Three short lines give us a quiet, unsettling scene. A pig has been slaughtered and hung from a house, apparently the last of its kind there. The title, "Whole hog," points to the old idea of using every part of the animal, though it also hints at going all the way, with nothing held back. Then the poem shifts outward: moon on the marsh.
The speaker never says how they feel, and that restraint is part of the effect. They simply set the hanging carcass beside the calm, silvery landscape and let us notice the contrast. One image is physical and a little grim. The other is cool and beautiful. Together they suggest that death and beauty exist in the same night, without either one cancelling the other.
"The last pig" could mean the final one of the season, or perhaps the end of a way of life. The poem doesn't confirm either, but that sense of an ending gives the stillness a faint note of loss. The mood is hushed, watchful, and matter-of-fact.