On St. Croix, mongooses came in 1884 to protect cane; they were later linked to native ground lizard loss and a racer’s presumed extinction

Mongooses brought to St. Croix in 1884 to control cane rats were linked to the loss of a native ground lizard, which now survives mostly on small islands.

In 1884, St. Croix had a rat problem in its sugarcane fields, and a small predator seemed like the perfect answer. According to a study in the journal Oryx by Nicole Angeli and Lee Fitzgerald, small Indian mongooses were brought to the island to control those rats. Over the following decades, a native lizard disappeared from nearly all of its historic range there, and mongooses had a hand in that.

Pest fix gone wrong

The small Indian mongoose, introduced to St. Croix to protect sugar cane from rats. (Wikimedia Commons)

St. Croix is about 218 square kilometers (roughly 21,800 hectares). Between 1754 and 1800, its plantations shifted from cotton to sugarcane. Rats became a problem in those fields, so mongooses were released in 1884 to control them. The island’s landscape was changing too. By 1917, nearly 90% of the island’s native forests and woodlands had been cleared for farming or logging, the study notes. The mongoose arrived in the middle of those changes.

Two native animals in trouble

The St. Croix ground lizard is a small animal. It preys on tiny animals in the leaf litter. Angeli and Fitzgerald note that the lizard vanished from 99.97% of its historic range on the main island. The researchers say that this loss could be because of two reasons. First, farmland had replaced its habitat, and second, mongooses hunted it. Lizards had disappeared from the eastern part of the island by 1920. The ones were seen in the town of Frederiksted in 1969.

A St. Croix ground lizard. Today, about 3,000 survive on four small islands.

Two lizard groups managed to survive on small islands off the shore, the Protestant Cay and the Green Cay. Mongooses were not present on these islands. Scientists introduced lizards to two more islands. Nine lizards were introduced to Ruth Island in 1989, while 57 lizards were brought to Buck Island in 2008. According to Angeli and Fitzgerald, there are about 3,000 lizards surviving on these four islands, and more than 2,000 of them are on Buck Island. Together, the islands cover only 85 hectares, so storms like hurricanes are still a risk. Another warning comes from Treglia and colleagues. The Puerto Rican ground lizard was first reported in St. Croix in 2006. If it reaches the cays, it may prey on and compete with the native lizard for food.

Could they come home?

By the late 1950s, sugarcane farming nearly ended, and forests started coming back. Even then, reintroduction to the main island was long considered unwise, because mongooses were expected to prevent any new population from taking hold. The Oryx authors argue that the regrown habitat often creates new opportunities for reintroduction even though the predators remain. They found that today’s mix of land types is statistically similar to a map drawn back in 1750. Their model indicates that the island could support more than 142,000 lizards. The mongooses are still there, and only 3.65% of St. Croix is mongoose-free. So the authors ranked sites by size and suitable habitat, giving priority to places where mongoose control is already in place or possible. Their top three were Sandy Point National Wildlife Refuge, Altoona Lagoon, and the Southgate Coastal Reserve. Reintroductions were planned for 2020 to 2023. In March 2022, the U.S. Virgin Islands Department of Planning and Natural Resources announced it had released two experimental populations, in enclosures, onto the main island, at the University of the Virgin Islands wetlands and the Sandy Point National Wildlife Refuge, where they will be monitored.

One animal, brought in to solve one problem, ended up leaving a mark for well over a hundred years. But that's not the end of the story. With good science and little patience, the lizard might just return to the island it once called home.