Research

Forage research: Study looking at vegetation consumed by Bitterroot Valley elk herds

2013-06-16T14:34:00Z 2013-06-16T17:57:37Z Forage research: Study looking at vegetation consumed by Bitterroot Valley elk herdsBy PERRY BACKUS - Ravalli Republic Ravalli Republic
June 16, 2013 2:34 pm  • 

DARBY – High above the valley floor, on a relatively flat bench covered in cheatgrass, a pair of young researchers are hunched down low over the earth, searching for something more.

Their fingers slide over the tops of the tiny green plants found inside the half-meter square made of well-worn PVC pipe painted fluorescent orange.

One after another, they rattle off the Latin names for the grasses and forbs they find growing there while carefully documenting each in writing.

Once they complete that chore, the PVC pipe square gets a little toss and the two carefully shear off all the plant life that lands inside and place the vegetation inside a paper bag to be analyzed later this year.

Then they walk uphill another few steps and do it all over again and again.

All summer long, Nicole Hupp and Ellen Brandell will repeat that process at 30 different sites in the east and west forks of the Bitterroot River as part of a major effort to learn more about the natural history of the valley’s elk herd.

Now in its third and final year, an ambitious and comprehensive study co-sponsored by the University of Montana and Montana Fish, Wildlife and Parks has been assessing elk calf mortality, cow elk migration routes and pregnancy rates of southern Bitterroot elk.

That study began following a precipitous drop in elk numbers, especially in the West Fork of the Bitterroot.

Many initially blamed predators for the decline.

In the first two years, researchers have started to gain a better picture of the predator/prey relationship, but they know there’s more to the story.

“When you think about it, what would a natural history book on elk be if it didn’t consider what an elk eats,” Hupp said. “There’s so much more to learn.”

Mark Hebblewhite is leading this portion of the study. The UM associate professor has done similar research in Canada’s Banff National Park.

In his mind, it’s really a story about the classic food web.

Elk are in the middle. So to really understand the full picture, researchers need to know what eats them and what it is that they eat.

When they put that all together, researchers will have a better understanding of the relative importance of forage and predation for Bitterroot elk.

The research so far has provided a peek into the differences for elk living in the east and west forks of the Bitterroot.

In the east fork, a good portion of that elk herd follows the melting snow up over the mountains and into the Big Hole Valley for the summer months in search of succulent new growth.

It could be part of what makes the east fork herd more resilient than those elk living a little further west.

While many people believe that an elk’s diet focuses primarily on grasses, Hebblewhite said that’s not what the research shows so far.

Last year, Hupp and others collected elk scat from both the east and west fork areas. This past winter, it was painstakingly analyzed to see what elk really do eat.

As it turns out, the most important component was forbs during the vital spring and summer grazing period. Elk also graze on grasses and shrubs.

Those flowering plants like balsamroot and lupine provide that flush of protein that’s both important during spring when cow elk are nursing their calves and that time just afterward when they are desperately trying to put on weight in preparation for winter.

“Elk spend up to 12 to 14 hours a day foraging,” Hebblewhite said. “If they can select areas where they don’t have to hunt and peck, it can have a huge impact for them later on in the year.”

It’s the reason that elk migrate. They are searching for plants with the highest levels of digestible energy, which are young forbs.

“We’ve seen where elk have eaten 30 to 40 percent of the new lupine,” Hebblewhite said. “Those kinds of forbs are really important to their diet.”

It’s still too early in the study to say with certainty how the difference in soil conditions and amount of forested lands in the east and west forks of the Bitterroot impact the production of the young forbs so necessary to elk.

Researchers do know that a high percentage of the elk in the East Fork’s French Basin are migratory.

While there have been other studies in the past that look at elk forage, Hebblewhite said this study will be able to tie information that they uncover about forage quality with body condition of cow elk and their newborn calves gathered by researchers through the winter, spring and fall.

That portion of the study is supported financially by the U.S. Forest Service, which is interested in learning more about how its land management efforts impact elk habitat.

A second portion of funding comes from an agency that’s never had much of a reason to spend money here.

NASA helped fund the purchase of a series of time-lapse cameras that will help integrate information gathered by this vegetation study with other similar efforts occurring from Idaho to Greenland.

Those close-up images will be integrated into much larger-scale satellite photographs that could help document changes in growing seasons across that large swath.

Hebblewhite said researchers studying the Clarks Fork elk herd near Cody, Wyo., have already documented that the growing season has declined by up to 40 percent due to drought and higher temperatures.

“It used to last 12 weeks and now it’s eight weeks,” he said. “The growing season is ending in mid-July instead of mid-August. That’s a huge phytological change to have the browning-up occur that much earlier.”

For a cow elk, that change in timing can be critical.

During spring and early summer when forbs are plentiful, Hebblewhite said cow elk use most of the energy they consume to produce milk for their calves.

“They are not actually gaining weight,” he said. “You can count their ribs. It’s the most nutritionally stressful time of the year for them. When their calves start to wean in July, that’s when it matters most for them as they prepare for winter.”

That fact could spell trouble for the Bitterroot herd if the rains suddenly stop.

“We are already seeing lupine seeding and beargrass blooming,” Hebblewhite said. “That could mean that growing season could be done by mid-July here in the Bitterroot.”

Reach reporter Perry Backus at 363-3300 or pbackus@ravallirepublic.com.

Copyright 2016 Ravalli Republic. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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