DNA genotypes reveal red fox (Vulpes vulpes) abundance, response to lethal control and limitations of contemporary survey techniques

Abstract

Context. Scat genotyping has not been routinely used to measure fox (Vulpes vulpes) abundance and our study sought to provide a benchmark for further technique development and assessment of field methods.Aims. This study sought to provide a comparative assessment of some common methods used to determine fox density and contrast their success with scat DNA genotyping.Methods. DNA recovered from fox scats was used to genotype individual red foxes and determine their abundance at four transects. Population indices were also developed from bait take, scat counts and sand plot tracks using index-manipulationindex (IMI) procedures on the same transects. Known samples of foxes were taken from two treatment transects using cyanide delivered in the M-44 ejector to manipulate the population and to recover foxes at the end of the trial.Key results. Replicated counts on a 41-km-spotlight transect at the field site before and after the population manipulation had low variance and good correlation (r 2 = 0.79, P < 0.01). Scat genotypes revealed 54 foxes in eight days and, when combined with biopsy DNA from recovered foxes, a minimum known to be alive (KTBA) density of between 1.6 and 5 foxes km -1 was calculated for the transects. Overall, 15/30 (50%) of all recovered foxes had not been detected by scat genotyping, 23/53 (49%) of KTBA genotypes were detected only once and 5/54 (9.5%) of foxes were found to have moved between two transects.Conclusions. At transects where population manipulation occurred, surviving individuals contributed significantly more scats than at the control transects and some individuals were detected at bait stations at a much greater frequency. This strongly suggested that they had contributed disproportionately to some IMI density estimates that were probably influenced by a change in the activity of some individuals rather than changes in population density alone. At one transect, eight foxes were confirmed to be present by spotlight surveys and were detected by scat and KTBA genotypes, yet were undetected by scat, bait station and sand plot indices.Implications. Scat and other DNA-based survey techniques provide a great deal of information about the identification and movement of individuals and if DNA sampling methods can be made more efficient they have the potential to provide accurate abundance estimates that are independent of the control technique.

Lethal 1080 baiting continues to reduce European Red Fox (Vulpes vulpes) abundance after more than 25 years of continuous use in south‐west Western Australia

“…) are more likely to be attracted by the bait lure at hair traps whereas wary and/or bait averse foxes may remain undetected (Marks et al . ). The collection of faecal DNA is less biased by individual behaviour and this has been used successfully to assess the effectiveness of fox baiting campaigns including detecting individuals that avoided lethal control (Piggott et al .…”

“…Historically baiting effectiveness has been difficult to evaluate because conventional techniques such as trapping and observation rarely provide quantitative data on changes in density and survival (Saunders & McLeod ; Marks et al . , ; Vine et al . ; Kirkwood et al .…”

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

“…Identifying scats to species may allow population density estimates through occupancy modelling, whereas identifying individual animals allows mark-recapture analysis (Marks et al 2009;Gleeson et al 2010). Identifying individuals can also tell us about their movements and behaviour.…”

“…Control of invasive predators is often hindered by the difficulty of detecting them in the field; often they are cryptic, highly mobile, and occur at low density (Witmer 2005;Marks et al 2009;Clayton & Cowan 2010). However, even very low densities of invasive predators can threaten populations of vulnerable native species (e.g.…”

First in, first served: uptake of 1080 poison fox baits in south-west Western Australia

“…Second, a better understanding of fox presence and landscape use in forested habitats would be beneficial. Regularly monitored sand pads are an effective means of monitoring predator and prey presence in a forested area (Claridge et al 2010) and DNA genotyping of fox scats has successfully been used to estimate fox abundance and movements (Marks et al 2009;Berry et al 2012). Remote tracking with radio and GPS collars is a suitable method for determining habitat preferences and use of space (Lucherini and Lovari 1996;White et al 2006), which could be used to improve bait deployment.…”