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Abstract

Tunas make sharp descents and ascents around dawn and dusk called spike dives. We examine spike dives of 21 southern bluefin tuna (Thunnus maccoyii) implanted with archival tags in the Great Australian Bight. Using a new way to categorize this behavior, we show that spike dives are similar among all the fish in the study. The dive profiles are mirror images at dawn and dusk and are precisely timed with respect to sunrise and sunset. We analyze the possible reasons for spike dives, considering the timing of spike dives, the characteristic dive profile, and the tuna's magnetic habitat. In addition, we present anatomical evidence for elaboration of the pineal organ, which is light mediated and has been implicated in navigation in other vertebrates. The new evidence presented here leads us to suspect that spike dives represent a survey related to navigation.

Item Type:	Article
Authors/Creators:	Willis, J and Phillips, J and Muheim, R and Diego-Rasilla, F J and Hobday, AJ
Keywords:	Migration - Pineal gland - Compass - Magnetic navigation - Polarized light - Archival tags
Journal or Publication Title:	Behavioral Ecology and Sociobiology
ISSN:	0340-5443
DOI / ID Number:	https://doi.org/10.1007/s00265-009-0818-2
Additional Information:	The original publication is available at www.springerlink.com
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