Mule deer have been in decline in Johnson County – and across the state and the West – for more than a decade. A combination of factors has played against mule deer populations, but a crucial piece of the mule deer’s winter food supply – mahogany – has been a key player in that decline.
The Bureau of Land Management’s Buffalo Field Office and the Wyoming Game and Fish Department have banded together with a goal of stabilizing the mule deer population. This year alone, the organizations have improved more than 600 acres of critical mule deer winter range in Johnson County.
Since 2011, the project has enhanced more than 2,800 acres of winter range areas along the southern Bighorn Mountains in Johnson County by removing conifer trees from curl-leaf mountain mahogany stands. Mahogany, a crucial part of the mule deer’s winter food supply, has been out-competed with encroaching conifer stands that kill the mahogany by blocking out sunlight.
“We’ve traditionally been an oil and gas and grazing office, but there’s been kind of a cultural shift here where we’re focusing more on habitat. And the benefits would be, one, mitigating the impacts of oil and gas development; two, reducing that competition between wildlife and livestock on our grazing lands; and benefiting (Greater) Sage Grouse habitat. The benefits are really just endless,” said Jim Verplancke, natural resource specialist with the BLM and lead wildlife biologist on the project.
A declining population
“There are a number of factors working against mule deer on the population front, but nobody has really been able to narrow down what the cause is. Most likely, it’s a broad range of effects that are causing the decline,” Verplancke said.
Some of those include oil and gas development in the Powder River Basin; the 2012 drought, which affected the habitat for several years after the actual drought ended; a spell of particularly harsh winters between 2007 and 2012 that resulted in low fawn recruitment; a large number of predators, particularly mountain lions; and competition with elk, Verplancke said.
In addition to those factors is the threat to the mahogany stands, which are important for mule deer survival and a major source of food on the winter range, according to the BLM. In southern Johnson County, conifer species are outcompeting mahogany stands.
Managing for mahogany
Of the four varieties of mahogany in the southern Bighorns, curl-leaf mountain mahogany is the least studied and subsequently the least understood. There’s not a lot known about it, Verplancke said.
What is known is that it doesn’t produce seed every year. It grows in areas with more rocks than soil, and it loves the sun.
The species is shade-intolerant, meaning it will die if it doesn’t get copious amounts of sunlight. When it’s encroached upon by an overstory of conifers that block out the sun, it withers away.
Ponderosa pine, Douglas-fir and juniper grow much faster than mahogany. And as they grow, their canopies can also block out the sun and choke out the mahogany.
“We see immediate results when we remove the conifers from the mahogany. They’re there one day and gone the next,” Verplancke said.
Removing trees opens up the canopy, which allows much needed sunlight for the mahogany. There are plenty of trees left for thermal cover and protection for mule deer and other big game species, Verplancke said.
Limber pine, a BLM sensitive species – which, according to the BLM – is a species that warrants protection, is also treated in the project. Instead of cutting it, crews remove limbs up to 5 feet off the ground on trees with a diameter of 8 inches or larger. This removes the pine needle build-up on the ground and opens up the canopy, Verplancke said.
The slash is scattered on-site in open areas between the mahogany, and piles are kept below knee height, he said. These precautions are taken to limit fuel for wildfires.
“You run the risk, if you take too much down, you have more fuel on the ground than you can actually scatter. We could actually create more fuel on the ground, so it’s kind of a volatile situation,” Verplancke said.
The effects of fire
Fire is what jumpstarted the need to improve mahogany stands in Johnson County in the first place. In 2006, the 12,500-acre Outlaw Cave wildfire burned 815 acres of mahogany, about 8 percent of the mahogany on the winter range, according to the BLM.
“We really don’t want to see that happen again,” Verplancke said. “That motivated us to start to remove the conifers from the mahogany. What the conifers do is they provide the fuel that will carry fire through the mahogany. The mahogany itself typically doesn’t burn well, but when you add that fuel, being the conifers, that will carry it through the landscape.”
Removing conifers near mahogany stands helps to reduce the wildfire fuel, which can decrease fire intensity and frequency, according to the BLM.
Additionally, removing trees can free up groundwater for more desirable plant species, Verplancke said. A single juniper tree can use up to 35 gallons of water a day, and when you remove hundreds of them from the landscape, you free up a lot of water, he said.
Planning for mule deer
The habitat improvement project actually began in 2010, when Game and Fish approached BLM about doing some habitat work in the Middle Fork of the Powder River for mule deer, Verplancke said.
“Historically, mule deer has been a real cash cow for Game and Fish in this area,” he said.
Beginning in 2011, phase one of the project focused on the Ed O. Taylor Wildlife Habitat Management Area and the Middle Fork of the Powder River Recreation Area. It expanded in 2012 to include other state and private lands adjacent to the Taylor site. More than 2,000 acres of mahogany stands were cleared of conifers during phase one.
Game and Fish administered the project during phase one, with BLM assisting on the ground with planning and oversight.
But when the lead Game and Fish biologist for the project retired in 2012, the two agencies switched roles, and BLM took the lead as the contracting agent, Verplancke said.
With BLM at the helm, phase two began in 2013. In phase two, 2,350 acres of mahogany near the Middle Fork area were targeted for habitat improvement, including more remote areas that can be difficult to access. So far, almost 800 of those acres have been completed, more than 600 of them during the 2015 season.
Verplancke said that scheduling issues with a contractor prevented work being done on the ground in 2014.
“It was unfortunate but gave us a lot of opportunity to do some on-the-ground mapping and laying out units,” Verplancke said. “This year, that’s why we were able to cover so much acreage, because we had things very well laid out for when our people were on the ground.”
The project has an annual budget of $40,000, excluding BLM expenditures, that comes from external grants. BLM has spent that money every year except for 2014.
To date, about 2,800 acres of curl-leaf mountain mahogany have been improved.
Private contractors hired by the BLM, and Game and Fish and BLM crews have removed small conifers from mahogany stands, including ponderosa pine, Douglas-fir, juniper, and, to a lesser extent, limber pine.
Competing with elk
The project also helps to reduce competition between mule deer and elk in shared crucial winter range, Verplancke said.
“We’ve got interaction here between mule deer and elk where it appears that the elk are outcompeting mule deer in the crucial areas. Elk don’t browse on the mahogany. They’re grazers, where mule deer are browsers. So we’re making the habitat more suitable for mule deer so we can disperse that competition between the two species,” Verplancke said.
To put things into perspective, the mule deer population in the area is less than 50 percent of Game and Fish’s herd objective and has been for more than a dozen years. On the other side of the fence, elk populations in the same area are at 200 percent, he said.
“The interaction between those two species, the elk are out competing the deer,” Verplancke said.
What comes next
It’s unknown if the habitat improvement has bolstered mule deer numbers, Verplancke said. A formal study hasn’t been implemented, and, even if it had, there isn’t any baseline data to compare it to.
Still, he said, based on anecdotal evidence, mule deer appear to be using the habitat more.
Pellet counts, counting scat piles to estimate deer density, have shown that deer are using the habitat more than elk now, and ground crews have reported seeing more mule deer herds in the area.
That could be from a variety influences, though, including climate, fewer predators, less interaction with elk or improved habitat, he said.
The BLM plans to continue with the project, and Verplancke hopes to get more private landowners on board.
Crews have been predominately working the south side of the Middle Fork Canyon but hope to move to the north side of the canyon soon, he said.
“We’re looking for more partners to access. When we get north of here, a lot of those public lands are landlocked by private parties. So we’d like to very much get more partners so we can continue to access those federal lands,” he said.
The treatments can – and have – also taken place on private land. And the treatment is just as effective in sagebrush habitat as in mountain mahogany stands, Verplancke said.
Private landowners benefit because the treatments free up groundwater and make more area available for grass production, which could mean less competition between livestock and wildlife.
“If you can keep the deer in the mahogany and off your haystacks, that’s a benefit,” Verplancke said.
The Wyoming Conservation Corps and the Montana Conservation Corps have also assisted with groundwork. The Wyoming Conservation Corps Youth Crew, ages 10-18, from Casper, also assisted by helping to scatter slash and pull noxious weeds.
Johnson County Weed and Pest, in conjunction with Game and Fish and the BLM, has also treated 700 acres for cheat grass between the Middle Fork of the Powder River and Outlaw Cave Road.
Wyoming Wildlife and Natural Resource Trust, Mule Deer Foundation and Rocky Mountain Elk Foundation provide financial support for the project.