Impact of roe deer Capreolus capreolus browsing on understorey vegetation in small farm woodlands

Abstract

The impact of around nine roe deer Capreolus capreolus/km(2) on ground and shrub vegetation was assessed in a sample of six small woodlands on a largely arable estate in Dorset, southern England. In January 1996, 30 exclosures of 2 X 2 x 1.5 in and 30 paired controls were set up. Measurements of vegetation density at six height categories using a cover board were taken in late winter and mid-summer in each of the four years 1996-1999. Mean cover values were calculated for each woodland, and they indicated that the density of vegetative cover was reduced by deer browsing in winter and in summer. The effect of the browsing increased significantly within the four-year study period, and plant species composition had changed by the end of the study period. Our results suggest that roe deer may be having a substantial and potentially widespread effect on vegetative structure and composition in small farm woodlands in arable ecosystems in central southern England. The implications of this, for the characteristic wildlife and game species found in this common woodland habitat, are discussed.

Full text

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© WILDLIFE BIOLOGY · 10:2 (2004)
During the past few decades deer populations in the UK
lowlands have expanded both in number and range
(Prior 1995, Putman & Moore 1998, Taylor 1981, Rat-
cliffe 1987). In the next decade, the roe deer
Capreolus
capreolus
is expected to continue to increase in range,
although not in density, while the fallow deer
Dama
dama
is predicted to increase in density but not in range
(Putman & Moore 1998).
The main area of range expansion by roe deer in the
lowlands coincides with the areas that have seen the
Impact of roe deer
Capreolus capreolus
browsing on understorey
vegetation in small farm woodlands
Rufus B. Sage, Kate Hollins, Catherine L. Gregory, Maureen I.A. Woodburn & John P. Carroll
Sage, R.B., Hollins, K., Gregory, C.L., Woodburn, M.I.A. & Carroll, J.P. 2004:
Impact of roe deer
Capreolus capreolus
browsing on understorey vegetation
in small farm woodlands. - Wildl. Biol. 10: 115-120.
The impact of around nine roe deer
Capreolus capreolus
/km2on ground and
shrub vegetation was assessed in a sample of six small woodlands on a large-
ly arable estate in Dorset, southern England. In January 1996, 30 exclosures
of 2 ×2 ×1.5 m and 30 paired controls were set up. Measurements of vege-
tation density at six height categories using a cover board were taken in late
winter and mid-summer in each of the four years 1996-1999. Mean cover val-
ues were calculated for each woodland, and they indicated that the density of
vegetative cover was reduced by deer browsing in winter and in summer. The
effect of the browsing increased significantly within the four-year study peri-
od, and plant species composition had changed by the end of the study peri-
od. Our results suggest that roe deer may be having a substantial and poten-
tially widespread effect on vegetative structure and composition in small farm
woodlands in arable ecosystems in central southern England. The implications
of this, for the characteristic wildlife and game species found in this common
woodland habitat, are discussed.
Key words: browsing, roe deer, understorey vegetation, woodland
Rufus B. Sage, Kate Hollins*, Catherine L. Gregory**, Maureen I.A. Woodburn
& John P. Carroll***, The Game Conservancy Trust, Burgate Manor, For-
dingbridge, Hampshire SP6 1EF, UK - e-mail addresses: rsage@gct.org.uk (Ru-
fus B. Sage); kate.hollins@fpcr.co.uk (Kate Hollins); comphelp@harper-
adams.ac.uk (Catherine L. Gregory); mwoodburn@gct.org.uk (Maureen I.A.
Woodburn); jcarroll@smokey.forestry.uga.edu (John P. Carroll)
Present addresses:
*Faulks Perry Cully and Rech, Environmental Consultants, Lockington, Hall,
Lockington, Derby, DE74 2RH, UK
**Harper Adams University College, Newport, Shropshire TF10 8NB, UK
***DB Warnell School of Forest Resources, University of Georgia, Athens,
GA 30602-2152, USA
Corresponding author: Rufus B. Sage
Received 15 November 2002, accepted 12 June 2003
Associate Editor: Nigel G. Yoccoz
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largest increase in farm woodland plantings, i.e. parts
of central southern and western England (Putman &
Moore 1998). In arable areas both roe and fallow deer
are able to use small farm woodlands for feeding and
cover, using field crops as an additional or primary
food source (Putman 1986, Kaluzinski 1982, Cibien,
Bideau, Boisaubert, Biran & Angibault 1995, Moore,
Hart, Kelly & Langton 2000). As a consequence of this
expansion, there is potential for browsing damage to veg-
etation in these woodlands (Putman & Moore 1998).
However, in their review, Putman & Moore (1998)
found very little published work on the extent of dam-
age and consequences of browsing by deer in small farm
woodlands (although see Moore, Hart & Langton 1998
and Moore et al. 2000 on fallow deer in young broad-
leaved plantations). Commercial forestry plantations
(Staines & Welch 1984, Gill 1992a, Ratcliffe & Mayle
1992, Tixier & Duncan 1996) and coppice woodlands
(Kay 1993, Tabor 1993, Putman 1995) are the areas
where the impacts of roe deer have been more com-
prehensively studied.
A greater understanding of the damage potential by
deer in woodlands that occupy a relatively small pro-
portion of the landscape is therefore desirable if the qual-
ity of these woodlands as habitats for other wildlife is
to be maintained. This project aimed to investigate the
impact of, primarily, roe deer on vegetative structure and
composition in a sample of small woodlands in a large-
ly arable farmland area in central southern England.
Study area
The study was undertaken on a 400-ha estate in east Dor-
set (SU 016 196) known to contain roe deer (Fig. 1). In
total, 40% of the estate was arable land, 13% grass, 13%
set-aside (arable land left uncropped for one or more
years) and 10% mature broadleaf woodland. The rest
was scrub, edge habitats and some new woodland plant-
ings. Typical woodland understorey vegetation consisted
of bluebells
Hyacinthoides non-scripta
, wood anemone
Anemone nemorosa
, ground ivy
Glechoma hederacea
,
dogs mercury
Mercurialis perennis
, cleavers
Galium apa-
rine
, and woody species such as hazel
Corylus avellana
,
sycamore
Acer pseudoplatanus
, beech
Fagus sylvatica
,
and bramble
Rubus fruticosus
.
The land is flat or gently sloping at a mean altitude of
125 m. Rainfall occurs throughout the year and averages
around 730 mm a year. The monthly mean daily min-
imum temperature occurs in February (1.5°C) and the
monthly mean daily maximum in July (20.8°C).
Methods
A sample of six separate small mature woodlands, be-
tween 1 ha and 13 ha, were selected for study. In each,
we erected either four, five or six deer exclosures, in total
30 (see Fig. 1). The exclosures were located within a
predefined area of wood edge, within 60 m of the actu-
al wood boundary. The precise location was selected
using two random numbers to determine pacing distance
(accounting for the size of the area) in a random start-
ing direction from a central point. A second plot, used
as an unfenced control, was located 5 m to one of four,
randomly selected, sides.
Each 2 ×2 m area by 1.5 m high exclosure was con-
structed using four 7 cm ×2 m steel posts driven into
the ground to support a fence of 4 cm chicken wire with
a 10 cm space left at the bottom for smaller herbivores.
Surveys of the paired plots were carried out in late win-
ter/early spring (March/April) and in late summer (Au-
gust) in each of the four years 1996-1999 inclusive. A
cover board (Nudds 1977) was used to measure vege-
tation density at the following height categories 0-10 cm,
10-20 cm, 20-50 cm, 50-100 cm, 100-150 cm and 150-
200 cm above ground level. These data were recorded
as the proportion of each of a row of five 10-cm wide
panels on the board at each height category that was
Figure 1. The study site contained 10% broadleaved woodland () in
a primarily arable landscape (see text) with fields bordered with man-
aged hedgerows typically < 3 m high. The 30 exclosures are marked
() within the six woodland blocks.
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obscured from level viewing. The board was placed at
one side of the plot and viewed from the other side in
the same direction each time from just outside the
fence, at a distance of 2 m across the exclosure.
Plant species within the plots were also recorded in
the whole plot area (2 ×2 m). The abundance of each
species as an approximate proportion of the plot area was
estimated to the nearest 5%.
Deer densities on the estate were estimated by the
estate game manager in spring each year. He drove
around the estate in late March/early April on each of
three mornings using a route that would enable view-
ing all open areas, wood edges and hedges (both sides).
Counts were undertaken during the 2-3 hour period
starting 30 minutes after dawn and avoiding wet and/or
windy conditions. This count method has been devel-
oped by The Game Conservancy Trust to assess pop-
ulation sizes of gamebirds. In these types of habitats, the
three-visit count has been shown to include on average
90% of male and 65% of female pheasants
Phasianus
colchicus
(Game Conservancy Trust, unpubl. data).
While this count is not an established methodology
for deer, by repeating visits in this largely open habi-
tat, familiarity with herds and individuals suggested that
a good estimate of the deer actually using the open
habitats was being made. However, because some indi-
viduals may confine themselves to the small wood-
land patches, the estimate should be considered a min-
imum count. These counts provided estimates of nine
deer/km2on the 4-km2estate in 1996, 1997 and 1998
and seven deer/km2in 1999. All were roe deer except
for a total of three fallow deer (less than one/km2) in
1999.
Analyses
The study design allows a replicated study of the effect
of grazing between woodlands in an area exposed to deer
grazing pressure. For each wood and each visit, we
calculated the mean cover values across exclosure plots
and across control plots of each cover height category.
A similar measure of mean plant species abundance was
also calculated. The number of plots in each wood im-
1996 1997 1998 1999
YEAR (1-10cm)
0
20
40
60
80
100
MEAN % COVER
1996 1997 1998 1999
YEAR (10-20cm)
0
20
40
60
80
100
MEAN % COVER
1996 1997 1998 1999
YEAR (20-50cm)
0
10
20
30
40
50
60
70
80
90
100
MEAN % COVER
1996 1997 1998 1999
YEAR (50-100cm)
0
10
20
30
40
50
60
70
80
90
MEAN % COVER
1996 1997 1998 1999
YEAR (100-150cm)
0
10
20
30
40
50
MEAN % COVER
1996 1997 1998 1999
YEAR (150-200cm)
0
5
10
15
20
MEAN % COVER
Unfenced
Fenced
A)
1996 1997 1998 1999
YEAR (1-10cm)
0
20
40
60
80
100
MEAN % COVER
1996 1997 1998 1999
YEAR (10-20cm)
0
20
40
60
80
100
MEAN % COVER
1996 1997 1998 1999
YEAR (20-50cm)
0
10
20
30
40
50
60
MEAN % COVER
1996 1997 1998 1999
YEAR (50-100cm)
0
10
20
30
40
50
MEAN % COVER
1996 1997 1998 1999
YEAR (100-150cm)
0
10
20
30
40
MEAN % COVER
1996 1997 1998 1999
YEAR (150-200cm)
0
5
10
15
20
25
MEAN % COVER
Unfenced
Fenced
B)
Figure 2. Percentage cover (± 1 SE) of vegetation in fenced and unfenced plots for A) summer and B) winter. The values are means across all
six woods for the height categories indicated. The overall difference in these mean values between fenced and unfenced plots increased over time
in both seasons (see text for multivariate test results).
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proved the accuracy of each woodland mean but did not
contribute to the basic sample size for analysis, which
was six woods.
As proportions, all cover board data were transform-
ed to angles (arcsine(p)1/2). The difference in cover
between exclosure and control for each wood/visit was
calculated and used in subsequent analyses.
For the analysis of the difference in vegetative cov-
er, a multivariate ANOVA was used including all six
height categories as dependant variables simultane-
ously. 'Wood' was included as a categorical independent
variable and 'Year' as a continuous one together with the
interaction term 'Wood*Year'. These were tested for
overall significance using the multivariate test statistic
Wilks’ Lambda. Data collected during the summer and
winter were tested in separate models.
For the analysis of species composition in 1999 a
paired t-test was used to compare the abundance of
common plants for each wood between fenced and
unfenced plots. Mean values were calculated for each
wood across exclosure plots and across control plots and
transformed to angles for analysis. As before, winter and
summer data were investigated separately.
Results
In the overall multivariate test of the cover board data,
presented as the difference in cover between fenced and
unfenced plots, the interaction term 'Wood*Year' was
significant in both summer (Wilks’ λ= 0.002, F30,30 =
3.73, P < 0.001) and winter (Wilks’ λ= 0.012, F30,30 =
2.00, P = 0.03). This indicates a relationship over the
four-year study period that was not consistent across all
woods. Closer inspection of the mean relationships
between cover and year for all woods shows that the
mean difference in cover was almost always positive (i.e.
more cover in fenced plots) and tended to increase over
time, particularly for the height categories above 10 cm
(Fig. 2).
In the last year of the study, the unfenced plots con-
tained more grass, more bare ground and less cleaver
than the fenced plots (Fig. 3). The species abundance
data had high variance, and there were no other sig-
nificant differences in cover between plot types at P <
0.05.
Discussion
Ratcliffe & Mayle (1992) suggest that five deer/km2of
woodland may lead to some changes in vegetation
structure in continuous woodland, whereas Prior (1995)
suggests a sustainable maximum of 14 deer/km2in
immature broadleaf and 21 deer/km2for mature broadleaf
woodland. Cibien, Boutin & Maizeret (1988), found that
a density of 20 roe deer/km2led to a decrease in ivy
Hedera helix
and an increase in moss and Butcher’s
broom
Ruscus aculeatus
. More generally, Gill (1992b)
describes a decrease in shrub and herbaceous biomass
and an increase in grasses, ferns and mosses.
Using deer densities to predict ecological change can,
however, mask some of the subtle aspects of the roe deer-
forest relationships because they depend on environ-
mental conditions. To account for this, indicators of eco-
logical change that reflect deer population size in rela-
tion to their habitat have been developed. Some relate
to the deer themselves, where juvenile body mass (Gail-
lard, Delorme, Boutin, Van Laere & Boisaubert 1996)
or mandible size (Hewison, Vincent, Bideau, Angibault
& Putman 1996) can be used to provide an index of pop-
ulation size or ecological change, whereas others, such
as the browsing index (Morellet, Champely, Gaillard,
Ballon & Boscardin 2001), relate to their habitat. The
browsing index enables land managers to track changes
in deer population size by measuring the frequency of
browse damage to woody plants alone.
TREESEEDLING
NETTLE
BRAMBLE
DOGS MERCURY
IVY
CLEAVER
GROUND IVY
GRASS
BARE
SPECIES - SUMMER
0
20
40
60
80
MEAN % COVER
Unfenced
Fenced
TREESEEDLING
NETTLE
BRAMBLE
DOGS MERCURY
IVY
CLEAVER
GROUND IVY
GRASS
BARE
SPECIES - WINTER
0
20
40
60
80
MEAN % COVER
A)
B)
**
*
*
**
Figure 3. Percentage cover (± 1 SE) of dominant vegetation in fenced
and unfenced trial plots in A) summer and B) winter 1999, the last year
of data collection. * indicates the difference between plot types based
on wood means (N = 6) significant at P < 0.05.
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Our estimated deer population of around nine roe
deer/km2had a cumulative effect on the amount of
vegetative cover in our sample of six small farm wood-
lands in winter and in summer. Figure 2 suggests the
effect extended above the normal browse range of deer,
typically up to 1.15 m (Prior 1983), as potentially taller
annual plants were curtailed earlier in their growth pe-
riod. An effect on species composition by the end of the
four-year study period had also occurred. Together
these changes represent substantial ecological change.
While the number of deer using our study site wood-
lands was unlikely to be excessive in the context of the
density figures given above, the environmental condi-
tions were of a particular kind. The land-use mix on our
study site, dominated by farmland, meant that there was
effectively a much greater density of deer/km2of avail-
able woodland on the estate. The overall deer density
we observed translates to a much higher one if only wood-
land is considered.
The changes in woodland vegetative structure and spe-
cies composition that we observed could be beneficial
to the types of woodlands depending on management
objectives. Browsing is a natural ecological process
that can maintain or enhance the conservation interest
of habitats (Putman & Moore 1998). For other wildlife,
however, shrubby woodlands tend to provide habitat for
more species for a greater part of the year than wood-
lands that have a sparse understorey. For example many
woodland songbird species, particularly migrant species
occur in greater densities in shrubby woodland (Fuller
& Henderson 1992, Moss 1978). Woodland small mam-
mal communities and many butterfly and moth species
also benefit from woodlands with shrubs and a ground
flora (Gurnell 1985, Ferris & Carter 2000). Woodlands
with plenty of cover will hold many more pheasants dur-
ing the shooting season and provide better breeding hab-
itats for the species during spring and summer (Rob-
ertson, Woodburn, Neutel & Bealey 1993, Robertson,
Woodburn, & Hill 1993). Woodlands with greater hid-
ing cover are also preferred by the deer themselves (Mys-
terud & Østbye 1999). Therefore, our study indicates
that browsing of small farm woodlands by roe deer
could be negatively impacting the conservation value
and aspects of a woodland’s commercial value by re-
ducing the amount of shrubby cover.
After four years of study, we noted that one or two
fenced exclosures in one woodland were starting to
provide a support structure for some rambling shrub spe-
cies, particularly bramble, thus biasing this vegetative
growth towards increased growth in these plots. While
this was accounted for during data collection, this effec-
tively terminated the study. We recommend that pro-
posals for longer studies using replicated plots in sim-
ilar habitats, should account for this by using a larger
plot size with a central assessment area. Some of our ex-
closures may also have been excluding hare
Lepus eu-
ropaeus
although they were designed to include them.
We suggest that the minimum gap size at the base of deer
exclosures used in similar work should be increased by
perhaps 50 mm.
Acknowledgements
- the Honourable Tim Palmer gave us per-
mission to work on the estate, David Butler and Laura Smith
helped with data collection, Dudley Miles, Roger Draycott,
Deborah Ricketts and Ken Tucker helped set-up the exclosures,
and Hugh Oliver Belasis, The British Ecological Society and
The Game Conservancy Trust provided funding.
References
Cibien, C., Bideau, E., Boisaubert, B., Biran, H. & Angibault,
J.M. 1995: Seasonal diet and habitat use in field roe deer
(Capreolus capreolus) in the Picardie region. - Gibier Faune
Sauvage, Game and Wildlife 12: 37-49.
Cibien, C., Boutin, J.M. & Maizeret, C. 1988: Impact of roe
deer (Capreolus capreolus) on vegetation in relation to
population density and type of woodland. - Zeitschrift für
Jagdwissenschaft 34: 232-241.
Ferris, R. & Carter, C. 2000: Managing Rides, Roadsides and
Edge Habitats in Lowland Forests. - HMSO, Forestry Com-
mission Bulletin 123, 78 pp
Fuller, R.J. & Henderson, A.C.B. 1992: Distribution of breed-
ing songbirds in Bradfield Woods, Suffolk, in relation to
vegetation and coppice management. - Bird Study 39: 73-
88.
Gaillard, J-M., Delorme, D., Boutin, J.M., Van Laere, G. &
Boisaubert, B. 1996: Body mass of roe deer fawns during
winter in 2 contrasting populations. - Journal of Wildlife Man-
agement 60: 29-36.
Gill, R.M.A. 1992a: A review of damage by mammals in north
temperate forests. 1. Deer. - Forestry 65: 145-169.
Gill, R.M.A. 1992b: A review of damage by mammals in north
temperate forests: 3. Impact on trees and forests. - Forestry
65: 363-388.
Gurnell, J. 1985: Woodland rodent communities. - In: Flower-
dew, J.R., Gurnell, J. & Gipps, J.H.W. (Eds.); Symposia of
the Zoological Society of London No.55. Oxford University
Press, Oxford, pp. 377-411.
Hewison, A.J.M., Vincent, J.P., Bideau, E., Angibault, J.M.
& Putman, R.J. 1996: Variation in cohort mandible size as
an index of roe deer (Capreolus capreolus) densities and pop-
ulation trends. - Journal of Zoology 239: 573-581.
Kaluzinski, J. 1982: Composition of the food of roe deer liv-
ing in fields and the effects of their feeding on plant pro-
duction. - Acta theriologica 27: 457-470.
Kay, S. 1993: Factors affecting severity of deer browsing dam-
84375 WILDLIFE 2-2004-v1 13/05/04 14:10 Side 119

120 © WILDLIFE BIOLOGY · 10:2 (2004)
age within coppiced woodlands in the south of England. -
Biological Conservation 63: 217-222.
Moore, N.P., Hart, J.D., Kelly, P.F. & Langton, S.D. 2000:
Browsing by fallow deer (Dama dama) in young broadleaved
plantations: seasonality, and the effects of previous brows-
ing and bud eruption. - Forestry 73: 437-445.
Moore, N.P., Hart, J.D & Langton, S.D. 1998: Factors influ-
encing browsing by fallow deer (Dama dama) in young
broadleaved plantations. - Biological Conservation 87:
255-260.
Morellet, N., Champely, S., Gaillard. J-M., Ballon, P. & Bos-
cardin, Y. 2001: The browsing index: new tool uses brows-
ing pressure to monitor deer populations. - Wildlife Society
Bulletin 29: 1243-1252.
Moss, D. 1978: Diversity of woodland songbird populations.
- Journal of Animal Ecology 47: 521-527.
Mysterud, A. & Østbye, E. 1999: Cover as a habitat element
for temperate ungulates: effects on habitat selection and
demography. - Wildlife Society Bulletin 27: 385-394.
Nudds, T.D. 1977: Quantifying the vegetative structure of wild-
life cover. - Wildlife Society Bulletin 5: 113-117.
Prior, R. 1983: Trees and Deer, how to cope with deer in for-
est field and garden. - B.T. Batsford, London, 208 pp.
Prior, R. 1995: The roe deer: conservation of a native species.
- Swan Hill Press, Shrewsbury, 230 pp.
Putman, R. 1986: Foraging by roe deer in agricultural areas
and their impact on arable crops. - Journal of Applied Ecol-
ogy 23: 91-99.
Putman, R. 1995: Deer damage in coppice woodlands: An anal-
ysis of factors affecting the severity of damage and options
for management. - Quarterly Journal of Forestry 89: 45-54.
Putman, R.J. & Moore, N.P. 1998: Impact of deer in lowland
Britain on agriculture, forestry and conservation habitats.
- Mammal Review 28: 141-164.
Ratcliffe, P.R. 1987: Distribution and current status of sika
deer in Great Britain. - Mammal Review 17: 39-58.
Ratcliffe, P.R. & Mayle, B.A. 1992: Roe deer biology and man-
agement. - HMSO, Forestry Commission Bulletin 105, 28
pp.
Robertson, P.A., Woodburn, M.I.A. & Hill, D.A. 1993: Fac-
tors affecting winter pheasant density in British wood-
lands. - Journal of Applied Ecology 30: 459-464.
Robertson, P.A., Woodburn, M.I.A., Neutel, W. & Bealey, C.E.
1993: Effects of land use on breeding pheasant density. -
Journal of Applied Ecology 30: 465-477.
Staines, B.W. & Welch, D. 1984: Habitat selection and im-
pact of red deer Cervus elaphus and roe deer Capreolus
capreolus in a sitka spruce plantation. - Proceedings of
the Royal Society of Edinburgh 82: 303-319.
Tabor, R.C.C. 1993: Control of deer in a managed coppice.
- Quarterly Journal of Forestry 87: 308-313.
Taylor, K. 1981: The northerly spread of muntjac in the Mid-
lands. - Deer 5: 185-186.
Tixier, H. & Duncan, P. 1996: Are European roe deer
browsers? A review of variations in the composition of their
diets. - Revue D’Ecologie (La Terre et la Vie) 51: 3-17.
84375 WILDLIFE 2-2004-v1 13/05/04 14:10 Side 120