The World's Longest Fences

On our latest show, Ray spoke with Peter Marra of the Smithsonian Conservation Biology Institute about the harm that cats can do to bird populations. Yes, it's sad to say, but those sweet, furry critters kill billions of birds a year in the United States alone. With this sobering statistic on our minds, we were glad to read a recent news item: a five-mile cat fence has been built on Hawaii's Big Island around the Mauna Loa volcano. Whereas individual homeowners can choose to erect fencing to contain their felines, the National Park Service decided to build a single huge one to help protect the endangered Hawaiian Petrel. 

Only about 75 breeding pairs of the Hawaiian Petrel live in Hawaiian Volcanoes National Park, and cats are a serious threat to them. (Many more petrels live outside the park, but the species is still considered endangered.) Cats are not native to the Hawaiian islands, but they have taken nicely to the environment--including learning to scrabble up the sides of volcanoes to hunt vulnerable native species. The Hawaiian Islands are home to several conservation fences, of which the one on Mauna Loa is the longest. The new fence, which took four years to construct, encircles upper Moana Loa, enabling the petrels to rear their young in relative peace. It's six feet tall, with a curved top designed to be impossible for cats to climb. You can read all about the fence's construction here

Pest-proof fencing was pioneered in New Zealand and Australia, where invasive species are a recent enough phenomenon that it is often possible to tell which invader wiped out what native species. While the Mauna Loa cat fence is the longest in the United States, the longest fence of any kind in the world is the Dingo Fence in Australia, which is 3,488 miles long and protects sheep from dingo attacks.