Ir. Nat. J. Volume 28 No 1 2005
Loss of territoriality in a local badger Meles meles
population at Kilmurry, Co Cork, Ireland
D. P. SLEEMAN AND M. F. MULCAHY
Department of Zoology, Ecology and Plant Science, University College, Cork
A rural badger population was studied from 1990 to 1994, using sett surveys, bait
marking and trapping. The population declined, due mainly to road casualties and
persecution, from 29 animals in six territories in 1990, to five animals without territories in
1994. There was an unexpected elasticity in some of the territories, and territoriality
2
ceased at a density of less than one badger per km . The implications for badger surveys,
and for the problem of transmission of bovine tuberculosis from badgers to cattle are
discussed.
The concept of territoriality in badgers was first suggested by Southern and Linn
(1964) who noted that the setts in Wytham Wood, in Oxfordshire, England, were “spaced out,
presumably because each group prefers to keep neighbours at arm's length”. This was
followed by Hans Kruuk's work (Kruuk 1978, 1989) in which plastics of different colours, with
a sticky substance and peanuts, were fed at badger main setts, subsequently allowed
territories to be outlined, by the finding of such colours at frontier latrines (clusters of dung
pits). This method, combined with trapping and location of badgers’ paths, allowed territories
to be identified. This methodology for detecting badger territories has now become standard,
and was used, along with other field techniques, in this study.
Densities of badgers vary between high densities of 20 adults to km2 in better habitats
without persecution to low densities of up to two per km2 (Neal and Cheeseman 1991).There
is a natural and understandable tendency to site studies of animals in areas where the target
species is abundant, despite the fact that such dense populations may be atypical. For
example much of the available data about badgers is from Wytham Wood, Oxfordshire (Kruuk
1989), and Woodchester Park, Gloucestershire, in England (Rogers et al. 2000) or Little
Island, Co Waterford in Ireland (Gormley and Southey 1999), which contain three of the
highest known badger population densities.
There is information on territoriality in badger populations in Ireland to be found in the
two year study in the East Offaly area (O'Corry-Crowe et al.1993, 1996), and from various
habitats in Northern Ireland (Feore and Montgomery 1999). In England Cheeseman et al.
(1993) carried out studies at Woodchester and Tuyttens et al. (2000) nearby at North Nibley,
both areas that had formerly had high badger densities. Relevant also is the detailed study of
the effects of removal of male badgers from a social group in Sussex, England, by Roper and
Lüps (1993).
The aim of this paper is to examine changes in patterns of territoriality in a declining
badger population.
Methods
This population of badgers was initially a medium density badger population, which
was the subject of an investigation from 1987 to 1994 (Sleeman 1992, Sleeman and Mulcahy
1993, Southey et al. 2001), when the investigation was terminated as the population was
considered too low to merit further study. The study area considered here was the core inner
area of 10km2, examined for the years 1990-1994 inclusive. The area is on old red sandstone
and is predominantly pasture. The area was bisected by the, now disused, Cork to Macroom
railway line. The reasons for the decline in the population were road accidents and also
illegal persecution by people, which by its nature was unquantifiable. (The badger is a legally
protected species in Ireland.) The persecution involved digging of setts, the application of
slurry to setts (Table 1) and suspected illegal poisoning, not always aimed at badgers. For
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Ir. Nat. J. Volume 28 No 1 2005
Table 1. A summary of recorded incidents of badger persecution at setts in the area 1990-1994
(Illegal poisoning was also suspected).
Dug
Bulldozed
Slurry
applied
Illegally
snared
Main setts
Other setts
5
3
1
1
1
1
1
0
Total
8
2
2
1
Table 2. Numbers of badgers, identified frontier latrines, territories and density of badgers in
Kilmurry area 1990-1994
Year
No. of adult badgers
No. of identified frontier latrines
No. of active main setts
No. of territories
Density of badgers (per km2)
1990
1991
1992
1993
1994
29
43
6
6
2.9
19
45
7
4
1.9
17
24
6
2
1.7
12
18
7
1
1.2
5
25
4
0
0.5
Table 3. Badger movements detected by bait-marking and areas of territories in Kilmurry area
1990-1994
Year
No. of movements shown by
bait-marking
Mean distance of movements
(km)
1990
1991
1992
1993
1994
42
32
14
11
9
0.45
0.51
0.63
0.87
1.20
example, in Spring 1992 sett F was dug to try to recover a dog, which had got lost in a sett
while hunting foxes Vulpes vulpes; and in Spring 1993 the decline from twelve to five
badgers is likely to have been due to illegal poisoning, probably by a herbicide, aimed, not at
badgers, but at dogs 'worrying' sheep (Sleeman et al. 1995).
The methods, which included bait-marking of territories, badger capture and sampling
as well as some radio-tagging, have been described in detail elsewhere (Sleeman 1992,
Sleeman and Mulcahy 1993). Bait-marking happened in Spring (March-May) and each
identified main sett was fed a mixture of coloured plastic pellets, peanuts and treacle at a rate
of roughly one bucket per main sett every four days. Badgers were trapped using metal,
slightly modified, MAFF type traps (Cheeseman and Mallinson 1979) (locally made, with 2
inch, or 1 inch, mesh), which were bedded down with soil, and pre-baited with peanuts for 4-5
days until the badgers were using the area freely. Trapping took place over 1-3 nights and in
total there were 72 captures. Badger population density was estimated by direct enumeration.
The territories were described as such only if recaptures, radio-tagging and badger path
locations, as well as bait marking (Delahay et al. 2000), suggested that real territories existed,
and at least four or more latrines were detected, marked by plastic pellets fed in a mixture at
the badgers' main setts. This study of badgers differs from others in Ireland in which territories
have been assumed after few, or no, latrines have been marked (O’Corry-Crowe et al. 1993,
Feore 1994, Feore and Montgomery 1999), but we feel this more robust approach gives more
accurate results. We used the standard definition of mammal territories as a defended area
(Burt 1943), however we did allow overlap in territories once in 1991 (Figure 1).
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Ir. Nat. J. Volume 28 No 1 2005
Table 4a. Numbers of adult badgers in each social group in Kilmurry area 1990-1994
Year
A
B
C
D
I
F
1990
1991
1992
1993
1994
11
3
3
4
2
4
7
3
2
3
2
2
3
3
2
2
2
2
2
0
3
3
0
1
0
0
2
1
0
1
Table 4b . Area (in ha) of each identified territory in Kilmurry area 1990-1994
Year
A
B
C
D
I
F
1990
1991
1992
1993
1994
132
54
64
37
71
61
297
109(&E)
None
None
146
None
104
35
None
None
None
None
111
None
None
None
None
None
None
None
None
None
None
None
Results
Badger numbers and density
The numbers of adult badgers declined steadily from 1990 to 1993, and then fell by
more than half to five individuals in 1994 and density declined throughout the period (Table
2). The numbers of identified frontier latrines also declined until 1993, but increased slightly in
1994. Seventeen badgers were found dead in these years, eleven were cubs and six were
adults. Of these, nine were road casualties and eight were found dead above ground, and of
the latter, five were found at setts. One other investigation in Ireland has reported 50 per cent
of identified dead badgers outside setts (O'Corry-Crowe et al. 1996).
Main setts, territories, and social groups
Two of the main setts were located in Iron-age ring forts (F & I), two on a disused
railway line (B & D), two in scrub (C & E) and one in woodland (A). The first year six main
setts were bait-marked and six territories identified (Figure 1). In 1991 seven main setts were
bait-marked, but only three territories identified (Figure 1, Table 2). In that year the territories
of B and E were combined and the overlap between A and I counted as part of both
territories (Table 4). By 1992 there were six active main setts to be bait-marked and this
revealed only two territories (Figure 1). In 1993 only one territory was identified (Figure 1) and
finally in 1994, none (Table 2, Figure 2). The enlargement of the territories of social groups A
and B in 1991 to about double what they were in 1990 and 1992 (Table 4) suggests that, in
these cases at least, badger territories on this Irish farmland are more fluid than expected.
The areas of the territories varied (Table 4) and there was no direct relationship between
numbers of badgers and size of territory.
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Ir. Nat. J. Volume 28 No 1 2005
Figure 1. Badger territories in the Kilmurry area of Co Cork from 1990-1993 inclusive. The
dotted lines indicate defined territories (see text for details). The large open circles
are main setts (burrows) and the smaller black circles are frontier latrines. Where
different coloured plastic pellets, fed to the badgers in a mixture at the setts, was
found in a latrine then it was joined to the main sett by a straight line. If two different
colours of plastic were found in the same dropping, indicating visits to 2 main setts
then the latrine is indicated by a circle joining both lines( = ).
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Ir. Nat. J. Volume 28 No 1 2005
Figure 2. The non-territorial badger population in the Kilmurry area of Co Cork in 1994
(Symbols as in Figure 1)
It is of interest that while the overall numbers of badgers declined, the number of main
setts considered active, due to observation of signs of badger activity such as digging, did not
decline at the same rate, and by 1994, when only five adult badgers remained, four main setts
were considered active. Clearly there was no straight-line relationship between numbers of
badgers and active main setts. Presumably greater movements of badgers to several main
setts make main setts that are otherwise deserted appear active. Added to this, the low
badger density may allow more frequent use of the main setts by other animals such as foxes
- which may also make these setts appear more active.
Latrines, bait-marking and associated movements
The numbers of latrines identified stayed more or less the same in 1990 and 1991,
then declined in 1992 and 1993, and increased slightly in 1994 (Table 2). It ought to be borne
in mind that the number of latrines would not directly reflect quantity of droppings produced.
The numbers of latrines, in which plastic bait markers were found, did decline steadily (Table
3). The distances moved, detected by bait markers, increased from 0.45 to 1.20km, as the
population declined (Table 3).
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Ir. Nat. J. Volume 28 No 1 2005
Other movements
Movements up to 1990, mainly detected by radio location, have been reported
elsewhere (Sleeman 1992). Three other movements were detected, which are worthy of
note. In June 1991 a lactating female badger from sett F was found moribund on pasture to
the east of the study area, 10km (6 miles) from the sett at which she had been captured
several times. She was surrounded by cattle when found, and was shot. She tested positive
for tuberculosis on culture. The remains of another adult female were found in November
1991, again on pasture, this time 11km (6.5 miles) from the sett at which she had been
captured. She was from sett I. Finally a mature male from the same sett I was found 4km (3
miles) away: a victim of road traffic.
Discussion
In the study area, where badgers were found, they existed in well defined territories at
a density of 2+ per km2, or in much less well defined territories at a density of a single
badger per km2 , or without territories at a density of less than one badger per km2. One other
study in Ireland has shown badger territoriality at two sites: with badger densities of 1.6 per
km2 to 11.9 per km2 but weak, or no territoriality; and at a density of 0.86 badgers per km2 ;
the latter was in an upland area in Co Antrim (Feore and Montgomery 1999). Hutchings et al.
(2002) have suggested a continuum of variation in badger marking behaviour at boundaries in
Britain , from areas of high to low badger population densities. Here the picture of both longer
movements (Table 2; see also Sleeman 1992) and fewer territories shows this variation
occurring in the same place. The expanding movements detected by bait-marking were
similar to but more marked than those reported by both Cheeseman et al. (1993) and Roper
and Lüps (1993). These expanding movements are in turn small when compared with longdistance movements detected in the area in 1989-1990 (Sleeman 1992). It is not known to
what extent this may be due to changes in badger behaviour due to persecution.
The activity at main setts did not reflect the changing numbers of badgers, as has
been reported elsewhere (e.g. Wilson et al. 2003), which finding diminishes the value of the
use of main setts in badger surveys and highlights the need for improved techniques of
surveying badgers. It was also clear that badgers in this study area selected areas where
humans had dug the soil (the Iron-age forts and old railway line) for their setts.
Active research is ongoing on vaccination of badgers against TB (e.g. Gormley and
Southey 1999, Delahay et al. 2003). Such vaccine is likely to be delivered using oral baits.
Even at the lowest density found in this study, biomarked baits were consumed by four of the
five badgers that remained (Southey et al. 2001), which suggests oral biomarked baits
containing vaccine could be fed successfully to disturbed populations of badgers.
In the past, it has been suggested that badger behaviour at the edges of their
territories could explain the 'spill-over' of tuberculosis to cattle, especially by urine at so-called
linear features (hedges, roads etc.) (e.g. Brown et al. 1992, White et al. 1993). If territorial
behaviour no longer occurs at certain low densities, might we expect disease transfer to
cease?
However at present it is the opinion of most investigators, that transfer of tuberculosis
from badgers to cattle occurs, either when there is a dead or terminally-ill infected badger
which is nosed or licked by cattle, or when infected badgers visit cattle troughs or houses
(Garnett et al. 2002, 2003). Both such events were recorded during the study described here.
Also the increased movements, recorded as the population declines, may cause tuberculosisinfected badgers to expand their range onto previously uninfected farms and cause infection:
the so-called perturbation effect (Tuyttens et al. 2000). This perturbation effect has become
much speculated about in Britain against a background of worsening tuberculosis levels in
cattle (e.g. Donnelly et al, 2003, Roper 2003, Godfray et al. 2004, Bourne et al. 2004). It is
notable that during the present study only three bovines, all in the one herd, were detected by
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Ir. Nat. J. Volume 28 No 1 2005
testing, with tuberculosis, and only one had TB lesions; and no increase in disease was
observed in badgers during the population decline.
The high rate of human-caused mortality reported here appears to be frequent for
badgers (e.g. Roper and Lüps 1993) and other carnivores, for example British polecats
Mustela putorius (Birks and Kitchener 1999) and Swiss lynx Lynx lynx (Breitenmoser et al.
1993), all of which are, like the badger in Ireland, protected by legislation. This illustrates a
global problem between humans and carnivores, which can become a conservation concern
(Treves and Karanth 2003).
Acknowledgements
We wish to thank all the people of Kilmurry area, especially Connor Duggan and
Teddy Fitzgerald and also Billy Mc Ateer, Ted Duffy (Department of Agriculture) and Don Mc
Mahon (Wildlife Service). We also thank Tim Anderson who set up the study area, Alan
Whitaker and Ian O'Boyle, Marc Shorten for help with later stages of this paper.
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