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 squirrels1. 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. Woodland improvement scheme – Oak, Ash, Sycamore, Alder etc Farmed block – Oak, Scots Pine

Very high overall

Galvin Old estate woodland. Woodland improvement scheme – Oak, Ash, Sycamore, Chestnut, Hornbeam, Willow

Very high overall

Preston Old estate woodland. Planted shelter belt – Oak.

High in Oak belt

Farrell Planted farmland. Blocks of Sycamore and Ash/Sycamore mix.

Very high in Sycamore

Fanning Planted farmland. Blocks of Ash, Sycamore and Oak.

High in Sycamore and Oak

Finnegan Planted shelter belt on farmland. Blocks of Sycamore/Sitka Spruce mix.

High in Sycamore

Murray Old broadleaf wood – Partially felled and subsequently planted with Oak, Beech, Ash and Alder. Adjoining block of Douglas Fir, Sitka Spruce, Cherry and Ash.

High overall

Dalgan Planted shelter belt adjoining remnants of estate woodland. Blocks of Oak/Ash/Sycamore mix.

Very high in shelter belt

Barry Planted blocks of Ash and Sycamore.

Medium to High

Tracey Planted blocks of Ash and Sycamore.

Medium

Donadea Forest park based in old estate woodland. Planted blocks of Norway and Sitka spruce, Ash. Mature beech and oak throughout site.

Medium

Carton House Woodland surrounding modern golf course development. Demesne-style estate with blocks of mature mixed broadleaf trees. Small amount of new planting.

Medium

Boyd Finnegan

Dalgan

Galvin

Fanning

Preston

Murray

Farrell

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

import Single 2

‘Farrell Supplies’ France Single 2 ‘Dingle Poultry’ Ireland Single 2 ‘Generic Chinese’ China Single 2 ‘Dingle Poultry Multicatch’

Ireland Multi 1

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 3

Are 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 trapping

of 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 present

Control measures

Other notes

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 / Shooting

Pheasant & deer shoot

Hilton Park Co. Monaghan Red / Grey / Pine marten

None Greys plentiful in 1980’ very few contemporary sightings. Pine martens frequent

Nahillah Co. Cavan Red / Pine marten

None Greys plentiful in 1980’ very few contemporary sightings. Pine martens frequent

Lisnaveagh Co. Carlow Grey Warfarin

Rathsallagh Co. Carlow Grey Warfarin

Ballinure Co. Carlow Grey Warfarin

Oak Park Teagasc Research Centre

Co. Carlow Grey None Extensive damage to oak

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 / Pine marten

Warfarin Reds apparently persisted during warfarin control of greys 10-20 years ago

Stradbally Hall Co. Laois Grey Warfarin Control is secondary result from rat control using warfarin

Ballykilcavan Co. Laois Red / Grey / Pine marten

Trapping Possible pine marten predation of greys

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), Dick

Schaible (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 under

particular 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, Scotland

Figure 5.14 - Grey squirrel damage to mature beech at Dalkeith Estate,

Scotland