Short-Term Puzzle Feeder Enrichment Increases Food Engagement but Not Stress-Related Behaviour in Captive...

Environmental enrichment is widely used in zoos to improve welfare and facilitate successful reintroductions, yet evidence for its effectiveness in callitrichids - particularly golden-headed lion tamarins Leontopithecus chrysomelas - remains limited. As these primates spend up to half of their daily activity budget foraging in the wild, food-based enrichment may significantly improve welfare in captivity. Here, we investigated the effects of food puzzles on six zoo-housed golden-headed lion tamarins (three pairs) over 17 days (5 control, 12 treatment). Food engagement time and behaviours that may reflect stress or arousal states (grooming and activity) were recorded during structured observation periods. We found that food puzzles significantly increased feeding engagement, from an average of 15 min with standard food bowls to 47 min with puzzles (~3-fold increase). In contrast, no statistically significant changes were detected in grooming or activity levels. Although short-term exposure did not reduce stress-related behaviours, the more equitable distribution of allogrooming and the decrease in self-grooming observed in most individuals suggest potential group-level benefits. Our findings underscore the potential benefits of food puzzles which reliably extend foraging time in captive golden-headed lion tamarins. Our work also highlights the need for longitudinal, multi-zoo studies to evaluate effects on social dynamics and welfare.