How we calculate sustainable kangaroo populations

Each year our ecologists carry out extensive assessments of grass conditions and kangaroo populations at priority Canberra Nature Park reserves. A sustainable ‘target’ number of kangaroos is calculated for each site. The number of kangaroos to be culled is then calculated by comparing this target number to the current population size.

Grassy layer monitoring

Surveys are done every year to check the grassy layer in each reserve. Measurements include the main types of grass, grass height, the percentage of grass that is green, and the percentage of grass cover. This helps estimate how much the grass will grow in the next year and how many kangaroos the reserve can support to keep the grass height within the target range of 5 to 15 cm.

The number of kangaroos each reserve can support changes every year based on these annual vegetation checks. If a reserve has been overgrazed or is experiencing hot, dry weather with little grass growth, fewer kangaroos will be kept to help the grass recover. When grass grows well, more kangaroos can be supported, reducing the need for active management in some years.

The outcomes of these surveys are published each year in the Eastern Grey Kangaroo - Conservation Management Advice reports.

Estimating kangaroo populations

Kangaroo population estimates are calculated through robust, scientifically recognised methods. These methods are direct counts, sweep counts and walked line transect 'distance' counts. The appropriate method is chosen for each reserve based on the size, vegetation, and terrain.

These methods for counting kangaroos are described below and in the Eastern Grey Kangaroo: Controlled Native Species Management Plan. They are also in the peer reviewed publication How many macropods? A manager's guide to small-scale population surveys of kangaroos and wallabies.

Kangaroo population surveys and the resulting management recommendations consider only 'independently mobile' kangaroos. No attempt is made to count young in the pouch due to their difficulty to detect at young ages and often do not survive to adulthood. Pouch young are not included in culling targets.

Direct counts

Direct counts involve searching the entire site and counting individual kangaroos without missing any or counting any more than once. This method:

is only suitable for small sites with open vegetation
requires a high amount of knowledge about the site and the behaviour of the animals.

Repeat counts are undertaken to validate the results. Direct counts are successfully used by ACT Government ecologists to count kangaroos in various small reserves including Mulanggari Nature Reserve and Crace Nature Reserve.

Sweep counts

Sweep counts involve a coordinated line of people walking across a site and counting the kangaroos that move through the line. This method is suitable:

for sites larger than those that can be counted using the direct count method
where the vegetation and terrain allow for good visibility from one counter to the next.

Repeat counts are undertaken to validate the results.

This count method is successfully used at Gungaderra Nature Reserve.

Walked line transect 'distance' counts

Walked line transect surveys are suited to larger or more heavily vegetated sites where kangaroos cannot be reliably counted by a direct or sweep count. This type of survey involves an observer walking along fixed linear transects and recording the distance and compass bearing to groups of kangaroos. Observers walk a total of approximately 44 km of transects per site which takes approximately 11 days. Surveys are undertaken in the early morning when kangaroos are evenly dispersed across the grazing landscape and are most likely to be detected from the transect lines.

These measurements are used to calculate the density of kangaroos across the whole site with the method called 'distance' sampling. Walked line transect counts and distance sampling are commonly used world-wide for estimating wildlife density. It is the most commonly used method for estimating kangaroo populations in the ACT and is used at sites such as Mulligans Flat Woodland Sanctuary, Farrer Ridge Nature Reserve and Red Hill Nature Reserve.

ACT Government conservation management advice

The below reports provide details of:

kangaroo population estimates
vegetation survey results
kangaroo management recommendations.

These reports are published online annually after the completion of the Conservation Culling program.

Conservation Management Advice reports

Kangaroo Management program reviews

The ACT Government is committed to open, transparent reporting and communication with the community about the Kangaroo Management Program.

Independent review of the Eastern Grey Kangaroo Controlled Native Species Management Plan

An independent review of the 2017 Eastern Grey Kangaroo Controlled Native Species Management Plan was released in March 2024.The review made 34 recommendations that aim to contribute to the program’s continuous improvement. Overall, the independent reviewer noted the “planning, implementation, monitoring and reporting for kangaroo management in the ACT is extremely impressive, and an outstanding exemplar for adaptive management”.

Find out about the Independent Review of the Eastern Grey Kangaroo Controlled Native Species Management Plan [PDF 2.8 MB].

A revised Eastern Grey Kangaroo Controlled Native Species Management Plan is expected to be released for public feedback in 2025.

Independent veterinary audits

Independent veterinary audits of the Conservation Cull are undertaken periodically. Outcomes from these audits can be found in the following reports:

Other reviews and responses

Opinions on kangaroo management

The ACT Government commissions a random telephone survey to find out the opinions of ACT residents towards kangaroos and kangaroo management.

The latest survey revealed 66% of the community support the ACT Governments kangaroo management program.

View the full reports: