Figure 2.

The novel extractive foraging tasks presented to the Asian short-clawed otters. These differ from those presented to the smooth-coated otters (figure 1), as in this second iteration of the experiment on the second study species we wanted to create a more explicit range of task difficulties. Tasks were also slightly smaller to accommodate the smaller size of this otter species. (1) A simple plastic box (40 × 100 × 100 mm); (2) a plastic box with two clips (45 × 100 × 85 mm); (3) a plastic tub with a screw-top lid (130 × 75 mm diameter); and (4) a frozen reward on a bamboo cane that had to be moved up and to the right to fit through the hole. The numbering of the tasks is in intended order of difficulty, with 1 being the easiest, and 4 being the most difficult. These tasks were baited with peanuts and one fish head per task at the New Forest Wildlife Park, and peanuts and mealworms mixed with either half a mouse or day-old chick legs at Paradise Wildlife Park. Task 4 required a different type of reward due to its design, so this was a block of ice with shrimp or mealworms frozen inside.