Fig. 4. Comparative performance of searchers with different numbers of sensors and different integration areas (big or small). Sensor arrays are illustrated by `spokes' from the array center to the center of each sensor and by a filled area of integration (top). With all models, performance falls off rapidly outside the 0.5-0.9 range of weighting rheotaxis. With any weighting within this range, at least 70% of searchers reached the source within the 10,000 time steps simulated (A,B). However, the median time taken to reach the source varied 20-fold (C,D). All models with the large integration area outperformed all those with the small integration area. In addition, models with more sensors were better than those with fewer. With the two-sensor models, the larger array was marginally superior. The more complicated center-of-gravity models (B,D) are not superior to the simple best-sensor models (A,C).