Aerial survey of vertebrates in the Mann River district, central Arnhem Land

Abstract

An aerial survey of large vertebrate fauna was undertaken in the Mann River district of central Arnhem Land in September 2000. 'The survey covered 3936 km^ of the eastern and central part of the Arnhem Plateau and 1944 km^ on the adjacent low¬ land. A total of 747 individual animals from eight species were observed during the survey. Of these, four species were native (antilopine wallaroo, black wallaroo, emu and euro) and four were feral (Ituffalo, cattle, horse and pig). The majority of sight¬ ings (92%) were of feral animals, of which 78% were buffalo. The distribution of feral animals was largely similar to that of previous surveys with a high concentration in the upper Mann River and McCaw Creek regions. Sightings of native species were scattered throughout the survey area. The uncorrected density estimates (km'^ + SE) for species observed in this aerial survey were: buffalo 0.74 + 0.08; cattle 0.10 ± 0.04; horse 0.009 ± 0.008; pig 0.007 + 0.003; black wallaroo 0.02 ± 0.006; and emu 0.006 + 0.003. Intnxhiction.\rnhem Land is a large area of Northern Australia that is owned and managed by Aboriginal people, .\rnhem Land covers over 95,000 km^in the north-east of the North¬ ern Territory and encompasses an array of habitats from coastal and inland water systems, to monsoon forest, open woodland and the escarpment of the Arnhem Pla¬ teau (Cole 1978). The area is home to a large number of feral animals such as buffalo {Buba/us bubalii), cattle (Bos laurus), horses (Equus caballus) and pigs {Sussenfd) that were introduced to the Northern Territory in the late 1800's (Chaloupka 1982). WTiile some feral animals arc utilised as a food resource by Aboriginal communities (Altman 1987), they can also cause significant environmental damage and are a potential disease threat when densities are high (Bayliss ;md Yeomans 1989a). The continued monitoring of feral vertebrate populations in Arnhem Land is important to ensure that densities are maintained at appropriate levels.

Population estimate of Asian Water Buffalo and wild cattle in the Arafura Swamp, central Arnhem Land

“…that buffalo density was extremely high in certain areas of tiie Kakadu region and at their peak in the 1980s the mean density of buffalo at Kapalga research station was estimated as being 15 km'^ in open forest compared with 34 km'^ at the edge of the floodplain(Ridpath & Waithman 1988). It appears that buffalo are responsible for adverse and long-term environmental damage but management options are limited due to the expense of controlling their numbers in remote and inaccessible habitats.The buffalo density (when corrected for perception bias only) in the Arafura Swamp was calculated at 0.87 ± 0.26 km'^, which is similar to the buffalo density estimates of 0.74 ± 0.08 lorr^ from a survey of the nearby Mann River district in 2001(Koenig et al 2003) and a 1998 survey for a similar area of 0.85 km'^ (K.Saalfeld, unpubl.). The landform types in the Arafura Swamp sur\'ey area are predominantly a mixture of floodplain and open woodland and the estimated buffalo densities arc relatively low in comparison to the pre-BTEC population mean density in Kakadu National Park of 5.6 km-^(Skeat et al 1996).Wild cattle estimates made during a survey of the Mann River district(Koenig et al 2003) were much lower (0.10 ± 0.04 km'^ compared with those of the Arafura Swamp area (0.86 ± 0.25 km-^).…”