Map finds native water mammal rakali thriving in Melbourne's waterways

A native water mammal once dismissed as a “water rat” is quietly thriving in Melbourne’s waterways, according to a new University of Melbourne mapping project. Conservation biologist Kylie Soanes reported that the rakali was sighted more than 700 times across Greater Melbourne, with hotspots at the St Kilda breakwater, Southbank and Coburg Lake. The findings reveal a growing population of the small, semi-aquatic rodent, which has adapted well to urban environments. The study highlights the resilience of rakali, which have long been difficult to track due to their ability to slip or chew through monitoring equipment. The latest data shows that they have successfully integrated into city life, appearing in drains, fountains, ponds and rivers throughout Victoria. Despite their resemblance to invasive black or brown rats, rakali can be distinguished by their white-tipped tails and golden bellies. These features help identify them as a unique native species rather than a common pest. The term “rakali,” derived from the Ngarrindjeri language of the Lower Murray region, was adopted in 1995 as part of a broader effort to rebrand native species and reduce the stigma associated with pest rodents. This shift in terminology reflects a growing recognition of the ecological importance of native wildlife. Dr. Soanes noted that rakali are far from pests and play a beneficial role in urban ecosystems. They are capable of controlling populations of invasive black and brown rats, offering a natural form of pest management. This behavior was documented in footage from Sydney, where a rakali was observed ambushing a black rat on the foreshore of Sydney Harbour. The video, captured using motion-sensing cameras by researchers at the University of Sydney under the leadership of Professor Peter Banks, marks the first recorded instance of such an interaction. Researchers suggest that rakali could serve as a valuable tool in managing invasive rodent populations, particularly given their size and predatory capabilities. As the largest of Australia’s native rodents, rakali possess physical traits that enable them to thrive in aquatic environments. Their water-repellent fur and partially webbed hind feet allow for efficient swimming, while their streamlined bodies and long, rudder-like tails contribute to their agility in water. These adaptations make them effective hunters in both freshwater and coastal habitats. Rakali are opportunistic feeders, often sharing rocky shores with little penguin colonies at the St Kilda breakwater. While they primarily consume marine invertebrates and crustaceans, researchers have observed instances of rakali preying on penguin eggs or chicks. Despite this predatory nature, the species exhibits a surprising level of refinement in its feeding habits. Dr. Soanes described their dining etiquette as “very polite,” noting that they carry prey to flat rocks or logs, dissect them neatly, and leave behind clean piles of bones and shells. These behaviors make rakali easy to spot, especially in areas where they frequent. The presence of unusual accumulations of bones and shells can indicate the activity of these animals. Additionally, rakali are known for their ability to safely consume cane toads, which are toxic at all life stages. By carefully removing the toxic glands, they can eat only the non-toxic portions of the toad. The mapping project, part of the University of Melbourne’s “Map of the Month” initiative, aims to increase public awareness of native species. Previous projects have focused on tracking native bee species, highlighting the importance of biodiversity in urban settings. The latest rakali map is available on the university’s Pursuit website, providing detailed insights into the distribution and behavior of the species. Water is the best place to begin searching for rakali, as they rely heavily on aquatic environments for food and shelter. Their continued presence in Melbourne’s waterways underscores their adaptability and the potential for further ecological benefits in urban landscapes.