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Unusual Night Lizard Returns after Eradication of Invasive Species

The views expressed are those of the author and are not necessarily those of Scientific American.


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Island Night LizardA rare reptile found only on a few islands off the California coast has become the latest species to recover and leave the protection of the Endangered Species Act, the U.S. Fish and Wildlife Service reported this week. The island night lizard (Xantusia riversiana) originally faced threats from nonnative species such as goats, pigs and cats, which ate up both the lizards’ habitats and the sedentary animals themselves.

Most of the island night lizards’ habitat in the Channel Islands is in federal hands: the U.S. Navy owns San Clemente and San Nicholas islands, and the National Park Service (NPS) has control over Santa Barbara Island. The two government bodies teamed up to remove invading goats, sheep and rabbits, a process that was completed by the mid-1990s. Getting rid of the feral cats took a bit longer: They weren’t removed from San Nicholas Island until 2010.

Island Night LizardThe work did the trick, though. Although no one has accurate counts of how many lizards existed when they went onto the endangered species list back in 1977, they are definitely plentiful today. More than 15,000 lizards live on San Nicholas Island, over 17,000 can be found on Santa Barbara Island and a nearby islet, and a whopping 21.3 million lizards are estimated to live on the 145-square-kilometer San Clemente Island. (Populations were never thought to be all that low on San Clemente because the risks were greater on the other two, smaller islands.)

In addition to eradicating the nonnative animals the NPS and the Navy have also reestablished native plants that the invading herbivores had eaten away and removed exotic plants that had further choked the native ecosystem.

Although some of their threats were removed nearly 20 years ago, island night lizards definitely needed the time to recover. Females don’t reproduce until they are about five years old, after which they only breed every other year. The lizards don’t lay eggs; instead they give birth to live, fully developed young, a rarity among reptiles. Broods can be as small as two lizards, so the depleted populations could not increase very quickly. The lizards, which can live up to 25 or 30 years, maintain small home territories averaging just 17 square meters where they rely on a few types of thorny shrubs and cactuses for protection from natural predators such as owls.

The Fish and Wildlife Service, the Navy and the NPS will monitor night lizard populations and their habitats for the next nine years to ensure their recovery.

Photos: Charles Drost / National Park Service, U.S. Navy (uncredited)

John R. Platt About the Author: Twice a week, John Platt shines a light on endangered species from all over the globe, exploring not just why they are dying out but also what's being done to rescue them from oblivion. Follow on Twitter @johnrplatt.

The views expressed are those of the author and are not necessarily those of Scientific American.





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