Here and Gone

It sounds like a case of hello and goodbye. A team of biologists led by Penn State’s Blair Hedges recently announced the discovery of 24 new species of the lizards known as skinks, all from islands in the Caribbean. At the same time, they reported that all of these new species are either extinct or on the verge of extinction, likely the victims of the wily mongoose.

Jamaican skink on tree
Joseph Burgess

A Jamaican skink, another of the two dozen newly discovered species. This fauna has been nearly exterminated by the mongoose, a predatory mammal introduced to the Caribbean islands from India in 1872.

Primarily through examination of museum specimens, the team identified a total of 39 species of skinks from the Caribbean islands, including six species currently recognized, and another nine named long ago but considered invalid until now. Hedges and his team used DNA sequences to help draw distinctions, but most of the taxonomic information, such as counts and shapes of scales, came from examination of the animals themselves.

“Now, one of the smallest groups of lizards in this region of the world has become one of the largest groups,” said Hedges, professor of biology. “We were completely surprised to find what amounts to a new fauna, with co-occurring species and different ecological types.”

These New World skinks, which arrived in the Americas about 18 million years ago from Africa by floating on mats of vegetation, are unique among lizards in that they produce a human-like placenta, Hedges noted. “While there are other lizards that give live birth, only a fraction of the lizards known as skinks make a placenta and gestate offspring for up to one year,” he said.

Ironically, this lengthy gestational period may have given predators like the mongoose a competitive edge over skinks, since pregnant females are slower and more vulnerable, Hedges speculated.

The mongoose was introduced from India in 1872 by farmers trying to control rats in the sugarcane fields of Cuba, Hispaniola, Puerto Rico, Jamaica, and the Lesser Antilles. It spread around the islands over the next three decades. Hedges’ data shows a sharp decline in skink populations soon after the introduction of the mongoose, he noted. “By 1900, less than 50 percent of those mongoose islands still had their skinks, and the loss has continued to this day.”

graph depicting the surge of the mongoose population and the concurrent decline of the skink population from the years 1850 through 2000
Blair Hedges

This newly discovered skink fauna increases dramatically the number of reptiles categorized as “critically endangered” by the International Union for Conservation of Nature, Hedges noted. He explained that there are two reasons why such a large number of species went unnoticed for so many years, in a region frequented by scientists and tourists.

“First, Caribbean skinks already had nearly disappeared by the start of the 20th century, so people since that time rarely have encountered them and therefore have been less likely to study them,” he said. “Second, the key characteristics that distinguish this great diversity of species have been overlooked until now.”

Caitlin Conn, a member of the research team, said the new data could help researchers to plan conservation efforts, study the geographic overlap of similar species, and understand in more detail the skinks’ adaptation to different ecological niches.

Blair Hedges, Ph.D., is professor of biology, sbh1@psu.edu. Caitlin Conn, B.Sc., is currently a researcher at the University of Georgia. At the time of the study she was an undergraduate in Penn State's Schreyer Honors College. Funding for this research comes from the National Science Foundation. Findings were reported in the journal Zootaxa.

Last Updated January 10, 2014