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Methods

GPS collars and activity sensors The models of GPS collars used in these experiments were GPS3300S and GPS4400S (Lotek Wireless Inc., Canada: Host software Ver. 1.9. 6 for GPS3300 and Ver. 2.4. 0 for GPS4400). These collars contained a dual-axis motion sensor (activity sensor) that records up-down (Y-act) and side-side (X-act) movements (±7.5 degree) of the animal’s head and neck. The data from each sensor were stored in the collar memory every 5 minutes, with a maximum event of 255 counts. We used the total number of X-act and Y-act at 5-minute intervals as the “activity value”(=(X-act+ Y-act) counts/5 min).