Photo credit: Murray Guy
DNA sequencing local lesser white-toothed shrews: is it a unique sub-species?
– Helen Miller & Katharine Sawyer
The Scilly Shrew is an iconic member of Scilly’s land-dwelling wildlife. Originally believed to be a distinct species of shrew, since the 1950s it has been reclassified as a regional variation of the lesser white-toothed shrew as found in the channel islands of Jersey and Sark [1]. This reclassification was based on observations of the teeth of samples from the different islands [1].
No significant research has been carried out into the classification of these species since, and with modern DNA sequencing and radiocarbon dating techniques, it is possible to re-explore both the relationships between populations on the respective islands, and potentially how and from where the shrews originally came to Scilly. Archaeology can help here with there being shrew bones found at three archaeological sites across the islands. Radiocarbon-dating these remains can add to the story of how they got here, and when.
The proposal of this project is to sequence the DNA of a Scilly Shrew, to compare it with existing DNA analysis of other lesser white-toothed shrews from other populations around the world to see if we can gain any insight into how and from where these shrews came to Scilly. Additionally, we would like to sequence the DNA of a lesser white toothed shrew from Jersey, Sark or one of the French Atlantic Islands to provide a DNA-based investigation of the relationship between the Scilly Shrew and these other island shrews. [2]
[1] https://www.tandfonline.com/doi/pdf/10.1080/00222935808650961
[2] http://naturalhistoryofscilly.info.websitebuilder.prositehosting.co.uk/shrew-paleogeography
June 2024
Progress has been made on our mission to sequence the DNA of the infamous ‘Scilly Shrew.’ We are excited to be working with Andy Young and MD Sharma at the University of Exeter who have the knowledge and technology to find out if our local shrews are unique to Scilly, or if they are the same species of lesser white-toothed shrew found on the islands of Jersey and Sark. We hope that this research will allow us to identify how the shrews made their way to the islands originally. As of now, it is unclear whether the shrews came here by crossing a land bridge from the mainland, or if they were brought here on passing ships. A single pair introduced to the islands intentionally or unintentionally would mean very little diversity in the DNA. In contrast, if they came here by themselves, there would have been multiple pairs and the diversity in their DNA would be much greater today. By pinpointing the root of the Scilly Shrew’s origins we will be able to find out if they came from the same place as the other lesser white-tooth shrews or if they evolved independently. This is an exciting development for our first research project within the CRN. There is even the potential for Scilly’s community to get involved with the DNA testing themselves on the islands, using a special type of technology designed to be used in remote places away from laboratories.
If this project interests you or you would like to be involved, please get in touch with us at hello@scillyresearch.org.
October 2024
Katharine Sawyer became involved with the project after speaking with the Isles of Scilly Wildlife Trust about the research premise. She started investigating the evidence for Scilly shrews from archaeological excavations. She already knew there was evidence from Nornour (and possibly elsewhere) for the presence of shrews and thought that it might be worth getting the bones radiocarbon dated as an additional aspect of the research, if they could be found. The thought process was that if the bones were found to be contemporary with the Ancient Village, then the question of the shrew's provenance could become more interesting. Katharine went through the museum records to find letters suggesting that the shrew bones found at the Nornour excavations in the 60s may have been sent to the University of Oxford. They are currently searching for the bones amongst their collection.
If you know anything further about the story of where these shrew bones may be, please get in touch with us at hello@scillyresearch.org.
January 2025
Some light research by the CRN team has uncovered an intriguing new layer to the story of the Scilly shrew, revealing that there's more to the narrative of its declassification than previously thought.
At the heart of this renewed investigation are two big questions: What is the Scilly shrew - is it a distinct sub-species, or simply a geographically isolated colony of the lesser white-toothed shrew? And how did it get to here in the first place? These two questions are inextricably linked.
First described in 1924 as Crocidura cassiteridum, a distinct subspecies of shrew, the Scilly shrew was later declassified in the 1950s after comparative studies showed that its bones were not significantly different from those of the lesser white-toothed shrew, which is most closely found on the Channel Islands and mainland Europe. Today, the Scilly shrew is considered a subspecies of Crocidura suavolens, the lesser white-toothed shrew.
Despite the ongoing, almost 100-year, conversation surrounding the shrew's classification, the scientific community has been reluctant to revisit this conclusion. Even after the rise of DNA sequencing technologies, these technologies haven't been used to weigh in on the debate. Part of the reason for this delay could be tied to the reputation of the original researcher, Martin Alister Campbell Hinton, former Keeper of Zoology at London’s Natural History Museum, who proposed the Scilly shrew as a distinct subspecies. Hinton's name became controversial in the 1970s, when he was briefly linked to the infamous Piltdown Man hoax - a scandal that rocked the scientific world in the early 20th Century. In 1912 a skull was brought forward to the Geological Society of London claiming to be fossilised evidence of a 'missing link' between humans and apes found in a Piltdown gravel bed. In the 1950s it was discovered that this discovery was entirely faked, using the jaw of an Orangutan and the skull of a Human. The items had been boiled, stained and filed to emulate authentic wear - every found item had been planted. When the hoax was exposed it was a scandal, scientists had based their theories of evolution around the discovery for 40 years. The priority then was to find the identity of the hoaxer. The man who had made the discoveries, Charles Dawson, was the first to have the finger pointed at him. He was an amateur though, and people doubted he had the expertise to pull off such an elaborate hoax. Sir Arthur Conan Doyle's name was also thrown into the mix. He was a member of the same archaeological society as Charles Dawson and his background as a physician gave him the expertise necessary to pull this off. Hinton's name was also brought forward as a possibility in the 70s. He had died the decade prior, and the discovery of some similarly cut and stained fossil animal bones amongst his possessions had made him prime suspect for some people. There are innocent explanations for this, Hinton was a Zoologist and had volunteered at the Natural History Museum at the time of the discovery, he was interested in a great scandal in his field, and he may have been simply exploring how the hoax was possible. Though Hinton was never proven to be involved, his association with the hoax overshadowed his other work, and may have inadvertently discouraged further scrutiny into his shrew findings.
In 2016, after decades of suspicion, research establishing Charles Dawson's likely responsibility finally cleared Hinton's name of any involvement in the Piltdown hoax. Yet the shadow of that scandal remained over his reputation for nearly 40 years, possibly influencing a reluctance to revisit his shrew theory. But here at the CRN, we believe in thoroughness - and with new technologies at our disposal, it's time to revisit the question using DNA evidence. That's why we're diving back into the 'what' of the Scilly shrew's classification.
But the 'how' remains an even more pressing question. Even if they are simply a group of lesser white-toothed shrews, how did the lesser white-toothed shrew - a species native to the Channel Islands, mainland Europe, Asia, and Africa - end up on the remote Isles of Scilly, but not the rest of the United Kingdom? This is the real mystery. The idea that a lone colony of lesser white-toothed shrews could have found its way to Scilly raises fascinating possibilities - were they introduced, have they been here since the Bronze Age, or did they hitch a ride and stowaway on boats from France or Spain? We know they can make it on a boat journey to the mainland, but can they make it further? If confirmed as lesser white-toothed, it would make the presence of these shrews in the UK a remarkable, unique event, one that deserves further exploration. There is more to discover here, and we need to dig deeper into the 'how'.
We're just getting started, and we'd love to have you on this exciting journey with us. If you're as intrigued by this mystery as we are, or if you'd like to be involved in the research, get in touch with us at hello@scillyresearch.org. We're just getting started, and we'd love to have you on this exciting journey with us.
March 2025
DNA extraction was successful!
The above picture is a gel image of the DNA extracted from the Scilly shrew specimen. They have identified, isolated and purified the DNA fragment which will then be prepared for sequencing. The nucleotide sequence is what they're then going to determine from the sample, and then compare to that of the lesser white-toothed shrew.
If this project interests you or you would like to be involved, please get in touch with us at hello@scillyresearch.org. We're hoping that once the DNA has been sequenced, that we can host some workshops about DNA sequencing process on the islands. Keep an eye on this page for further information.