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Feral Cats: Too Long a Threat to Hawaiian Wildlife Background Domestic cats (Felis catus) were first brought to Hawaii aboard sailing ships of European explorers and colonists. The job of these predators was to control mice and rats on the ships during the long voyages. As in other places, cats were taken in and adopted by the families of Hawaii and soon became house- hold pets known as popoki. But cats have always been very well equipped to live and hunt on their own. On tropical archipelagos like the Hawaiian Islands where no other predatory mammals of comparable size existed, abundant and naive prey were particu- larly easy game, and cats soon thrived in the wild. Although the details of when cats first came to live in the wild remain little known, adventurers, writers, and naturalists of the day recorded some important observations. Feral cats were observed in remote wilderness around Kilauea volcano on Hawaii Island as early as 1840 by explorer William Brack- enridge. Mark Twain was so impressed by the great abundance of cats when he visited Honolulu in 1866 that he reported his observations in the Sacramento Union newspaper, which were later reprinted in his book Roughing It: I saw... tame cats, wildcats, singed cats, individual cats, groups of cats, platoons ofcats, companies ofcats, regiments ofcats, armies ofcats, multitudes ofcats, millions ofcats... Cats Prey on Native Birds in a Variety of Habitats Cats were also common in remote and isolated communities, as noted by the famous traveler, Isabella Bird, during her visit to Waimanu Valley on Hawaii Island in 1873. By that time, a dis- turbing but little known phenomenon was beginning to happen to the unique birds of Hawai' i. At least 30 species or subspecies U.S. Department cd the Interior U.S.Gentu0icel Survey This feral cat was photographed by a remote camera in Hawaii Volca- noes National Park Isee page 3). of endemic forest birds were either greatly reduced in number or became extinct between 1870 and 1930. One of the earli- est naturalists to implicate feral cats as a causal factor in these losses was R.C.L. Perkins, who wrote in 1903: On Lanai, in walking up a single ravine, I counted the re- mains of no less than twenty-two native birds killed by cats, and these must all have been destroyed within two days, as previously the whole gulch had been washed out by a heavy flood 7fvo cats were actually shot on this occasion as they were devouring their prey, and several others seen, but, owing to the fact that they are extremely shy and mostly nocturnal in habits, few people who have not lived much in the woods have any idea of their numbers. In Hawaii today, cats range from relatively high densi- ties near sea level where abandoned pets are frequently fed by well-meaning animal -lovers, to sparse isolated populations in remote rain forests and even alpine areas on the islands of Maui and Hawaii. Cats kill songbirds, which nest, feed, and roost in trees, and ground nesting birds, such as quail and other intro- duced game birds. Native sea birds and other species that nest on the ground or in burrows are particularly vulnerable to preda- tion by cats. For example, endangered 'ua'u (Hawaiian Petrel; Pterodroma sandwichensis) are particularly vulnerable because they raise their single chicks in lava crevices and nestlings can- not fly for more than 15 weeks after hatching. Adult 'ua `u are also often killed by cats, causing serious population declines 6nrauce it tmkec each bird five to six vears to reach Lea "ua u are rare ano enuengereu lung-nveu seabirds that feed an fish and squid offshore but nest in lava crevices at high elevation on volcanoes. (Photo by W. Banko) Right. This adult 'ua'uwas killed by a cat high on the slopes of Mauna Loa in Hawaii Volcanoes National Park. (Photo by f. R. Warshauer, USGS) ® Printed an recycled paper USGS FS 2a06.i006 January 2006