Overcoming the challenges of measuring the abundance of a cryptic macropod: is a qualitative approach good enough?

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 overestimation 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 (R 2 = 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.

Opportunistic observation effort and seasonal-spatial fidelity: a qualitative approach, applied to an Orcinus orca first record

“…With additional development of corroborative approaches such as the observation effort based on qualitative analyses here, it is possible to chip away at impediments to the research of many challenging cetacean populations, not just killer whales (e.g. Bain et al ., 2014).…”

“…This effect need not be the end state (e.g. Ochoa-Pachas, 2021); although opportunistic data tend to fall in the qualitative domain, many of these data can also be standardized and often calibrated by quantitative means, providing additional valuable information (Bain et al ., 2014). Qualitative determinations of area-specific effort draw heavily on Purposeful or Purposive sampling (also Judgmental or Authoritative) (Explorable.com, 2009; Lopez and Whitehead, 2013; Palinkas et al ., 2013) where, from a body of potential observers, the investigator selects one or more who have substantial knowledge of area usage (information-rich).…”

Severe, large-scale bushfire threatens metapopulation function of quokka (Setonix brachyurus) in south-western Australia

“…Counting fresh faecal pellet groups has been demonstrated to be an effective method for rapidly determining a quantitative estimate of abundance for quokkas in the southern forest (Bain et al 2014). The technique is widely used by land managers in this region due to the ability for the method to be applied at large spatial scales with a result that is highly comparable to the outcomes of more intensive methods, such as mark-recapture techniques (Bain et al 2014).…”

“…At each site, two transects 1 km in length were surveyed for quokkas, and the occurrences of all fresh faecal pellet groups (deposited overnight) within 2.5 m of the transect were recorded (Bain et al 2014). The transect surveys were repeated twice within a 2-month period for each site.…”

Using technology to improve the management of development impacts on biodiversity

“…The reasons for inadequate implementation of the MH are varied and often context specific. Common constraints include, among others, gaps in the availability, access, or awareness of relevant information on baselines and impacts (e.g., Jacob et al, 2016); high cost and/or low feasibility of collecting baseline and monitoring data (e.g., for bird and bat fatalities in offshore wind farms, Lindeboom et al, 2015, or cryptic species, Bain et al, 2014, Williams et al, 2018); absence of affordable and effective technical solutions for minimizing impacts (e.g., cost of burying power transmission lines to prevent bird collisions, Bernardino et al, 2018; ineffectiveness of fish ladders to maintain bi‐directional migration, Agostinho et al, 2012); inadequate availability of finances and knowledge required for biodiversity impact mitigation (e.g., Krause et al, 2021); and limited empirical evidence for the effectiveness of mitigation options (Christie et al, 2020). The application of new technologies has potential to help overcome these challenges, increasing the feasibility and effectiveness of mitigation and monitoring (Bergal‐Tal & Lahoz‐Montfort, 2018; Joppa, 2015; Lahoz‐Monfort et al, 2019; WILDLABS, 2016).…”