Caecotrophs are soft, nutrient-rich droppings that rabbits (and other hindgut fermenters) eat directly from their bottom to absorb vitamins and protein — a normal, essential behaviour, not a problem.
They’re distinct from the normal hard, round faecal pellets. Eating them (caecotrophy, a form of coprophagy) lets the animal extract nutrients its gut can only produce on a second pass.
Sticky caecotrophs left uneaten and stuck to the fur can signal too rich a diet or an animal that can’t reach its bottom — and, in warm weather, a flystrike risk.