Fig. 2. Smart animal-borne video system confirms that seals predominantly forage on small fish in pelagic waters.

(A) Pelagic foragers in red [observed in n = 45 of 48 seals, representative data for one seal (2017_U20)] encountered small fish, whereas benthic foragers in blue [observed in only n = 3 of 48 seals, representative data for one seal (2017_5712)] encountered large fish (table S1). (B) Along migration routes, the video recording locations (larger open circles) were located at the farthest points from the colony due to the delay timer of 36 days. As in (A), note that video was recorded for only 1 min per dive (red or blue segments on depth plot), when the criteria of depth (400 m) and acceleration triggers (black lines) were met. These trigger settings maximized the video coverage of foraging dives, under the limited video recording capacity of each tag (4 hours). See movies S1 to S5 for original movies, where seal’s snout and whiskers are present in the camera frame, as noted in the bottom left still image. All prey footage lists are available in the Supplementary Materials (movies S2 and S5); the lists with higher resolution images are also available in the ADS (Arctic Data archive System) of the National Institute of Polar Research (https://ads.nipr.ac.jp/dataset/A20210316-001).