Is culling of grey squirrels a viable tactic to conserve r..

OTHER METHODS TO STOP RED SQUIRREL DECLINES

There are four alternative approaches to red squirrel conservation
that do not involve cullinggrey squirrels. The first is the
establishment of red squirrel populations on islands that haveno grey
squirrels. Current islands that harbour red squirrel populations
include the Isle ofWight, islands in Poole harbour and Angelsey
(Harris et al., 1995; Rushton et al., 1999).Red squirrels have been
introduced to the isle of Arran in Scotland (Poulsom et al.,
2005).There are several other islands, particularly in Scotland, that
currently have suitablewoodland but no red squirrels (Scottish
Squirrel Group, 2004); including Mull in Scotland(Shuttleworth, 2005).
Establishing viable populations on islands will secure the future of
redsquirrels in Britain. In addition, should grey squirrels ever
become introduced onto these islands, the experience on Anglesey has
shown culling would be an effective strategy toremove them.

The second aspect that would aid red squirrel conservation would be
the development of aSQPV vaccine. While this would not stop ecological
replacement of red squirrels, it wouldslow their decline. Recently
McInnes & Middleton (2005) estimated the cost of developing aSQPV
vaccine. Initial costs ran to £416,000 for three years; however, they
acknowledge thatthis does no include extensive field trials, nor an
indication of timescale. Though large, thesecosts are smaller than the
£1.1 million planned for red squirrel conservation in northernEngland
(NWT, 2006). SQPV is widespread in grey squirrels in northern England,
where ithas already been found in red squirrels (McInnes & Nettleton,
2005), and so despite the £1.1million pledged to their conservation,
red squirrels populations in northern England willcontinue to decline
as a result of SQPV.

In the absence of SQPV, red and grey squirrels have been shown to
coexist for many years(e.g. Harris, 1973/74; Bryce et al., 2002). This
is because in some habitats, grey squirrels donot have such a
competitive advantage over red squirrels. Without SQPV and any
greysquirrel intervention, it is probable that red squirrel
populations would survive in areas wherethey have a greater
competitive advantage over grey squirrels. Habitat is a key aspect
toconserving red squirrels (Lurz et al., 1998), as they require a
dependable seed supply (Lurz etal., 1998; 2000), which depends on tree
composition (Lurz et al., 1998) and forest age structure (Gurnell &
Pepper, 1993). To ensure a constant seed supply may mean altering
felling patterns and forest design plans (Lurz et al., 2003). Red
squirrels appear to have theability to utilise production conifer
plantations (Lurz et al., 2000), which presents a paradox,as the
majority of commercial forestry in Britain comprises blanket, similar
aged, non-nativeconiferous species with low biodiversity levels
(Willis & Garrod, 1998). However, changes in management practises are
being urged so that future plantations have higher biodiversitylevels.
These include recommendations such as leaving some stands to develop
old-growthconditions (Fuller & Brown, 2003; Humphrey, 2005), increase
structural diversity by leavingdeadwood, increasing tree species
composition, habitat restoration (e.g. to peatlands),mimicking natural
disturbances regimes and using species of local genetic origin (see
Quine,2003). If such regimes are implemented, plantations may have
great benefits to biodiversity(Humphrey et al., 2003), but without
these changes, planting more monoculture plantationeven to aid red
squirrel conservation would be an ecological disaster.

Ecological replacement of red squirrels by greys is linked to the
reduced ability of juvenilereds to be recruited in the population
(Wauters & Gurnell, 1999; Wauters et al., 2000) andreduced fecundity,
possibly through reduced breeding condition (Gurnell et al.,
2004).Supplementary feeding of red squirrels may be one way to
counteract this affect and so mayhelp increase red squirrel
persistence, particularly in deciduous woodland. This could onlyoccur
in the absence in SQPV, but this strategy could be useful if found to
promote redsquirrel population persistence.

OTHER ECOLOGICAL AND ECONOMIC IMPACTS OF GREY SQUIRRELS

Other negative impacts of grey squirrels: tree damageOther than the
well documented decline in red squirrels, grey squirrels are cited as
having amajor economic impact by damaging trees in commercial
plantations. Much evidencesupports the damage that grey squirrels can
cause to woodland (Kenward, 1983); however,red squirrels are also
known to causes significant damage to trees (Tittensor, 1970), to
theextent they were considered a major pest prior to the introduction
of grey squirrels (Ritchie,1920). Both species (Table 3) and age of
tree influences grey squirrel damage. The twoprimary species damaged
across several studies were sycamore and beech; other species
areattacked to varying degrees depending on site (Lawton & Rochford,
1999). Thin barkedspecies of between 10 and 40 years are at particular
risk (Kenward et al., 1988). Damage canresult in loss of apical
dominance, infection of wood through the wounds, loss of vigour or
even death (Gurnell & Mayle, 2003). Several factors are known to
affect the rate of damage.Juvenile squirrel density is correlated to
bark stripping intensity (Kenward et al. 1988a),whilst tree quality
gave the best correlation to damage levels (Kenward, 1989).
Thepercentage ground cover (Kenward et al., 1991), number of seed
bearing tree species(Kenward et al., 1988b) and growth rate of the
attacked tree (Mountford & Peterken, 1999)are other important
variables affecting level and intensity of grey squirrel damage.
Damageis not linked to food availability (Kenward et al., 1988a).
Identifying factors that can predictdamage is of particular use in
planning control strategies (Mayle et al., 2004). Current silviculture
techniques may increase damage, as the choice of fast-growing species
(Table 3)and growing trees close together encourages fast vertical
growth, which all increase thesusceptibility of woodlands to damage
(Lawton, 2003).Table 3. The percentage of stands of different species
showing occurrence of damage(Mayle, 2003 cited in Huxley, 2003) in
comparison to the percentage area of woodland inEngland (Forestry
Commission, 2001)Tree species% stands showing damageArea (% total
woodland)Sycamore1004.9Beech666.5Oak4016.1Ash3310.6Lodgepole
pine33-Scots pine16-Norway spruce16-Larch84.7Sweet chestnut8-The
financial cost of grey squirrel damage is somewhat controversial and
must be balancedagainst the costs of squirrel control over a long
period. For example, Kenward & Dutton(1996) estimated the costs of
moderate to severe squirrel damage to beech. Over an 85 yearrotation
this was estimated at £1700/ha (Kenward & Dutton, 1996). Considering
that themain vulnerable age group is 10-40 year (Mayle et al., 2004),
annual cost of damage worksout at £57/ha/annum. Over the thirty year
period, the cost of squirrel control with warfarin isconsiderably
cheaper (Table 1), but only if it is sustained and totally eliminates
damage. As a consequence, the costs of control may outweigh the
benefits (Lawton & Rochford, 1999;Forestry Commission, 2006). If taken
across all woodland in Britain, the cost of squirreldamage can be
viewed as substantial (Huxley, 2003), but it is difficult to
extrapolate financial losses over both a period of cropping and with
variable damage intensity.

At present we know that the exact benefits of controlling grey
squirrels can be highlyvariable. For example, both Mountford (1997)
and Rayden & Savill (2004) cite continuedtree damage despite grey
squirrel control programs. Squirrel control may even increasedamage to
woods; agnostic behaviour is cited as one reason for squirrel damage
and this ishigher when populations are increasing or when large
numbers of immigrants are movinginto a vacant area, conditions that
can be caused by culling of squirrels (Lawton & Rochford,1999). There
are two strategies to control grey squirrel damage: to control grey
squirrelnumbers or controlling the extent of the damage (Lawton &
Rochford, 1999). To counteractthe need for squirrel control, better
use of silviculture techniques, including the selection ofless
susceptible species and reducing planting density, could greatly
reduce squirrel damage,and so reduce both the need for continuous
control, which in turn has considerable financialbenefits. The only
way to further understand this issue is to model the economic costs of
greysquirrel damage, and the costs and benefits of different control
strategies, both culling andhabitat management.

Other negative impacts of grey squirrels: bird predation Grey
squirrels are often cited as predators of bird’s eggs and fledglings
(Monckton, 1991),yet proper quantitative data are lacking (Hewson &
Fuller, 2003; Hewson et al., 2004) andthe majority of evidence is
anecdotal. A recent survey indicated that of eight woodland
birdspecies showing declines, only two rarer species may have showed a
decline related to greysquirrel abundance (Amar et al., 2006).
However, this evidence cannot be directly linked topredation. Of the
remaining six species, the authors suggested that changes in
woodlandstand structure, such as increased woodland age, reduction in
active management andincreased deer browsing, may be responsible for
these declines (Amar et al., 2006). Thefocus on grey squirrels ignores
the fact the red squirrels themselves are important predatorsof bird’s
nests both in urban (Jokimäki & Huhta, 2000) and rural environments
(Nour et al.,1993).It has also been suggested that grey squirrels
compete with hazel dormice(Muscardinus avellanarius) for food and
woodland bats for resting sites (Hewson et al.,2004). However, direct
evidence to support these hypotheses is absent. Both red and
greysquirrels fill similar ecological niches; as a consequence it is
likely that red squirrels too are important predators of bird’s nests
and competitors in the same way greys are. The focus onthe negative
aspects of grey squirrels ignores the same role played by the native
red.

Positive impacts of grey squirrels

A survey in 2002 by The Mammal Society indicated that 45% of people
liked grey squirrelswhilst only 24% dislike grey squirrels (Fig. 1).
Clearly, many people enjoy the grey squirrelas part of the environment
(Mayle et al., 2004), but outside any intrinsic value, there has
beenno direct focus on the role of grey squirrels as beneficial to the
environment. Damage totrees can be beneficial (Forestry Commission,
2006), as wounding can provide habitat forsaproxylic fungi and
invertebrates, which in turn provide food for woodland birds.
Treeskilled by squirrel damage can also provide valuable nesting sites
for a range of species.Deadwood is an important part of woodland
biodiversity (Humphrey et al., 2002). Barkstripping in particular is
focused on sycamores (Table 3), an invasive species (Royal
ForestrySociety, 2006). Grey squirrels may actually help control
sycamore growth in some forests.The extent to which grey squirrels act
as seed dispersers is unknown, though they excise theradicle of
acorns, causing germination failure (Pigott et al. 1991); however,
whether thisalters the long term dynamics of woodland is
unknown.01020304050DislikeNo strong
feelingLikeResponse%ofrespondantsFigure 1. The percentage of
respondents (n = 3606) who disliked, had no strong feeling, orliked
grey squirrels, based on a scale of 1-10 (1-3: dislike; 4-7: no strong
feeling; 8-10:like)(Baker & Harris, unpublished data)

WHAT ARE THE IMPACTS OF CULLING STRATEGIES ON GREY AND REDSQUIRRELS

The evidence as to whether grey squirrel culling benefits red
squirrels is controversial. Ashas been shown on Angelsey, the removal
of grey squirrels led to a population increase andrecolonization of
areas of the island by red squirrels (Shuttleworth et al., 2002).
Thiscontrasts with Thetford Forest, where long term trapping found no
benefits to red squirrels(Gurnell et al., 1997; Gurnell & Steele,
2002); control strategies, although expensive, arepredicted to allow
red squirrel populations to persist (Rushton et al., 2002; 2006).
However,the exact positive or negative affects of grey squirrel
control is unclear. In American redsquirrels (Tamiasciurus
hudsoncius), removal of individuals led to immigration of males
andfemale of breeding condition (Klenner, 1991). Ultimately
immigration can compensate forculling losses e.g. in red foxes (Vulpes
vulpes) (Baker & Harris, 2006). In addition, both theincrease of
reproductive individuals in an area, or overcompensation by a culled
population,can lead to an increase in density (Choisy & Rohani, 2006)
and associated tree damage.Culling also has serious implications for
the spread of disease; culling can ultimately increasethe possibility
of cross-species transmission (Donnelly et al., 2003, 2005; Chisy &
Rohani,2006), by altering density or by disturbing population spatial
structure (Tuyttens et al., 2000;Woodroffe et al., 2005). In the
context of grey squirrels, increased culling could lead togreater
movement of individuals which may increase the spread of SQPV to novel
redsquirrel populations.

HOW CAN WE CONSERVE RED SQUIRRELS?

Conserving red squirrels in Britain remains a challenge. There is no
longer a ‘native’ red squirrel due to the frequent introductions from
Europe and habitat defragmentation which hasallowed gene flow between
previously sub-divided populations.The red squirrel iswidespread and
common over much of its distribution (Lurz et al., 2005), and so it
isquestionable why such large sums of money should be spent conserving
this species.Conservation effort on red squirrels in Britain is
disproportionate to its importance in globalconservation. Red
squirrels can be reintroduced again to Britain, if an effective and
humaneway of reducing/eliminating grey squirrels is eventually found.
There appears to be littleevidence to support the benefits of culling
grey squirrels for red squirrel conservation,particularly in the
long-term. Grey squirrels cannot be exterminated from Britain by
culling.
Previous attempts to control grey squirrels when grey squirrel
distribution was markedlysmaller did not stop or slow the spread. With
SQPV and continued ecological replacementby grey squirrels, red
squirrels will continue to decline in Britain.

Since culling is not a tactic that will benefit red squirrel
populations, is long-term and costly,novel techniques need to be
considered in grey squirrel population management for redsquirrel
conservation. Creating island refugia would ensure their persistence
in Britain, whiledeveloping a SQPV vaccine would markedly slow
population declines. A significant stepforward would be to identify
techniques that would lead to a decline in grey squirrelpopulations.
These might include the release of a biological control agent or a=
virus-vectored immunocontraceptive (VVIC), although currently
prognosis for either technique isvery low. Concern would be raised
about transmission of a VVIC to red squirrels; however,even if red
squirrels also became extinct along with greys, red squirrels could
bereintroduced, as has happened in the past. Another possibility would
be to examine ways ofallowing red and grey squirrels to coexist.

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Jim Webster wrote:
> "Ronald 'More-More' Moshki" <sector_four RemoveThis @yahoo.com> wrote in message
> news:1162936514.751966.244940@h54g2000cwb.googlegroups.com...
> Have never seen a red squirrel---here in Eastern PA.
>
> they aren't as good to eat as greys

Jim Webster is a child rapist, first graders only.