JG talk Birkbeck 080313 - Home — Birkbeck, University of …€¦ · · 2016-12-08Birkbeck...
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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