Using complementary remote detection methods for retroﬁtted eco-passages: a case study for monitoring individual koalas in south-east Queensland
C. E. DexterA,C, R. G. ApplebyA,B, J. P. EdgarB, J. ScottA and D. N. JonesA
A Environmental Futures Research Institute, Sir Samuel Grifﬁth Centre (N78), Grifﬁth University, 170 Kessels Road, Nathan, Qld 4111, Australia.
B Wild Spy Pty Ltd, 11/25 Depot St, Banyo, Qld 4014, Australia.
Context. Vehicle-strike has been identiﬁed as a key threatening process for koala (Phascolarctos cinereus) survival and persistence in Australia. Roads and trafﬁc act as barriers to koala movement and can impact dispersal and meta population dynamics. Given the high cost of wildlife mitigation structures such as purpose-built fauna-speciﬁc underpasses or overpasses (eco-passages), road construction and management agencies are constantly seeking cost-effective strategies that facilitate safe passage for fauna across roads. Here we report on an array of detection methods trialled to verify use of retroﬁtted road infrastructure (existing water culverts or bridge underpasses) by individual koalas in fragmented urban landscapes in south-east Queensland.
Aims. The study examined whether the retroﬁtting of existing road structures at six sites facilitated safe passage for koalas across roads. Our primary objective was to record utilisation of retroﬁtted infrastructure at the level of the individual.
Methods. We used a combination of existing monitoring methods such as GPS/VHF collars, camera traps, sand plots, and RFID tags, along with a newly developed animal-borne wireless identiﬁcation (WID) tag and data logging system, speciﬁcally designed for this project, to realise the study aims.
Key results. We were able to verify 130 crossings by koalas involving a retroﬁtted structure or a road surface over a 30-month period by using correlated data from complementary methods. We noted that crossings were generally uncommon and mostly undertaken by only a subset of our tagged individuals at each site (21% overall).
Conclusions. An important element of this study was that crossing events could be accurately determined at the level of the individual. This allowed for detailed assessment of eco-passage usage, rather than the more usual approach of simply recording species’ presence.
Implications. This study underscores the value of identifying the constraints of each individual monitoring method in relation to site conditions. It also highlights the beneﬁts of contingency planning to limit data loss (i.e.using more than one method to collect data). We suggest an approach that uses complementary monitoring methods has signiﬁcant advantages for researchers, particularly with reference to improving understanding of whether eco-passages are meeting their prescribed conservation goals.