Recently completed aerial surveys show a marked decline in elk numbers in game management units 10 and 12, which comprise the Lolo Elk Management Zone.
Survey results indicate the elk population in the Lolo Zone has declined from 5,110 to 2,178, a 57-percent reduction since 2006. The greatest declines were observed in numbers of elk cows, calves and spike bulls. Overall, bull numbers were down zone-wide, with a shift in bulls to older animals.
"This survey, combined with ongoing research showing wolves are the primary cause of elk mortality today, is further scientific evidence of the impact wolves are having," Fish and Game Director Cal Groen said. "The rate of this decline in just four short years should help people understand there is an urgency to manage for a balance in this area."
Appropriate management options in response to this latest survey data are being explored.
Wolf predation is the major source of mortality on this elk herd and is affecting population size because too few calves are surviving to replace the adults that die each year. Predation is preventing recovery from a decline that began in the late 1980s and a steep decline following the severe winter of 1996-97.
This survey information corroborates ongoing research being conducted in the Lolo Zone that shows survival of radio-collared adult elk and six-month-old calves has been poor. Modeling efforts based on research survival data estimate declines of 11 to 15 percent annually.
Idaho Fish and Game's aerial surveys of most elk zones are conducted on a three- to five-year rotation. Surveys provide estimates of the size of the population as well as demographic data, such as numbers of elk cows, calves and bulls.