HAMILTON – In an elk’s world, the east and west forks of the Bitterroot are about as different as night and day.
Not only do elk have a better chance of becoming a predator’s next meal in the West Fork, the groceries they have to pick from have far less nutrition.
Their kin in the East Fork also carry extra body fat into the winter months and the cows are more likely to be pregnant and produce a calf in the spring.
That is some of the information shared recently by Montana Fish, Wildlife and Parks researchers at a well-attended meeting in Hamilton hosted by the Ravalli County Fish and Wildlife Association.
Titled “Top Down and Bottom Up Effects on Elk Survival and Recruitment in the Bitterroot Valley,” the talk offered a synopsis of information gathered during a three-year Upper Bitterroot Elk Ecology and Elk Calf Predation Project.
The study was a cooperative venture between FWP and the University of Montana, with much of the cost borne by a number of conservation and sportsmen’s organizations, including the Ravalli County Fish and Wildlife Association.
The study followed a dramatic drop in elk calf survival rates that started around 2005. The West Fork was especially hard hit, with elk numbers dropping from about 2,000 in 2005 to 754 in 2010.
Before study began, many blamed the drop on the area’s newest predator – wolves.
Researchers captured calves and fitted them with an ear tag fitted with a radio transmitter that emitted a mortality signal when one died. As quickly as possible, they would seek out the location of the transmitter and determine the cause of the calf’s death.
Mountain lions emerged as the top predator of elk calves in both the east and west forks.
That discovery led to another study to determine density of mountain lions in the area and eventually increased hunting quotas for the predator.
While much of the public’s focus on the study centered on the predator issue, another equally important aspect of research was ongoing.
At the meeting in July, the study’s lead researcher, Kelly Proffitt, offered insights into the role habitat played on elk populations in both the east and west forks.
“Habitat drives ungulate populations,” Proffitt said.
While not that far apart in distance, the east and west forks represent two completely different habitat types.
The West Fork’s mostly forested, rugged mountainous terrain contrasts with the East Fork’s rolling grasslands, where large fires in the recent past have helped create better summer and winter range.
The research team established 236 sampling plots in the east and west fork areas where they systematically looked at the composition of plant species, the weight of the grasses and forbes that grew at each site, and then sent cuttings to a laboratory to determine how digestible the forage was for elk.
They also collected elk pellets to determine what plants the animals keyed in on.
When all the results were in, they found that the East Fork far outperformed the West Fork in growing the kinds of forage that packed on the kind of pounds cow elk need to make it through winter months while carrying a calf.
That’s something they saw when they captured the cow elk that were fitted with radio collars as part of the study.
The researchers used an ultrasound device to both measure body fat and to determine if the captured cow elk was pregnant. They found that not only was there a significant difference in body fat between the two populations, but the pregnancy rates were far lower in the West Fork cow elk as well.
About 73 percent of the cow elk sampled in the West Fork were pregnant. It was closer to 90 percent in the East Fork.
“We wanted to understand the whole story on what was going on with elk in the two areas,” Proffitt said.
The population of adult cow and calf survival are the two main factors that drive elk population, she said.
The information gathered through this study should help biologists predict different outcomes of varied management strategies.
State wildlife managers have already used some of the information gathered by the study to increase mountain lion quotas and lengthen the season for black bears.
Proffitt said the researchers plan to return to the southern Bitterroot next spring to repeat the calf survival study and re-measure mountain lion density.
“Our goal in coming back will be to determine if the mountain lion population has changed,” she said. “We also want to see if the changes in management have led to an increase in elk calf survival.”
FWP wildlife manager Mike Thompson said the study has changed the tone of the discussion.
“When we started down this road, we are all kind of searching for answers,” Thompson said. “We all had theories. We all came in angry. It was hard to sort all of this out.”
Thompson said former FWP biologist Craig Jourdonnais deserves a lot of credit for pushing this study forward.
Thompson knew they were on the right track in moving forward with the comprehensive study when, following a meeting in Darby, people came up and said that while they were angry that the state had messed up their elk herd, they believed the study was the right thing to do.
“Because of what we’ve learned, today we’re all talking a little more of a common language,” Thompson said.