Data from: Isotopic evidence for the consumption of Galliformes by the red fox (Vulpes vulpes) in rural southern England
Data files
May 26, 2026 version files 29.51 KB
-
fox_consumer.csv
12.68 KB
-
fox_discrimination.csv
255 B
-
fox_sources_meansd.csv
308 B
-
README.md
2.37 KB
-
Stable_isotope_analysis_uninformative_indiv.R
6.48 KB
-
Stable_isotope_analysis_uninformative.R
7.42 KB
Abstract
Anthropogenic resource subsidies can drive mesopredator population growth, altering predator–prey dynamics. The red fox Vulpes vulpes is a generalist canid that can readily exploit such subsidies. In the UK, tens of millions of pheasants Phasianus colchicus, and red‑legged partridges Alectoris rufa are released annually for sport shooting, potentially contributing to the country’s relatively high fox densities compared to mainland Europe. Yet, the scale of this dietary contribution remains unquantified. We used stable isotope analysis (δ¹³C and δ¹⁵N) of fox ear hair and common vertebrate prey to estimate diet composition across central southern England, a region with c. 2.5 million gamebirds are released each year. Samples from 117 foxes collected between 2018 and 2023 on sites with and without gamebird releases, alongside tissue from key prey species, informed Bayesian stable isotope mixing models. Model estimates showed that mammals predominated in the regional fox diet (mean 61% on releasing sites; 50% on non‑releasing sites), although the Galliformes category comprising pheasants and partridges also made a substantial contribution (posterior means 43.1% on releasing sites and 32.5% on non‑releasing sites), with overlapping 95% credible intervals between site types. These results imply that gamebird releases represent a regionally substantial food source for foxes, with the potential to intensify their ecological impacts if they sustain greater fox densities.
Dataset DOI: 10.5061/dryad.rv15dv4ph
Description of the data and file structure
Human-provided food sources can increase populations of adaptable predators like red foxes. This study found that released gamebirds, such as pheasants and partridges, form a significant part of fox diets in southern England, suggesting that large-scale gamebird releases may help sustain higher fox populations and increase their ecological impacts.
Files and variables
File: fox_consumer.csv
Description of variables:
- Samples: sample ID
- d13C: tracer 1
- d15N: tracer 2
- Date: date sample was collected
- Easting: BNG easting
- Northing: BNG northing
- grid1km: BNG 1km grid square
- Sex: sex of a fox
- Releasing_status: management status of the sample location
- Moult_period: moult period of the sample collection date
- Releasing_moult: composite variable of the above
File: fox_discrimination.csv
Description of variables:
- Source: prey source
- Meand13C: TDF for 13C
- SDd13C: SD of TDF
- Meand15N: TDF for 15N
- SDd15N: SD of TDF
File: fox_sources_meansd.csv
Description of variables:
- Meand13C: source mean for 13C
- SDd13C: source SD for 13C
- Meand15N: source mean for 15N
- SDd15N: source SD for 15N
- n: sample size
File: Stable_isotope_analysis_uninformative.R
Description: Code to run BSIMMs. This R script performs Bayesian stable isotope mixing models using the MixSIAR package to estimate fox diet composition from carbon and nitrogen isotope data. It runs and compares multiple models with different ecological variables, generates diagnostic plots and summaries, and saves the final results for further analysis.
File: Stable_isotope_analysis_uninformative_indiv.R
Description: Code to run BSIMMs with an individual sample as a random effect. This script runs Bayesian stable isotope mixing models in MixSIAR to estimate individual-level fox diet using carbon and nitrogen isotope data. It fits and compares multiple models (with individual and treatment effects), then outputs diagnostics, plots, and a final model comparison table.
Code/software
Code run in R version 4.2.3. Required R packages: MixSIAR, rjags