Science for Policy Research findings in brief Project 4.2.3.4 Using eDNA to track cryptic threatened burrowing petrels on Macquarie Island following pest eradication In brief Background Sub-Antarctic Macquarie Island is This study used DNA from the scats sites. Significantly, we located new undergoing environmental change and feathers from burrowing petrels populations of existing species, following multiple successful on remote, sub-Antarctic Macquarie populations of returned species, eradications of feral animals. In 2000, Island to determine the diversity of and identified differences between cats were eradicated, and this was these seabirds on the island and to birds of the same species from followed by eradications of rabbits, assess the use of environmental DNA Macquarie Island and other rats and mice in 2014. These invasive (eDNA) for this type of application. sub-Antarctic islands. species had a negative impact on many of the native species of the The island has undergone Our research shows a successful island, particularly the eight species environmental change following application of DNA techniques to of burrowing petrels that breed there, eradications of invasive cats, rats, inventory cryptic species on remote through predation on adult birds, mice and rabbits, and the study islands in Australia. The method chicks and eggs, and destroying their examined whether eDNA can help is especially relevant to islands in nesting habitat. As a result, several to determine what species of Australia and globally, where field species of burrowing petrel had burrowing petrels occur now, trips are necessarily infrequent become threatened, with some driven including looking for species and researchers can only spend to extinction from the island itself that were driven to extinction. limited time. and retreating to offshore rock stacks Burrowing petrels are “cryptic” The research was led by the Australian and Bishop and Clerk Islets (33km species, in that they can be difficult Government’s National Environmental south of Macquarie Island). to detect, which makes them hard to Science Program through the Now that cats, rabbits, rats and mice monitor with conventional methods. Threatened Species Recovery have been eradicated, there is strong The use of DNA to identify species Hub, in collaboration with the interest about whether populations represents a useful way to confirm Australian Antarctic Division, Marine of burrowing petrel will increase and expand upon the conclusions Conservation Branch, and Tasmanian on the island and if, in fact, some of conventional ground searches. Parks & Wildlife, Department of species will now return to it. Primary Industries, Parks, Water We mapped occurrences of species and Environment, Tasmania. Currently, Tasmanian DPIPWE Parks of burrowing petrels at surveyed and Wildlife rangers and government White-headed petrel burrows can exceed 2 m in length, scientists spend time on the island so occupants are difficult to detect. Image: Jez Bird surveying these birds, but they can be hard to detect. Burrowing petrels are particularly difficult to monitor due to Further reading their cryptic nature: birds only return to land at night, and only at certain times of year; different species can look incredibly similar; breeding sites can be fragile and hard to access; Further Information and the burrows are often so long it Justine Shaw – [email protected] is difficult to identify the occupants. Background (continued) What we did There is a suite of threatened species We developed and used DNA analysis The known sites (group 1) we assessment tools that can provide techniques to ground truth field visited were predominantly where valuable information about which surveys of cryptic burrowing petrels on occurrence of white-headed petrels, species are present in a landscape Macquarie Island, and to detect any grey petrels, blue petrels or Antarctic and how they are distributed there unanticipated species which may also prions had been confirmed. Samples and, importantly, whether the have returned to the island following from mixed or unknown species presence of species shows change the feral animal eradications. (group 2), were collected from a under different environmental and range of breeding sites or during Team members collected 222 anthropogenic pressures. Before this survey transects across the island. scat and 108 feather samples from research, however, scats and feathers For each sample we collected, we Macquarie Island that were later of unknown seabird species were recorded the GPS co-ordinates, date analysed in the laboratory for DNA not commonly used to back up with and the freshness of the scat samples, (Figure 1). We used these data to empirical evidence the inferences to test whether old samples still identify which burrowing petrel made from conventional ground- had sufficient DNA. species were present on the island searching on remote islands. Such and mapped the locations where A considerable amount of laboratory DNA analysis may be able to provide they were detected (see Figure 2). work was necessary to investigate a way to identify burrowing petrel the genetics of these seabirds, as species in the region, and detect We also assessed how well DNA little work had previously been any shifts in species diversity on analysis of scats and feathers can done for the species. We designed post-eradication Macquarie Island. be used to determine the diversity burrowing petrel primers for two gene of cryptic burrowing petrels on Environmental DNA (eDNA) regions. We also accessed existing Macquarie Island. samples can include indirect sample genetic sequences from the families collections, such as water or soil, We collected the scat and feather Procellariidae (prions, shearwaters, or more direct sample collections, samples between November 2017 fulmarine petrels and gadfly petrels), such as tissue samples or scats to and March 2018, and again in July to Pelecanoididae (diving petrels), identify the main species, their November 2018. We collected the Oceanitidae (southern storm petrels) prey or parasites. samples from either 1) breeding sites and Hydrobatidae (northern storm of known species; or 2) breeding sites petrels) from online repositories. with mixed or unknown species. Research aims The research aimed to explore a novel method for detecting threatened burrowing petrels on post-eradication Macquarie Island. This aim involved the following: • Developing a low-impact genetic technique for surveillance of cryptic burrow- nesting threatened species • Determining the threatened petrel species present on Macquarie Island, including the presence of any new species • Determining which petrel species are present in “colonies” of burrows, to ascertain whether they are single-species or multi-species colonies. Figure 1. Workflow for DNA detection of burrowing petrels from scat and feather samples. Key findings The DNA that we extracted from scats Table 1: Burrowing petrel species detected on Macquarie Island from scat and feather DNA. and feathers on Macquarie Island Common species Less common species to detect burrowing petrel species (> 5 locations > 30 samples) (<5 locations < 30 samples) diversity gave valuable insights into Antarctic prion, Pachyptila desolata Diving petrel, Pelecanoides sp. the distribution of species around the Blue petrel, Halobaena caerulea Fairy prion, Pachyptila turtur island (see Figure 2). We detected DNA with exact matches to reference Sooty shearwater, Ardenna griseus Soft-plumaged petrel, Pterodroma mollis sequences for seven of the burrowing White-headed petrel, Pterodroma Fulmar prion, Pachyptila crassirostris petrels species previously recorded lessonii – DNA sequences indicative, but inconclusive. to breed on Macquarie Island (or Grey petrel, Procellaria cinerea offshore islands). An additional two (winter breeder) sequences could only be identified to genus (Table 1). One of the sequences closely matched both South-Georgian diving petrels (Pelecanoides georgicus) and common diving petrels (P. urinatrix) and the other sequence closely matched both fairy prion (Pachyptila turtur) and fulmar prion (Pachyptila crassirostris), with only one base pair difference in each case. This was due to the close genetic similarities between these species in this gene region. There was no significant difference in the success rate of scats and feathers to detect species, with 94% and 87% success, respectively. Burrowing petrels are cryptic and difficult to survey as they burrow underground to nest and are not easy to view. Given the difficulty of monitoring such species, researchers typically make assessments based on hand searches, acoustic playback, spot-lighting and burrow- scopes. Our sampling at the established and known colonies or areas of burrows (group 1) revealed that the species thought to occur there were indeed present, providing confidence in previous survey methods. In several instances, our research also detected burrowing petrel species at new locations. Diving petrels and fairy prions are rarely detected on Macquarie Island, with the latter previously recorded only on offshore rock stacks and Bishop and Clerk Islets. However, we found diving petrel Figure 2. Sampling locations on Macquarie Island in 2017–18 where burrowing petrel species DNA in samples from five locations identification was confirmed using DNA from scats and feathers. NB: we couldn’t distinguish around the island and fairy prion between fulmar and fairy prion DNA in two samples. Acknowledgements Thanks