► Introduction & Client | Over the last decade, there has been a notable increase of interest in discussions surrounding animal welfare, driven by a deeper understanding of the mental states of animals. This growing awareness has triggered a global push to improve laws and regulations in animal welfare, prompting zoos worldwide to increase their efforts in enhancing the quality of life for their captive animals.

Environmental enrichment has emerged as a crucial tool in increasing animal welfare, supported by studies showcasing its positive impact on reducing aggression and abnormal behaviour in captive animals. ARTIS Zoo actively applies environmental enrichment into its practices and collaborates with the University of Amsterdam to delve deeper into the behaviour and needs of their animals. Scientific research at ARTIS Zoo includes an ongoing exploration into whether primates can recognize time intervals.

► Project Scope | In an effort to further enhance the lives of their animals, ARTIS Zoo has joined forces with the faculty of Industrial Design Engineering of TU Delft to design a versatile device serving as both an enrichment tool and a research device. The project focusses on designing a feeding solution that mimics the natural foraging behaviour of the yellow cheeked gibbon and black crested macaque, taking into account both physical behaviour as well as cognitive abilities.

► Literature research | Literature research has delved deeper into animal welfare, environmental enrichment, and primate behaviour, resulting into important insights. Primates can forage efficiently because of their physical advantages over other animals while also using the WWW-memory (What, where and when). Primates use synchrony, temperature, solar cues and sensory cues to locate ripe fruit. Yellow cheeked gibbons forage in the high trees for fruit, while black crested macaques forage mostly on the ground between bushes and grass.

A vision has been shaped: The product should give the primates more autonomy over their feeding process while triggering the cognitive memory, decision making and problem solving abilities.

► Requirements | The design considerations for the device were carefully outlined, addressing the distinct needs of stakeholders:

Primate Usage: Concentrated on promoting foraging behaviour to reduce inactive periods.

Zookeeper Usage: Prioritizing a user-friendly design to maximize usability.

Researcher Usage: Enabling dual-purpose functionality for both enrichment and research, with remote control capabilities.

Safety Considerations: Ensuring material, assembly, and food safety through detailed specifications.

► Design | The final design (Figure 1.1) takes the form of a fruit, which needs to be peeled by primates to reveal food inside. The device closes automatically and can be locked and unlocked remotely. Iterative design improvements enhance user usability, material sturdiness, and food safety.

► User testing | User testing with gibbons at ARTIS Zoo showcases significant interest and interaction, supported by observational data indicating heightened engagement between gibbons, increased foraging activities, social behaviour and extended active periods in the presence of the device.