Modern zoo animal welfare assessment has moved beyond simple checklist-based inspections toward outcome-based frameworks that measure how animals actually experience their lives.
Zoo welfare assessment has undergone a conceptual revolution in the past two decades. The shift from input-based to outcome-based assessment reflects a deeper understanding that a large cage with poor social conditions may deliver worse welfare than a smaller but enriched and appropriately social environment. The Five Domains framework - assessing nutrition, physical environment, health, behaviour, and mental state - provides a comprehensive lens that captures animal experience rather than just facilities. Qualitative Behavioural Assessment enables welfare scoring based on observable emotional indicators that go beyond the absence of disease. The challenge now is standardising these approaches across institutions so that welfare data can be compared and improvements driven by evidence rather than anecdote.