The Mariana wandering butterfly is not the only Pacific Island territory species languishing on the candidate list without protection. Eleven other species are on the current candidate list and have languished unprotected there for an average of eleven years: the sheath-tailed bat, Guam tree snail, Langford's tree snail, Humped tree snail, Sisi, fragile tree snail, Tutuila tree snail, many-colored fruit dove, spotless crake, friendly ground dove, and Mariana eight-spot butterfly.
First placed on the candidate list: 1997
Years waiting for protection:
Range: Guam and the Commonwealth of the Northern Mariana Islands (island of Rota)
Habitat: Forests with the host plant Maytenus thompsonii

The Mariana wandering butterfly inhabited forests on the islands of Guam and Rota in the Mariana Archipelago. It was known to be endangered by the 1970s, but was not placed on the federal candidate list until 1997. During the delay it was extirpated for Guam and reduced to a single population of seven butterflies on Rota.

Five other Guam species paid the ultimate price for bureaucratic listing delays. The Guam bridled white-eye (Zosterops conspicillatus conspicillatus) was petitioned for listing in 1979, put on the candidate list in 1982, went extinct in 1983, and was belatedly put on the endangered species list in 1984. The Guam rufous fantail (Rhipidura rufifrons uraniae) was petitioned for listing in 1981, put on the candidate list in 1982, and went extinct in 1984. The Guam cardinal honey-eater (Myzomela cardinalis saffordi ) was petitioned for listing in 1979, put on the candidate list in 1982, and went extinct in 1984. The Guam white-throated ground dove (Gallicolumba xanthonura xanthonura) was petitioned for listing in 1979, put on the candidate list in 1982, and went extinct in 1986. The Guam broadbill (Myiagra freycineti) was petitioned for listing in 1979, put on the candidate list in 1982, went extinct in 1984, and was belatedly put on the endangered species several day after it was last seen.

The Mariana wandering butterfly larvae co-evolved with and feed only on Maytenus thompsonii, a forest herb endemic to the Mariana Islands. It has adapted to survive 150 mph typhoons, but not human-induced habitat destruction. The first wave involved alien goats, pigs, cattle, and deer brought by Spanish explorers. They altered the Mariana Islands’ forest understory and changed the localized climate which was previously regulated by forest itself. In 1914, Japanese occupying forces began clearing forests for sugar cane production, but sufficient forest remained on Guam in the 1930s for the butterfly to be considered common. World War II brought extensive bombing, military development, and the defoliation of vast areas. Following the war, establishment and operation of huge United States military bases prevented the return of native forest. Repeated introductions of alien plants and non-native predators and parasites also contributed to the decline of the butterfly and its host plant. The Mariana wandering butterfly became extinct on Guam in 1979. Its host, Maytenus thompsonii, is still common on Rota, but only one butterfly population of just seven individuals is known. No eggs or larvae were found.

Today, alien predatory and parasitic insects, some purposefully introduced by state agricultural agencies, constitute the greatest threat to the last tenuous population. In addition, browsing of Maytenus thompsonii by alien deer and cattle, as well as road and infrastructure development, pose severe threats not just to the extant population, but to areas essential to the butterfly’s recovery.

graphic Andrew Rodman ©2002
May 3, 2004
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