Abstract

AbstractThe Earth's atmosphere and the Earth's magnetic field protects local life by shielding us against Solar particle flows, just like the sun's magnetic field deflects cosmic particle radiation. Generally, magnetic fields can affect terrestrial life such as migrating animals. Thus, terrestrial life is connected to astronomical interrelations between different magnetic fields, particle flows and radiation. Mass strandings of whales have often been documented, but their causes and underlying mechanisms remain unclear. We investigated the possible reasons for this phenomenon based on a series of strandings of 29 male, mostly bachelor, sperm whales (Physeter macrocephalus) in the southern North Sea in early 2016. Whales’ magnetic sense may play an important role in orientation and migration, and strandings may thus be triggered by geomagnetic storms. This approach is supported by the following: (1) disruptions of the Earth's magnetic field by Solar storms can last about 1 day and lead to short-term magnetic latitude changes corresponding to shifts of up to 460 km; (2) many of these disruptions are of a similar magnitude to more permanent geomagnetic anomalies; (3) geomagnetic anomalies in the area north of the North Sea are 50–150 km in diameter; and (4) sperm whales swim about 100 km day−1, and may thus be unable to distinguish between these phenomena. Sperm whales spend their early, non-breeding years in lower latitudes, where magnetic disruptions by the sun are weak and thus lack experience of this phenomenon. ‘Naïve’ whales may therefore become disoriented in the southern Norwegian Sea as a result of failing to adopt alternative navigation systems in time and becoming stranded in the shallow North Sea.

Highlights

  • Multiple strandings of sperm whales (Physeter macrocephalus), defined as two or more animals stranded at about the same time, in or near the same place, are infrequent but worldwide occurrences

  • We investigated the possible reasons for this phenomenon based on a series of strandings of 29 male, mostly bachelor, sperm whales (Physeter macrocephalus) in the southern North Sea in early 2016

  • This approach is supported by the following: (1) disruptions of the Earth’s magnetic field by Solar storms can last about 1 day and lead to short-term magnetic latitude changes corresponding to shifts of up to 460 km; (2) many of these disruptions are of a similar magnitude to more permanent geomagnetic anomalies; (3) geomagnetic anomalies in the area north of the North Sea are 50–150 km in diameter; and (4) sperm whales swim about 100 km day−1, and may be unable to distinguish between these phenomena

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Summary

Introduction

Multiple strandings of sperm whales (Physeter macrocephalus), defined as two or more animals stranded at about the same time, in or near the same place, are infrequent but worldwide occurrences. Sperm whale strandings (single animals or groups) have been documented in the North Sea since the Middle Ages (Smeenk 1997; Vanselow & Ricklefs 2005; Pierce et al 2007). Sperm whales do not normally occur in the North Sea because of a lack of suitable habitat, some animals enter the North Sea, probably on their way south between Shetland and Norway, where they may encounter difficulties. These animals appear disorientated and may eventually become stranded, often still alive

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