Fig 1.
Camera-trap locations in seven fox territories (T1-T7) in Bristol.
The estimated territorial boundaries are shown by dotted lines and camera-trap locations by black circles. The lighter grey indicates built up areas; darker grey buildings; and green open spaces such as parks, playing fields, cemeteries and allotments. The centre of the study area is 51.48623°N, 2.62468°W. Map drawn in QGIS with the OpenLayers plugin [71].
Fig 2.
Example of autumn and spring identification sheets for one fox.
These illustrate the multiple features used to ensure that it could be identified under different lighting conditions, from both sides, and when only some parts were visible on the camera-trap photo.
Table 1.
Morphological features selected for individual identification.
Fig 3.
Illustration of how a fox’s appearance can vary with lighting conditions.
Top row: photos of the same fox taken in the same location (A) with a flash at dusk and (B) without the flash in daylight. The coat colour appeared different but tail shape, signs of lactation and a dark line on the right hindquarter remained consistent. Bottom row: photos of another fox taken in the same location (C) with a flash in the dark and (D) with a flash when an outside light was also on in the garden. While the coat colour appeared different, the dark lines on the throat and above the elbow and a white spot on the left foreleg remained consistent.
Fig 4.
Temporal persistence of identifying features over consecutive seasons in four adult foxes.
Seasons 1 to 4 are summer to spring for Apricot and Strawberry and autumn to summer for Aurora and Zeus. While coat thickness and fat deposition changed seasonally, other features were visible in every season.
Fig 5.
Relationship between the proportion of photos that were unidentifiable and the proportion of foxes ear-tagged on each territory.
The circles denote each 40-day survey and the shaded ribbon the standard error.
Table 2.
The ten foxes with ear tags chosen from a random selection of surveys that were used to test the effects of artificial marks on the ability to identify individuals, organised by season, and the number of photos when each individual was identified without relying on their tags.
Table 3.
The number of non-resident foxes ≥ 5 months old that were identified on each territory each season after deleting an increasing proportion of photos.