Faecal density counts for monitoring changes in red fox numbers in rural Britain

Abstract

1. Quantifying animal density is a fundamental requirement for the successful management of canid species. Faecal transects along linear features represent a cost-effective means of quantifying relative density. However, it is unclear whether such counts can be utilized to estimate absolute density. 2. In Britain, due to proposed legislative changes in permitted culling practices, and as part of a wider monitoring programme, the current and future density of red foxes Vulpes vulpes is of applied interest. In this study, we counted fox faeces in 444 1-km squares throughout mainland Britain to construct a baseline index of fox density against which future changes could be measured. By incorporating estimates of the defecation rate and the proportion of scats associated with linear features, we estimated absolute density in seven landscapes. These estimates were compared with existing data on fox density. 3. On average, captive foxes consumed 0-85 kg food day-1. Defecation rate (8 scats fox-1 day-1) was not affected by the type of food consumed. 4. The proportion of scats associated with linear features was determined by feeding individual free-living foxes a known amount of food containing an indigestible marker. On average, 5.7% of scats were deposited along linear features. 5. Mean fox density in landscapes ranged from 0.21 to 2.23 foxes km-2. These estimates agreed closely with the limited data available on fox density in Britain. The total rural fox population was estimated to be 225 000 foxes (95% confidence interval 179 000-271 000). Including foxes in urban areas, the total national population is estimated to be approximately 258 000 individuals. 6. Synthesis and applications. The results suggest that faecal density counts have the potential to be used to estimate fox density over large spatial scales, although further work on estimating the proportion of scats associated with linear features and the use of faeces in territorial marking by canids is required.