Australia’s kangaroo population is a ubiquitous presence across the continent’s diverse ecosystems. These iconic marsupials roam vast expanses of rangelands, scrub, and open plains. Monitoring this large, mobile national herd requires a sophisticated, continent-wide effort to ensure environmental balance and population sustainability.
The National Kangaroo Population Estimate
The national kangaroo population estimate, based on the latest widespread surveys, places the number in the tens of millions. In 2019, the Australian government estimated approximately 42.8 million kangaroos lived within the commercial harvest areas of four major states. Since this figure only covers commercial zones, the actual total population is significantly higher, encompassing millions of animals in non-surveyed remote areas and protected zones. This population is highly volatile, having dropped from a high of around 53.2 million animals in 2013.
Key Species Included in the Census
The national population figure counts the four largest and most widespread macropod species across the mainland. The species primarily monitored are the Red Kangaroo, the Eastern Grey Kangaroo, the Western Grey Kangaroo, and the Common Wallaroo (also known as the Euro). Each of these species occupies a distinct geographical niche.
The Red Kangaroo is the largest species, adapted to the arid interior and typically found in the central and western rangelands. The Eastern Grey Kangaroo thrives in the more fertile eastern regions, extending from Queensland through Victoria. The Western Grey Kangaroo inhabits the southern parts of Western Australia and South Australia, including coastal areas. The Common Wallaroo is smaller and often found in rocky, hilly habitats across various states.
Methodology: How Kangaroos Are Counted
National population estimates rely predominantly on aerial surveying, which is the most cost-effective way to count animals over immense distances. This method involves flying low-altitude surveys along defined, straight-line paths called transects, which are systematically distributed across commercial zones. Aircraft maintain a constant, slow speed and low height to maximize visibility.
Trained observers count kangaroos seen within a defined strip on either side of the flight path, often aided by external markers. Observers record the distance of each sighting from the transect line, which is central to the distance sampling technique. This distance information is fed into mathematical models that calculate the probability of detection and correct for missed animals.
The raw counts along the transects calculate an average population density for the area, which is then extrapolated to the entire survey block. Combining these density estimates with the total area produces a robust estimate of the total population size. Surveys are conducted during winter months or in the early morning and late afternoon when kangaroos are more active and visible.
Factors Influencing Population Fluctuation
The largest driver of population fluctuation is the variability of the Australian climate, particularly the cycle of rainfall and drought. High rainfall leads to a boom in vegetation, providing abundant food and water that supports high survival and reproductive success. Conversely, severe drought depletes resources, causing high mortality and a rapid crash in the population. Commercial harvesting and conservation culling programs also manage regional numbers, but these are secondary factors to the climate.