The gathering, which included drum circles and solemn worship, was filled with a sense of mission. As they packed into a tepee, faces aglow around a raging fire, the protesters seemed ready for wherever that dispute may take them. One man said he would sleep out there every night if he had to, and another said he would go so far as to chain himself to an excavator.

But that fervor has been tricky to sustain. Only two days after the rally, Mr. Trump signed executive orders reviving both the Dakota Access and Keystone XL oil pipelines. For the tribe, the losses were demoralizing and depleting. Since then, the Ramapoughs’ events have seen scant news media attention and thinning crowds.

With countless other crises to manage under the new administration, many local activists seem to have diverted their attention elsewhere.

“As always,” Mr. Perry said, “it’s the Ramapoughs against the world.”

It was an overcast morning in March, and Mr. Perry was sitting inside the tepee on his designated tree stump. The survival of the Ramapoughs, he knew, was in the hands of the tribe alone, and there was something both empowering and grim about that fact. The task often feels so daunting that he said he found it helped to focus on small, concrete tasks — “things I know I can do.” That morning, a storm appeared to be looming over the mountain, so his goal was simply to maintain a fire inside the tent.

“Let’s just keep her going,” Mr. Perry said, as he poked the fire with a stick.

Gusts of wind whipped against the tepee, and the fire began to flicker. Soon the blaze was down to embers.

Then a flap lifted and in walked Two Clouds, a bundle of logs in each arm. The chief lowered himself back onto his stump and watched as the young man arranged the wood in a careful stack atop the embers. The fire was soon burning and it was beginning to feel warm inside.