BBOWT Water Vole Recovery Project

Home , Foudry Brook, River Chess, River Misbourne

Berks, Bucks and Oxon Water Vole Recovery Project

2016 Report

Water vole carrying food for young, Chris Hughes, River Windrush

Julia Lofthouse, Mammal Project Officer

Gavin Bennett, Mammal Project Assistant

Contents

1 Introduction

2 Water Vole Surveys

Survey Methodology Survey Participants Survey Results

3 Mink Control

Background Information Mink Control Results 2015- 2016 Analysis of Mink Control Schemes

4 Alert Maps and Local Key Areas 2017

5 Water Vole Recovery Project Updates 2016

Bayswater Brook Ewelme Stream and River Thames Great Ouse and Padbury Brook Holy Brook and Sulham Brook Hurst Ditches Kennet & Avon Canal Lower River Kennet, Foudry Brook and River Thames at Sonning Lower River Windrush Mill Brook Oxford Canal River Alderbourne River Glyme and River Dorn River Ock, Sandford Brook and River Stert Upper Thames

1 Introduction

The water vole Arvicola amphibius is Britain’s fastest declining mammal which has been lost from approximately 89% of its former range since 1900. In the 1950s-60s changes in river engineering practices and agricultural intensification caused the water vole population to decline. These changes resulted in habitat loss and degradation which caused fragmentation and isolation of water vole populations. Since the 1980s an introduced predator, the American mink Neovison vison has decimated water vole populations as its range has expanded throughout England, Scotland and Wales. Mink are able to counter the water voles’ anti-predatory behaviours since they swim well, hunt efficiently and female mink are small enough to enter water voles’ burrows.

The Berks, Bucks and Oxon Wildlife Trust launched its Water Vole Recovery Project in 1998. The aim of the project was to arrest the decline of water voles within the three counties and to work to stabilise and increase the water vole population. A three year baseline survey was conducted 1998- 2001 during which the project established the location of many breeding colonies of water voles. These sites were designated Local Key Areas for water voles. Local Key Areas are monitored on a regular basis through a rolling survey programme. The areas are revised following annual survey results in line with criterion in use by the National Water Vole Mapping Project. This criterion designates Local Key Area boundaries based on the past five year’s survey results. Map 1 shows the Local Key Areas in 2016.

2 Water Vole Surveys

Survey Methodology

Surveys were completed using the standard methodology outlined in the Water Vole Conservation Handbook1. Survey stretches were approximately 500m in length, where possible located between visible landmarks to ease location of the start and end points of each section.

All surveys were completed using a standard form which included information on the following points:

 Habitat type  Shore/ bank substrate  Channel morphology  Management including grazing and level of disturbance  Bankside vegetation (using the DAFORN scale)  Adjacent land use  Water vole field signs tally chart  Otter, mink, brown rat field signs presence or absence  Detailed sketch map indicating the locations of any water vole, otter, mink and brown rat activity

All surveyors attended a training day where they were taught to identify field signs of water voles and other riparian mammals and to complete the survey form. Each surveyor received a copy of the survey methodology guidelines and a risk assessment for surveying. Surveys were conducted from the bankside only unless water levels were below wellington boot height when wading in channel was permitted. Only volunteers who had received specific training and equipment were permitted to use waders to complete surveys. Most surveys were completed between 1st April and 31st July 2016 to allow time for collation of results. Surveyors were asked to make every effort to ensure that they surveyed the entire section in order to accurately report on the status of the water vole at their allocated sites. However where vegetation was dense or banks were steep with limited access some field signs may inevitably have been overlooked.

1Strachan, R and Moorhouse, T (2006) Water Vole Conservation Handbook: Second Edition. Wildlife and Conservation Research Unit, Oxford University

Survey Participants

Prior to the survey the landowner was contacted by the either the Project Officer or the volunteer surveyor to request access permission. Surveys were not completed on land where access was denied. A summary of the number of surveys completed by the Water Vole Recovery Project in 2016 is contained in Table 1.

Table 1: Summary of participants in the 2016 water vole survey

Number of Surveys Project Officer 43 Project Assistant 157 Volunteer Surveyors 79 BBOWT’s Conservation Trainee Team 85 Total 364

A total of 364 sections of watercourse were surveyed. 35 Water Vole Recovery Project surveyors participated.

Survey Results

Each survey section was classified as positive or negative depending on whether or not reliable water vole field signs were recorded. An overview of the location and results of these surveys are shown in Map 2 and a summary of the number of surveys completed on each watercourse is contained in Table 2 along with an indication of when the most recent comprehensive survey of the watercourse was undertaken prior to 2016.

Trends in water vole activity over the short-term and long-term were also assessed for each watercourse surveyed. Trends were derived by comparing the number and extent of positive and negative surveys conducted. To assess the short-term trend surveys conducted were compared with the most recent survey previously conducted on the watercourse. If water voles were identified on stretches where they had not been recorded during the previous survey, voles were considered to have expanded their range. Conversely if voles were not identified on a stretch where they were previously recorded, this was considered to be a decline. A population was considered stable when no change in the number or extent of positive and negative surveys was observed. Where water voles were not found to be present the trend was recorded as ‘None’ and where insufficient data was available to make an assessment the trend was recorded as ‘Unknown’. The same criteria was used to assess the long-term trends on each watercourse except survey results were compared with all previous surveys conducted by the project over the years.

Further details of the 2016 water vole survey results on each watercourse and a comparison of survey results in previous years can be found in the project updates.

Table 2: Summary of the 2016 water vole survey results and population trends

+ denotes an increase in water vole population - denotes a decline in water vole population = denotes no change in water vole population o denotes no water voles present or insufficient data to assess trend

Watercourse Surveys

Positive Negative Total Previous Short- Long- Survey term term

River Kennet 4 10 14 2015 + =

Kennet & Avon Canal 15 30 45 2015 - -

Holy Brook 1 5 6 2015 - -

Foudry Brook 0 4 4 2008 o -

Hurst Ditches 0 3 3 2015 - -

Sulham Brook 0 2 2 2014 - -

River Thames at Sonning 0 4 4 - o o

Great Ouse 0 4 4 2014 = +

Padbury Brook 0 2 2 - o o

River Chess 1 0 1 2015 - -

River Misbourne 0 1 1 2015 = +

River Alderbourne 0 6 6 - o o

Black Bourton Brook 0 5 5 - o o

Clanfield Brook 3 2 5 2013 + -

Great Brook 11 3 14 2013 + o

Highmoor Brook 2 0 2 - o o

Norton Ditch 0 5 5 - o o

Shill Brook 24 10 34 2013 + o

Wadley Stream 2 2 4 - o o

River Ock 15 21 36 2013 = =

Sandford Brook 12 8 20 2013 = =

Bayswater Brook 0 7 7 2013 - -

Oxford Canal 6 16 22 2015 - =

River Dorn 0 7 7 2013 - -

River Glyme 0 32 32 2013 - -

River Stert 3 7 10 2013 = =

Radley Brook 0 2 2 2015 - -

River Thames at Wallingford 0 4 4 - o o

Ewelme Stream 0 2 2 2015 - -

Ginge Brook 0 1 1 2015 - -

Mill Brook 11 7 18 2014 + +

Lower River Windrush 37 5 42 2013 + +

Total 147 217 364 3 Alert Maps and Local Key Areas 2017

Updated water vole alert maps and Local Key Area maps have been produced based on 2016 survey results and in line with criterion in use by the National Water Vole Mapping Project. Alert maps may be used by Local Authorities so that planners can identify the location of water voles vulnerable to development pressures. The trends in Local Key Areas was also analysed to determine whether each area was declining, stable or increasing. Map 3 shows the short term trend for each Local Key Area based on whether the area had declined increased or remained stable from the previous year. Map 4 shows the long term trend for each Local Key Area which compared the size of the most recently designated Local Key Area to that of previous years.

Map 6 shows the updated Local Key Areas designated for 2017. The Water Vole Recovery Project will focus its activities including surveying and monitoring of water voles, development and co- ordination of mink control and the provision of habitat management and enhancement advice within and around these areas in 2017.

4 Mink Control

Background Information

The Water Vole Recovery Project recognises the need for monitoring and control of American mink to protect water vole populations from predation and advocates the humane control of mink in line with the Wildlife Trust’s Mink Control Policy. The project promotes the use of mink rafts devised by the Game and Wildlife Conservation Trust (formerly the Game Conservancy Trust) installed at 1km intervals along a watercourse as this strategy has proven extremely effective at detecting and trapping mink enabling them to be removed from entire sub-catchments. The use of mink rafts ensures that traps are only set when mink have been positively identified in an area. They therefore reduce the effort required in checking routinely set live-capture traps and also minimise the risk of trapping non-target species. Since 2004 BBOWT’s Water Vole Recovery Project has been developing mink raft schemes along watercourses in the three counties in order to protect known water vole colonies from predation.

Mink Control Results

The results of mink control undertaken July 2015 to June 2016 have been collated in Table 3 overleaf. Further details of the mink control scheme on each watercourse and details of mink capture records submitted to the project for 2015- 2016 can be found in the project updates.

A total of 61 mink were trapped and dispatched between July 2015 and June 2016 consisting of 13 females, 11 males and 37 of unspecified gender. Map 5 shows an overview of mink control and mink captures for this period in relation to water vole Local Key Areas.

Table 3: Summary of mink control schemes co-ordinated by the Water Vole Recovery Project, Partner Organisations and Landowners July 2015- June 2016

l Brook l

tcombeBrook

ngstoneBrook

ChildreyBrook Collegelake DintonPastures EwelmeStream Brook Great BrookHoly KennetAvon & Canal Ki Le MoorDitch OxfordCanal RadleyBrook RiverChess RiverCole RiverColne RiverGlyme RiverKennet RiverLambourn RiverLoddon RiverMisbourne RiverPang RiverRay RiverThames RiverWindrush SandfordBrook Shil Wilts Berks & Canal RiverGreat Ouse Total

BulstakeStream

Number of 1 1 2 4 1 1 3 2 1 1 1 7 1 3 9 5 5 27 7 2 4 3 8 10 18 1 3 1 8 136 rafts/traps

Number of 1 1 1 1 1 1 1 2 1 1 1 2 1 3 1 3 5 11 3 1 3 2 2 8 8 1 3 1 2 70 landowners

Number of landowners 1 1 1 1 1 1 1 2 1 1 1 2 1 3 1 3 5 10 3 1 3 2 2 7 7 1 3 1 2 67 providing data

Total Mink 0 0 1 9 0 0 0 0 0 0 0 0 0 0 0 0 0 30 0 1 0 0 7 13 0 0 0 0 0 61 Trapped Analysis of Mink Control Schemes

Based on a model strategy of one raft installed every kilometre of waterway, the percentage proportion of each LKA defended during 2016 was calculated. Levels of mink monitoring and control were then categorised using the scale outlined in Table 4 below. Factors such as distribution of mink rafts and configuration of watercourses were not taken into account in this assessment.

Table 4. Levels of mink monitoring and control

% Proportion of LKA defended Level of mink monitoring and control

0 None 1- 25 Low 26- 50 Medium 51- 100 High

With the exception of the River Lambourn, all LKAs assessed as having a medium or high level of mink monitoring and control (i.e. greater than 26% defended) were found to have stable or increasing water vole populations in the long term. All except the Middle Kennet also had stable or increasing water vole populations in the short-term although care should be exercised in interpreting this data since water vole populations will experience natural fluctuations in numbers. Issues other than mink predation may have contributed to the long-term decline of water voles on the River Lambourn where there is only a small population of water voles present and the river is a winterbourne through part of the LKA.

Most LKAs with low levels of mink monitoring and control showed long-term decline of water voles, the two exceptions being Abingdon and the Mill Brook. Abingdon LKA is extensive and the discovery of new populations of water voles on previously unsurveyed watercourses within the area may have contributed to the apparent stabilisation of water vole numbers. The complex network of waterways within the LKA may also offer water voles better protection from dispersing mink. Water voles on the Mill Brook have suffered mink predation in recent years and, following their near extinction, the water vole population is now expanding despite a current lack of mink monitoring and control.

These results suggest that medium levels of mink monitoring and control, with 26% or more of the LKA protected, are necessary to ensure that water vole populations remain stable or increase in the long-term. Experiences on the River Kennet suggest that this level of effort needs to be maintained in order to protect water vole populations. These results can be used to strategically plan future mink control by the Berkshire, Buckinghamshire and Oxfordshire Water Vole Recovery Project and the following recommendations are made:

 The project should aim for medium or high levels of mink monitoring and control within each LKA with a minimum of 26% of the area defended

 Medium or high levels of mink monitoring and control should be maintained in the long-term

Based on these recommendations, target numbers of additional mink rafts to be deployed in each LKA in order to achieve a 26% defence of the area is summarised in Table 5 overleaf. The degree to which these targets can be achieved in practice will be dependent upon landowner co-operation and finding volunteers to monitor rafts and dispatch trapped mink. Other constraints such as the presence of suitable sites to install rafts and project funds will also have a bearing on these targets being met on the ground.

Table 5. Target numbers of additional mink rafts in LKAs in 2017

Current Target mink number Local Key Area Comments monitoring additional and control rafts

Bayswater Largely unsuitable for mink control. No water voles at last None 4 Brook survey

Largely unsuitable for mink control. No water voles at last Hurst None 7 survey

Water voles recovering after mink predation. Needs renewed Mill Brook None 6 efforts to identify mink control sites Extensive Local Key Area. Some sites unsuitable for mink Abingdon Low 47 control although still scope to develop existing scheme further River Cole and Working to develop further mink control in conjunction with Low 17 River Thames RSPB Working to re-establish mink control scheme in conjunction River Chess Low 3 with the Chilterns Chalk Stream Project and River Chess Association Additional mink rafts should be installed on Canal & River Oxford Canal Low 4 Trust land now that dispatch has been approved

Current efforts focused around small existing water vole Theale Low 3 population. Scope to develop scheme on nearby waterbodies

Needs renewed efforts to establish mink control through River Glyme Low 1 Glympton Estate. No water voles at last survey

Largely unsuitable for mink control. No water voles at last Ewelme Stream Low 1 survey

Renewed efforts to resurrect mink control scheme in recent Middle Kennet Medium 0 years have been successful Scheme has recently been developed in conjunction with River Misbourne Medium 0 Herts & Middlesex WT. Scope for development through enhancement project Lower river well defended in conjunction with Lower River Windrush Medium 0 Windrush Valley Project

Great Ouse Medium 0 Site currently well defended by local landowners

Site currently well defended although work needed to River Lambourn High 0 improve distribution of rafts throughout the Local Key Area

Any opportunities to develop mink control schemes within and around LKAs should be taken but it is suggested that in 2017 the project should focus efforts on improving mink monitoring and control in LKAs with current low levels of protection and where water voles are still known to be present. The following sites should therefore be prioritised for establishing or expanding mink control schemes:

 Mill Brook  Abingdon  River Cole and Thames  River Chess  Oxford Canal  Theale

Map 1. Water vole Local Key Areas 2016

Text Abingdon Local Key Area K Bayswater Brook Local Key Area Ewelme Stream Local key Area Great Ouse Local Key Area Hurst Local Key Area

Oxfordshire Middle Kennet Local Key Area Buckinghamshire Mill Brook Local Key Area Oxford Canal Local Key Area River Chess Local Key Area Text River Cole and Thames Local Key Area River Glyme Local Key Area River Lambourn Local Key Area River Misbourne Local key Area River Windrush Local Key Area Theale Local Key Area

Berkshire

0 5 10 20 30 40 50 Kilometers Ordnance Survey © Crown Copyright and database right 2016. All rights reserved. License number 100050351. Aerial Photos ©Infoterra Ltd. 2010 and © GetMapping Plc. 2015. Contains public sector information licensed under the Open Government Licence v2.0. Map 2. Water vole surveys 2016 overview

Text Negative water vole survey K Positive water vole survey Unsurveyed Local Key Areas 2016 Watercourses

Oxfordshire Buckinghamshire

Text

Berkshire

Text Local Key Area Declining K Local Key Area Stable Local Key Area Increasing

Oxfordshire Buckinghamshire

Text

Berkshire

Text Local Key Area Declining K Local Key Area Stable Local Key Area Increasing

Oxfordshire Buckinghamshire

Text

Berkshire

(! 0 mink trapped .! 1 mink trapped !. 2 mink trapped K .! 3 mink trapped (! (!(!(!(!(!(! .! 4 mink trapped .! 5 mink trapped Oxfordshire 7 Mink Trapped (! Buckinghamshire .! (! Abingdon Local Key Area ! (!(! ((! (! (! Bayswater Brook Local Key Area (! (! (! Ewelme Stream Local key Area (! .!( (!(!(!(! .!(! (!(!(! (!(!(! Great Ouse Local Key Area (!(!(! ! Hurst Local Key Area ( (!(!(! (!(! ! (! (! (! (! Middle Kennet Local Key Area (! (! (!(!(! .! (! Mill Brook Local Key Area .!.! (!(! (! Oxford Canal Local Key Area (! .! .! River Chess Local Key Area (! (! (! (! (! (! (! (! River Cole and Thames Local Key Area (! ( (! (!! (! (! ((!(! (! River Glyme Local Key Area (! (! (! River Lambourn Local Key Area River Misbourne Local key Area (! (! River Windrush Local Key Area (!(! .!(! (!(! Berkshire (! !. Theale Local Key Area (!(! (!(!(! .!.! .!!.(! (! Watercourses .!(!!..!.!.! ! (! .! .!.!(( (!(!(!(!(!(! .! (! County Boundaries

0 5 10 20 30 40 50 Kilometers

Ordnance Survey © Crown Copyright and database right 2016. All rights reserved. License number 100050351. Aerial Photos ©Infoterra Ltd. 2010 and © GetMapping Plc. 2015. Contains public sector information licensed under the Open Government Licence v2.0. Map 6. Water vole Local Key Areas 2017

Text K Abingdon Local Key Area Bayswater Brook Local Key Area Ewelme Stream Local Key Area Great Ouse Local Key Area

Oxfordshire Hurst Local Key Area Buckinghamshire Middle Kennet Local key Area Mill Brook Local Key Area Oxford Canal Local Key Area Text River Chess Local Key Area Upper Thames Local Key Area River Glyme Local Key Area River Lambourn Local Key Area River Misbourne Local Key Area Theale Local Key Area

Berkshire