Kangaroos are one of Australia’s most recognizable marsupials, but determining their exact numbers is a complex, dynamic process. The population shifts dramatically based on environmental conditions, meaning any figure provided is always a scientific estimate rather than a precise census. Estimation is further complicated by the vast, varied terrain and the different species involved.
The Current National Estimate
The total kangaroo population across Australia is typically in the tens of millions. For the commercial harvest areas, the Australian government estimated the population at around 42.8 million in 2019, a decline from a high of 53.2 million in 2013. This total only accounts for the areas surveyed for population management and commercial use, meaning the actual number of kangaroos across the entire country would be higher. These population figures are not static and can fluctuate wildly due to natural pressures and human management. The numbers are a composite of regional estimates, meaning the population in a specific state or region can boom or collapse independently of the national trend.
Counting Methods and Accuracy
Kangaroo population estimates are derived using scientifically recognized methods, primarily large-scale aerial surveys. Wildlife managers use fixed-wing aircraft or helicopters to fly along pre-determined parallel flight paths known as transect lines. Trained observers count the kangaroos they see below, noting the distance of the animals from the flight path.
The raw counts are then analyzed using distance sampling to calculate population density across the surveyed area. This method accounts for kangaroos missed by observers because they were further from the flight path or obscured by vegetation. For smaller areas or rougher terrain, researchers may employ ground-based methods like walked line transect counts. While these techniques provide reliable indices of abundance, they remain estimates because factors like weather, dense ground cover, and natural camouflage influence visibility and require a correction factor.
Factors Driving Population Fluctuations
The most significant factor influencing kangaroo population dynamics is the natural cycle of rainfall and drought. Following periods of abundant rain, high food availability causes a rapid increase in reproductive success and survival rates. Conversely, prolonged periods of drought are the primary natural driver of population decline, as a lack of food and water leads to mass starvation and reduced breeding.
Human management, specifically commercial harvesting and culling programs, also plays a substantial role in population control. State governments set annual quotas for the commercial harvest based on the previous year’s population estimates. Predation, primarily by dingoes, acts as another natural control on kangaroo numbers, particularly on juveniles.
Major Species and Geographic Distribution
The national estimate is comprised mainly of four widespread species: the Red Kangaroo, the Eastern Grey Kangaroo, the Western Grey Kangaroo, and the Antilopine Kangaroo. Each species occupies a distinct geographic range, contributing to the total national figure.
The Red Kangaroo, the largest marsupial, is primarily found across the arid and semi-arid inland regions, thriving in the open rangelands of central Australia. Eastern Grey Kangaroos inhabit the more fertile eastern third of the continent, extending from Queensland down to Victoria, where their population density can be high in suitable open woodland habitats.
Western Grey Kangaroos are distributed across the southern part of Western Australia and areas of South Australia, including the Murray–Darling basin. The Antilopine Kangaroo, sometimes referred to as a wallaroo, is restricted to the tropical monsoonal woodlands of far northern Australia.