where N(0,Z) represents environmental noise, where a value is drawn from a normal distribution with mean 0 and a standard deviation of Z (0.005). Resource types with high H (Fig. 1 c, dashed lines) take longer to learn, while resource types with high S have a shallow increment in rewards during initial learning (Fig. 1 c, gray lines). Note that for simplicity we assume that while for different foragers the same resource items can provide different energy, depletion from the environment and the number of items that can be eaten is the same. This can be interpreted as foragers consuming a certain amount of resource in a given amount of time irrespective of how well it is processed, but that energy obtained depends on processing. Moreover the item is then no longer available for other foragers.