Fig. 5

Analytical methods for horizontal movement data. Diagrams show hypothetical track of a central place forager, star represents central place. a Two patterns of movement can typically be detected in predator tracks; extensive movements with high displacement and low turning angle (grey lines) and intensive movements with low displacement and high turning angles (blue lines). Intensive movements are commonly taken to represent area-restricted search (ARS) behaviour. b Fist-passage time (FPT) is the sum of temporally-regularised location fixes required to leave a circle of given radius in both forward and backward directions from time point t _i (yellow dots). Residence time (RT) includes total time spent in the circle from present (iii-iv), previous (i-ii) and future (v-vi) time steps (green lines), provided that time outside the circle (gap between intersection points ii-iii or between iv-v) is not above a user-defined threshold. c Areas of high FPT / RT can be identified by sliding the circle along the track at each time step. Red dashes denote the areas in space (left) and time (right) taken to represent ARS. d Demonstration of a three-state HMM output. Right-hand plot shows posterior Weibull distributions of displacement for three discrete states. Using biological rationale, movement states can be used to infer behaviours (e.g. state 3 with high displacement may be travelling, states 1 and 2 may be either foraging or resting). Presence/absence of diving can be included in the model to distinguish between foraging and resting at the surface [121]