5 CRISIS methodology - Assessment of grey squirrel
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5 CRISIS methodology - Assessment of grey squirrel control options 5.1 Site selection The project initially focused on grey squirrel control in 10 selected woodland areas in Meath known to have populations of grey squirrels 1 . The location of the pilot woodlands and information on their ownership, area and species distribution are shown in Figure 5.1. The pilot woodland areas vary from pure broadleaf woodlands planted over the last 10-15 years, to mature estate woodlands some of which have been rehabilitated through the Woodland Improvement Scheme in the last 10 years (or a combination of both). Each of the woodlands selected is known to be typical of the kind of woodland present in the Midlands. The level of damage due to grey squirrels varies between the various woodlands and appears to be worst in or in the vicinity of old broadleaf woodland. Squirrel populations also appear to vary considerably between the various pilot woodlands but there is no recorded evidence of red squirrels having been seen at any of the sites over the last 10 years. However, the species is known to have been present in a number of the woodlands in earlier years and its current absence is very likely related the presence of grey squirrels. Subsequent control trials were also carried out in the Coillte owned Donadea Forest Park and at Carton House Golf Club, both in Co. Kildare (see Section 5.3.2); grey squirrels were known to be numerous at both these sites. Donadea, with an area of 230 hectares, is of a much larger scale than the smaller privately owned woodlands selected for the project and is fairly typical of a former demesne-style landscape comprised of mixed woodland. It was initially used as a monitoring site during the course of the project for indexing the general densities of grey squirrels in the country and gathering public opinion on grey squirrel control. Consultation with the local community group indicated little opposition to controlling grey squirrels in Donadea, although most individuals hoped that this would be part of a long-term plan to return red squirrels to the forest. Donadea was subsequently used to test various trap designs (see Section 5.4). 1 The support of Teagasc Farm Foresty Advisor Liam Kelly during the site selection process is hereby acknowledged
Table 5.1 - Summary of project sites for grey squirrel control.
Site Composition Future risk of damage due to
tree species makeup or
proximity to squirrel holding
habitat
Boyd Old estate woodland. Very high overall
Woodland improvement scheme
– Oak, Ash, Sycamore, Alder etc
Farmed block – Oak, Scots Pine
Galvin Old estate woodland. Very high overall
Woodland improvement scheme
– Oak, Ash, Sycamore, Chestnut,
Hornbeam, Willow
Preston Old estate woodland. High in Oak belt
Planted shelter belt – Oak.
Farrell Planted farmland. Blocks of Very high in Sycamore
Sycamore and Ash/Sycamore
mix.
Fanning Planted farmland. Blocks of Ash, High in Sycamore and Oak
Sycamore and Oak.
Finnegan Planted shelter belt on farmland. High in Sycamore
Blocks of Sycamore/Sitka Spruce
mix.
Murray Old broadleaf wood – Partially High overall
felled and subsequently planted
with Oak, Beech, Ash and Alder.
Adjoining block of Douglas Fir,
Sitka Spruce, Cherry and Ash.
Dalgan Planted shelter belt adjoining Very high in shelter belt
remnants of estate woodland.
Blocks of Oak/Ash/Sycamore
mix.
Barry Planted blocks of Ash and Medium to High
Sycamore.
Tracey Planted blocks of Ash and Medium
Sycamore.
Donadea Forest park based in old estate Medium
woodland. Planted blocks of
Norway and Sitka spruce, Ash.
Mature beech and oak
throughout site.
Carton House Woodland surrounding modern Medium
golf course development.
Demesne-style estate with blocks
of mature mixed broadleaf trees.
Small amount of new planting.
Boyd
Finnegan
Galvin
Dalgan
Murray
Farrell Fanning
Preston
Treacy
Barry
Donadea
Forest Park
Carton
House
Figure 5.1 - Locations of project sites for grey squirrel control.
5.2 Damage assessments
A baseline survey of tree species composition, damage frequency and severity of damage was
carried out in each woodland at the start of the project. In order to statistically monitor any
effects that grey squirrel control might have on reducing the level of tree damage, a
standardized sampling method (based on Forest Research Practice Note 001 - Nearest
Neighbour Method for Quantifying Wildlife Damage to Trees in Woodland (Pepper 1998))
for each woodland was adopted, wherein a tree was selected at random and assessed for the
following variables:
• Tree species
• Diameter at breast height (DBH)
• Height
• Damage severity (Scale of 1 to 5; 1 = bark stripped up to size of palm of hand; 5
= majority of bark removed from tree)
The nearest 6 trees to the first tree selected were also assessed, giving a cluster of 7 trees. A
distance of 50 to 100m was then measured along a straight transect through woodland and
another cluster sample taken; this was repeated along parallel transects until at least 20
clusters had been assessed. A diagram covering this method of sampling is shown in Figure
5.2; trees marked in red represent a randomly selected tree, which forms the centre of a seven-
tree cluster, marked in yellow. Arrows represent the set distance paced through the plantation
to ensure a representative sample of the woodland was assessed for damage.
Figure 5.2 - Cluster method for sampling grey squirrel damage in a
woodland
In this way, both the species composition and the level of damage throughout the sites were
assessed. Damage assessments in the project sites took place before any control was applied
therein; further assessments took place in the summers of 2006 and 2007 to measure the
success of any control that had taken place. The findings of these assessments are given in
Section 6.1.
This standardized method was subsequently applied in several other woodlands outside the
initial eleven project sites; these assessments took place in areas where damage was
particularly severe, or where the risk posed to various provenances (oak) needed to be tested.
Sites analysed in this manner were:
• Borris House, Co. Carlow
• Oak Park, Co. Carlow
• Coillte Oak Provenance Trial, Shillelagh, Co. Wicklow
The findings of these are given in Section 6.2.
5.3 Grey squirrel control trials
5.3.1 Warfarin hoppers
The following methodologies were utilized during the course of the project for the control of
grey squirrels via poisoning
5.3.1.1 Warfarin usage
Best practice from the UK as detailed in Mayle et al. (2003) was applied in relation to using
warfarin for grey squirrel control in the project sites. Hoppers with a weighted door were
sourced from Strangford Agencies in Bangor, Northern Ireland. Whole maize, which was
used as a ‘prebait’ was purchased from several distributors including Fane Valley Grains in
Newry, Co. Down and L.E. Animal Feeds in Kilpedder, Co. Wicklow. Warfarin-treated
whole wheat was purchased from Pied Piper Chemicals in Thurles, Co. Tipperary.
A second type of control bait, ‘Eradirat’ was also considered for use. This is a maize-based
compound that contains no active poison and functions through causing lethal dehydration in
rodents. Early trials however found it to exceptionally vulnerable to moisture and clogging in
the hoppers; it was discounted for this reason.
5.3.1.2 Application of warfarin in the field
Hoppers were tested at all sites except Donadea Forest Park and the Barry and Treacy sites;
the same basic method of hopper-based control was applied in each case. Suitable hopper
siting locations were identified; where possible, these were usually in or near grey squirrel
‘holding habitat’, where squirrels are most likely to build dreys, or along likely movement
corridors such as fence or hedgelines. Best practice (again from the UK) for hopper
deployment suggests a hopper density of 1-4 per hectare of woodland and spaced every 200
metres; this was observed wherever possible. Where young plantations occurred in proximity
to grey squirrel ‘holding habitat’ (i.e. established woodland where squirrels are more likely to
build their dreys and/or reproduce), efforts were made to concentrate hoppers in and around
the locations containing mature trees. Examples of the distribution of hoppers on two of the
project sites are shown in Figure 5.3 and Figure 5.4.
Figure 5.3 - Hopper siting points at Dalgan Park, showing an even
distribution in the area of mature woodland. Image © Ordnance Survey
Ireland
Figure 5.4 - Hopper siting points at Fanning site, showing bias towards
areas of sycamore and holding habitat. Image © Ordnance Survey
Ireland
A temporally staggered approach was taken in relation to rolling out control via hoppers in
the project sites; i.e. control did not take place in all sites at the same time. This was in order
to take into account changes in grey squirrel behaviour due to seasonal shifts. This staggering
is depicted in Figure 5.5 as a Gantt chart showing the initiation dates and duration of
prebaiting and active control in the project sites.
Figure 5.5 - Gantt chart reflecting staggered approach to control cycles
( = Prebaiting / = Active Control)
Once hoppers were distributed at each site, a prebait period was initiated. This involved
filling each hopper with whole maize and ‘broadcasting’ further bait on the ground in the
vicinity of the hopper during the pre bait period. No warfarin-treated bait was used at this
stage. Hoppers were then left in-situ for at least ten days, during which period, the levels of
maize therein was monitored. At no point were the hoppers allowed to be fully emptied of
maize. This prebait period ensures maximum exposure of squirrels to the warfarin-treated bait
when it is subsequently added, as animals will already be drawn to the hoppers to feed. An
example of a hopper during prebaiting is shown in Figure 5.6.
Figure 5.6 - Hopper during prebaiting, before and after squirrel feeding
activity
Once the minimum 10 day prebait period had elapsed (assuming that definite signs of feeding
were found at each hopper), the bait at each site was switched for warfarin-coated maize.
Again, levels were monitored in the days following the initiation of this active control.
Usually after several days, the speed of bait uptake would slow and eventually cease,
indicating that all the squirrels feeding from a certain hopper had been eliminated. At this
point, the hoppers were removed from the woodland and set up at a new project site.
Squirrels exposed to sufficiently lethal levels of warfarin usually retreat to their dreys, slip
into unconciousness and die; it is unlikely to find any dead squirrels on the ground, but if any
are, best practice recommends that they be collected and burned. No dead grey squirrels were
located during any poisoning cycle throughout the course of the project.
5.3.2 Trapping
5.3.2.1 Location of trapping trial
The application of trapping for grey squirrel control was tested at Carton House, County
Kildare in April 2007, in association with Mr. Peter Lynch of Waterways and Wildlife
Management. The purpose of this trial was to assess the feasibility of trapping from logistical
standpoints, and to determine the costs involved including labour and equipment. Advice on
trapping methodology was also sought from Mr. Joe Barry, one of the project landowners
who regularly employs grey squirrel trapping successfully in his woodlands.
Carton House estate covers 445 hectares, and includes 3 kilometres of waterways and 100
hectares of diverse mature woodland. The Estate has Special Area of Conservation Status and
is home to many rare species including freshwater lamprey, mollusks, crayfish and the vertigo
snail. Rare plants include Hairy St. John’s Wort and Figworth. Carton is also home to a herd
of red deer, badgers, otters, foxes, owls, buzzards, nightjar, jay, kingfisher, hawks, falcon and
bats. The mature woodland areas comprise a mixture of oak, sycamore, beech, ash and some
conifers; no damage was recorded on any of the mature trees, though it is impossible to
confirm that it does not exist high up in the canopy. Some new planting of beech and oak has
taken place around the estate, but these plantations are currently too young for squirrel
damage to be an issue. Carton was selected for this trial owing to the presence of high
numbers of grey squirrels in the area and for the experience and expertise that Mr. Lynch
could readily provide on-site.
Trapping was focused in two areas of the estate, the ‘Shell Cottage Wood’, to the southeast,
and the ‘American Garden’, adjacent to the original Carton House itself (see Figure 5.7). Both
sites, whilst having excellent access, were reasonably private from golfers and walkers; any
trapping employed therein could therefore be done with the minimum of impact upon the
general public.
Figure 5.7 – Aerial photo of Carton House Estate showing trapping
locations. Image © Ordnance Survey Ireland
5.3.2.2 Trap model and sourcing
A standard mink/squirrel live cage trap was deployed for use during this stage of the project.
These were sourced from Strangford Agencies, Comber, County Down. Traps were built by a
company in the UK entitled ‘The Trap Man’ (Figure 5.8). Twenty eight traps in total were
used during the trapping trial, distributed between the two respective sites. These traps were
subsequently compared to several other designs of live-catch traps at Donadea Forest Park;
see Section 5.4.Figure 5.8 - ‘Trap Man’ mink trap used during project 5.3.2.3 Siting of traps Traps were sited in the two selected trapping areas where they could be easily located by squirrels, but efforts were made to minimize their visibility to passing members of the public. This usually involved setting traps at least 10 metres away from paths and roadways, and on the opposite sides of trees, stumps or other such cover. Where necessary, some camouflage was built around the trap, concealing it from eye level, but leaving it clearly visible from above. Traps were sited at ‘stations’ either singly or in pairs; these stations were located at least 50 metres apart and as evenly throughout each woodland as was possible. 5.3.2.4 Prebaiting No prebaiting per se was carried out during the Carton House trial. This was because it was intended to gather information on the pattern of catches that occurs as squirrels discover traps within their respective ranges. It was expected that no animals would be trapped on the first few days, with numbers caught rising to a peak before falling away again as the majority of animals in area were removed. Ordinarily, some prebaiting before active trapping is recommended as best practice to minimize labour costs.
5.3.2.5 Active trapping Active trapping took place during eight consecutive days in April 2007; traps were set the evening before and checked the next day at around noon. Traps that had not caught any animals were re-baited and reset for the next day if necessary (some may have sprung from being jostled by squirrels from outside, etc.). Traps were checked in the same sequence in the two respective sites to ensure that no traps were overlooked. 5.3.2.6 Dispatch Where an animal was trapped, the same protocol was observed in each case. The trap was moved from its station and placed on the ground. Grey squirrels were humanely dispatched using a .22 rifle with silencer which was fired through the roof of the trap, directly against the head of the animal; trapped squirrels will tend to press themselves into the top corners of a trap, making such a dispatch method the quickest and simplest to apply (see Figure 5.9). Death was instantaneous, following which the door of the trap was levered open and the body tipped from inside. Bodies were then disposed of in the undergrowth for carrion feeders such as foxes and corvids to find. Owing to the nature of the trap, several rats were caught during the course of the trial; these were also dispatched using the same rifle method. A stoat was also caught on one occasion; this animal was quickly released without harm. Upon conclusion of the trial, all traps were removed from the two sites. The findings of this trapping trial are presented in Section 6.4.
Figure 5.9 - Grey squirrel dispatch in trap 5.3.3 Shooting 5.3.3.1 Location of shooting trial An assessment of the labour cost and best practice for grey squirrel control via shooting was tested, again in association with Mr. Peter Lynch, at Carton House and Lyons Estates respectively. Lyons Estate, owned and restored by the late Dr Tony Ryan, consists of almost 250 hectares of woodland, gardens, lakes and stud pasture. Damage by grey squirrels to many imported ornamental trees such as the Dawn Redwood (Metasequoia glyptostroboides) is widespread and severe around the demesne. An ongoing systematic ‘shoot on sight’ policy has been employed by Mr. Lynch on the estate over recent years, which has reduced the occurrence of new damage to some degree. Persistent reinvasion by greys from neighbouring lands necessitates the ongoing control programme. 5.3.3.2 Methodology Shooting took place during April 2007 on both estates. In comparison to the trapping approach, attempts were made to cover the entire woodland areas at both sites via driving around for a minimum of two hours and watching for any signs of squirrel activity. At Carton House Estate, areas which had already been covered by the trapping trial were excluded from
the shooting trial, owing to probable low numbers of squirrels therein. Several ‘laps’ of each site could be made using this method. Driving by its very nature is dependent on the road access to a woodland; it may not be feasible when dealing with large blocks of young plantations. However, the benefits of using a vehicle are twofold; firstly it reduces labour cost resulting from the time taken to walk around large areas of woodland and secondly, grey squirrels are often more accustomed to vehicles and are less likely to run away compared to their reaction to a person on foot. 5.3.3.3 Dispatch The vehicle was brought to a stop upon encountering any grey squirrels on the respective estates and where possible no more than 25 metres from the target animal. A .22 rifle with silencer was then aimed from the car window (see Figure 5.10); this provided stability for the gun and reduced the risk of disturbing the animal. Only a single shot was necessary to dispatch a squirrel in this situation. Such control is best carried out early in the morning, when squirrels are most active and there is less chance of encountering members of the public. Public safety is always a concern when dealing with guns; when using a rifle to dispatch squirrels, one should ensure that the background landscape is safe for shooting into. Grey squirrels are most easily targeted when they are on the ground; this is the most advisable location to target them.
Figure 5.10 - Grey squirrel control using shooting 5.3.3.4 Disposal As for cage trapping, animals were disposed in the undergrowth for scavengers. Those involved in the control would then return to the vehicle and continue their patrol of the estate. 5.3.3.5 Alternative shooting approaches Grey squirrels may also be dispatched using a standard shotgun and cartridge. This is understandably only applicable for persons on foot, and not suitable for use within a vehicle or for dealing with animals in traps. Patrols of woodlands may take place in a similar fashion to that for driving, though such work will obviously take longer, resulting in only one ‘lap’ of a site being possible in a day, depending on the area of woodland being dealt with. Control on foot, however, has the benefit of allowing access to areas where vehicles cannot easily travel, owing to a lack of suitable tracks etc. In some instances, such patrolling approaches may not be necessary. In woodlands where there are focal feeding points such as pheasant feeders or favoured fruiting trees (such as sweet chestnut – Castanea sativa), it may be feasible to stay in one position, and dispatch animals as they arrive to access the food resource. Alternatively, artificial feeding stations (resembling bird tables baited with whole maize) may be erected specifically for this purpose.
Such a ‘focal’ shooting approach has been known to work for one landowner in Kildare, who is able to control the grey squirrel population on his estate for the entire year in just one or two days of intensive shooting. 5.4 Testing of trap designs Where more widespread application of grey squirrel trapping is envisaged in Ireland, it is vital that a correct and durable trap is used. Estimates put the cost of traps at 10-15% of the total outlay for the first year, though traps can be reused in subsequent years at no additional cost. There are currently about half a dozen brands of squirrel traps that are made in or are available for import into Ireland (in most cases these are standard mink traps). A trial assessing the suitability of these trap designs was carried out in Donadea Forest Park in Kildare in April 2008. A meeting with Liam Kelly (Teagasc Farm Forestry Advisor), Karen Bothwell (Coillte Forest Manager), Peter Lynch (Independent Wildlife Manager) and Joe Barry (Woodland Owner, Journalist & Advisory Group Member) to discuss the feasibility of a trap trial was arranged by the project team in April 2008. The various designs of trap were displayed and after some discussion, it was agreed that a field test of all the traps would be the best method of assessing the strengths and weaknesses of each design; it was also agreed that Donadea would form an ideal location to carry out such a trial due to high numbers of grey squirrels seen there during thinning marking earlier in the year. The experiment took place in a 8.5 hectare block of mature oak in Donadea. The oak sub- compartment is shown in red in Figure 5.11. Several squirrel bait stations were set in the oak stand in March 2008 and it became apparent these were frequently visited by squirrels. These stations were subsequently used as sites to set the various trap designs, as squirrels were already drawn to these locations for food. Seven types of traps were tested out over a period of three days. Table 5.2 shows the sources of the various traps and the probable country of manufacture, while photographs of each design are found in Appendix 11.2.
Figure 5.11 - Map of Donadea Forest Park indicating main tree species
blocks and location of trapping trial
Table 5.2 - Trap designs used during the course of the trial
Source Country Type of trap Number of traps
‘Trap Man’ UK Single 2
‘Parker’ UK Single 2
‘Griffin-Hawe’ Unknown Single 2
import
‘Farrell Supplies’ France Single 2
‘Dingle Poultry’ Ireland Single 2
‘Generic Chinese’ China Single 2
‘Dingle Poultry Ireland Multi 1
Multicatch’
On-site, traps were placed in groups of three or four of varying designs. Following the same
scheme applied during 2007 trapping at Carton House Estate, whole maize was used as bait,
as it has been found to be most efficient, regarding both cost and attractiveness to squirrels
(when compared to peanuts or more complex mixed baits).
Trapped squirrels were disposed of humanely on-site with an air rifle by the Project Officer,
who applied for a gun licence for this specific purpose. The number of squirrels caught in
each design of trap on each day was recorded for analysis.5.5 CRISIS methodology – Public relations and education
The raising of public awareness regarding squirrel management and conservation in Ireland
was one of the key objectives set for the CRISIS project. This was achieved through two main
approaches: Firstly, through raising public awareness generally through the media and an
ongoing series of presentations to key stakeholder groups by the Project Officer and Project
Manager and secondly, a pilot educational programme based at several at schools in County
Meath.
5.5.1 Public relations
Early in the project, it was noted that public interest in the issues surrounding the risk the grey
squirrel poses to forestry and red squirrel conservation was quite high, though access to
factual and/or useful information was lacking; numerous emails and phone calls were
received from individuals enquiring about how they should go about getting rid of their local
populations of grey squirrels, or asking how best to protect red squirrels in their locality. The
project team therefore set out to raise the profile of the ‘squirrel issue’ in Ireland. However, a
conscious decision was made not to over-publicise the notion of widespread culling of grey
squirrels, owing to the possible negative sentiment such a concept may have aroused. The
public was engaged through several channels including the print, radio and television media,
lectures and information stands at several appropriate events.
In order to gauge the public sentiment regarding squirrel-related issues towards the end of the
project in 2008, a short questionnaire was circulated to members of the public attending
Dublin Zoo’s Native Species Weekend in April at which the project team operated a stand for
the weekend. Six questions were asked on the questionnaire as follows:
• Question 1
Are you an adult or a school student?
• Question 2
Are you aware that there are two species of squirrel in Ireland, the native red squirrel
and the introduced American grey squirrel? (Answer yes or no)
• Question 3Are you aware that the grey squirrel is responsible for the decline in numbers of red
squirrels in Ireland? (Answer yes or no)
• Question 4
Are you aware that the grey squirrel causes widespread damage to young trees in
Ireland? (Answer yes or no)
• Question 5
How do you feel about the idea of controlling grey squirrel numbers (for example, by
trapping them) to help protect the native red squirrel and our young forests? (Possible
answers - Support control of grey squirrels / Against control of grey squirrels / No
opinion)
• Question 6
Do you think that Ireland should be doing more to conserve the native red squirrel?
(Answer yes or no)
The findings of this survey are shown in Section 6.8.
5.5.2 Education
One of the key deliverables of the project was the development of an education initiative
regarding squirrels in Ireland. However, the curricula of both primary and secondary schools
are already somewhat crowded. In order to gain some idea of the degree to which such an
initiative was feasible, information packs on the issues addressed by this project were
circulated to six schools in Meath. Teachers were asked to contact the project team if they
were in a position to assist in the development of an education programme.
Of these, only two schools responded, Ashbourne Community School and Dunshaughlin
Community College. Ideas for their interaction with the project were presented to the
respective Science teachers, Irene Hughes and Geraldine Horgan. Several meetings were held
with the teachers and students of these schools during the course of the project. An awareness
questionnaire similar to the one used at Dublin Zoo was also circulated to staff and students at
Ashbourne Community School.5.6 CRISIS methodology – Information gathering from third
parties
During the course of the project, efforts were made to gather as much information as possible
from individuals and organisations involved in grey squirrel management and/or red squirrel
conservation, in both Ireland and the UK. It was hoped that through such interaction a more
comprehensive perspective on all the issues involved could be achieved.
5.6.1 Interaction with third parties in Ireland
Ongoing correspondence was maintained with several parties involved in red squirrel research
in Ireland. A visit was made to NUI Galway to meet Dr Colin Lawton and Alan Poole to
discuss the objectives of CRISIS and to visits NUI Galway’s red squirrel translocation
experiment site in Connemara, Co. Galway. This red squirrel translocation experiment in
Derryclare formed part of Mr. Poole’s Ph.D. thesis, which was funded by the Irish Research
Council for Science, Engineering and Technology (IRCSET). Large tracts of coniferous
forestry (predominantly Coillte-owned) are found in the western counties of Ireland. They
remain naturally inaccessible to squirrel populations owing to a lack of dispersal corridors
providing connectivity to them (much of surrounding landscape is devoid of hedgerows).
These blocks of forestry are likely to become important in the future conservation of the red
squirrel, as it will be particularly difficult for grey squirrels to colonise such areas. The
concept of introducing red squirrel populations to such forests is feasible, but any
translocations are subject to strict criteria set by the IUCN (International Union for
Conservation of Nature). Sites must be assessed for their suitability to support red squirrel
populations, and acceptable donor populations must also be identified. Adhering to these
criteria and testing their feasibility in Ireland was a key part of NUI Galway’s project in
Connemara.
The project involved the translocation of 19 animals, 10 males and 9 females, which were
trapped in the Coillte-owned Portumna Forest Park and moved to two holding pens in the
Derryclare site. Squirrels were provided with food and water in the pens, one of which is
shown in Figure 5.12. Only one animal died during the captive stage of the experiment. Since
the opening of the holding pens, no squirrel has returned to them; all took up residence in the
surrounding forest. Supplemental feeders were also placed in several areas around the forest
to ensure the translocated animals did not become malnourished. Radiotracking and trappingof the released animals revealed that although several died during the early stages of the translocation, the population has now stabilized and has begun to breed. Under supervision by Dr Lawton, a second translocation funded by NPWS has taken place at Beleek wood in Co. Mayo, also owned by Coillte. The findings and recommendations from these translocation projects will be key to any future similar conservation-oriented translocations Figure 5.12 – Red squirrel holding pen at NUI Galway translocation site Contact was also initiated with several individuals actively involved in grey squirrel control or research. Mr. Andy Verney, a part-time gamekeeper is currently contracted by four private estates around Carlow and Wicklow to manage their grey squirrel population. Mr. Verney primarily uses poison hoppers for this purpose, but when necessary supplements this with trapping and shooting. A second contact, Mr. Kim McColl has been controlling grey squirrels on his farm near Kilcullen for several years; greys had previously been causing widespread damage to beech and sycamore. Mr. McColl exploits the attraction of grey squirrels to a single area of sweet chestnut trees on his farm; some prebaiting also takes place around these trees. Squirrels seen feeding on the tree seeds or bait are then systematically shot on sight; control usually takes place over 2-3 days in the Autumn when the chestnuts are at their most palatable to squirrels. This once-a-year intensive method appears to have been very successful, with minimal new damage being noted in the farm woodland for the past couple of years.
Correspondence took place regularly with Mr. Micheal McGoldrick and Dr John Rochford of Trinity College Dublin. Mr. McGoldrick’s Ph.D. research involved the genetic analysis of grey squirrel populations, as well as testing several Irish populations for the presence of pox virus. This work has yet to be examined or published, but as related in Section 3.9, Mr. McGoldrick’s work has confirmed the presence of pox antibodies in several grey squirrel populations in the Republic of Ireland. Only the most southerly population tested (at Brittas Castle, Tipperary) was found to be pox-negative (M. McGoldrick, pers. comm.). This suggests that grey squirrels in the southern parts of their distribution do not currently carry the pox virus. However, given its occurrence across the rest of the grey squirrel’s range, this is unlikely to persist indefinitely. Regular contact was made with Dr Tom Hayden and Dr Favel Naulty of the Zoology Department in UCD, who were commissioned by Ms. Margaret Gormley of the OPW in 2006 to investigate the grey squirrel population in Dublin’s Phoenix Park, which is causing significant damage in many areas (up to 80% of newly planted native trees have been stripped). A trapping and radiotracking scheme has been ongoing in the park over the past two years. Findings from the work suggest that there are at least 600 grey squirrels in the park, and plans are currently being put in place for a more comprehensive removal scheme. Similar ongoing contact was established with Mr. Peter Wyse Jackson (Director) and Mr. Paul Maher (Curator) of Dublin’s Botanic Gardens. Grey squirrels are found in very high numbers in the Botanic Garden and the last red was sighted almost ten years ago. Although no damage has as yet been noted on trees in the Gardens, the staff are concerned about the numbers of greys, as they have been known to attack members of the public, who are often seen feeding them. At present, there is approximately one squirrel-related ‘incident’ per month. After some discussion with the project team, the management of the Botanic Gardens have initiated a very low profile control programme, operating during daylight hours before and after opening times. Numerous visits were made to estates in several areas of the country to meet with the owners and/or gauge the degree of grey squirrel damage therein (see Table 5.3). The most severe damage done to individual trees was seen at Lyons Estate on Co. Kildare, where every Dawn redwood (Metasequioa glyptostrobides) tree planted had been stripped from base to tip. During the early stages of the project, evidence of possible grey squirrel control by pine martens in several areas of the midlands was gathered from several landowners during visits
to their woodlands; further anecdotal evidence supporting this was collected during the course
of the squirrel survey.
Table 5.3 - Details of visits to various locations within Ireland
Estate name Location Species Control Other notes
present measures
Ardenode Stud Co. Kildare Grey Shooting
Lyons Estate Co. Kildare Grey Shooting Severe bark damage to several species
of ornamental tree
Ballyarthur Co. Wicklow Red / Grey Trapping Grey squirrel shot and stuffed here in
1936
Castlehoward Co. Wicklow Red / Grey Shooting
Castleforbes Co. Longford Red / Grey None Site of original grey squirrel
introduction – Gamekeepers claim that
reds are still present and grey numbers
have fallen due to pine marten
predation
Glendalough House Co. Wicklow Red / Grey Shooting Gamekeeper has observed no decrease
in numbers of reds, despite continued
influx of greys, which are shot when
possible
Charleville Co. Wicklow Grey None Pine martens present
Ballinacor Co. Wicklow Red / Grey Trapping / Pheasant & deer shoot
Shooting
Hilton Park Co. Monaghan Red / Grey None Greys plentiful in 1980’ very few
/ Pine contemporary sightings. Pine martens
marten frequent
Nahillah Co. Cavan Red / Pine None Greys plentiful in 1980’ very few
marten contemporary sightings. Pine martens
frequent
Lisnaveagh Co. Carlow Grey Warfarin
Rathsallagh Co. Carlow Grey Warfarin
Ballinure Co. Carlow Grey Warfarin
Oak Park Teagasc Research Co. Carlow Grey None Extensive damage to oak
Centre
Borris House Co. Carlow Grey None Worst levels of damage seen at any site
yet visited – Woodland Improvement
Scheme including oak, birch, beech and
sycamore
Abbeyleix Co. Laois Red / Grey Warfarin Reds apparently persisted during
/ Pine warfarin control of greys 10-20 years
marten ago
Stradbally Hall Co. Laois Grey Warfarin Control is secondary result from rat
control using warfarin
Ballykilcavan Co. Laois Red / Grey Trapping Possible pine marten predation of greys
/ Pine
marten
5.6.2 Interaction with third parties in the UK
Contact was initiated with several individuals and organisations in the UK during the course
of the project. There was regular correspondence with a number of these, including Dr.
Brenda Mayle (Forest Research), several members of the ESI such as Charles Dutton and
Miles Barne, Huw Denman (‘SelectFor’ forestry consultants), John Griffin (NIFS), DickSchaible (NIFS) and John Milburne (EHSNI); updates on the status of CRISIS and squirrel
research elsewhere were exchanged regularly with such parties. Visits to several locations in
the UK (and Europe) were made during the project to see first hand the work being carried
out in the fields of grey squirrel management and red squirrel conservation, or to meet some
of the individuals that contact had already been initiated with. There included: The Forestry
Commission, Alice Holt Research Station, the Red Squirrel Protection Partnership in
Northumberland, the Duke of Bucclecuch Estate at Dalkeith in Scotland, the European
Landowners Association in Brussels, attendance at meetings of the European Squirrel
Initiative and a workshop presentation on protecting Northumberland’s Red Squirrels at
Castle Morpeth. In addition, the symposium on Invasive Mammals, held by the Mammal
Society in London Zoo on November 24 and 25th 2006 was attended by the Project Officer.
This provided an opportunity to hear what other groups and/or governmental organisations
are doing with regards alien species that are disrupting ecosystems worldwide, as well
providing a forum to network with individuals specifically involved in red squirrel
conservation and grey squirrel management. Key points were noted from various speakers’
talks.
The Australian attitude to control of invasive species is to measure the success of any such
control by the prevention of ecosystem damage as opposed to the numbers of animals culled;
such ecosystem damage may only occur at a specific threshold of animal density (Glen
Saunders). Ecosystem damage is defined as disruption to normal ecological relationships
caused by an organism that does not ordinarily belong therein (e.g. tree damage by grey
squirrels in Ireland).
• Bounty systems can be successful, but may be vulnerable to exploitation when
only applied on a state-wide (as opposed to island-wide) basis - i.e. animals
culled beyond a state or country border may be translocated to claim extra
bounties (Glen Saunders).
• In fragmented habitat, 750m between blocks of woodland is the key threshold
distance for grey squirrel dispersal. Distances greater than this significantly slow
the spread of greys. Rivers and their associated riparian habitat are key in forming
grey squirrel dispersal corridors. In red squirrel preservation buffer zones, future
broadleaf planting must be carefully planned to avoid the creation of new grey
squirrel spread routes (Peter Lurz). In other words, tree planting for biodiversity
may negatively impact on red squirrels, and in areas where reds are underparticular threat from greys, alternative forestry policy and management may
need to be applied.
• Control not the same as eradication; controlling resident animals not the same as
dealing with dispersing itinerant animals; control for tree protection not the same
as for red conservation (John Gurnell).
Trapping cost (i.e. ‘Person-Days’) is directly related to size of woodland; small high-access
sites may only require 1 or 2 full-time trappers; large medium/high-access areas may require
up to 12 full-time trappers to be successfully (John Gurnell). (‘Medium/high access’ refers to
the degree to which site is connected to surrounding woodland from where squirrels may
disperse from – e.g. hedgerow corridors).
• Still no hard evidence linking grey squirrels with bird population decline (Brenda
Mayle).
• Better to class trees at risk by DBH as opposed to age due to differences in
growth rate between species and in different quality soils (Brenda Mayle).
• Damage to trees is more likely when certain criteria (‘damage triggers’) are
fulfilled – i.e. Proximity of a risk site to holding habitat where squirrels may build
up their numbers; densities of more than 5 squirrels per hectare in and around risk
woodland; high proportion of juveniles in population, which may be responsible
for the majority of damage (Brenda Mayle).
• Control applied before March may be wasted effort, as re-colonisation from
outside site may restore numbers to pre-control levels before damage period
begins. Control is optimal if carried out in holding habitat (Brenda Mayle).
• Immunocontraception, if successful, would probably still need to be applied in
combination with initial lethal control (Brenda Mayle).
• Funding for the development of a squirrel pox vaccine for reds has been applied
for – no decision has yet been made on this (Brenda Mayle).The Project Manager and Project Officer travelled with Andy Verney to Newcastle in Northumberland on October 3rd 2007 in order to meet with representatives of the Red Squirrel Protection Partnership (RSPP) and Richard Wales of the Red Squirrels in South Scotland project (RSSS) (for details of these schemes see Section 3.12). A visit was also made on that date to Dalkeith estate on the outskirts of Edinburgh to see at first hand how grey squirrels are controlled by shooting. Dalkeith Estate runs a constant no-tolerance approach to grey squirrels, which, despite this intensive control, re-invade the estate at an extremely rapid rate (the estate managers shot over fifteen squirrels on the morning of the project team’s visit; see Figure 5.13). Significant damage to mature beech found on the estate is shown in Figure 5.14. The Project Manager also attended a one-day conference on Protecting Northumberland’s Red Squirrels on October 5th 2007. Organized by the Castle Morpeth Borough Council the conference was attended by some 110 participants including borough councillors, two members of the House of Lords, representatives from a range of public organizations, NGO’s and members of the public. It was apparent from the proceedings that there is much interest in Northumberland and elsewhere on the conservation of the red squirrel and the removal of the grey squirrel threat. Lord Redesdale was the keynote speaker and outlined progress with the RSPP initiative (see Section 3.4Error! Reference source not found.). As stated in Section 3.7, the Project Manager attended a one day conference on immunocontraception in Brussels on November 21st 2007. The meeting was arranged by the European Squirrel Initiative (ESI) and was aimed at raising awareness at EU level of the need for funding for related R&D; the current status of IMC research and its future were discussed in depth at the meeting.
Figure 5.13 - Grey squirrels shot during single morning at Dalkeith
Estate, ScotlandFigure 5.14 - Grey squirrel damage to mature beech at Dalkeith Estate,
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