Assessment of wild living beaver populations on the River Exe and River Taw.
Abstract
Following increasing reports of wild beavers (Castor fiber) in both the River Exe and River Taw catchments, Devon, UK, Natural England commissioned a survey of beaver activity within these catchments. These surveys were undertaken during February-April 2023 on foot and canoe. These surveys covered 260 km of channel length in total: 182 km on the Taw and 78 km on the Exe. These areas covered sections of significant tributaries and headwaters on the River Mole, the Little Dart, River Dart, River Clyst and River Culm. Less than half of landowners contacted gave permission for access. Out of the originally identified target of 163 km of river that had been identified for survey, access was not available for 43 km (26%). Survey from a canoe was used as far as possible but the majority of both these catchments were not suitable for canoe access. Based upon local knowledge and public reports the survey team expanded the project remit to cover a total of 258 km (based upon this expanded scope this resulted in closer to 17% not being available for survey). A total of 418 Beaver field signs were recorded, with cut wood being the most common. Across both catchments, beaver activity was fairly concentrated in the mid- to lower-main river stems. Only three lodges and three burrows were found, given high water levels during the majority of the survey. Old and aged field signs were recorded, with coppice aging indicating at least a minimum age of 3-4 years in some parts. Damming throughout the catchments was low, but where found occurred in distinct clusters in clearly active territories. Populations in both catchments were presumed to be small and mobile given the field signs detected, with dispersing individuals not all settled into breeding territories. An estimated six active territories and further two areas of activity with at least a single individual were estimated for the River Exe and estimated population range of 14-25 individuals before this year's kit emergence. An estimated four active territories and further six areas of activity with at least a single individual were estimated for the River Taw and estimated population range of 10-22 individuals before this year's emergence of kits. Very few management impacts were observed, most likely due to such small populations and the populations being in the early establishment phase.