Castlepook’s marked reindeer femur is especially thought-provoking because it may indicate a brief episode of human butchery without demonstrating settlement, hunting strategy, or a lasting population in Ireland. This distinction changes how we might view Late Pleistocene mobility: people could have reached a shifting, ecologically connected island landscape only intermittently, perhaps following animal corridors or exploiting chance carcasses. Derryvree’s wetlands also suggest that apparently harsh tundra contained useful local resources. How should direct dating, microscopic study, and comparison with Upper Palaeolithic sites in Britain and continental Europe help distinguish a single opportunistic visit from repeated seasonal human use of Ireland?