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Aerial survey of donkey and horse populations in the Victoria River District 2006



Aerial survey of donkey and horse populations in the Victoria River District 2006


Saalfeld, Keith


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Made available via the Publications (Legal Deposit) Act 2004 (NT).


2001 and 2006 Aerial survey. 2001 survey was published by Parks and Wildlife Commission of the Northern Territory, Palmerston (N.T.) 2006 survey was published by Department of Natural Resources, Environment and The Arts, Palmerston (N.T.)




Feral livestock -- Northern Territory -- Victoria River Downs; Donkeys -- Northern Territory -- Victoria River Downs; Horses -- Northern Territory -- Victoria River Downs

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Introduction Feral donkeys and feral horses are recognised as a major problem in the Victoria River District (VRD) of the Northern Territory (Letts et al., 1979; McCool et al., 1981; Choquenot, 1988a & b; Saalfeld, 1998.). A series of aerial surveys of the District were conducted during the 1980's and 90's to determine population abundance and distribution for the development of control programs (Graham et al., 1982; Choquenot, 1988 a & b; Saalfeld, 1998.). These programs were initially conducted during the early 1980's, but in the late 1980s and early 1990s little or no control was carried out and both donkey and horse populations increased to levels exceeding those of the early 1980s (Saalfeld, 1998). In 1996 an aerial survey of feral donkeys and horses was carried out to estimate the abundance of donkeys and horses in the VRD. The results of this survey were utilised to develop a coordinated control program for the district and in 1999 the VRD was declared a pest control area (Holznagel, 2002). Off-take levels for each property with greater than 1,000 donkeys and horses combined were determined with the objective to reduce the combined total number of donkeys and horses on each property to 1,000 individuals or less. Control notices were issued to each property in the control area requiring the appropriate off-take for the property. A completion date of 31 August 2001 was set in the notices. Details of the control program, compliance to the notices and the overall outcome of the control operations are reported in Holznagel (2002). This technical report details the results of a follow-up survey of the VRD conducted in July 2001. The survey was designed to cover the area of the 1996 survey and the declared control area. Relative estimates of population abundance and density and mapped density distributions have been derived for both donkeys and horses and compared with similar data from the 1996 survey accounting for known off take on each property. The results in this report have been utilised in determining the ongoing feral animal management requirements in the VRD, particularly the assessment of the effectiveness of the current control program (Holznagel, 2002). Methods The survey was based on the methodology of Choquenot (1988 a & b) and Saalfeld (1998). The survey was flown in the early dry season of 2001, between 2 July and 2 August 2001. The survey area (Figure 1) was divided into survey blocks (Table 1 & Figure 2) on the basis of one degree squares (one degree latitude by one degree longitude) to facilitate survey planning and population analysis. Each block was systematically sampled by east-west transects (Figure 2) of 400m width at a 11.112 km (6' latitude) separation, giving a sampling intensity of 3.6% (Table 1). Details of exact area and when each survey block was flown are given in Table 1. The area of the 2001 survey was greater than that of the 1996 survey (Saalfeld, 1998) and included areas not covered in 1996.