麻豆传媒

News — New research challenges the perception of declining pure dingo numbers due to crossbreeding, revealing wild dingo populations with reduced dog ancestry but a higher proportion of pure dingoes than previously believed.

Published in Molecular Ecology, the study's findings indicate that previous estimations of dingo-dog hybrids in the wild were greatly exaggerated. The research also suggests that the current methods employed to control "wild dogs" may inadvertently harm pure dingo populations.

Hybridisation poses a threat to the genetic integrity of dingoes, as they are genetically separate from domestic dogs but still capable of interbreeding. This cross-species breeding, known as hybridisation, puts pure dingo populations at risk of genetic dilution, potentially leading to their vulnerability and eventual extinction.

Dr. Kylie Cairns, a conservation biologist from UNSW Science and the study's lead author, emphasizes that contrary to long-held concerns, dingoes are not breeding themselves into extinction. She states that their research indicates that dingoes are largely preserving their distinct identity, which has significant implications for their conservation and management.

More pure dingoes than hybrids

In their study, a team of researchers led by UNSW Sydney examined the extent of dingo hybridisation in various regions of Australia. They employed a novel genome-wide test to analyze the DNA of 391 wild and captive dingoes. By conducting extensive ancestry modeling and biogeographic analysis, they discovered that wild dingoes possess significantly less dog ancestry than previously indicated by genetic studies.

Dr. Cairns explains that the previous method used for assessing dingo ancestry relied on a small set of genetic markers and had a limited reference population. This outdated approach led to an overestimation of dog ancestry in dingo samples, sometimes by more than 30 percent. Consequently, animals that were actually pure dingoes or had historical backcrosses were mistakenly identified as crossbred. The new genome-wide test utilized in the study provides a more accurate assessment of dingo ancestry.

Dr. Cairns highlights the significant improvement brought about by the new genome-wide test. Instead of examining only 23 genetic markers as in the previous method, the new test enables analysis of 195,000 points across the genome. This substantial increase in data points translates into a substantial enhancement in the reliability and accuracy of the results.

The study's findings challenge previous reports regarding the pure dingo population in Victoria, which had suggested a mere 4 percent. However, the research revealed that 87.1 percent of the animals tested in Victoria were indeed pure dingoes. Additionally, 6.5 percent were identified as historical dingo backcrosses, with over 93 percent dingo ancestry. These results indicate a significantly higher prevalence of pure dingoes in Victoria than previously believed.

Likewise, the study's findings challenge the assumption of pervasive dingo-dog hybridisation in New South Wales and Queensland. Contrary to expectations, the majority of animals tested in these regions were determined to be pure dingoes. Only two wild canids were identified as having less than 70 percent dingo ancestry. These results indicate a higher prevalence of pure dingoes in New South Wales and Queensland than previously assumed, further underscoring the importance of accurate assessment methods in understanding dingo populations.

Limited signs of hybridisation within the dingo population were also observed in the Northern Territory, South Australia, and Western Australia.

Dr. Cairns asserts that the prevalent belief regarding widespread dingo-dog hybridisation in Australia is largely influenced by the utilization of outdated DNA testing techniques. She emphasizes that in reality, most dingoes in the wild are pure dingoes, with the remaining animals displaying a significant dingo genetic composition. This statement highlights the need to reevaluate existing assumptions about the prevalence of dingo-dog hybridisation in Australia.

"Even in regions of Australia with elevated dingo-dog hybridisation, it is not as pervasive a threat as previously thought."

None of the animals included in the sample were found to be 50 percent hybrids, indicating that there were no direct offspring of a dog and a wild dingo. The small number of animals that did not possess pure dingo genetic composition were primarily identified as historical backcrosses, having a single dog ancestor in their lineage from four or five generations ago.

Dr. Cairns explains that although there has been some historical hybridisation, the process is not currently happening at a significant rate. She notes that in cases where hybridisation does occur, the offspring of hybrids tend to gradually revert back to their dingo heritage over time. This observation suggests that the natural course is for the hybrids to eventually align more closely with their dingo ancestry.

The study unveiled notable regional disparities in dingoes, revealing the presence of four distinct wild dingo populations throughout mainland Australia.

Dr. Cairns acknowledges that the study did not encompass samples from every corner of Australia, suggesting that there may be additional variations in dingoes yet to be discovered. She also mentions the possibility of dog DNA being integrated into the dingo genome as an evolutionary advantage, which is an area the researchers plan to explore in future studies using the new testing methodology.

The study's findings align with research conducted on other species, highlighting the effectiveness of genome-wide analysis in accurately identifying ancestry. This valuable information can be utilized by policymakers to make informed decisions regarding dingo management strategies.

Professor Mike Letnic, a conservation biologist from UNSW Science and senior author of the study, emphasizes that the existing management decisions have relied on outdated DNA testing technology with limited resolution. He emphasizes the significance of the study's more advanced approach, utilizing higher-density genomic data to assess dingo populations with greater accuracy. This approach enables the formulation of management strategies based on the best-available evidence, thereby enhancing the effectiveness of dingo conservation efforts.

Informing evidence-based dingo management

In Australia, the policy terminology of "wild dog" has been commonly employed, assuming extensive dingo-dog hybridisation and a scarcity of pure dingoes.

Dingoes, dingo-hybrids, and feral domestic dogs are all classified as invasive species under biosecurity legislation in Australia, falling under the umbrella term of "wild dog." Consequently, they are subject to eradication measures such as aerial baiting or trapping in various regions of the Australian mainland, including National Parks where native wildlife is protected.

Dr. Cairns raises concerns about the convenience of categorizing all dingoes as wild dogs. This term, she argues, overlooks the fact that numerous pure dingoes and dingo-dominant backcrosses are being targeted for lethal control. She highlights that the treatment of dingoes is unique among native species, as they face lethal control measures in all types of landscapes, including those where they should be protected.

Absence of dingoes in certain environments can lead to overpopulation of kangaroos, foxes, and feral cats, posing threats to native animals and causing significant alterations to vegetation.

Professor Letnic emphasizes that while dingoes may pose a threat to certain livestock, they should not be considered pests in all situations. He highlights the critical role that dingoes play as apex predators in preserving ecosystem function and biodiversity. Thus, it is crucial to strike a balance in their management and ensure the preservation of dingo populations in specific areas of the landscape.

The implementation of lethal control methods, especially during the dingo breeding season, may unintentionally raise the risk of hybridisation by diminishing the pool of pure dingo mates. Nonetheless, further research is necessary to establish a conclusive connection between lethal control measures and increased hybridisation.

Dr. Cairns explains that although the prevalence of hybrids is not as high as previously believed, instances of dingo-dog hybridisation do occur in regions characterized by intensive lethal control practices and a higher presence of domestic pet dogs. This observation suggests a potential correlation between hybridisation and the combination of lethal control measures and the proximity of domestic dogs.

The researchers propose a revision to the definition of "dingoes" in conservation policy, recommending the inclusion of historical dingo backcrosses with at least 93 percent dingo ancestry. This distinction would differentiate them from "feral domestic dogs" and contribute to a more accurate classification system in conservation efforts.

Dr. Cairns asserts that such a revision would provide a more precise reflection of the identity of wild canids in Australia and acknowledge the significance of dingoes as both a native species and a culturally important entity.