As mule deer numbers have plummeted and seem abnormally slow to rebound, white-tailed deer are gaining an ever-larger range.
Once scarcely seen in the state and largely confined to agricultural areas and stream bottoms, the adaptive whitetails are now forging into Beartooth Mountain canyons and even into the high plateau country of Yellowstone National Park where they previously were rarely, if ever, seen.
“We’ve got a heck of a lot more whitetail than we’ve had in years,” said Shawn Stewart, Fish, Wildlife and Parks’ Red Lodge biologist. “All of the major canyons have whitetails where they never were before.”
There’s proof of the whitetail expansion in FWP’s record keeping. When Stewart first started flying over the East Rosebud trend area in the mid-1980s, whitetail numbers were around 300. Last year they were up to 1,600, a record high.
Mule deer populations, on the other hand, are trending in the opposite direction. Their numbers used to fluctuate on a 10-year cycle of highs and lows. Now they are staying down.
“Mule deer always showed some cyclical behavior,” said Ray Mulé, regional wildlife manager in Billings for Fish, Wildlife and Parks. “Their numbers were low at the middle of decades and were high at the beginnings and ends. We should be going into the high end but we’re not fitting the pattern right now.”
Several factors are at play, Mulé said, the most important of which are changes to mule deer habitat. Rural building has increasingly chopped up traditional mule deer territory. These scattered suburbs tend to favor whitetail, Mulé said.
Deer and their fawns that hang out around homes are less likely to become food for predators like coyotes, bears and mountain lions, since they shy away from people. Areas like the Beartooth Front are also outside the range for diseases like epizootic hemorrhagic disease, which often takes a toll on whitetail deer. Whitetails are also more likely to graze on alfalfa fields and raid landowner haystacks.
More elk in some areas
Along with an increasing number of whitetail deer, elk numbers have also climbed in many areas of the state where they used to be seldom seen. With a limited amount of biomass to go around for the various large ungulates, there’s more competition for food in winter when resources are scarce.
“Elk numbers go up and mule deer numbers go down, but nobody has been able to find a direct correlation other than there’s less biomass for mule deer,” Mulé said.
Whitetails also tend to be more aggressive breeders. When conditions are good, whitetail does will often give birth to twins, which is rare among mule deer.
“Whitetails tend to increase at the expense of mule deer,” Mulé said.
“They are just a real good competitor,” he said, noting that one college professor joked that after a nuclear war, white-tailed deer would be one of three species to survive.
Mule deer are often dependent on sagebrush for winter forage. That point was driven home after the devastating Derby fire in 2006 wiped out thousands of acres of prime sagebrush habitat along the Beartooth Front. It could be 30 to 50 years before those slow-growing plants come back and mule deer numbers rebound in that territory, Mulé said.
And the winter range that is left is more crowded with whitetails, Stewart said.
“My concern is that will stifle or slow the return of mule deer to those areas,” Stewart said. “Maybe it will never happen. I don’t know.”
At the Columbus game check station, manned each weekend during the hunting season, the number of white-tailed deer shot by hunters has climbed to the point that the harvest nearly matches that of mule deer.
“Whitetails are just going through the roof in some of that country,” Mulé said. “Over the years the harvest has gotten a lot closer.”
A little-known fact is that white-tailed deer were planted in the East Rosebud drainage above Roscoe by FWP in the early 1940s, Stewart said, a testament to how scarce the animals once were in Montana. When Stewart was a youngster growing up in Livingston, there were no whitetails to be found in the Yellowstone River valley, he said.
“Now they’re everywhere. It’s good habitat. For years they stayed on the riparian corridors; that’s really not the case anymore.”
Are mule deer doomed? Will they be out-competed and maybe interbred into extinction by the more aggressive white-tailed deer?
“I think there will be mule deer on the landscape for years to come,” Stewart said.
But it’s not unlikely that their population may never climb to the highs that they once achieved.
Stewart pointed to a few havens for mule deer in the Red Lodge area, but added that west of the Stillwater River where the Derby fire burned, mule deer numbers have “gone to heck.”
“It used to be you could go up Rock Creek and count 100 to 250 mule deer from the ground,” Stewart said. “Now, if you can count 50 you’re doing real well.”