in the world. Aerial poison bait drops are still used today. Parts of the Dingo Fence are lit at night by cold cathode fluorescent lamps which are alternately red and white. They are powered by long life batteries which are charged by photovoltaic cells during the day. At minor and farm crossings, a series of gates allow vehicles to pass through the fence. Where the fence intersects major roads and highways, cattle grids are used to allow high-speed vehicles through. History The earliest pest exclusion fences in Australia were created to protect small plots of cropland from the predation by marsupials. In the 1860s and 1870s, introduced rabbit populations began to spread rapidly across southern Australia. By 1884, a rabbit-proof fence was built. Having been unsuccessful at keeping rabbits out, and more successful at keeping out pigs, kangaroos, emus and brumbies, and as more sheep farms were established, the interest for a dingo-proof barrier increased enough that government funds were being used to heighten and expand the fence. In 1930, an estimated 32,000 km of dog netting in Queensland alone was being used on top of rabbit fences. Prior to 1948, the idea of a Dingo Barrier Fence Scheme had not come into fruition as a statewide project for which annual maintenance and repair were kept. Since this time, there have been pushes to move away from a method of barrier-exclusion to complete extinction of the dingo and wild-dog cross-breeds. Poisoning the species with compound 1080 (sodium monofluoroacetate) baits has been seen as a much cheaper alternative than fence maintenance. A compromise in the form of the continued use of poison and the shortening of the fence from its previous length of over 8000 km has been made. In 2009 as part of the Q150 celebrations, the dingo fence was announced as one of the Q150 Icons of Queensland for its role as an iconic "innovation and invention". Environmental impact It seems that there are fewer kangaroos and emus on the northwestern side of the fence where the dingoes are, suggesting that the dingoes' presence reduces the populations of those animals. It has also been suggested that the larger kangaroo populations inside the fence have been caused by the lack of dingo predation, and competition for food leads to lower sheep stocking rates than would be possible without the fence. Believed to have been introduced into Australia by Aboriginals between