Birdwatchers and tourists who like seeing native birds and wildlife thriving in their natural habitat will welcome two new developments, one in Australia and the other in Hawaii, designed to keep feral cats at bay.
A cat-proof fence is planned for the Dudley Peninsula on Australia’s Kangaroo Island and another has been completed at Hawaii National Park in Hawai‘i.
The Kangaroo Island fence will divide the island into two areas, Australian Geographic reports. Twenty feral cats will be fitted with radio-collars to monitor their movements, and test the efficiency of the fence. An estimated 5000 feral cats are devastating the island’s native birds and small animals, including the southern brown bandicoot, Kangaroo Island echidna, Kangaroo Island dunnart and southern emu wren.
US National Park Service crew working on cat-proof fence in lava fields
In Hawaii National Park, work is complete on what could be the largest cat-proof fence in the United States, designed to protect the federally endangered ‘ua‘u, or Hawaiian petrel, from the birds’ primary threat: feral cats.
The seafaring ‘ua‘u nests in deep lava rock burrows on the rugged high-altitude slopes of Mauna Loa, and, despite the remote location, are not safe from cats. In order to protect the species, the National Park Service (NPS) teamed up with the National Fish and Wildlife Foundation, US Fish and Wildlife Service, American Bird Conservatory, Hawai‘i Pacific Parks Association, and the Pacific Cooperative Studies Unit at the University of Hawai‘i (PCSU), to build the eight-kilometre long cat barrier fence in Hawai‘i Volcanoes National Park.
While Australia has immense fences designed to exclude rabbits and dingoes, the world’s first fully predator-proof fence is believed to be that at Zealandia, formerly known as the Karori Wildlife Sanctuary, a protected natural area and big tourist attraction in Wellington, New Zealand. The perimeter fence there is 8.6 kilometres in length. That’s longer that the one in Hawai‘i. Mice are the only introduced animals to have successfully penetrated the New Zealand fence. The sanctuary has inspired many similar projects throughout New Zealand, with predator-proof fences now protecting the biodiversity of other areas of forest.
In Hawai‘i, the specifically designed barrier is more than two metres high, and has a curved top section that prevents cats from climbing over it.
Construction began in Hawai‘i in 2013, and was limited to January through May to avoid disturbing nesting birds. The seabirds spend most of their lives at sea, and come to land only during breeding season. ‘Ua‘u return to Hawai‘i Volcanoes National Park briefly in April to prepare nest sites, and return in early June to lay a single egg.
The fluffy chicks hatch in August and remain in their burrows until November when they fledge or take their first flight out to sea. Adults, eggs and chicks are extremely vulnerable to predators throughout the long breeding season as all activity occurs on the ground.
The high-altitude project was gruelling. NPS and PCSU fence crews worked and camped at elevations between 2400 and 3000 metres, in steep and loose lava rock terrain, and in weather that ranged from hail, and high wind, to extreme heat. The site is very remote and all materials, gear and staff had to be flown in and out. But the discomfort paid off: the fence now protects more than 240 hectares of ‘ua‘u nesting habitat on Mauna Loa.
“To our knowledge, this is the largest fence of its kind in the US. To build such a fence is an incredible feat, and an important victory for a native species that is extremely rare on Hawai‘i Island,” said NPS biologist Kathleen Misajon.
“Through the partnership of the cooperating organizations, the cat-proof fence will protect these amazing seabirds and support the expansion of this small population,” she said.
Southern emu wren, one of many native species threatened by feral cats on Kangaroo Island. (Source- JJ Harrison, Wikimedia)
The endangered Hawaiian petrels are more typically seen on neighbour islands. The species is very rare on Hawai‘i Island, with just 75 nesting pairs in Hawai‘i Volcanoes National Park, and another small population on the slopes of Kohala. The park and cooperating partner agencies have studied this remnant population of ‘ua‘u on Mauna Loa since the early 1990s, both on the ground and more recently, through remote game cameras. The birds only come and go at night, nest in deep cracks and crevices in the lava, and are rarely seen.
Both parents take turns incubating a single egg and later, feeding the chick. They fly from high atop Mauna Loa to forage in the Pacific Ocean, ranging as far north as Washington State before returning to the nest to feed their chick.
Edited by Peter Needham