Endangered southern cassowary
Cassowaries are endangered and continue to lose habitat and be killed by vehicles and dogs.
We must act to ensure this special rainforest bird is given a secure future.
The importance of cassowaries
Besides being a keystone species in the Wet Tropics Rainforests, cassowaries are of great cultural significance to many Indigenous Rainforest peoples, and are an icon of tourism in Far North Queensland. Being a keystone species means that they play an integral part in the maintenance of the forest ecosystem.
Their most significant contribution to the ecology of the forest is as a disperser of rainforest fruits. Cassowaries eat up to 150 different fruit species; it is estimated that 70 to 100 plant species depend almost entirely on the cassowary for seed dispersal.
Cassowaries are the only native animals large enough to eat many of the larger fleshy rainforest fruits with large seeds. The cassowaries digestive system is gentle on the seed allowing it to travel through the gut unharmed. When they are excreted the seeds are embedded in the dung - their own mini compost pile.
The smell from the dung keeps seed predators, such as the white tailed rat, away from the seeds and the fertiliser helps to keep the seed moist and feed the germinating seedling. The seed remains in the cassowary's gut for approximately 10 hours, ensuring they are deposited some distance away from the parent tree.
Threats to cassowaries
Cassowaries 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. Land clearing 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.
- The average rate of land clearing between 1975 and 1983 throughout the wet tropics region was calculated to be 1,424ha 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 may 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.
Cassowary life history
Breeding: The mating time for cassowaries begins around May - June. Females mate with more than one male - this is known as polyandry. The female will mate with one male until a clutch is laid, then she will move onto another male, until several clutches have been laid. Breeding usually occurs from June to October, when fruit sources are at their peak.
Nesting: The cassowaries’ nest is made from leaves and grass on the forest floor and about 1 metre in diameter. The females lay an average of 4 blue/green eggs, which are approximately 10 cm by 16 cm, and weigh 500 to 600 grams.
Incubation: This is solely the male’s responsibility. The male will sit on the nest for about 50 days, generally going long periods without food and water, surviving mostly on food reserves.
Chicks: The newly hatched chicks are striped black/dark brown and cream with pale brown heads and tiny wattles.
For the first 7 months, the young chicks follow the adult male and imitate his actions. From this they learn how to forage for fruits and insects.
After about 7 month the chicks know how to forage, know the available feeding sites and water areas and they begin to lose their characteristic stripes.
Sub-Adults: Young cassowaries are most vulnerable at this stage in their lives. The male abandons the sub-adults when they are between 7 and 16 months of age, evicting them from his territory.
Those that survive the initial separation slowly develop adult characteristics - the skin on their heads begins to turn blue in colour, their wattles turning pink and the casque (horny protuberance on top of the head) starts to develop.
Adult: The life-span of a cassowary in the wild is uncertain, however in captivity there have been reports of individuals reaching approximately 40 years of age. Adults have a coarse, glossy black plumage, a tall helmet (casque) and brilliant blue neck and red wattles. Females are usually larger than the males - (1.8 metres tall and 60 kg in weight compared to 1.5 meters and 35 kg).
Current status of cassowaries
There are three species of cassowary - the Single Wattle Cassowary found in Northern New Guinea and the Dwarf Cassowary found in the mountainous rainforest of New Guinea, and the Southern Cassowary (Casuarius. c. johnsonii ) found in north eastern Australia. Cassowaries are listed as Endangered under both Queensland and Commonwealth legislation.
Australia has two separate populations of cassowaries in, one in the Wet Tropics Rainforest region between Townsville and Cooktown. The second is in a small number of scattered blocks of rainforest along the East Coast of Cape York Peninsula as far south as the McIlwraith Range. Although the cassowary has a wide range within the Wet Tropics area, they are not regularly distributed, and in most places population numbers are quite low. There are an estimated 1000 -1500 cassowaries left in Australia.
Interesting cassowary facts
- Cassowaries are capable swimmers.
- Europeans first saw cassowaries in 1597 when one was taken from Banda Islands and brought to Amsterdam on a Dutch merchant vessel.
- The last recorded human fatality was in 1926 when a 16 year-old boy was killed near Mossman by a bird, which he and/or his dogs had been attacking.
- Cassowaries were traditional food for the Aborigines.
- Adult cassowaries are shy and solitary, however they will attack to protect their chicks or in self-defense.
To survive, cassowaries need large areas of rainforest. There is a need for protection of existing habitat and greater control of dogs and pigs. As well as creating protected areas such as National Parks, some people are establishing nurseries of cassowary food plants to restore rainforest on cleared land and create corridors to link remaining patches of vegetation.