Saccadic movement strategy in a semiaquatic species - the harbour seal (Phoca vitulina).
Moving animals can estimate the distance of visual objects from image shift on their retina (optic flow) created during translational, but not rotational movements. To facilitate this distance estimation, many terrestrial and flying animals perform saccadic movements, thereby temporally separating translational and rotational movements, keeping rotation times short. In this study, we analysed whether a semiaquatic mammal, the harbour seal, also adopts a saccadic movement strategy. We recorded the seals' normal swimming pattern with video cameras and analysed head and body movements. The swimming seals indeed minimized rotation times by saccadic head and body turns, with top rotation speeds exceeding 350 deg s-1which leads to an increase of translational movements. Saccades occurred during both types of locomotion of the seals' intermittent swimming mode: active propulsion and gliding. In conclusion, harbour seals share the saccadic movement strategy of terrestrial animals. Whether this movement strategy is adopted to facilitate distance estimation from optic flow or serves a different function will be a topic of future research.
Georg-August-University of Göttingen, Department of Cellular Neurobiology, Schwann-Schleiden Research Center, Julia-Lermontowa-Weg 3, Göttingen 37007, Germany.
Bart R H
0000-0002-1816-3241
BRH
Geurten
University of Rostock, Institute for Biosciences, Sensory and Cognitive Ecology, Albert-Einstein-Str. 3, Rostock 18059, Germany.
Benedikt
B
Niesterok
University of Rostock, Institute for Biosciences, Sensory and Cognitive Ecology, Albert-Einstein-Str. 3, Rostock 18059, Germany.
Guido
G
Dehnhardt
University of Rostock, Institute for Biosciences, Sensory and Cognitive Ecology, Albert-Einstein-Str. 3, Rostock 18059, Germany frederike.hanke@uni-rostock.de.
Frederike D
0000-0002-1737-3861
FD
Hanke
D000818:Animals; D008124:Locomotion; D057849:Optic Flow; D046049:Phoca / Q000502:physiology*; D012438:Saccades; D013550:Swimming
Optic flow; Pinnipeds; Vision