Maintaining species-specific behaviors is essential to animal welfare in zoological institutions. Wild western lowland gorillas spend the majority of their time foraging, whereas zoo-housed gorillas engage in significantly less foraging and more resting. This study examined how different types of environmental enrichment influenced the activity and foraging levels of gorillas at Brookfield Zoo.
Four western lowland gorillas (three adult females and one adult male) were observed over six weeks. Each week, a new enrichment type was added while previous enrichments remained in place. These included:
1. Frozen treat blocks
2. Unpredictable feeding times
3. Additional training sessions
4. Automatic belt feeders (with tubes containing treats)
5. Enhanced feeders (more tubes, added scents)
6. Bark boards (plastic panels with embedded food)
Each gorilla was observed individually using instantaneous sampling across 840 minutes during the study period. Behaviors were categorized using an ethogram.
– Activity and foraging levels increased significantly with the introduction of automated, unpredictable feeders and bark boards.
– Peak troop activity reached 47.48%; foraging peaked at 27.87%.
– No significant changes were seen in abnormal behaviors.
– Individual differences were notable:
– G3 showed the largest increase in activity.
– G1 showed the largest increase in foraging, benefiting most from distributed, non-monopolizable enrichment.
– G2 (a mother with an infant) showed the least change, likely due to caregiving demands.
– G4 (dominant silverback) was most impacted by bark boards.
Unpredictable, dispersed feeding methods such as automatic belt feeders can effectively stimulate natural foraging and increase activity in captive gorillas. Incorporating multiple enrichment types and schedules enhances behavioral diversity and offers individualized benefits. The study emphasizes that timing and variability of enrichment can be as important as the enrichment type.
These findings support the role of dynamic enrichment strategies in promoting welfare and encouraging naturalistic behaviors in zoo-housed primates. The results also hold implications for enriching other species through similar automated feeding technologies.
