Harbour seals (Phoca vitulina) can steer by the stars
- 527 Downloads
Offshore orientation in marine mammals is still a mystery. For visual orientation during night-time foraging and travelling in the open seas, seals cannot rely on distant terrestrial landmarks, and thus might use celestial cues as repeatedly shown for nocturnally migrating birds. Although seals detect enough stars to probably allow for astronavigation, it was unclear whether they can orient by the night sky. The widely accepted cognitive mechanism for bird night-time orientation by celestial cues is a time-independent star compass with learned geometrical star configurations used to pinpoint north as the rotational centre of the starry sky while there is no conclusive evidence for a time-compensated star compass or true star navigation. Here, we present results for two harbour seals orienting in a custom made swimming planetarium. Both seals learned to highly accurately identify a lodestar out of a pseudo-randomly oriented, realistic projection of the northern hemisphere night sky. Providing the first evidence for star orientation capability in a marine mammal, our seals’ outstanding directional precision would allow them to steer by following lodestars of learned star courses, a celestial orientation mechanism that has been known to be used by Polynesian navigators but has not been considered for animals yet.
KeywordsOffshore orientation Astronavigation Marine mammals Harbour seals
This work was supported by a grant of VolkswagenStiftung to G. D. We thank the Schulmuseum Leipzig for kindly providing the star projector. The experiments comply with the German animal protection legislation.
- Batschelet E (1981) Circular statistics in biology. Academic Press, LondonGoogle Scholar
- Bennet ATD (1996) Do animals have cognitive maps? J Exp Biol 199:219–224Google Scholar
- Emlen ST (1967) Migratory orientation in the indigo bunting, Passerina cyanea. Part II. Mechanisms of celestial orientation. Auk 84:463–489Google Scholar
- Gellermann LW (1933) Chance orders of alternating stimuli in visual discrimination experiments. J Genet Psychol 42:206–208Google Scholar
- Gladwin T (1970) East is a big bird: navigation and logic on Puluwat atoll. Harvard University Press, CambridgeGoogle Scholar
- Lewis D (1975) We, the navigators: the ancient art of landfinding in the Pacific. University Press of Hawaii, HonululuGoogle Scholar
- Wehner R (1984) Astronavigation in insects. Annu Rev Entomol 29:277–298Google Scholar