ESSEX, Mont. — The long freight trains climb slowly over Marias Pass, through snow-draped mountains south of Glacier National Park and north of the Great Bear Wilderness, snaking through some of the wildest country in the Lower 48.

Some 25 trains a day, each a chain of 90 to 120 cars, make the journey over the Rocky Mountains in northern Montana at speeds up to 25 miles per hour. They have long been a threat to grizzly bears, and last year was the worst with eight of the bears — a federally protected species — run over by trains. On one day in June, a mother and her two cubs were killed by trains in two separate incidents. The long-term average for grizzly deaths by train is two a year.

“A train can sneak up on you,” said John Waller, the supervisory wildlife biologist for Glacier National Park, as he stopped to watch one chug through the forest. “They are amazingly quiet on the down grade and there are a lot of times the sound is blocked, coming in and out of the valleys.”

The death rate of grizzlies in this region has been rising, attributed not only to trains, but to poaching, cars and the removal of troublesome bears. In 2018, a record number — 51 — were killed in the Northern Continental Divide Ecosystem, millions of acres in and around Glacier Park. And last year, 51 bears were killed. In 2017, just 29 bears were killed or euthanized.