River Frome Dorset UK – Mute Swan

July 2014

The Solway Firth (54°45’N, 03°40’W) is a large coastal area consisting of estuaries, intertidal sediments and saltmarshes, fed by nine major freshwater inputs. In terms of the shellfish assemblage, the key species of interest to fishermen are cockles (Cerastoderma edule L.), whilst shorebirds consume cockles, mussels (Mytilus edulis L.) and Baltic tellin (Macoma balthica L.) (Howell et al., 2007). The area is of high importance for shorebird conservation, supporting internationally significant populations of many species. As a consequence of its importance for shorebird conservation, the Solway Firth has been designated as a Special Protection Area (SPA), Site of Special Scientific Interest (SSSI) and Ramsar site. The Solway estuary is recognised as a site of international importance for both Eurasian oystercatcher (Haematopus ostralegus L.) and red knot (Calidris canutus L.), supporting the second and tenth largest populations respectively, within the UK (Holt et al., 2012).

Issues

Effective wildlife management is needed for conservation, economic and human well-being objectives. However, traditional population control methods are frequently ineffective, unpopular with stakeholders, may affect non-target species, and can be both expensive and impractical to implement. New methods which address these issues and offer effective wildlife management are required.

Modelling

We used an individual-based model to predict the efficacy of a sacrificial feeding area in preventing grazing damage by mute swans (Cygnus olor) to adjacent river vegetation of high conservation and economic value. The accuracy of model predictions was assessed by a comparison with observed field data, whilst prediction robustness was evaluated using a sensitivity analysis. We used repeated simulations to evaluate how the efficacy of the sacrificial feeding area was regulated by (i) food quantity, (ii) food quality, and (iii) the functional response of the forager. Our model gave accurate predictions of aquatic plant biomass, carrying capacity, swan mortality, swan foraging effort, and river use.

Results

Our model predicted that increased sacrificial feeding area food quantity and quality would prevent the depletion of aquatic plant biomass by swans. When the functional response for vegetation in the sacrificial feeding area was increased, the food quantity and quality in the sacrificial feeding area required to protect adjacent aquatic plants were reduced. Our study demonstrates how the insights of behavioural ecology can be used to inform wildlife management. The principles that underpin our model predictions are likely to be valid across a range of different resource-consumer interactions, emphasising the generality of our approach to the evaluation of strategies for resolving wildlife management problems.

Funding and Collaboration

Centre for Ecology & Hydrology Algorithm (Grant Number NEC3579; Natural Environment Research Council)

Related Paper:

Wood, K.A., Stillman, R.A., Daunt, F. & O’Hare, M.T. (2014). Can sacrificial feeding areas protect plants from herbivore grazing? Using behavioural ecology to inform wildlife management. PLOS One, 9, e104034, doi: 10.1371/journal.pone.0104034