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INTRODUCTION
The European badger (Meles meles) shows large
intraspecific variation in social organization which is
understood to reflect ecological, demographic and behav-
ioral plasticity (Palphramand et al. 2007). Populations
throughout Europe present a two-order of magnitude vari-
ation in density, which parallels considerable variation in
social spacing. Population density varies from less than
one ind./km
2
in Poland (Kowalczyk et al. 2000) and the
South of Spain (Revilla & Palomares 2002), to over 38
ind./km
2
in some areas of Britain (Johnson et al. 2002). In
brief, low density populations are found at the northern
(e.g. Broseth et al. 1997) and southern (e.g. Revilla &
Palomares 2002) edges of its distribution range while
higher densities occur at medium latitudes, reaching a
maximum in the British Isles and Ireland (see review in
Johnson et al. 2002). In general terms, it seems that bad-
ger population density is higher in environments with
minor differences between seasonal characteristics (i.e.
temperature, rain, etc.) compared to more variable ones.
Associated with this, the spatial distribution of individu-
als within populations is highly variable. In low density
populations, groups are usually composed of one (Pigozzi
1987) to 3 individuals (Do Linh San et al. 2007a, Revilla
et al. 2001) and territory size reaches several square kilo-
meters, up to 25 km
2
(Kowalczyk et al. 2003). In contrast,
in high density populations, groups can include over 25
individuals, including several adults of both sexes (e.g.
Rogers et al. 1997) and territories rarely reach one square
kilometer, being as small as 0.14 km
2
(Cheeseman et al.
1981).
The badger has become a model in mammal socio-
biology because its plasticity in social organization has
been understood as a primitive level of sociality in carni-
vores (Woodroffe & Macdonald 1993). Sociality in bad-
gers does not seem to be a result of the benefits of coop-
erative activities, as these have rarely been detected, but
rather a result of a resource exploitation strategy. The
most persistent ecological theory for the evolution of spa-
tial groups is the Resource Dispersion Hypothesis (RDH;
Macdonald 1983). In brief, it asserts that, when resources
are patchily distributed in space and/or time, the smallest,
economically defensible territory able to support its pri-
mary holders would usually be rich enough to support
additional individuals with little or no cost to the primary
holders. Therefore, a benefit is not necessary for spatial
groups to develop, or benefits are considered almost neg-
ligible. Territoriality is supposed to be an adaptation for
the defence of a limiting resource (Woodroffe & Macdon-
ald 1993). Accordingly, different resources have been
proposed as the key factors driving badger territoriality,
VIE ET MILIEU - LIFE AND ENVIRONMENT, 2009, 59 (2): 227-236
SPATIAL ECOLOGY OF EUROPEAN BADGERS (MELES MELES)
IN MEDITERRANEAN HABITATS OF THE NORTH-EASTERN
IBERIAN PENINSULA. I: HOME RANGE SIZE, SPATIAL
DISTRIBUTION AND SOCIAL ORGANIZATION
G. MOLINA-VACAS
*
, V. BONET-ARBOLÍ, E. RAFART-PLAZA,
J. D. RODRÍGUEZ-TEIJEIRO
Animal Biology Department, Universitat de Barcelona, 645 Avenue Diagonal, 08028 Barcelona, Spain
* Corresponding author: guillemolina@ub.edu
ABSTRACT. – Although there are some radio-telemetry studies on badger spatial organization
in sub-humid Mediterranean lowlands, cork oak woods and Atlantic highland forest (in the
South, West and North of the Iberian Peninsula respectively), the present study is the first car-
ried out in the Mediterranean forests of the NE Iberian Peninsula in the parks of Collserola and
Montserrat, close to Barcelona. The home range of 13 adult badgers (6 males and 7 females)
was examined with the aim of providing results to compare with previous studies in order to
advance in the understanding of badger social organization with special regard to low density
populations in Mediterranean environments. Mean home range size was 307.6 ha ± 96.4 (± SE)
and 72.8 ha ± 15.1 for males and females respectively for MCP95 and 287.4 ± 79.1 and 85.1 ±
26.6 for FK95 with differences between Parks. In addition, the home ranges of Collserola males
were over four times larger than those of females, while for Montserrat this figure was 1.5.
Moreover, badger groups were formed by one to three individuals in Collserola, and at least
three individuals in Montserrat. This discrepancy points to a distinct social organization associ-
ated with differences in population densities (0.6 ind./km
2
in Collserola and 1.9 ind./km
2
in
Montserrat) and landscape structure conditions. Our results suggest that the home range config-
uration of males is driven by female distribution in space.
EUROPEAN BADGER
IBERIAN PENINSULA
MEDITERRANEAN HABITATS
MELES MELES
SOCIAL ORGANIZATION
SPATIAL ECOLOGY
HOME RANGE SIZE
228 G. MOLINA-VACAS, V. BONET-ARBOLÍ, E. RAFART-PLAZA, J. D. RODRÍGUEZ-TEIJEIRO
Vie Milieu, 2009, 59 (2)
and their distribution would determine badger spatial
organization. In the original form, RDH focuses on food
dispersion as the main factor (Macdonald 1983). Don-
caster & Woodroffe (1993) argued that the distribution of
setts, which are considered a key resource for the species
(Roper 1993), rather than food, determines territory size
and shape, resulting in territories that are larger than need-
ed in relation to food abundance and, thus, allow more
individuals to stay (Sett Dispersion Hypothesis, SDH).
Finally, the Anti-kleptogamy Hypothesis (AKH; Roper et
al. 1986) proposes that the availability of breeding oppor-
tunities is the most important factor in male spatial distri-
bution. Accordingly, territoriality in males would have a
mate-guarding function, as also proposed by Revilla &
Palomares (2002).
In order to improve our understanding on badger socio-
spatial organization in low-density Mediterranean popu-
lations, and also in a global context, we studied the home
range size, group size and population density of two bad-
ger populations of the North-Eastern Iberian Peninsula by
means of radio-tracking, den-watching, and camera trap-
ping between 1997 and 2007. The specific objectives of
the present investigation were 1) to describe badger socio-
spatial organization in our study areas to assess which of
the above-mentioned explanatory hypotheses fits best
with the obtained results, and 2) to compare our data with
other European studies.
MATERIALS AND METHODS
Study areas: The Park of Collserola (41º27’N, 2º6’E) is an
85 km
2
natural space belonging to the Catalan Coastal Cordille-
ra, which spreads over about 100 km in a North-South direction,
parallel to the Mediterranean Sea, roughly 10 km away from the
coastline. This space is naturally separated from the rest of the
cordillera by the rivers Besòs to the NE and Llobregat to the
SW. Its south-eastern limit is formed by the city of Barcelona
and the rest of its perimeter is almost closed by a belt of cities
and highways except for two narrow corridors to the north. It is
basically composed of slates with some granite outcrops on the
northern side and calcareous outcrops to the south. Altitude
ranges from 50 to 512 m above sea level. Mean annual tempera-
ture and rainfall are 14ºC and 672 mm respectively, with wide
seasonal variations in both factors. Summer is usually the hot-
test and driest season, whereas spring and autumn are the wet-
test ones and winters are mild. The inner 80 % of the park sur-
face is covered by dense woodland, largely dominated by the
Aleppian pine (Pinus halepensis) and the holm oak (Quercus
ilex), with very dense undergrowth. At the periphery, vegetation
mostly consists of Mediterranean scrub patches, basically com-
posed of tree heath (Erica arborea) and rock rose (Cistus sp.).
These peripheral areas hold most of the small amount of agricul-
tural activity remaining inside Collserola (8 % of its area). Even
though some areas of Collserola can be classified as sub-urban
habitats, most of it retains the features of a wild natural space.
The second study area is located on the southern side of
Montserrat Mountain Natural Park and in its agricultural sur-
roundings (41º36’N, 1º48’E), 40 km NW of the city of Barcelo-
na (16 km apart from Collserola Park) with an area of over
50 km
2
. The Montserrat massif shows a particular relief with a
columnar appearance. It is formed basically by conglomerates
created by alluvial sedimentation. Large alluvial cones were
raised by Alpine tectonics which originated the Catalan Pre-
coastal Cordillera. Altitude ranges from 250 m to 1224 m. Cli-
mate is typically Mediterranean, similar to Collserola, but is
drier and hotter on the southern side. Wood and scrub are the
dominating vegetation types with the same species as in Collse-
rola Park. This vegetation alternates with croplands: olive crops
(Olea europaea), vineyards (Vitis sp.) and cereal crops. The two
populations live in similar habitats, however with the following
differences. Montserrat is less woody and more patchy and has a
higher proportion of fruit crops relative to cereal crops. In addi-
tion, these Parks have notable differences in connectivity levels
and human pressure. The badgers in Collserola and Montserrat
are considered as separated populations owing to the high level
of infrastructures that isolate Collserola from the rest of the sur-
rounding natural habitats.
Badger capture and tadio-telemetry: Trapping took place
between 1997 and 2006. Badgers were captured with padded leg
hold traps (Victor Soft Catch 1.5, Woodstream Corp Lititz, PA)
placed on well-used badger paths near setts or latrines, which is
the most effective method for capturing badgers in Mediterra-
nean landscapes (Bonet-Arbolí 2003, Loureiro et al. 2007,
Muñoz-Igualada et al. 2008, Rafart-Plaza 2005). Traps were
checked and defused every day at dawn to avoid trapping
domestic animals, and were activated again at dusk. All the Rec-
ommendations of the Animal Welfare Protocol of the European
Union were followed and no badger was injured during han-
dling. Badgers were anesthetized by intramuscular injections of
combinations of ketamine and xylazine hydrochloride (Kreeger
1997), diazepam or medetomidine (Palphramand et al. 2007).
Sex, body mass to the nearest 0.1 kg and morphometric mea-
surements were taken. We estimated the age of animals on the
basis of tooth wear, body mass and date of capture (Da Silva &
Macdonald 1989). Only adults were equipped with a radio-
transmitter (TW-5, Biotrack Ltd.). We used a portable VHF
receiver (R1000, Communications Specialists Inc.) and a hand-
held three element Yagi antenna (Biotrack Ltd.) for radio-track-
ing data collection. Locations were taken with the triangulation
method (White & Garrot 1990), as direct observation was
impossible in most badger ranges because of the dense under-
growth of the wood.
The radio-tracking protocol was established as follows. The
night (19h00-07h00, in solar time) was divided into four periods
of three hours each. Each radio-tracking session consisted of
one or two periods, during which we recorded as many locations
as possible. We recorded all bearings for each radiolocation
within a 10-minute interval to reduce error associated with bad-
ger movement and within 45-135º intervals for cross bearings.
Exceptions to this were the first night after the release of the ani-
SPATIAL ECOLOGY OF BADGERS IN NE IBERIAN PENINSULA 229
Vie Milieu, 2009, 59 (2)
mal and when a particular animal was difficult to find. In these
cases, radio-tracking took place for the whole night. Each indi-
vidual was followed for at least one session every ten days when
possible.
Space use analyses: Radio-tracking data and spatial estima-
tors were calculated with Range VII software (South et al.
2005). Thirteen out of the 15 monitored badgers had reached
home range stabilization according to the Incremental Area Plot
method (hereafter IAP; Harris et al. 1990), which represents the
accumulated area used with the increasing number of fixes.
Only active locations outside the sett (n = 640) of these 13 bad-
gers were used for the analyses. No major changes in the envi-
ronment were noted during the 10-year study period, so we ana-
lyzed all territories irrespective of the year during which data
were collected. To avoid problems in home range estimators
caused by unequal time intervals between locations we first ran-
domly deleted locations until they were at least one hour apart in
the same night-period (De Solla et al. 1999). When individual
home ranges overlapped with others simultaneously, a Multi-
Response Permutation Procedures test (MRPP, Biondini et al.
1988) was performed in order to test for significant differences
in space use. If significance was not reached, badgers were con-
sidered as members of the same group, the home range of which
was obtained by merging all fixes. In spite of criticism (Borger
et al. 2006), the Minimum Convex Polygon (hereafter MCP) is
the method employed most frequently in home range studies.
However, MCP requires a subjacent uniform distribution of
data, and it is therefore not necessarily optimal for comparing
data across studies. Otherwise, the Kernel method seems to be a
better index for home range description, but it also has the prob-
lem that the bandwidth selection method has a great influence
on the results, which prevents robust comparisons between stud-
ies (Laver & Kelly 2008). Thus, home ranges were estimated
using both methods in order to provide better comparability with
other studies: Minimum Convex Polygon with 95% of locations
(MCP95) and fixed kernel estimator (Worton 1989) with 95% of
the utilization distribution (FK95) as recommended by Laver &
Kelly (2008). For fixed kernel estimates an optimal smoothing
parameter was created for each home range (Kenward et al.
2001) by multiplying the smoothing parameter found by the
minimum square method (hcv) by a correcting factor (Worton
1995, Seaman & Powell 1996, De Solla et al. 1999). This factor
was searched, by trial and error, at 0.01 intervals starting from 1
hcv and was accepted when K95 was the smallest range that
allowed a single shape as a home range (avoiding unconnected
patches) as expected for territorial species like the badger
(Blundell et al. 2001, Borger et al. 2006, Hodder et al. 1998).
Comparisons between sexes and areas concerning mean values
of home range estimators (MCP and FK, Table I) were conduct-
ed with the Mann-Whitney test using SPSS 15 for Windows
(SPSS, Chicago, IL). We obtained similar results for both esti-
mators, so in the text we only show the results of FK to avoid
redundant data.
Group size and population density: Group size was estimated
in a systematic way for a wooded area of Collserola only, where-
as a coarser estimation was obtained for Montserrat. The proce-
dure for the calculation of group size was based on the simulta-
neous monitoring of all known setts in each home range on a
given night. Badgers were very suspicious and shy, and our pre-
vious experience showed that, in most cases, they would not
come out of a sett if humans were around. In addition, each indi-
vidual used between at least three and ten setts during their
tracking period (Bonet-Arbolí 2003), so a lot of people would
be required to simultaneously watch all setts at night. Therefore
sett monitoring was performed by sign surveys during two con-
secutive mornings in order to ascertain which setts had been
used by badgers on a given night and in a given range. The sett
watching procedure usually extends for three consecutive nights
in order to deal with the possibility of badgers occasionally
sleeping away from their usual setts. In our case, we decided to
perform the censuses over several non-consecutive nights in the
course of one year (07/1998-07/1999) in each territory because,
although a clear seasonal pattern of sett use exists in Collserola
(Bonet-Arbolí et al. 2005), badgers frequently, and unpredict-
ably, move away from their favorite setts for several consecutive
days within seasons. This monitoring schedule was also useful
to dilute the effect that transients visiting a given range for a few
days (particularly males, see results) would have on the overes-
timation of group size in such a low density population. There-
fore, results are given as the mean number of individual ± stan-
dard error across monitoring sessions, in each home range. Cen-
suses started when the limits of each monitored range had been
established by means of radio-tracking, and sometimes extended
beyond the death of the tracked individual.
The estimation of the number of badgers based on the num-
ber of active setts requires knowledge of all setts in a range.
Besides the discovery of new setts thanks to the radio-tracking
of badgers, a systematic survey (1992-1995) conducted in an
area (A) of approximately 400 ha before the beginning of the
trapping period allowed us to find several setts of interest for
that purpose, because A was later partially included in three
adjacent badger ranges. The area of A represented 65 % of the
home range of F5 + F6, 20 % of the home range of M7 and 96 %
of the home range of F9 (Fig. 1). Sett surveys are highly time-
consuming in Collserola owing to the roughness of the land-
scape and the thickness of the vegetation such that it would have
been impossible to complete the survey of each territory within
the study period. Therefore we used the number of setts (S)
found inside A during that previous survey to extrapolate the
total number of setts (S
tot
) in each range. All setts were visited
several times during the study period and those that were clearly
abandoned by badgers were discarded for the subsequent calcu-
lations. In order to take into account those setts that would have
gone unnoticed during the survey, together with those built since
then, we calculated the survey efficiency from the number of
setts that the tracked individuals used within A and which were
already known from the previous survey. This figure was 75 %
(i.e. in 1992-1995 we found three out of every four setts present
in the surveyed area of Collserola at the time of radio-tracking).
Therefore, S
to t
= [(S/0.75)/A(ha)] * K95(ha) + outliers.
230 G. MOLINA-VACAS, V. BONET-ARBOLÍ, E. RAFART-PLAZA, J. D. RODRÍGUEZ-TEIJEIRO
Vie Milieu, 2009, 59 (2)
Outliers were setts used by the tracked individuals that were
located outside home ranges and setts not used by the tracked
individuals and located outside home ranges at a similar dis-
tance (mean distance of outlier setts used by the tracked indi-
viduals to the border of the home range in question).
Thus, the total number of active setts on a given night (AS
tot
)
as extrapolated from the number of setts actually found active
(AS) is: AS
to t
= (AS/S)*S
tot
.
Finally, two additional factors are needed to estimate the
number of badgers based on the number of active setts: the sett
changing rate (i.e. the frequency with which badgers change
from one sett to another between two consecutive days) and sett
sharing frequency.
Concerning the sett changing rate, the use of the same sett
on two consecutive days by an individual results in one active
sett/badger whereas sett shifting would result in two active setts/
badger. With radio-tracking data and using 23 series of two con-
secutive days spread over the four seasons (of all individuals in
these three territories), the probability of returning to the same
sett was 0.48 and the probability of moving to another sett was
0.52. Therefore, we assumed 0.5 frequencies for each situation
and we thus obtained ¾ badgers/active sett, if AS
tot
> 1.
Sett sharing frequency was estimated by opportunistically
setting camera-traps at setts that seemed to be in use all around
the ranges of Collserola where the censuses took place. We
detected two badgers on only one occasion out of the nine sam-
pled nights (12.5 %). Given this low figure we assumed that
each active sett was occupied by a single badger on a given day.
In Montserrat, a camera trapping survey was carried out over
two periods: the first one during the trapping sessions in order to
confirm badger activity in setts, and the second one, one year
later, to detect and identify the maximum number of individuals
per group. 373 camera/night were placed near sett entrances,
badger paths and latrines, in the three territories (two of them
holding one radio-tagged badger and one holding two) as well
as in an adjacent control area without tagged animals but with
known badger activity (Area O). Each camera was in place for
an average of only 3.73 days at a given site, so results were con-
sidered together with those obtained by live-trapping and must
be considered with caution. The minimum number of recorded
Fig. 1. – a, Location of study areas in the Iberian Peninsula (Montserrat Mountain Park in the upper left corner and Collserola in the
bottom right corner). b, c, and d, represent the home ranges of all radio-tagged badgers based on MCP95 contours in the UTM refer-
ence system. a, Montserrat study area at a scale of 1:20,000; b, Southern side of Collserola study area (7 individuals) at a scale of
1:33,000, and c, Northern side of Collserola study area (2 individuals) at a scale of 1:21,000. Solid and broken lines represent males
and females respectively. Stippled areas represent wooded patches. Only individuals with Incremental Area Plot (the increase in the
accumulated used area when adding more fixes) stabilization are represented.
SPATIAL ECOLOGY OF BADGERS IN NE IBERIAN PENINSULA 231
Vie Milieu, 2009, 59 (2)
individuals in each home range was used as an estimator of
group size.
Population density was calculated on the basis of total
recorded individuals across groups, per study area, and two fig-
ures are presented, one considering only the area occupied by
ranges on the one hand and a wider area encompassing all rang-
es on the other.
RESULTS
We obtained sufficient data for 13 radio-tracked bad-
gers that had reached home range stabilization as judged
from the IAP (6 males and 7 females, Table I, 578 fixes,
mean = 44.46 ± 30.17, range 20-127). These were all of
the Montserrat individuals (2 males and 2 females) and 9
badgers from Collserola (4 males and 5 females). In terms
of home range size, in Collserola we found differences
between the sexes (FK95: m = 388.1 ± 72.8 ha, f = 95.2 ±
37,3 ha; U = 1, P = 0.027). Two females (F5 and F6) had
overlapping home ranges (MRPP test, δ = 0.809, P = 0.42,
F5 + F6 FK95 67.0 % for F5 and 79.4 % for F6, Fig. 1)
and were therefore considered as belonging to the same
group. The magnitude of the difference between the sexes
did not seem as high in Montserrat Mountain Park (FK95:
m = 85.9 ± 32.8 ha, f = 59.7 ± 2.3 ha), but the small sam-
ple size precludes statistical analysis. In Montserrat, the
home ranges of M2 and F4 overlapped almost completely
(MRPP test, δ = 0.809, P = 0.79, M2 + F4 FK95 over-
lap = 81.7 % for M2 and 75.7 % for F4, Fig. 1). However,
in spite of a small overlap between the ranges of M1 and
F3, the locations of these two individuals were signifi-
cantly separated in space (δ = 48.287, P < 0.001, M1 + F3
FK95 overlap = 8.8 % for M1 and 5.2 % for F3, Fig. 1).
Therefore, M2 and F4 were considered members of the
same group, whereas M1 and F3 belonged to separate
groups. According to home range size tests, we distin-
guished three badger groups for further analysis: Montser-
rat badgers, Collserola males and Collserola females.
There was a significant difference between these groups
(Kruskal-Wallis test, FK95: H = 6.89, df = 2, P = 0.032):
Collserola males have larger home ranges than Collserola
females (FK: U = 1, P = 0.032) and Montserrat badgers
(FK: U = 0, P = 0.028), whereas Collserola females and
Montserrat badgers have similar home range sizes (FK:
U = 10, P = 1). According to IAP functions, we found two
different patterns of home range exploitation. Females
and males M1, M2 (Montserrat) and M13 (Collserola)
gradually reached the maximum size of their ranges by
regularly moving across their home ranges, whereas the
Table I. – Location, radio-tracking period, cause of the end of tracking, number of radio locations, and home range size (ha). M Male,
F female.
*
Montserrat Mountain Natural Park,
†
Southern side of Collserola Park, and
#
Northern side of Collserola Park.
Badger ID
Tracking period
Cause Fixes
Home Range
DD.MM.YY MCP95 FK95
M1
*
18.12.99-02.01.01 Battery ran out 44 117.7 118.7
M2
*
07.02.00-17.10.00 Broken collar 29 63.8 53.1
F3
*
23.02.00-08.09.00 Battery ran out 22 57.5 62.0
F4
*
08.02.00-12.10.00 Battery ran out 24 53.9 57.3
F5
†
17.02.97-22.07.97 Death (unknown) 45 77.4 58.1
F6
†
17.02.97-03.03.99 Death (unknown) 85 57.8 49.0
M7
†
24.01.98-09.07.98 Death (poaching) 34 284.6 314.4
F8
†
05.02.99-03.05.99 Death (road-kill) 9 - -
F9
†
03.03.99-19.08.99 Broken collar 28 88.2 135.9
F10
†
23.03.00-14.01.01 Death (Poaching) 29 23.7 12.1
M11
†
11.11.03-04.12.03 Signal loss 4 - -
M12
†
16.06.04-13.06.05 Broken collar 52 450.3 501.4
M13
†
31.07.05-17.11.06 Battery ran out 39 227.0 219.0
F14
#
16.02.06-10.03.06 Broken collar 20 151.0 221.0
M15
#
02.12.06-23.07.07 End of eld work 127 702.2 517.7
Mean Montserrat males ± SE (n = 2) 37 ± 8 90.8 ± 27.0 85.9 ± 32.8
Mean Montserrat females ± SE (n = 2) 23 ± 1 55.7 ± 1.8 59.7 ± 2.3
Mean Collserola males ± SE (n = 4) 63 ± 22 416 ± 106.5 388.1 ± 72.8
Mean Collserola females ± SE (n = 5) 41 ± 12 79.6 ± 20.9 95.2 ± 37.3
Mean males ± SE (n = 6) 54 ± 15 307.6 ± 96.4 287.4 ± 79.1
Mean females ± SE (n = 7) 36 ± 9 72.8 ± 15.1 85.1 ± 26.6
232 G. MOLINA-VACAS, V. BONET-ARBOLÍ, E. RAFART-PLAZA, J. D. RODRÍGUEZ-TEIJEIRO
Vie Milieu, 2009, 59 (2)
remaining males (all of them belonging to Collserola) and
female F3 (Montserrat) increased their home range by
exploiting different areas at different times, which entails
a sharp rise in the IAP curve (Fig. 2).
Census and group size in the wooded area of Collserola
During the census period, one to three badgers were
detected in home range F5 + F6 (mean: 1.5 ± 0.3, n = 7
monitoring sessions); zero to two individuals were detect-
ed in home range M7 (1.8 ± 0.5, n = 4, M7 was not found
during one of the censuses) and one individual was detect-
ed in home range F9 in the two monitoring sessions car-
ried out (F9). In home range F5 + F6, the monitoring ses-
sions were carried out after the death of F5. Therefore,
while this home range was used by at least two females in
1997, the number of animals during the following two
years was normally one (F6), although we detected two
individuals on one occasion and three individuals on
another. In home range M7, the most frequent number of
badgers detected was two, while it is clear that F9 ranged
alone during its tracking period. Taking into account the
size of the home ranges, badger density in the wooded
part of Collserola during the study period was 1.6 ind./
km
2
(considering only the area occupied by the three ter-
ritories). Given that these territories were adjacent, the
density within the MCP100 drawn around all locations of
all individuals (720 ha) was 0.6 individuals/km
2
.
In Montserrat at least three badgers were detected in
home range M1 : M1 and two other non-tagged adults,
which could be distinguished by the different tonality of
their hair. In home range F3 we found a minimum of three
badgers as well: F3 and two subadults, which were prob-
ably her previous year’s offspring. Home range M2 + F4
also contained three animals: M2, F4 and one non-tagged
adult. Finally, in Area O we again identified a minimum
of three individuals (one adult, one sub-adult and one cub)
by camera trapping. So we obtained a minimum group
size of three individuals (adults and sub-adults) per home
range and a population density of 1.9 individuals/km
2
.
Ranging patterns
Males seem to range over larger areas than females in
Collserola. For example, M7 was caught in January 1998
and was consistently detected within the eastern half of
its home range (Fig. 1) and slept in dens within that part
of the home range. In April, it started to exploit the neigh-
boring female home range (F5 + F6) and slept in a den in
the overlap zone, while occasionally returning to its for-
mer range to forage and rest. In July it disappeared from
the study area, returning in October to the F5 + F6 home
range, when it was shot by a poacher. Similarly, individu-
al M12 was caught near a sett in June 2004, in the western
part of its home range and its signal was lost after release.
In August, it was found foraging and sleeping in the oppo-
site (eastern) corner of its home range, and in February
2005 it returned to the original home range inhabited by
at least one female (as judged from the presence of signs
made by cubs). Finally its collar was broken when it
moved to a new area in June 2006.
Although one-night excursions far away from the nor-
mal range were performed by several individuals in both
study areas, no such movements lasting for several weeks
were observed for the Montserrat individuals or Collsero-
la females. The high mobility of males is further illustrat-
ed by the fact that two males disappeared from the area in
which they were caught, shortly after release. One of them
was caught the same day at the same sett that F10 was
caught, the signal of its transmitter having been lost the
night of its release. Another one was caught inside the
home range of M12, 8 months before M12, and after a
few days of tracking, it disappeared. Although a failure in
the radio system cannot be ruled out, this never happened
to Montserrat individuals or Collserola females. Indeed,
the sole Collserola female for which we could not gather
enough data to calculate its home range was followed for
two months before it was killed by a car. This female was
consistently using the western third of the F5 + F6 home
range (when F6 was already dead) but it slept outside the
limits of this home range.
In Montserrat the three studied territories contained at
least three members, with at least one of them containing
individuals of both sexes (M2 + F4). In contrast, in Coll-
serola, F9 was solitary in its home range, as revealed by
the systematic census carried out. Several one-day visits
at all known setts in the small range of F10 suggested that
this female was living solitarily as well. On the other
hand, F6 sometimes shared its home range with one or,
occasionally, two additional individuals (one of them was
F5 in 1997), but the census revealed that it was sometimes
ranging alone.
DISCUSSION
For both study areas we found population density val-
ues close to those obtained for the South and West Iberian
Peninsula (Revilla & Palomares 2002, and Rosalino et al.
2004 respectively). These results are also comparable to
those obtained by Kowalczyk et al. (2000) in Bialowieza
Primeval Forest, and place our populations at the corre-
sponding low population density level of the sclerophyl-
lous Mediterranean dry forests (Virgós & Casanovas
1999) in contrast to badger populations inhabiting the
British Isles (Johnson et al. 2002). Along with the low
population densities, territories were large, particularly in
the case of Collserola males. Only badgers from Poland
and the south of the Iberian Peninsula (Revilla et al. 2001)
have larger home ranges than Collserola males at a lower
population density (Kowalczyk et al. 2003).
Even though the small sample size in Montserrat pre-
SPATIAL ECOLOGY OF BADGERS IN NE IBERIAN PENINSULA 233
Vie Milieu, 2009, 59 (2)
cludes statistical analysis, it is clear that the magnitude of
the difference between male and female home range sizes
is much greater in Collserola than in Montserrat (Table I):
Collserola males had a mean home range size over five
times that of females for MCP95 and over four times for
FK95, whereas for Montserrat this figure was less than
two for both estimators (Table I). In addition, for MCP95
the smallest male home range in Collserola (M13) was
1.5 times larger than the largest female home range (F9)
while in Montserrat the smallest male home range (M2)
Fig. 2. – Incremental Area Plot for MCP95 for individuals which reached the home range stabilization (M1 to M15). Same plotting was
conducted for FK95 with similar results (MRA= Maximum Range Area).
234 G. MOLINA-VACAS, V. BONET-ARBOLÍ, E. RAFART-PLAZA, J. D. RODRÍGUEZ-TEIJEIRO
Vie Milieu, 2009, 59 (2)
had a size comparable to that of females.
Similar, but less marked, tendencies for male home
ranges to be larger than those of females have been report-
ed for some other low density populations (Do Linh San
et al. 2007b, Kowalczyk et al. 2003). No such striking
differences in home range size between sexes have been
reported for any other European population (e.g. Bodin et
al. 2006, Palphramand et al. 2007, Kowalczyk et al. 2003,
Remonti et al. 2006). Nevertheless, the situation in Coll-
serola is similar to that of Hinode in the suburbs of Tokyo
where male badgers have territories three times larger
than females (Kaneko et al. 2006). This difference in
home range size is attained by males by exploiting differ-
ent areas of their territories at different times of the year
(as judged from IAP patterns). Therefore, all evidence
strongly suggests that males are more mobile than females
and exploit or occasionally visit different areas at differ-
ent times. In Montserrat, even though the sample size was
small, all evidence points to the fact that badgers form
classical mixed-sex groups of small size like other Euro-
pean low density populations. In Collserola, the basic ter-
ritorial unit seems to be a solitary female, which would be
the first animal to settle in an empty area based on the
richness in trophic resources (Tuyttens et al. 2000b, Tuyt-
tens et al. 2000a). It may subsequently associate with
other individuals under unknown conditions, probably
females, as suggested by the fact that the only two indi-
viduals tracked at the same time that completely over-
lapped their ranges were two females (F5 and F6). Assum-
ing that both sexes have similar overall metabolic require-
ments, and therefore the difference in home range size
can not be explained by differences in energetic needs,
the large difference in home range size in Collserola sug-
gests that females are the key resource in male spatial
organization, as predicted by the AKH (Neal & Cheese-
man 1996, Roper et al. 1986).
We found a notable difference in population density
between the two Parks (Collserola 0.6 individuals/km
2
,
Montserrat 1.9 individuals/km
2
), in spite of them having
similar habitat, weather and soil conditions. This may
reflect the fact that, even though there are few habitat dif-
ferences between Collserola and Montserrat when group-
ing habitats into main categories, Montserrat Park has a
higher proportion of fruit crops than cereals, which could
provide higher food availability. In addition, the Collse-
rola badger population is physically isolated from other
surrounding natural reserves and suffers a higher influx of
people than Montserrat, which means higher levels of
badger sett disturbance, poaching and road-kill risk. Nev-
ertheless, it has to be borne in mind that the systematic
census was carried out in a wooded part of Collserola and,
even though this is representative of 80 % of the Park’s
area, several indications suggest that density may be high-
er in the agricultural periphery. For example, visual obser-
vations on one night revealed at least three badgers wan-
dering around a sett used by M12 in the agricultural
periphery of Collserola (G Molina-Vacas pers obs). This
suggests that group size in agricultural areas may be high-
er than in wooded areas. Given that territories were simi-
lar in size, density may be higher as well. In contrast, we
found a strikingly small home range in that agricultural
part of Collserola (the range of F10 was less than half the
size of the range of the other females) and its female
inhabitant was apparently living solitarily. Therefore, a
higher density could also be reached by the juxtaposition
of very small territories in the richest parts of the Park
(i.e. the agricultural ones, see Molina-Vacas et al., this
issue) inhabited by one, or a few females. More research
in the agricultural periphery of Collserola is needed in
order to ascertain which the prevailing mode is.
Although it was not the aim of the present paper to dis-
cuss territoriality in our populations, all indications sug-
gest that badgers of Montserrat and Collserola are indeed
territorial, as is the case for all the studied populations of
any density to date, with the possible exception of the
Bristol population (Harris 1984). First, the intrasexual
home range overlap is almost a case of all or nothing (c.f.
Fig. 1). Second, F9 and F6 were tracked simultaneously
for 2 months without trespassing over their common
range borders. Shortly after F6 died, after which its range
remained empty for some months, F9 made a two-night
excursion deep into the F5 + F6 range. Finally, a fight
between two unknown individuals was observed on the
border of the F5 + F6 range, which was marked with a
combination of visual (i.e. paths) and chemical (i.e.
latrines) signs (Bonet-Arbolí 2003).
At first glance, the spatial organization of badgers in
Collserola is similar to the typical mustelid spacing pat-
tern (Powell 1979), with the likelihood of females form-
ing groups, probably due to the greater tolerance between
females of this species compared to other mustelid spe-
cies (Woodroffe & Macdonald 1995). The pattern
observed in Collserola was first observed by Kruuk
(1978) in Wytham Woods. Kruuk observed that 45% of
the studied individuals belonged to a specific kind of
social group, which he named joint ranges, in which the
males’ ranges overlapped with those of females from dif-
ferent main setts.
We suggest that, at low densities, where females range
alone or in very small groups, males need to encompass
several female territories in order to increase their mating
opportunities, and this could be achieved at low risk for
males of encountering other aggressive males. This spa-
tial strategy in males is only achievable if female territo-
ries are not too large, which is the case in both study areas,
probably due to the existence of sufficient food resources.
Where home range richness is very low and females need
to have large territories to satisfy their nutritional needs
(Broseth et al.1997, Rodriguez et al. 1996, Revilla & Pal-
omares 2002) males would be unable to encompass more
than one female home range, thus giving rise to pairs as a
basic unit of social organization. In contrast, at high den-
SPATIAL ECOLOGY OF BADGERS IN NE IBERIAN PENINSULA 235
Vie Milieu, 2009, 59 (2)
sities, where several females cohabit, one home range is
enough to ensure a high number of mating opportunities,
and the probability of encountering aggressive neighbor-
ing males is high, so that it would be advantageous for a
male to be a permanent member of a multi-female group.
Ac k n o w l e d g e m e n t s . – We thank Professor T J Roper and
three anonymous referees for their helpful comments that great-
ly improved an earlier version of the manuscript. We are grate-
ful to Collserola Park for financial support and Barcelona Zoo
veterinary services and Can Balasch Biological Station for their
veterinary and logistical support. VBA and ERP received fel-
lowships from the Generalitat de Catalunya during part of the
work. We also appreciate the help of A Barroso and the Montser-
rat Mountain Park guards for their help with the trapping and
radio-tracking tasks. Badgers were trapped and manipulated
with permission of the Departament de Medi Ambient i Habitat-
ge of the Catalan government, the ethical inter-universities com-
mission of Catalonia, the Parks’ authorities and the hunters’
associations. The English version of this manuscript has been
revised by R Rycroft from the UB’s Linguistic Advice Service.
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Received October 30, 2008
Accepted February 9, 2009
Associate Editor: E Magnanou
