Author Spotlight: How long do giant squid grow?

Unleashing the Kraken: on the maximum length in giant squid (Architeuthis sp.)

C.G.M. Paxton, University of St Andrews

Anecdotal accounts of giant squid length are longer than actual measured specimens. And scientists’ estimates of maximum giant squid length are shorter than actual measured specimens. The reason for this seeming paradox is that the longer measurements are thought to be inaccurate, or the result of stretching of the tentacles (the two longest arms). A new study by Dr Charles Paxton of the University of St Andrews suggests that, given the variation in length exhibited in measured specimens, giant squid of total length of 20 m are rather probable, although some of the giants reported as anecdotes may be exaggerations or inaccuracies.

jzo12347-toc-0001-m
Architeuthis clarkei. Plate I in Robson (1933), vol. 103, issue 3, Proceedings of the Zoological Society of London

The length of the longest specimen of giant squid ostensibly measured is 19 m (extracted from the gut of a sperm whale from the Indian Ocean) but the roundness of the figure is suspicious, and the 19-m figure is not wholly reconcilable with the photo that accompanies it. Another specimen of 16.81 m length was described in New Zealand in 1888, however the ratio of the two long tentacles to the mantle (body) length was suspiciously high, leading some researchers to suggest that the tentacles were stretched.

Nevertheless, if the spread of the lengths in available specimens is considered and, given the length of the longest reliably measured mantle (the squid’s “body”) known, 2.79 m, squid of total length of a least 20 m are not implausible. There remains the interesting question of the maximum length of squid that could be taken by the only known predator of adult giant squid, the sperm whale? From the indigestible beaks of the squid found in the guts of sperm whales, a minimum estimate can be made, and it appears that adult bull sperm whales have swallowed giant squid with mantle length of at least 2.69 m. Given that it is unlikely that we have found the longest specimen of giant squid ever eaten by a sperm whale, it remains plausible that large bull sperm whales could take squid as much as 3 m in mantle length, a fight that would be the most awesome wildlife scene yet to be captured on camera.

Charles Paxton

 

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