Threats to Cassowaries
September 30th, 2007Cassowaries face a range of threats arising from human activities. These include loss and fragmentation of habitat, predation by introduced pets and other animals, death and injury from motor vehicles.
Habitat Destruction: Whether it is land clearing for farming, urban development or logging, habitat loss and destruction is the major threat to the survival and well-being of cassowaries. Land clearing impacts on cassowaries in several ways: Direct loss of habitat leads to a decrease in cassowary numbers. Most animals that lose their habitat due to clearing are not successful in establishing themselves elsewhere and usually die due to stress, predation and or starvation. Landclearing negatively affects the ability of adults to establish and determine territory and status – clearing may for example destroy part of the territory of 2 neighbouring birds. Birds in areas neighbouring clearing are placed under stress due to displaced cassowaries trying to establish new territories.
Fragmentation of habitat: clearing usually results in the creation of isolated and fragmented pockets of habitat. As a result of fragmentation cassowaries are forced to cross hostile environments such as open fields and roads, exposing them to vehicle impacts and dogs. Fragmentation may also prevent cassowaries from dispersing to other areas, resulting in the creation of genetically isolated subpopulations, decreasing the overall genetic variability of the population.
Clearing Facts: · The average rate of land clearing between 1975 and 1983 throughout the wet tropics region was calculated to be 1, 424 ha. per year.
· By 1997, 80.7 percent of all natural vegetation in the wet tropical lowlands, core cassowary habitat, had been cleared.
· Up to 85 percent of cassowary habitat has been cleared in the Russell River to Murray River lowlands.
· The habitat loss on the Atherton Tablelands has been nearly as extensive as the damage on the lowlands.
· Cassowaries in the Wet Topics have been separated into 10 subpopulations due to the fragmentation of their habitat
Vehicles: A great many roads have been put through cassowary habitat. Many birds may have several roads passing through their territory, and dispersing birds many have to cross numerous roads before finding a suitable area to settle. Each time a cassowary crosses a road it runs the risk of being hit by a motor vehicle. Some people also mistakenly feed cassowaries, attracting them to human habitation and greater exposure to death and injury from cars and dogs. Between February 1986 and September 1988, 17 cassowaries died as a result of road accidents in the Mission Beach area. After that the statistics did not get much better. In the same Mission Beach area, between 1989 and 1998 there were a total of approximately 40 cassowaries recorded dead due to traffic. Given that cassowaries are long-lived, slow-reproducing animals with lengthy parental care and low juvenile survival, each road death of an adult bird may potentially influence population dynamics and the population’s reproductive fitness.
Dogs: In packs, dogs usually harass cassowaries to exhaustion and sometimes even injury or death. Older birds, chicks and sub-adults often fall prey to dogs, due to the fact that they are not strong enough to protect themselves. Dogs may also chase cassowaries away from potential food and water sources. A great many people living around and within cassowary habitat own dogs. It is essential that dog owners do not allow their dogs to roam free where they might impact on native fauna. 5 cassowaries were the victims of dog attacks, between February 1986 and September 1988 in the Mission Beach Area. Dog attack is the second most drastic recorded source of cassowary mortality. Dog attacks also affect the feeding, movements and behaviour of cassowaries. The last cassowary to survive on Mt. Whitfield – a hill right behind Cairns, was killed by dogs.
Feral Pigs: Feral (introduced) pigs are ground feeding animals and they require much of the same food as the cassowaries do. Apart from having a similar diet (and therefore causing drastic effects in times when food is scarce) the pigs also destroy many cassowary nests, eat their eggs and are potential predators of chicks and young birds. Feral pigs also often contaminate water sources, and may potentially be major dispersal agents for die-back – a fungal-type disease which kills off patches of forest, further reducing food and habitat.
Disease: Although disease is only a small problem when compared to traffic accidents, it is still a valid threat. There is growing concern that diseases are being spread to the cassowaries through domestic animals and contaminated food. When cassowaries forage in rubbish dumps the contaminated food may cause them to get Tuberculosis or fungal diseases, which spread rapidly through cassowary populations. In addition, most animals become more prone to illness if they are under stress from such factors as increased exposure to potential predators and loss of habitat.





