For decades, bats were believed to be the only mammals found natively in Cayman. Now fossils are starting to tell a different story.
Analysis of bones found in caves, sinkholes and peat deposits in the Cayman Islands has revealed the existence of three new species that once roamed the islands.
The fossils, some of which appeared to have been consumed by Cuban crocodiles, were collected on all three of Cayman’s islands over the last 80 years.
Now, a team of researchers has identified the bones as belonging to two new large rodent species and a small shrew-like mammal that were unique to the Cayman Islands, existing nowhere else in the world.
The discovery of the species had been reported previously but they were scientifically described for the first time in a paper published in the Bulletin of the American Museum of Natural History this week.
Researchers believe they were driven to extinction following the arrival of European settlers in the Cayman Islands and the introduction of invasive species like rats and mice from ships in the early 18th century.
They speculate that one of the species – a small mammal similar to an agouti – may have been the animals described as “little beasts, like cats” by explorer Sir Francis Drake in his record of his visit to the islands in 1586.
Aside from that vague reference, there is no recorded evidence of the animals’ existence.
Professor Ross MacPhee, one of the authors of the study, says this is why the discovery of the fossils is so important.
“With only one possible sighting early in the course of European expansion into the New World, these small mammals from the Cayman Islands were complete unknowns until their fossils were discovered,” he said.
Some of the most significant fossil finds were made during the development of the Queen Elizabeth II Botanic Gardens in the early 1990s.
Fred Burton, who now works at the Department of Environment’s terrestrial resources department, was involved in that project and recalls the discovery.
“We were excavating a very small wetland and when we dug up the peat, it was full of bones,” he said.
Professor Gary Morgan, a paleontologist who regularly worked in the Cayman Islands and is one of the co-authors of the study, was on island at the time and immediately identified the bones as belonging to Cuban crocodiles, which were once abundant in the Cayman Islands.
Further analysis revealed the existence of fossilized bones belonging to the mystery mammals.
Mr. Burton said there had been multiple similar finds on all three islands dating back to the 1930s. He said advances in technology had now enabled researchers to put the pieces of the puzzle together to provide a scientific description of all three species.
Mr. Burton believes the fossil record, well preserved in Cayman’s peat beds, provides a fascinating insight into the world that existed before the islands were settled. and is ripe for further exploration.
“Part of the sad history of humankind is that we have been responsible, in some cases accidentally and in some cases on purpose, for the extinction of a huge amount of biodiversity,” he added.
Professor Samuel Turvey, one of the paper’s authors, said in a statement that humans were almost certainly to blame for the extinction of the three species.
He said, “It’s vitally important to understand the factors responsible for past extinctions of island species, as many threatened species today are found on islands. The handful of Caribbean mammals that still exist today are the last survivors of a unique vanished world and represent some of the world’s top conservation priorities.”
The paper names the two large rodents as Capromys pilorides and Geocapromys caymanensis and the shrew-like creature as Nesophontes hemicingulus.
Their closest living relatives are found today in Cuba and the researchers speculate that a common ancestor first arrived in the Cayman Islands on rafts of floating vegetation.
Dr. Morgan, the paleontologist who co-authored the study, has been visiting the Cayman Islands to study fossils since the 1970s. In an article for the Department of Environment’s Flicker magazine in 2017, he described finding evidence of a variety of species no longer found in the islands, including crocodiles and several species of bird, including a large eagle-sized raptor.