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


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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.
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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
is expected to continue to increase in range,
although not in density, while the fallow deer
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: (Ru-
fus B. Sage); (Kate Hollins); comphelp@harper- (Catherine L. Gregory); (Maureen I.A.
Woodburn); (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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116 © WILDLIFE BIOLOGY · 10:2 (2004)
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-
, and woody species such as hazel
Corylus avellana
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).
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
(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
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)
1996 1997 1998 1999
YEAR (10-20cm)
1996 1997 1998 1999
YEAR (20-50cm)
1996 1997 1998 1999
YEAR (50-100cm)
1996 1997 1998 1999
YEAR (100-150cm)
1996 1997 1998 1999
YEAR (150-200cm)
1996 1997 1998 1999
YEAR (1-10cm)
1996 1997 1998 1999
YEAR (10-20cm)
1996 1997 1998 1999
YEAR (20-50cm)
1996 1997 1998 1999
YEAR (50-100cm)
1996 1997 1998 1999
YEAR (100-150cm)
1996 1997 1998 1999
YEAR (150-200cm)
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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118 © WILDLIFE BIOLOGY · 10:2 (2004)
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.
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 <
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
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.
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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© WILDLIFE BIOLOGY · 10:2 (2004)
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-
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.
- 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.
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... One of the most common methods for doing so is through the use of cover boards, which rely on visually estimating of the relative proportion of a board of known dimensions that is being obscured by vegetation from a given vantage point (Jones, 1968;Nudds, 1977). Cover boards have received widespread use for estimating vegetation density for decades, particularly in the field of wildlife biology, benefitting from their conceptual simplicity and efficiency of field implementation (Duebbert and Lokemoen, 1976;Griffith and Youtie, 1988;Jones, 1968;Musil et al., 1994;Sage et al., 2004;Winnard et al., 2013). Although cover boards have been rarely used as such, they have much potential for use in conjunction with remote sensing technologies such as airborne light detection and ranging (lidar) (Kramer et al., 2016). ...
... Cover poles are simpler to analyze, given the ease with which one can quantify the proportion of vegetation cover in a single dimension, but cover boards, with their larger sample area, provide more detailed information to the analysis. Cover boards have been used extensively, particularly in wildlife habitat studies (Duebbert and Lokemoen, 1976;Griffith and Youtie, 1988;Jones, 1968;Musil et al., 1994;Sage et al., 2004;Winnard et al., 2013). ...
The ability to quantify understory vegetation structure in forested environments on a broad scale has the potential to greatly improve our understanding of wildlife habitats, nutrient cycling, wildland fire behavior, and wildland firefighter safety. Lidar data can be used to model understory vegetation density, but the accuracy of these models is impacted by factors such as the specific lidar metrics used as independent variables, overstory conditions such as density and height, and lidar pulse density. Few previous studies have examined how these factors affect estimation of understory density. In this study we compare two widely-used lidar-derived metrics, overall relative point density (ORD) and normalized relative point density (NRD) in an understory vertical stratum, for their respective abilities to accurately model understory vegetation density. We also use a bootstrapping analysis to examine how lidar pulse density, overstory vegetation density, and canopy height can affect the ability to characterize understory conditions. In doing so, we present a novel application of an automated field photo-based understory cover estimation technique as reference data for comparison to lidar. Our results highlight that NRD is a far superior metric for characterizing understory density than ORD (R2NRD = 0.44 vs. R2ORD = 0.14). In addition, we found that pulse density had the strongest positive effect on predictive power, suggesting that as pulse density increases, the ability to accurately characterize understory density using lidar increases. Overstory density and canopy height had nearly identical negative effects on predictive power, suggesting that shorter, sparser canopies improve lidar's ability to analyze the understory. Our study highlights important considerations and limitations for future studies attempting to use lidar to quantify understory vegetation structure.
... Woodland damage was less where deer made use of adjacent fields and this depended on the deer species in question i.e. fallow deer are larger and able to utilise less digestible forage than muntjac and roe deer and are therefore more likely to use these areas. Sage et al. (2004) monitored vegetation in experimental exclosures in small farm woodlands and reported reduced cover in grazed plots and some change in species composition over a four year period including an increase in grass cover. However Putnam and Moore (1998) highlight the importance of grazing to maintain characteristics of certain ecosystems and caution against referring to all herbivory impacts as 'damaging' as grazing reduction may also have negative impacts on ecosystems. ...
Technical Report
Full-text available
The aim of this project was to analyse existing wild deer research and identify specific research and evidence gaps which need to be addressed in order to meet the challenges for each of the five priorities outlined in Scotland’s Wild Deer - A National Approach (WDNA). The project was developed to facilitate more effective exchange of knowledge and provide a fuller understanding of the issues involved in deer management and therefore help deliver targeted, informed and sustainable deer management in Scotland. This report complements the recently published Deer Management in Scotland: Report to the Scottish Government from Scottish Natural Heritage 2016.
... The diet plasticity is based on two foraging strategies as a concentrate selector, i.e. consuming faster fermenting but less digestible diet with comparatively higher amount of toxic tannins, or as a grazer, i.e. consuming slowly fermenting but better digestible fibre diet with a smaller volume of toxic compounds (Demment and Van Soest 1985;Verheyden-Tixier et al. 2008). Finally, roe deer are generalists, who prefer feeding on herbs, twigs, leaves and fruits (Baleišis et al. 1998;Duncan et al. 1998;Sage et al. 2004). Roe deer utilize more than 250 plant species; however, uncommon species are consumed in higher proportions. ...
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We analyse the relationships between the main Cervidae [moose (Alces alces), red deer (Cervus elaphus) and roe deer (Capreolus capreolus)] species and a complex of environmental factors in an extensive fragmented landscape of Central Lithuania. The highest determining positive influence on moose density was the proportions of wet forest sites. In forest complexes with fewer proportions of wet sites, the most important factor was the total forest area. The proportion of shrub cover, upland and dense undergrowth area, and road density also has significant effect on moose density. The total area of forest complexes has the highest determining positive influence on red deer density. The highest density of red deer was calculated in large forest complexes (> 2,745 ha) with a < 17.6 % proportion of pine and < 36.5 % of deciduous forests. Other significant factors were core area, road density and urbanization level. Forest edge density has the highest influence on the roe deer populations. The highest density of roe deer was recorded on forest areas with > 51 m ha(-1) of edges in wet forest (> 25.4 %) dominating areas. The proportion of deciduous, coniferous mixed and pine forest, also shrub and density of edges also had significant effect.
... The variable indicating whether the pen was deer grazed outside of the releasing period or not, was not significant in the MANOVA test. It seems unlikely that the removal of deer grazing would not affect woodland plant structure (Putman and Moore, 1998;Sage et al., 2004). We suspect however that closed-up pheasant release pens are sometimes ineffective at excluding deer. ...
We compared common ground flora species and vegetation structure in open-topped pheasant release pens with control areas in 43 ancient semi-natural woodlands (ASNW) in England in Spring 1988. Relationships between vegetation parameters and factors such as the density of birds in the pen and pen size were identified. The release pens ranged from 1 to 20 years old, mean pen size was 0.5 ha and the mean stocking density was 2250 pheasants per hectare of pen. Overall, the release pens had more bare ground and reduced vegetation below 50 cm structure compared to the control areas. The release pens also had lower average species diversity and percentage cover of shade tolerant perennials, in particular winter-green perennials. Annual species and perennials preferring fertile or disturbed soil all increased in percentage cover as stocking density increased above recommended levels. Bare ground increased inversely with pen size. Perennials characteristic of shady habitats decreased as stocking densities went up. The reduction of winter-green perennials was greatest in smaller, older pens. In a sub-sample of five sites, average phosphate and potassium levels were significantly higher in the pens than in the controls while pH and magnesium were not different. We estimate that 1 in 12 of all woodlands in England contains a pheasant release pen. We make recommendations for reducing impacts of these pens in ASNW.
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The numbers of white-tailed deer and roe deer have strongly increased in Finland in recent decades. The white-tail deer has been introduced from North America whereas the roe deer is a species native to Northern Europe. There are many reasons for the population growth, such as warming winters with thinner snow cover, artificial feeding in winter, early translocations, and insufficient hunting pressure by humans and by large carnivores, such as lynxes and wolves. In this article, we aim to describe the effects of the dense deer population on Finnish wild plants and vegetation based on a wide literature review and a survey of citizens. In heavily grazed areas the decline of numerous flowering plants is evident. We compiled a list of approximately 150 species of vascular plants favoured by deer, among them even some nationally threatened species. In many areas herb-dominated vegetation has turned into vegetation dominated by grasses. Many plants are well adapted to grazing but repeated removal of flowers and shoots may prevent seed production or regeneration, and even stunted plants observed for example in Hepatica nobilis. The decline of flowering plants is likely to have an impact on local insect communities, especially pollinators such as bees, bumblebees, butterflies and hoverflies. The regeneration of almost all deciduous trees, but also pine, is disrupted because deer eat theseedlings and foliage of young individuals, and break tree trunks by rubbing their horns on them. Even elk browse on young trees. Overgrazing can be seen also in bilberry (Vaccinium myrtillus) populations that are reduced in height and fail to bloom and produce berries. Bilberry is an important key species for many other animals in the Finnish forests. Other dwarf shrubs, such as heather, are eaten as well. Impacts have been recorded on different habitat types – shores, meadows and various forest types.
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Natal dispersal is a process by which individuals move from their natal to reproductive ranges which is fundamental for population dynamics and persistence. Through for example the limitation of inbreeding or the capacity it provides to reach and colonize new habitats containing resources or mates, it can be highly beneficial to dispersing individuals. However, dispersal can also be costly for the individuals, through increased mortality or attrition, energy expenditure, or lost habitat opportunities and time. Its expression at the population level thus depends on the balance between costs and benefits, and theory states that dispersal may become counter-selected if costs outweigh benefits. In the current context of global change, we may expect (1) dispersal costs to increase with the degradation of environments and (2) increased dispersal costs to decrease dispersal success and geographical reach through evolutionary mechanisms. Moreover, because dispersal costs may vary with actual dispersal movement, we may wonder what are the discrete alternative tactics roe deer may use in contrasting environments (3). In this PhD, I aimed to address these three perspectives using two roe deer datasets from two geographically distinct populations (GPS data in Haute-Garonne and Capture-Mark-Recapture data in Deux-Sèvres, France), as well as a modelling approach. First, I show that, despite having a good body condition, dispersers incur costs in terms of mortality, reproduction and growth, and that climate change may increase mortality costs. Concomitant to these variations in costs, I also found that realised dispersal has diminished over the past 30 years by more than 30% in both sexes. Second, I identified at least six alternative dispersal tactics in roe deer, characterised by different movement timing, amplitude and duration, which may imply different outcomes in terms of costs and population dynamics. Lastly, my analyses suggest that dispersal might evolve towards tortuous and short distance movements when mortality costs increase, limiting the geographical reach of dispersal. Overall, these results highlight the concerning effects global changes may have on dispersal costs and dispersal evolution. Because dispersal is a species and context dependent process, more studies addressing the impacts of global changes on dispersal costs, ideally incorporating alternative dispersal tactics, will provide valuable information to better predict how species may cope with environmental changes.
Wild ungulates such as red deer, roe deer and wild boar are key drivers of forest ecosystems. Across the northern hemisphere, their range and abundance is increasing, while at the same time forest conversion and habitat fragmentation have led to a large variation in ungulate density and composition among areas. Understanding ungulate density impacts are important in order to prevent shifts towards undesired states, such as from forest to heathland. Here, we assess the effects of ungulate density on forest regeneration, development and functioning. We carried out a systematic literature review of 433 published studies in temperate forests, and used the data to model dose-response curves of the effects of ungulate density on three sets of forest attributes; tree regeneration (abundance, species richness and composition), forest structure (horizontal and vertical), and forest functioning (nutrient cycling in soil, timber and food production). Ungulate density averaged 23.6 km⁻² across studies. Ungulates had a negative effect on forest regeneration, structure and functioning in 70% of the evaluated cases. The dose-response curves had a sigmoidal, rather than a unimodal shape. Critical tipping points, where ungulates started to have a negative effect on forest regeneration, were found at an ungulate metabolic weight density of 115 kg km⁻² for forest regeneration, 141 kg km⁻² for forest structure, and 251 kg km⁻² for forest functioning, which is roughly equivalent to 10, 13 and 23 roe deer per km⁻². Forest regeneration was most sensitive to immediate browsing and trampling impacts of small seedlings, while forest functioning was least sensitive because of time lags. However, these effects may build up over time. We suggest research priorities for studying ungulate-plant interactions in temperate forests, and make management recommendations how to balance wildlife with a functioning forest.
Capsule: Where predators occur, Bullfinch populations are probably limited as much by landscape structure as by the abundance of key food species. Aims: To explore the interaction between food, cover and predation by comparing the seasonal patterns of the foraging behaviour of Common Bullfinches, with their frequency in the diet of Eurasian Sparrowhawks Accipiter nisus. Methods: Foraging Bullfinches were observed in northeast Scotland from 1997 to 2004, documenting seasonal patterns in foods, proximity to cover, and relative abundance in three habitats. Seasonal changes in predation were assessed from the plucked remains of passerines killed by Sparrowhawks. Results: The seasonal sequence and diversity of foods used by Bullfinches are described. Only rarely did they forage far from cover, mainly in December to February. Their relative abundance in three habitats suggested that they concentrated increasingly in uplands during winter, where they fed on heather seed at gradually higher elevations through to February. Within samples of plucked passerines, full-grown Bullfinches occurred predominantly in winter, newly fledged juveniles only in late summer and autumn. Bullfinches aggregated during autumn and winter, in particularly large groups when foraging on heather far from tree cover. Conclusions: Seasonal patterns of predation and foraging behaviour fit the idea that Bullfinches are vulnerable to predation when a limited choice of food obliges them to forage far from cover. In the presence of Sparrowhawks, the food supply of Bullfinches is determined not by food abundance alone, but by its abundance in close proximity to cover. Key foods are those used when seed availability is at a seasonal low, prior to the switch to buds. Bullfinch population size is probably determined by food supply within habitat configurations at two spatial scales.
In instances where vegetation plays a dominant role in the riparian landscape, the type and characteristics of species, particularly a dominant invasive, can alter water velocity at high flows when vegetation is inundated. However, quantifying this resistance in terms of riparian vegetation has largely been ignored or listed as a secondary characteristic on roughness reference tables. We calculated vegetation roughness based on measurements of plant stem stiffness, plant frontal area, stem density, and stem area of three dominant herbaceous plants along the Sprague River, Oregon: the invasive reed canarygrass, native creeping spikerush, and native inflated sedge. Results show slightly lower roughness values than those predicted for vegetation using reference tables. In addition, native creeping spikerush and invasive reed canarygrass exhibit higher roughness values than native inflated sedge, which exhibits values lower than the other two species. These findings are of particular importance where the invasive reed canarygrass is outcompeting native inflated sedge, because with invasive colonization, roughness is increasing in channel zones and therefore is likely changing channel processes. Direct depositional measurements show similar results.
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Browsing by fallow deer was assessed in young broadleaved plantations over 2 years. Most plantations were small and all were between 4 and 9 years old. Browsing was highly seasonal in occurrence, being rare in winter and most frequent in early summer. This seasonal pattern varied between tree species - cherry and rowan were browsed earlier than oak and sweet chestnut. The probability of browsing was also influenced by the previous browsing history of a tree; trees that were browsed in one month were more prone to browsing subsequently. Trees browsed in year 1 were also more likely to be browsed the following year. Browsing was also related to the extent of budding of individual trees, with trees that were in leaf being more prone to damage than those without leaves erupted.
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Nous présentons ici une synthèse des résultats des travaux de terrain sur le régime alimentaire du Chevreuil, avec l’objectif de comprendre les causes majeures de variation, et de définir les ressources alimentaires principales de l’espèce. Les méthodes utilisées pour étudier son régime, analyse de contenus stomacaux, analyse de fèces et inventaires d’abroutissement, présentent différents biais ; dans cette revue bibliographique nous utilisons les résultats issus de l’analyse des contenus stomacaux. L’utilisation des herbacées naturelles, des graminées et des conifères varie significativement entre les saisons. Il y a des différences importantes dans la contribution des fruits + graines, herbacées naturelles et cultivées, arbres et arbustes entre les trois types d’habitats pour lesquels des données sont disponibles (plaines cultivées, forêts de feuillus, forêts de conifères). Dans les plaines agricoles, le régime alimentaire est dominé par les fruits + graines et/ou herbacées, avec des ligneux au printemps et en automne. Dans les forêts de conifères les plantes principales sont, en hiver, les résineux et la bruyère ; en été, les herbacées et ligneux. Dans les forêts feuillues, ronce et ligneux dominent quelle que soit la saison, avec le lierre en hiver et, certaines années en automne, les glands. Ces résultats suggèrent que le Chevreuil est granivore ou frugivore lorsque les graines et les fruits sont suffisamment abondants ; et, qu’il devient brouteur quand cette nourriture préférée est rare. La niche alimentaire du chevreuil de plaine présente certaines similarités avec celle du sanglier (Sus scrofà). Les deux espèces utilisent beaucoup les fruits et les graines et augmentent leur consommation de la partie végétative des plantes en hiver. Sur d’autres continents, d’autres ongulés de taille similaire occupent la même niche, comme les cerfs du genre Odocoileus en Amérique du Nord et les petites antilopes de la tribu des Cephalophini en Afrique.
A botanical analysis was made of food contents taken from the rumen of 125 roe deer Capreolus capreolus (Linnaeus, 1758), obtained during the hunting season in an experimental field area. The roe deer's food over the annual cycle is formed by 85 plant species, but six species of cultivated plants are of basic importance.
(1) Song-bird populations were censused by the mapping method and vegetation profiles were measured on eighteen plots in planted and semi-natural woodland in Scotland over 1-3 years. (2) The diversities of the song-bird communities were calculated using a standard formula; the complexity of vegetation structure on each plot was measured by the diversity of the distribution of foliage within a number of height ranges. (3) With an optimum choice of height ranges into which the vegetation profiles were divided, the correlation coefficient between bird species diversity and foliage height diversity was 0.887. There were four height ranges: 0-0.6 m, 0.6-6.0 m, 6-15 m, > 15 m. (4) Use of numbers of song-bird species or total densities in place of bird species diversity resulted in lower correlation coefficients. (5) The increase in bird species diversity with increase in foliage height diversity was seen as the result of the exploitation of an increased number of available niches. (6) The regression line between BSD and FHD could be used to predict BSD when FHD was known.