The platypus: a peculiar mix of DNA
The platypus (Ornithorhynchus anatinus), a well known monotreme from Australia, is an animal that defies one’s imagination. With a bill like a duck, tail like a beaver and feet like an otter’s, this creature is a peculiar sight to see. Its life cycle is even more marvellous: the platypus lays leathery eggs, which hatch into puggles, which are nursed from the mother’s milk (Bino et al, 2019). This unique mix of reptile, bird and mammalian traits makes for a fascinating DNA profile, and helps scientists understand how early mammals evolved 250 million years ago (Warren et al., 2008).
Unfortunately, as many species in our current day and age, the platypus is threatened by ongoing urbanization. What exactly happens when the unique DNA of the platypus is exposed to the city? This is what an Australian study by Brunt and Smith (2025) set out to investigate.
Resistance modelling: creating a gene-flow map
To investigate the impact of the urban environment on the platypus DNA, the researchers used a clever technique called resistance modelling (Brunt & Smith, 2025). This tool helps us to understand how landscape features such as rivers and roads influence animal movement and gene flow, which is especially helpful in urban environments. Resistance modelling uses a map of the environment and assigns specific values to elements in the landscape. These so called resistance values express the species ability to move and exchange genes across populations: the lower the value of an area, the easier a platypus can travel and breed. As the platypus relies on both land and water to hunt and breed, rivers and wetlands will have low resistance values and will be easy to cross, whilst roads, buildings and concrete areas have high resistance values, and will be difficult to cross (McRae & Beier, 2007).
Fragmented waterways: the gene-flow dilemma
So, what happens when the connections between urban waterways fall apart? It turns out that this is a big issue for the platypus. In natural habitats, the platypus uses networks of rivers, wetlands, and canals to travel large distances (Coleman et al., 2021). This makes gene-flow easy to occur. However, Brunt and Smith found that in the urban landscape, cutting off this connectivity of rivers and water sources can easily disrupt gene-flow. If the platypus populations are less able to exchange genes in urbanized areas, this could lead to inbreeding, increasing the risk of genetic disorders, reducing fertility and reducing adaptability to environmental changes such as climate change. All in all: not hallmark signs for a thriving species (Brunt & Smith, 2025).
Riverside real estate: vegetation as a corridor
However, there is hope for the platypus. Apart from water availability, the presence of riparian vegetation is key to a healthy platypus populations. Not only do these plants provide food and shelter: they also provide a way for platypuses to travel between isolated water bodies (Coleman et al., 2021). Brunt and Smith found that presence of riparian vegetation could help individuals travel between water sources and exchange genes. This kept populations genetically healthy, even if waterbodies itself were isolated (Brunt & Smith, 2025).
The hopeful side of urban nature
Thus, are all urban environments inherently bad for platypuses? As we see, this is not quite the case. With the right conditions, cities can in fact support platypus populations that are genetically healthy. Urban areas with connected waterways and with patches of riparian vegetation in between the waterways did show genetically diverse and healthy platypus populations. In the light of urban planning, the protection of riverbanks, the maintenance of natural waterflows and the restoration of vegetation can certainly be beneficial to platypus gene flow, allowing platypuses to continue to thrive, even in the hearth of the city (Brunt & Smith, 2025).
References
Bino, G., Kingsford, R. T., Archer, M., Connolly, J. H., Day, J., Dias, K., Goldney, D., Gongora, J., Grant, T., Griffiths, J., Hawke, T., Klamt, M., Lunney, D., Mijangos, L., Munks, S., Sherwin, W., Serena, M., Temple-Smith, P., Thomas, J., . . . Whittington, C. (2019). The platypus: evolutionary history, biology, and an uncertain future. Journal Of Mammalogy, 100(2), 308–327. https://doi.org/10.1093/jmammal/gyz058
Brunt, T., & Smith, A. L. (2025). Habitat Quality and Water Availability Affect Genetic Connectivity of Platypus Across an Urban Landscape. Animal Conservation. https://doi.org/10.1111/acv.13011
Coleman, R. A., Chee, Y. E., Bond, N. R., Weeks, A., Griffiths, J., Serena, M., Williams, G. A., & Walsh, C. J. (2021). Understanding and managing the interactive impacts of growth in urban land use and climate change on freshwater biota: A case study using the platypus (Ornithorhynchus anatinus). Global Change Biology, 28(4), 1287–1300. https://doi.org/10.1111/gcb.16015
McRae, B. H., & Beier, P. (2007). Circuit theory predicts gene flow in plant and animal populations. Proceedings Of The National Academy Of Sciences, 104(50), 19885–19890. https://doi.org/10.1073/pnas.0706568104
Warren, W., Hillier, L., Graves, J. M., Birney, E., Ponting, C., Grützner, F., Belov, K., Miller, W., Clarke, L., Chinwalla, A., Yang, S., Heger, A., Locke, D., Miethke, P., Watters, P., Veyrunes, F., Fulton, L., Fulton, B., Graves, T., . . . Wilson, R. (2008). Genome analysis of the platypus reveals unique signatures of evolution. Nature, 453(7192), 175–183. https://doi.org/10.1038/nature06936
Featured photo: © Brendan Costello, some rights reserved (CC-BY)
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