Food and Shelter Trial (FST)
The FST used a modified arena into which we added (i) a shelter made of black-plastic (18cm x 5cm x 5.5cm), positioned at one end of the tank, and (ii) a food zone, comprising a black-plastic square (5cm x 5cm) with food glued to it at the other end (Figure 1b). The food was a mixture of Repashy Solient Green premix powder and ORGANIX shrimp granulate pellets (approximately 10) glued to the black-plastic square using aquarium safe glue (see Figure 1b). Shrimp were introduced via the black acclimation tube at the centre of the tank for 120 seconds, then tracked for 240 seconds after being released. Four traits were measured: Track Length, Time in Open, Food Latency, and Freezings. Predictions for Track Length and Freezings are as described above but note that movement of shrimp could not be tracked once they were within the shelter and food zones, so these traits are recorded only for the portion of the observation period that they are outside these zones. We predict that bolder individuals will spend more time in the open (i.e. outside the shelter zone) and have a short latency to enter the food zone (used as a willingness to feed). Summary statistics for the original variables measured in the FST assay are presented in Table S1.