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PRESSURES ON WILDLIFE – CONFLICTS AND ECOLOGICAL DEBATES Birkbeck Institute of Environment, University of London in conjunction with the Ecology and Conservation

Studies Society and the Linnean Society of London

‘Invasive grey squirrels threaten red squirrels: can anything be done?’ Prof J. Gurnell, Queen Mary, University of London.

8 March 2013  

Slide 1 

Invasive grey squirrels threaten red squirrels: can anything be done?

John Gurnell

…or can the British red squirrel be saved?

Slide 2 

1. Introduction –grey squirrels as an introduced species

2. Why do grey squirrels replace red squirrels?

3. Currently, what is being done in Britain

4. The European dimension

5. The future

Slide 3 

1. Introduction –grey squirrels as an introduced species

Slide 4 

Grey squirrel introductions

Italy

1948

Ireland

1911

Melbourne

1880

England

1876

Cape Town

1900

Vancouv er Island

1909

Slide 5 

Type Species No.

introduction

Established -Slight

Increase

Established -Large

increaseTree squirrels Sciurus anomalus 1 1

Sciurus carolinensis 74 6 53Sciurus niger 44 2 37Sciurus vulgaris 10 2 8Sciurus aureogaster 1 1Sciurus aberti 14 12Tamasciurus hudsonicus 10 10Callosciurus erythraeus 21 3 14Callosciurus finlaysonii 3 3Funambulus pennanti 3 2

Flying squirrel Glaucomys spp. 2Ground squirrels Atlantoxerus getulus 3 1

Spermophilus beecheyi 2Spermophilus fulvus 4 4Spermophilus parryii 5 4Spermophilus major 2 2Sciurotamias davidianus 1 1

Chipmunks Tamias striatus 8 6 1Tamias sibiricus 38 27Tamias townsendii 2 1

Worldwide squirrel introductions

Bertolino 2009

Slide 6 

Red squirrel

Handbook of British Mamm als 2008

Slide 7 

Grey squirrel

Gurnell, Lurz & Wauters 2012

1930 2012

Slide 8 

1930

points of introduction

33 known introductions and translocations between 1876 - early 1900s

Grey squirrels in the British Isles

1892 1919

18761911

1913

1890-1918

Rate of spread

• ~ 3 km/year (e.g. in Ireland)

• Can spread up to 14 km in a year.

• Spread has been described as Random dispersal with occasional major advances

(Williamson et al. 1986)

Shorten 1954  

Slide 9 

• Ecosystems;• Loss of native red squirrels;

• Damage to trees;

• ? Declines in birds ?

• Nuisance problems;• Damage to gardens plants;

• Damage to property.

Impacts of grey squirrels

Slide 10 

2. Why do grey squirrels replace red squirrels?

• A bit of background biology

• Theories

Slide 11 

The two species

Lurz 2010

Slide 12 

Squirrel breedingNOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV

MATING MATING

BIRTHS BIRTHS

JUVENILES JUVENILES

If food conditions (tree seed crop, including cached seed) poor, this

breeding pulse is reduced or skipped altogether.

Spring litters Summer litters

If food conditions (tree seed crop, including cached seed) good, some

females will produce 2 litters.

Gurnell 1987  

Slide 13 

Inter-annual cycles in numbers

Gurnell 1987

Slide 14 

Diet

Forestry Commission Scotland 2012

Up to 77% of changes from one year to the next can be explained by the availability of tree seeds - with the severity in winter weather also playing a part. Gurnell (1996)

Slide 15 

• Two species with ‘identical’ ecological requirements cannot coexist at the same time in the same place - the more efficient species will always outcompete the less efficient species for the resources they both require.

• The difference in efficiency does not have to be very large to be effective;

• Competition at the individual level is translated into population effects.

Theory - the red-grey squirrel problem is a classic tale of competition.

Slide 16 

Aggression between red squirrels and grey squirrels?

Studies in N. England and Italy

Wauters et al. 1999, 2000, 2005 

Slide 17 

Overall,

• No aggression between reds and greys

• No difference in space use in time or space

• No reduction in foraging behaviour andenergetics of reds whether greys were present or not.

• No differences in survival rate of adult red squirrels whether greys were present or not.

…but there are differences…

Slide 18 

Female breeding

0

10

20

30

40

50

60

70

Red-only Red-grey

Site

% f

em

ale

s la

cta

tin

g '

Spring

Summer

Mean of two sites of each type

p = 0.11

p=0.006

0102030405060708090

0 1 2

Female reds that produced n litters

Per

cent

Red-only

Red-grey

p=0.03

from Lurz 2010

Wauters et al. 1999, 2000, 2005

Slide 19 

JUVENILE RECRUITMENT(Number recruited of numberborn)

Foot

Len

gth

(m

m)

CountrySite

EnglandItalyRed-greyRed-onlyRed-greyRed-only

58.0

57.5

57.0

56.5

56.0

55.5

55.0

DEVELOPMEN TAL GROWTH OF RED SQUIRRELS

Juvenile recruitment and growth

% J

uve

nile

s R

ecru

ited

CountrySite

EnglandItalyRed-greyRed-onlyRed-greyRed-only

50

40

30

20

10

0

JUVENILE RECRUITMENT

from Lurz 2010

Wauters et al. 1999, 2000, 2005 

Slide 20 

Social hierarchies and dispersal

During the autumn at time of tree seed dispersal:

Reorganisation of the population:

Many animals will disperse, especially juveniles, some will be recruited – young red squirrels lose out.

Slide 21 

In addition to the presence of the alien invader, there is another problem….

………………………disease

Slide 22 

Squirrelpoxvirus infection

invariably lethal to reds within two weeks

carried by greys with no ill-effects – reservoir host

prevalence in grey squirrel populations 40%-80%

grey squirrels in England carry the virus; the grey squirrels in Scotland and Ireland did not until recently – so far they do not in Italy.

Slide 23 

Red decline is faster where the virus is present in grey squirrels

In Cumbria and Norfolk reds disappear 17-25 times faster than in Scotland and Italy, where there was/is no pox virus

Rushton et al. 2006

Slide 24 

Anglesey • Area - 714 km2

• Separated from mainland by Menai Strait

• Narrowest separation - 250 m

• Two bridges connect to mainland

In 1998

~ 40 red squirrels

In 1998

Large number of grey squirrels throughout island

2004-2007

• Red squirrel reintroduction

Slide 25 

But….

• Grey squirrels sti ll immigrate to the island:

So…maybe Anglesey behaves not as an ‘island’ but as a ‘peninsular’

• Money for interventions – short-term – no guarantees ………….if it ‘runs’ out

………the recovery could unravel in just a few years

Grey squirrels successfully removed by 2010 and red squirrel populations reinforced by reintroductions, despite problems with adenovirus infection

Craig Shuttleworth, pers. comm.  

Slide 26 

But…but…

In 2008, the first red squirrel crossed the Menai Straits and colonised woodland on the mainland.

In 2012 red squirrels were found breeding near within a few hundred metres of the Britannia Bridge, and grey squirrel control will be implemented in Gwynedd to try and protect these red squirrels.

Work carried out with the British Association for Shooting and Conservation, BASC

© BASC© BASC

Slide 27 

3. Currently, what is being done in Britain?

• Monitoring

• Local groups

• National initiatives

Slide 28 

Squirrel Groups/Projects in Wales

• Friends of Anglesey Red Squirrels

• Clocaenog Red Squirrel Project

• Mid Wales Red Squirrel Project

Squirrel Groups/Projects in Scotland:

• Ay rshire Red Squirrel Group

• Angus Squirrel Group

• Cowal Red Squirrel Group

• Dundee Red Squirrel Project

• Fif e Red Squirrel Group

• Grampian Squirrel Group

• Highland Red Squirrel Group

• Perth & Kinross Squirrel Group

• Red Squirrels in South Scotland

Squirrel Groups/Projects in England

• Red Squirrel Surv iv al Trust (RSST) – National Charity

• Sav e Our Squirrels (Red Alert North England)

• Northern Red Squirrels (NRS) – Umbrella group f or v olunteer red squirrel groups in the North of England

• 35 Local groups

• 22 Sub-groups

• Examples:

• Penrith & District Squirrel Group

• Grasmere Red Squirrel Group

• Arnside & Silv erdale Red Squirrel Group

• Morpeth Red Squirrels

• Ponteland Red Squirrels

• Westmorland Red Squirrel Society

• Formby (National Trust) Red Squirrels

• Isle of Wight Red Squirrel Project

Local Groups – Community Involvement

Slide 29 

UK Red Squirrel Group (UKRSG)

• Natur al England (NE, for mally English Natur e)

• Scottish Squirrel Gr oup, Scottish Natural Her itage

• England Squirr el For um (ESF), For estry Commission (England)

• Wales Squirr el For um, Countr yside Council for Wales (CCW)

• Joint Natur e Conservation Committee (JNCC)

• For est Resear ch, For estry Commission (FC)

• Nor ther n Ir eland Squirr el For um, Envir onment & Heritage Service(Nor ther n Ir eland)

• Scottish Squirrel Gr oup, For estry Commission (Scotland)

• Depar tment of Agricultur e and Rur al Development, Norther n Ir eland

• Wildlife Tr usts Other organisations

• Red Squirrels North England (RSNE) Projec t

• Red Squirrel Survi val Trus t (RSST) – Nati onal C harity

• Forestr y Commission (FC)

• Natural England (NE)

• Wildlife Trusts

• Scottish Squirrel Sur vey (SSS)

• European Squirrel Initi ati ve (ESI)

• British Associ ation for Shooting and C onser vation (BASC)

National Groups

Slide 30 

Three issues:

• Resources

• Grey squirrels spreading out

• Disease in red squirrels

Disease – increase rate of spread

Control – decrease rate of spread

Rate of spread

of greys

Slide 31 

RESOURCES - the official policy is to target resources on red squirrel refuge areas or red squirrel strongholds

• Area exclusion strategy

• Forest management

Scotland

Slide 32 

Partnership between Scottish Wildlife Trust (SWT), Scottish Natural Heritage (SNH), Forestry Commission Scotland (FCS) and the Scottish Rural Property and Business Association (SRPBA) and supported by the Scottish Government.

Slide 33 

Slide 34 

KielderForest Predicted Red squirrel

population size inKielder:

Current: 8248 ± 557

2015: 9402 ± 552

2025 8921 ± 596

Slide 35 

From modelling studies:

Pox is unlikely to spread through the whole of the system; current knowledge suggests it will ‘burn out’

Although disease outbreaks could cause hundreds of red squirrel deaths at the edges of the forest

Rushton, Lurz, Shirley& Gurnell

Kielder - concerns about grey squirrels and disease

Slide 36 

Control• Grey squirrel control strategy is not the same for both tree damage prevention and red squirrel conservation

• Strategy for controlling resident squirrels may not be the same as controlling itinerant squirrels

Kill trapping, e.g. Fenn, Kaniatraps;

Shooting;

Live trapping,

Poison;

Immunocontraception

Integrated management.

Slide 37 

4. The European Dimension

Slide 38 

Predicted grey squirrel spread in Italy to 2095

Collaborati ve projec t between Newcastle Uni versity and the Uni versity of Turin; funded by ESI

France

Switzerland

Italy

Slide 39 

• monitor the current distribution and relative densities of the different grey squirrel populations actually present in North Italy;

• execute eradication and control programmes, as foreseen in a national and regional legal framework, and investigating their success-rate

• develop an efficient public-relations campaign using both traditional and modern media, at the national, regional and local level (the areas where animals will be trapped), essential to obtain a wide consensus of the civic society.

EC-SQUARE PROJECT

Actions

ITALY

Slide 40 

ITALY

January 2013 -Ministerial decree signed by Ministers of the Environment, Agriculture and Economic Development – prohibits the trade in Grey, Pallas and Fox squirrels

LIFE project ECSQUARE

Slide 41 

5. The future

• Will red squirrels disappear from the mainland, if so when?

• Will interventions ‘save the day ’?

• Eradication/ reduction/control

• Disease

• Introductions

• Ireland

• Back to answer the question!

Slide 42 

Will red squirrels disappear altogether, if so when?

Based on current information, recent studies suggest:

Within 15 years – northern England

Within 40 years – central and southern Scotland.

Within 80 years – NE ScotlandGurnell, Lurz & Bertolino unpubl.

Slide 43 

Interventions

Slide 44 

Eradicate or control?

Based on Blackburn, T.M., Pyaek, P., Bacher, S., Carlton, J.T ., Duncan, R.P., Jaroaík, V.c ., Wilson, J.R.U., Richardson, D.M., 2011, A proposed unified framework for biological invasions. Trends in ecol ogy & evolution (Personal edition) 26, 333-339.

Slide 45 

Lawton & Rochford 1997

Grey squirrel populations recover within 10 weeks after removal

Cull

Cull

Slide 46 

Disease

Vaccine development

(Moredun Institute)

Control grey squirrels

Candidate vaccines developed

- await testing 

Slide 47 

If vaccine is developed – how is it to be delivered?

Slide 48 

“Wildlife reintroductions proceed from a seductively simple assumption: by releasing individuals of a species into a suitable habitat it is possible to restore natural biodiversity.” Seddon (1999)

Reintroduction/translocation/restoration

Examples:

Thetford, East Anglia - 1990s – failed, greys present

Anglesey - 2000s – success, greys removed

Ireland – 2000s – success, no greys

Cornwall, East Anglia - yet to be carried out

Slide 49 

Ireland

The Irish Squirrel Survey 2007

Slide 50 

So…

1) There is the potential to slow down rate of spread of grey squirrel and even reverse trend in parts of the mainland

2) Island populations valuable – Isle of Wight, Anglesey, Arran.

3) Peninsular populations?

4) So far we do not have the knowledge or techniques to effectively eradicate grey squirrels or prevent the spread of disease.

5) Resources required to achieve (1-3) and R&D (4) will be large – they are insufficient at present.

Slide 51 

Yes!…will be restricted to particular locations

…will require constant supply of resources

“…conservation is primarily not about biology but about people and the choices they make.”

Balmf ord & Cowling 2006

Of course:

To answer the question, “Can red squirrels be saved?”

Slide 52 

Acknowledgements

Tullie House Museum, Cumbria Wildlif e Trust , Northumberland Wildl ife Trust, Yorkshire Mammal Society , Forestry Commission Kield er Fo rest District, Red Squirrels in South Scot land, Scottish Wildl ife Trust,Westmorland Squirrel Group, Ian Court,  Neville Geddes, Tom Dearnley, Karen Ramoo,  Mel Tonkin , Ian Mackenzie, Steve Hewitt , Teresa Frost, John Ray, Geoff Oxford, Christin eWesterback and Simon O’Hare

Peter Lurz, Sandro Bertoloni, Luc Wauters.

THE END

Hopefully Not!

Ambr ogrio Molinari