The population of moose in the Jackson Hole area is continuing on the downward trajectory it has been on since the late 1980s, two recent surveys found.

In 22 hours of aerial surveillance, Wyoming Game and Fish Department biologist Doug Brimeyer recently counted 239 moose — the second-lowest tally in 28 years of record keeping.

Days after Brimeyer flew, volunteers around Jackson Hole participating in the Nature Mapping event Moose Day counted 60 of the animals. The previous low for the citizen count, now in its fifth year, was 94.

“The overall trend is still downward, and it’s pretty alarming,” Brimeyer said. “Last year — with the same effort, same pattern — I counted 298.”

The moose census, Brimeyer said, did turn up one positive sign: There were more calves relative to the number of adult females. The metric is a key indication of future population growth.

“Overall, calf ratios are up,” the Game and Fish biologist said. “We found 33 [calves] per 100 [cows]. It was 24 last year.”

There were three sets of twins, Brimeyer said.

“With really good habitat, you’ll see more twinning,” he said.

Participants in Moose Day, held the snowy morning of Feb. 23, observed a similar decline in numbers while driving and walking all around the valley.

Some 75 people spotted 36 percent fewer moose than last year, despite a 27 percent increase in the number of volunteer hours, said Morgan Graham, the event’s coordinator.

“We had a ton of comments from people who see moose five at a time in their yard every day and saw them on Friday and saw them on Sunday, but didn’t see them on the actual Moose Day,” said Graham, a GIS manager with Teton Science Schools. “So I’d take the numbers with a grain of salt. But it is interesting that it’s down to 60 and 94 was the previous low.”

Jackson Hole’s population of the large, gangly ungulate is unique in that the species existed in very low numbers in the ecosystem until the 1920s, then “exploded” after most large predators were removed and hunting limits were implemented, Wildlife Conservation Society biologist Joel Berger said.

Since then, moose have slowly depleted willows — a critical food source — in riparian areas, leading to their own decline, Berger said.

Berger and his wife, Kim Berger, studied the Jackson Hole moose population during the time when wolves and grizzlies were reoccupying their former turf in Jackson Hole.

The resurgence of the two large carnivore species, Brimeyer said, has played a role in the moose’s decline in the valley.

A Grand Teton National Park study now in its third year found that wolves home in on moose on the north end of the park during the winter months.

In places, Brimeyer has observed eye-popping declines in the ungulate species during his aerial counts.

“I think the biggest change that I’ve seen is the Willow Flats area near Jackson Lake Lodge,” Brimeyer said. “I would count 50 moose there when I first moved here in the mid ’90s. I counted one for the entire area this year.”

During the same time frame, near the Heart Six Ranch in the Buffalo Valley, Brimeyer has also observed declines of more than 90 percent.

Moose populations to the south of Jackson, however, are holding on much better, as are populations in the Bighorn and Snowy Range mountains, Brimeyer said.