Fecal bacterial communities of the platypus (Ornithorhynchus anatinus) reflect captivity status – implications for conservation and management

The duck-billed platypus (Ornithorhynchus anatinus) is currently listed as ‘Near-Threatened’ under the International Union for Conservation of Nature (IUCN) Red List based on observed population declines and local extinctions. A key part of the conservation strategy for this species is its captive maintenance; however, captive animals often undergo significant changes in their gut microbiome. The study of the gut microbiome in threatened wildlife species has enormous potential to improve conservation efforts and gain insights into host-microbe coevolution. Here, for the first time, we characterize the gut microbiome of wild platypus via fecal samples using high-throughput sequencing of the bacterial 16S rRNA gene and identify microbial biomarkers of captivity in this species. At the phylum level, Firmicutes (50.4%) predominated among all platypuses, followed by Proteobacteria (28.7%), Fusobacteria (13.4%), and Bacteroidota (6.9%), with twenty-one ‘core’ bacteria identified. Captive individuals did not differ in their microbial α-diversity compared to wild platypus but had significantly different community composition (β-diversity) and exhibited higher abundances of Enterococcus, which are potential pathogenic bacteria. Four taxa were identified as biomarkers of wild platypus, including Rickettsiella, Epulopiscium, Clostridium, and Cetobacterium. This contrast in gut microbiome composition between wild and captive platypus is an essential insight for guiding conservation management as the rewilding of captive animal microbiomes is a new and emerging tool to improve captive animal health, maximize captive breeding efforts, and give reintroduced or translocated animals the best chance of survival.