The dispersion and detection patterns of mtDNA‐assigned red fox Vulpes vulpes scats in Tasmania are anomalous

Abstract

Models used for resource allocation in eradication programmes must be based on replicated data of known quality and have proven predictive accuracy, or they may provide a false indication of species presence and/or distribution. In the absence of data corroborating the presence of extant foxes Vulpes vulpes in Tasmania, a habitat-specific model based upon mtDNA data (Sarre et al. 2012. Journal Applied Ecology, 50, 459–468) implied that foxes were widespread. Overall, 61 of 9940 (0·6%) surveyed scats were assigned as mtDNA fox positive by the fox eradication programme (FEP). We investigated the spatiotemporal distribution of the 61 mtDNA-assigned fox scats and modelled the probability of replicating scat detection in independent surveys using detection dogs based upon empirically derived probabilities of scat detection success obtained by the FEP using imported fox scats. In a prior mainland study, fox genotypes were recurrently detected in a consecutive four-day pool of scats. In Tasmania, only three contemporaneously collected scat pairs of unknown genotype were detected by the FEP within an area corresponding to a conservatively large mainland fox home range (639 ha) in a decade. Nearest neighbour pairs were widely spaced (mean = 7·0 km; circular area = 153 km2) and generated after a mean of 281 days. The majority of assigned mtDNA positive scats were found in urban and peri-urban environments corresponding to small mainland fox home ranges (30–45 ha) that imply higher scat density and more certain replication. Using the lowest empirically determined scat detection success for dogs, the failure to replicate fox scat detection on 34 of 36 occasions in a large (639 ha) home range is highly improbable (P = 0·00001) and suggestive of Type I error. Synthesis and applications. Type I error, which may have various sources, should be considered when scat mtDNA data are few, accumulated over many years, uncorroborated by observations of extant specimens, inadequately replicated in independent surveys within an expected spatiotemporal scale and reported in geographically isolated environments unlikely to have been colonized.

Wildlife detector dogs and camera traps: a comparison of techniques for detecting feral cats

“…In Tasmania, trained dogs detected 80% of fox (Vulpes vulpes) scats, even after the scats had been in the field for 63 days. After 91 days in the field, 99% of fox scats were genetically identifiable to species (Brown et al 2011;Caley et al 2015; but see also Marks et al 2014).…”

Understanding and integrating knowledge to improve invasive species management

“…The general public and decisionmakers, however, are more likely to seek certainty and deterministic solutions, with perceptions of risk moderating the acceptance of scientific findings (Tam and McDaniels 2013), and confidence in scientific information increasing as confirmation in the data increases (Kuhn 1962). Involving stakeholders in risk assessments can increase the transparency and credibility of decision-making (Kapler et al 2012), particularly when different data sets of species abundance and distribution contradict one another, as in Tasmania (Gonçalves et al 2014;Marks et al 2014;Sarre et al 2012). Increasing recognition that community stakeholders should be involved from the outset (Bomford and O'Brien 1995;Clout and Veitch 2002;Veitch et al 2011), despite differences in worldviews, leads to reflection on what is needed to overcome these barriers to enable greater levels of eradication success.…”

“…Recently, a group of independently operating scientists published research that questions the validity of the DNA evidence and thus the presence of foxes (Gonçalves et al 2014;Marks et al 2014), highlighting concerns over genetic studies of biological invasions (see also Darling 2014). Only 29 % of landholders, whose permission has been sought to lay baits on their property, have provided it, representing 55 % of the area necessary to bait to achieve eradication objectives (pers.…”

Inferring the Distribution and Demography of an Invasive Species from Sighting Data: The Red Fox Incursion into Tasmania

“…Subsequently, the scat-derived DNA evidence has been used to infer that the population was widespread in northern, eastern and southern Tasmania as of 2010 [ 15 ]. We note that the evidence underpinning this inference is contested [ 18 ].…”