Aerial survey of feral horses in the Australian Alps

Prepared for the Australian Alps Liaison Committee
Michelle Dawson, August 2009

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Introduction

The feral horse population in the Australian Alps national parks (AANP), extending from the Australian Capital Territory (ACT), through New South Wales (NSW) and into Victoria, has been monitored using helicopter aerial survey in 2001, 2003 and most recently in 2009. These three surveys have been conducted using standardised methods to enable comparison of populations over time. Aerial surveys followed eastwest transects spaced 2km apart across the main areas of the known distribution of horses in the Australian Alps national parks, excluding the Byadbo Wilderness in southern Kosciuszko NP and adjacent areas of the Alpine NP, and the Talbingo Dam area of north-west Kosciuszko NP. The survey only covered national parks, so feral horses in adjacent state forest and crown land were not included. Minor modifications to transects were made for the 2009 survey to account for some known changes in distribution since the previous survey in 2003.

Data from the 2009 survey was analysed using line transect techniques for two observers combined (after Walter & Hone 2003). The 2001 and 2003 surveys used this method, though an alternative method using mark-recapture distance sampling has recently been developed (Laake et al. 2008). The estimated size of the population from the 2009 survey is 7679 horses (coefficient of variation 25.4%). This represents an annual increase of 21.65% per annum since the previous estimate in 2003, which is close to the maximum intrinsic rate of increase for horses. If the population continues to grow at this rate it will reach over 13 800 horses by 2012, with a likelihood of increased environmental implications. The feral horse population has also increased its distribution since 2003.

More information about feral horses in the Australian Alps can be found in the Feral horse management factsheet. More information about pest animals in the Alps can be found on our research publications page.