Overcoming the challenges of measuring the abundance of a cryptic macropod: is a qualitative approach good enough?
Karlene Bain A B D , Adrian Wayne C and Roberta Bencini A
+ Author Affiliations
- Author Affiliations
A School of Animal Biology (M092), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
B Department of Parks and Wildlife, South Coast Highway, Walpole, WA 6398, Australia.
C Department of Parks and Wildlife, Brain Street, Manjimup, WA 6258, Australia.
D Corresponding author. Email: draconis@wn.com.au
Wildlife Research 41(1) 84-93 https://doi.org/10.1071/WR14065
Submitted: 8 April 2014 Accepted: 22 April 2014 Published: 22 May 2014
Abstract
Context: An understanding of population size and status is necessary for the implementation of appropriate conservation measures to recover threatened taxa. Mark–recapture studies at large spatial scales are impractical and expensive and a rapid survey technique is an attractive option to provide a measure of relative abundance for cryptic species, using indicators of activity.
Aims: The aim of our study was to use conventional methods for population estimation to calibrate a rapid survey technique for the quokka (Setonix brachyurus) in the southern forests of Western Australia, with a view to providing quantitative outcomes from this widely adopted monitoring approach.
Methods: We evaluated the accuracy of relative abundances obtained from the rapid survey technique by comparing them with abundance estimates obtained through established methods for the estimation of populations, including web-based mark–recapture and transect-based counts of activity indicators and sightings.
Key results: The rapid survey technique was effective at determining presence of quokkas but resulted in an over-estimation of population size because of inaccurate assumptions about occupancy and relative abundance of animals. An alternative survey method based on counts of fresh faecal-pellet groups was found to provide a more reliable and practical estimation of population abundance (R2 = 0.97).
Conclusions: Activity indices can be used to quantify population abundance, but only for indicators of activity that can be detected readily and for which freshness of activity can be determined.
Implications: Our findings suggest that a rapid survey based on activity indices can be used to evaluate quantitatively the population size of a species that is rare and potentially mobile at a landscape scale. The attraction of these techniques is that they provide a rapid and inexpensive survey option that is potentially applicable to any cryptic and/or threatened species and is practical for resource-constrained land managers.
Additional keywords: faecal pellets, indirect survey method, population size estimates, quokka, rapid survey, relative abundance, runnels, Setonix brachyurus, sightings, tracks.
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