Figure 2.

(a) Behavioral arena, baited, and with possum; (b–d) food-extraction problem-solving puzzles: (b) dog teat toy [top] a photograph of a closed puzzle, showing moving parts, and [bottom] a photograph of an open and baited puzzle in the field, with possum; (c) flap lid puzzles [left] a diagram of a closed and [right] a photograph of an open (i) single flap lid and (ii) double flap lid puzzle box; (d) slide lid puzzle [left] a diagram and [right] a photograph of a closed puzzle box. Green arrows show the direction of movement required to open the puzzles. Diagrams created using Tinkercad (© 2023 Autodesk, Inc).