Feral Animal Management
Feral animals in Kakadu are animals introduced by non-Aboriginal people, that were once either domesticated or native to another country and that now lives and breeds in the park. Among the feral animals in Kakadu are Asian water buffaloes, cattle, pigs, horses, donkeys, cats, dogs, rats, mice, house geckos and European bees. Cane toads were recorded in Kakadu for the first time on 12 March 2001.
The management objective for feral animals in Kakadu is to limit, as far as possible, their adverse effects on the environment while taking into account the views and economic interests of traditional owners.
Buffalos in Kakadu
Asian water buffalos were introduced into northern Australian settlements between the 1820s and the 1840s, as work animals and for meat. As these settlements were abandoned, the buffaloes were released and quickly spread across the lowlands of the Alligator Rivers region.
By the 1960s buffalo numbers had reached enormous proportions and the damage they were causing was obvious. Buffalos cause damage in a number of ways. Their sheer size, weight and hard hooves compact the soil and inhibit plant growth, causing erosion. Their habit of wallowing erodes river banks and muddies the water, making it unsuitable for many aquatic plants and animals. They eat large volumes of grasses and other plants, competing directly with native wildlife. And as they move from one wetland area to another they create 'swim channels': where these channels intersect with tidal creeks, saltwater is able to move into freshwater swamps, often killing a number of plants and animals intolerant to saltwater.
Buffaloes carry tuberculosis, which can be spread to domestic cattle. Because of the severe implications for the export meat industry, the Brucellosis and Tuberculosis Eradication Campaign was established nationwide to eradicate feral cattle and buffaloes from all areas. The Campaign provided funding to reduce buffalo numbers in the park.
The removal of buffaloes from Kakadu National Park began in 1979. Of an estimated population of 20 000 buffaloes, it is thought that only a few hundred remain (Press et al 1995).
The difficult nature of the country and the consequent costs make total eradication almost impossible. The Brucellosis and Tuberculosis Eradication Campaign ceased at the end of 1997. As a result Park staff have taken over responsibility for monitoring and controlling the buffalo numbers.
Since the reduction in buffalo numbers degraded areas have recovered dramatically. There are fewer buffalo wallows, there is clear water in billabongs, there is less salt intrusion, and plants such as red water lilies, grasses and sedge plants-valuable food for native animals-are reappearing.
Buffalo has become an important part of the diet of Aboriginal people in the region. A small herd of domesticated buffaloes is retained in the park to provide meat for Aboriginal traditional owners.
Other Feral Animals
Pigs
Pigs cause damage to a broad range of Kakadu's habitats. They degrade the environment around springs and small rainforest patches, especially in the wet season. They also dig up areas in their search for food and compete directly with magpie geese and Aboriginal people for bulbs that grow along the wetland shores. The ground they expose is vulnerable to weed infestation-pigs are thought to be the main agents of spreading the weed mimosa through the park. Park staff control pigs close to known mimosa infestations on an opportunistic basis and feral pig control work is conducted regularly..
Horses
Horses are particularly common in the southern woodlands of the park. They spread weeds and damage waterholes by eroding soil and fouling the water. Recent control measures have reduced the number of horses along the Kakadu Highway.
Cats
Cats are present in low numbers throughout the park. Casual observations and research from southern Australia suggest that cats' hunting activity is having a detrimental effect on native wildlife. Cats are not allowed to be kept as pets in the township of Jabiru. They are shot by park staff each wet season along floodplain and creek margins. Again, this is done on an opportunistic basis.
Dogs
Dogs that have become feral have some impact in that they interbreed with the dingo population in the park, changing the dingo gene pool. Jabiru residents are allowed to keep up to two dogs within the confines of the township and park residents can keep dogs at the discretion of the Director of National Parks.
Cane toads
Cane toads were found in Kakadu National Park on 12 March 2001. Cane toads are poisonous throughout most of their life cycle and current information suggests that they will have an initial impact on animals such as snakes, goannas and quolls, who will try to eat them. Evidence from other areas effected by Cane toads suggest numbers will stabilise after an initial period. No effective control measures are available. Cane toads in the park are likely to be one of the most pressing management problems facing Kakadu in the coming decade.