Two hard winters in a row are weakening the health of Yellowstone’s northern elk herd.
An annual report detailing a March 17-19 aerial count was released Thursday showing the population was holding fairly steady at about 5,800, but calf-to-cow ratios have been low and many animals appeared to be in poor health.
“We are probably going to see a little bit of a decline,” said Karen Loveless, a Fish, Wildlife & Parks wildlife biologist based in Livingston who helps conduct the counts.
“Conditions in the Dome Mountain area were unusually severe, and we observed low ratios of calves (11.5 calves:100 cows) and yearling bulls (4.4 yearling bulls:100 cows),” Loveless wrote in a synopsis. “Conditions in Gardiner Basin north of YNP appeared to be less severe as compared to Dome Mountain and within (Yellowstone National Park). Calf ratios were higher (22.3 calves:100 cows) in Gardiner Basin however many elk appeared to be in poor condition in this area as well. This is the second consecutive year with calf ratios below the threshold of 20 calves per 100 cows considered necessary to maintain a stable population. It is likely that additional winter mortalities will occur into spring, further reducing overall numbers and recruitment.”
Hard winters can affect elk populations in a couple of ways. They can result in poor health of the animals, which kills them outright, often in the spring as green grass starts growing. A difficult winter can cause a pregnant cow to absorb its fetus. Calves that are born may get poor nutrition from their weakened mother’s milk.
Loveless said there’s no evidence that brucellosis, a disease that infects the Northern Range elk herd and can cause elk cows to abort, seems to have any population level impacts.
“Low calf numbers are to be expected when winters are this tough,” Loveless said.
Yearling bull numbers have also declined, down 42 percent from 2016.
Most of the Northern Range herd — 75% this winter — continues to migrate out of the park, a trend that has remained high since 2011. Typically that migration to areas like the Gardiner Basin and Dome Mountain Wildlife Management Area is a trip to a place with less snow than they would encounter in the park. That wasn’t necessarily the case this winter.
About 2 feet of snow fell in mid to late February in the Paradise Valley.
“It got slammed,” Loveless said. “It was more severe in Dome Mountain than anywhere else. So the elk are really low.”
Heavy snow pushed elk onto agricultural land where they are not welcomed by ranchers who want to keep the brucellosis-infected wildlife separated from their cattle to avoid infection.
“It was a really challenging winter for managing commingling,” Loveless said.
Under its management plan FWP tries to keep livestock and elk separated, either by utilizing herders to move the elk out of ag fields, by calling hunters to kill animals or issuing kill permits to landowners. With so much snow Loveless said there was nowhere to push elk off of ag fields. What’s more, the elk were in such a weakened state that even shooting cracker shells at their feet didn’t prompt them to move, she said.
Last year's elk survey showed significantly more animals — up about 2,200 animals from 2017. The theory was that elk that traditionally migrated to Wyoming from the park in the winter were blocked by early snow and instead were diverted to the Paradise Valley.
In talking with her counterpart at Wyoming Game and Fish in Cody, Loveless said the biologist did see more elk up high in bighorn sheep country this February.
“Maybe this year more stayed and last year they got pushed down,” Loveless speculated.
The total elk count in 2017 was about 5,300 animals. This year the count was 5,800. So trend-wise the herd seems to be increasing if last year’s high count of 7,500 elk was a fluke.
One asterisk to the numbers is that in past years the government agencies that cooperate on counts make two flights — one by airplane and the other by helicopter. This year because of the federal government shutdown only one flight by helicopter was conducted. Helicopter flights, because the craft are more maneuverable and can hover, result in higher counts.
Elk populations in the Gardiner area are the bread and butter for some local hunting outfitters. In 2016 FWP made regulation changes to try to boost the bull elk population, much to the chagrin of some locals.
Yet the changes seem to be working. The number of older brow-tined bulls is up from 93 to 114, a 22% increase in Hunting District 313. Inside the park that number has increased from 339 to 410, or about 21%.
“We’re not seeing a decline in bulls, so in that respect it’s been successful,” Loveless said.
The ratio of bulls to cows isn’t great, though. “We observed a slight increase from 2.6 brow-tined bulls per 100 cows observed in 2016 to 3.4 in 2019, and a decrease in the proportion of 6-point and greater bulls from 44% to 27%,” Loveless wrote.
Hunter harvest numbers have not been calculated for this past season.
Looking back, “Since the hunting season structure was adjusted in 2016, we observed below average harvest of 103 bulls in 2016 when weather was mild, and above average harvest of 305 bulls in 2017 when severe weather resulted in an early elk migration out of the Park,” Loveless wrote. “Given the mild weather during the 2018 hunting season it is likely that harvest was more similar to 2016, and this may explain the slight increase in brow-tined bulls this year.”
Based on what this past season’s hunting success shows FWP will decide whether or not to suggest a change in the hunting regulations. Right now, hunters are sacrificing opportunity to help recover bull elk populations.
That may be helpful based on one trend that is showing up.
“Below average yearling bull and calf recruitment this year is likely to result in lower numbers of brow-tined bulls being recruited into the population over the next two years,” Loveless wrote.
“It’s turned into a social question,” she said.