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A Caicos Islands skink. Photo credit: Joseph Burgess
In 1872 the mongoose is introduced onto Caribbean islands. By 1900, skinks in the Caribbean declined by more than 50 percent. By 2000, skink numbers are down to less than 20 percent. Graph courtesy Blair Hedges, Penn State University.
Researchers have discovered 24 skink species in the Caribbean, including re-establishing nine species that had been described but were thought to be inaccurate descriptions. This, according to the paper published today in Zootaxa, puts the number of skink species in the Caribbean from six to 39.
Blair Hedges, a biology professor at Penn State University and the leader of the research team, said that half of the newly described species might be extinct and all of the species on the list are likely to be endangered on the Caribbean islands. The researchers discovered the new species primarily by examining museum specimens. They used DNA sequencing and combined that with classic taxonomic techniques such as counting the number of scales as well as describing the shape of those scales. A unique aspect of these skinks is they have a placenta, similar to a human placenta that enables these lizards to gestate their offspring for up to a year before live birth. Hedges said that this gestation period may have given predators an edge in seeking out and consuming the females, which are slower when pregnant.
Hedges believes that the introduction of the mongoose to control rats in sugar cane fields is responsible for the low numbers of skinks on the islands. "The mongoose is the predator we believe is responsible for many of the species' close-to-extinction status in the Caribbean," Hedges said in a press release put out by Penn State University. "Our data show that the mongoose, which was introduced from India in 1872 and spread around the islands over the next three decades, has nearly exterminated this entire reptile fauna, which had gone largely unnoticed by scientists and conservationists until now."
Hedges said the reason these species went unnoticed for so long was the fact that the skinks had already disappeared by the start of the 20th century and nobody was really studying them. He also said that the use of DNA testing followed up with the taxonomic work required to validate a species are techniques that were not available 100 years ago.