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Water vole latrines were studied on four of the principal rivers in the North Yorkshire Moors National Park. Water voles occupied ‘core’ and ‘peripheral’ sites on these rivers. Core sites were marked by latrines and held breeding colonies of voles; animals at core sites were readily captured. Peripheral sites were not marked by latrines, but showed erratic water vole activity as measured by activity indices (tracks m-1 of muddy bank month-1). It was never possible to catch voles at these peripheral sites, and there was no evidence of breeding.

Latrines on core sites were not maintained outside the breeding season. The appearance of latrines coincided with the start of the breeding season, and while they were maintained, latrines provided a useful guide to the number of animals in the area. A curvilinear response was obtained between latrine production and date, with production rising steadily from early spring until mid-to-late summer, which suggests that latrines signal sexual activity.

Future studies on the distribution of water voles should use a variety of techniques. Latrine surveys will only be applicable during the breeding season at core sites. Similarly, live-trapping will only detect water voles at core sites. Tracking provides the best evidence that water voles are present at peripheral sites even though they may not be breeding or entering traps.