Monday, January 30, 2012

Invasive Pythons Impact Native Wildlife: Evidence from Road Kill

The ecological damage done by the invasive brown tree snake on Guam has mad biologists, conservationists and ecologists paranoid about invasive snakes. In the United States invasive species management is estimated to exceed $120 billion annually. Invasive species, including invasive snakes alter habitat structure, competition between species, reduce native predator populations, alter the trophic structure of ecosystems, and they deplete or extirpate native prey populations. Now, Michael Dorcas and colleagues have documented the impact of the Burmese python, Python bivittatus, on the native wildlife of the Florida Everglades in a paper published today in the Proceedings of the National Academy of Sciences.

Between 1993 and 1999, prior to invasive snakes in south Florida, raccoons, opossums and rabbits were the most frequent road kill. But from 2003 to 2011, road kill surveys found a 99.3%fewer raccoons, 98.9% fewer opossums, and no rabbits or foxes; the surveys also found 94.1% fewer white-tailed deer and 87.5% fewer bobcats. During the 2003 to 2011 time frame annual removals of Burmese pythons rose from less than 50 per year to 300-400 per year. Raccoons, opossums, bobcats, deer and rabbits are all species documented in the diet of the invasive pythons in Everglades National Park. The native mammals are naive to the danger posed by the pythons, making them susceptible to python predation.

While raccoons, rabbits, and opossums are relatively common, concern for the predation pressure placed on endangered birds and mammals in south Florida has been expressed by conservationists and biologists. The entire study can be found on- line.

Dorca, ME, Wilson, JE, Reed, RN, Snow, RW, Rochford, MR, Miller, MA, Meshaka, WE, Andreadis, PT, Mazzotti, FJ, Romagosa, CM, Hart, KM. 2010. Severe mammal declines coincide with proliferation of invasive Burmese pythons in Everglades National Park. PNAS doi:10.1073/pnas.1115226109

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