2014 Survey of Feral Horses (Equus ferus caballus) in the Australian Alps

Dr Stuart Cairns and Geoff Robertson | 2015

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Introduction

Aerial surveys of feral horses in the Australian Alps have been conducted in 2001 (Walter, 2002), 2003 (Walter, 2003) and 2009 (Dawson, 2009), initially by Michelle Dawson (née Walter), as part of her PhD studies, and later again under contract to the Australian Alps Liaison Committee (AALC).

The results of the surveys, particularly the 2009 aerial survey, which estimated that there were 7,679 horses within the Australian Alps National Parks, have always been highly contentious with many stakeholders critical of the validity of survey results and subsequent population estimates. The criticisms were mainly to do with the precision of the population estimate, as well as the selection of the survey area. As a consequence the AALC decided that for the 2014 aerial survey to change the survey area and design to improve the accuracy and precision of the population estimates.

The survey area was increased to encompass the entire known distribution of feral horses in the Australian Alps, except for a small population of around 55 – 83 animals on the Bogong High Plains, Victoria (Parks Victoria 2015) and an estimated 10 – 30 horses in the Dinner Plain/Cobungra area. Areas of very steep terrain, some of which were included in the previous surveys, was excluded for the planning of the 2014 survey to ensure that the required constant height and aircraft speed for a helicopter survey could be maintained. There were some changes necessitated by Occupational Health and Safety (OH &S) requirements for helicopter operations.

These changes included the placement of an air safety observer into the front of the aircraft, which resulted in an altered seating and sighting configuration for the two horse observers. The AALC recognised that the changes to survey design and methodology make direct comparisons with the previous surveys difficult, but considerations of the rate of change of the population were considered to be of secondary importance relative to the accuracy and precision of the population estimates.

As well as improving the accuracy and precision of the estimate of the feral horse population across the whole Australian Alps, a second objective of the survey was to provide separate estimates of horse abundances in the northern Kosciuszko National Park (KNP) and the southern section of the park that abuts the Victorian border. Previously, owing to the low sampling effort and low number of sightings, only a whole-of-Alps estimate for the horse population was determined, which resulted in highly imprecise estimates for sub-sections.