

Officials say the pneumonia outbreak since late 2009 has killed more than 500 bighorn sheep in western Montana.

Associated Press