Full text of DOI:10.1007/BF03192435

STUDIES ON THE EUROPEAN HARE ꢀ7
Acta Theriologica 46 (3): 287–294, 2001.
PL ISSN 0001–70ꢀ1
Home ranges of brown hares in a natural salt marsh:
comparisons with agricultural systems
Peter J. G. KUNST, René van der WAL* and Sip van WIEREN
Kunst P. J. G., van der Wal R. and van Wieren S. 2001. Home ranges of brown hares in
a natural salt marsh: comparisons with agricultural systems. Acta Theriologica 46:
2
87–294.
This is the first study on spatial behaviour of brown hares Lepus europaeus Pallas,
778 based on radio-telemetry in a natural system, which we contrast with data from
1
agricultural systems. Radio tracking took place in a Dutch salt marsh over a 10-month
period, with intensive tracking sessions during April/May and December/January. Six
hares could be followed in both periods and in total 1224 fixes were collected. Average
home range size was calculated as 28.7 ± 8.ꢀ ha when using Adaptive Kernell method
(
Mimimum Convex Polygon: 27.3 ± 9.0 ha) on 90% of all fixes. Such values are in the
lower end of the range of those obtained for agricultural systems. Home range size did
not differ between sexes, day and night, or across seasons. However, the size of the core
range (ꢀ0% of fixes) was twice as large in May compared to the winter period, and thus
inversely related to food availability. Unlike in agricultural systems, use of space by
hares did not change over the course of the season. This probably reflects the patchy
nature of the natural habitat which provides food and shelter throughout the year in a
confined area.
Zoological Laboratory, University of Groningen, P.O. Box 14, 97ꢀ0 AA Haren, The
Netherlands (PJGK, RvdW); Tropical Nature Conservation and Vertebrate Ecology
Group, Department of Environmental Sciences, Wageningen Agricultural University,
Bornsesteeg 69, 6708 PD Wageningen, The Netherlands (SvW)
Key words: brown hare, agricultural systems, home range, radio telemetry, salt marsh
Introduction
During the last three decades, populations of brown hare Lepus europaeus
Pallas, 1778 have declined substantially throughout Europe (Tapper 1992). Although
changes in weather, hunting pressure, predation and disease have locally con-
tributed to this decline (Hutchings and Harris 1996), it has largely been attributed
to changes in agricultural land use and related conversion of the countryside
(
Tapper and Barnes 1986, Slamecka 1991). Except for set-aside programs, there is
little scope for substantial improvement in agricultural areas to change to such an
extent that hares can profit from it and have a revival. Therefore, nature reserves
are expected to become increasingly important for hares. However, knowledge
*
Corresponding author: Centre for Ecology and Hydrology, Hill of Brathens, Banchory, AB31 4BW
Scotland, e-mail: rvdw@ceh.ac.uk
[
287]

288
P. Kunst et al.
about hares is largely derived from agricultural systems, and little is known from
natural systems.
We focus on hares inhabiting a natural salt-marsh system and test whether
habitat use parallels the behaviour of hares in agricultural systems. Based on
radio-telemetry data, we established size and position of home ranges, and studied
changes over the season.
Since the size of home ranges in Lagomorphs was found negatively related to
food supply (Boutin 1984, Swihart 1986, Hulbert et al. 1996), we expected home
ranges in the salt-marsh system to be larger than in agricultural habitat. Moreover,
we hypothesised that home ranges are extended in winter, when food is in short
supply.
Study area
The study was carried out in the central part of a ꢀꢀ0-ha undisturbed natural salt marsh in the
eastern part of the Dutch island of Schiermonnikoog (ꢀ3°30’N, 6°18’E). Brown hares were introduced
in 1898 and the species is currently well established. Based on the number of shot hares, the
population was remarkably stable over the period 1971–1994 (Hunting Corporation Schiermonnikoog,
unpubl. data). Soon after the area obtained the status ‘national park’ in 199ꢀ, hunting was prohibited.
Annual autumn counts (line transect counts involving around 30 people) have revealed that in the first
–
1
–1
year after cessation of hunting, the number of hares increased from about 0.ꢀ hare ha to 1 hare ha
,
but in subsequent years no further increase has been observed. Densities compare with optimal
agricultural habitat from the past (Broekhuizen 197ꢀ). There are no foxes Vulpes vulpes on the island,
but feral cats Felix silvestris catus and birds of prey, particularly hen harriers Circus cyaneus and
marsh harriers Circus aeruginosus regularly attack both adult and juvenile hares and therefore have
to be considered a potential threat (Van der Wal et al. 1998).
Methods
Ten hares were captured and radio-tagged with collar transmitters in April 1996. Hares were
caught by driving them into an approximately 1-m high and 800-m long net positioned perpendicular
to the east-west axis of the island. Simultaneous radio tracking was performed from fixed positions on
two dune tops which were 220 metres apart, and were on either side of the place where the catching
net had been up. The position of radio-tagged hares was determined by intercepting the signal with
two Yeasu FT-290 receivers with loop antennas tuned on 30 MHz. The collar transmitters (made by
the Institute for Forest and Nature Management, IBN-DLO Arnhem, the Netherlands) had a range of
about 1 km. Each transmitter weighed 40 grams (including collar), and fitted batteries were predicted
to last for at least 800 days. Half of the transmitters had a dip switch which allowed the pulse
frequency to double when the hares’ neck and head bend downwards. Although we did not use the
change of pulse frequency as such, its rapidly changing nature indicated that hares were active during
both at night and day.
Accuracy of tracking was tested in advance by placing transmitters on four different locations in
the field at 100–ꢀ00 metre distance from the receivers, where after position was determined 30 times.
All fixes fell within an area of 0.002 to 0.4 ha.
In the periods 1 April – 28 May 1996 (‘spring’) and 1 December 1996 – 1ꢀ January 1997 (‘winter’),
tracking sessions were held on a close to daily basis, at different times during the 24 h period. In each
session a single hare was tracked from both location points within the same three minute period, after
which the next hare was located. This procedure was repeated three times in each session, and all
three locations of a single hare during a session were treated as independent observations in the

Hare home ranges in natural salt-marsh habitat
289
analyses. Three hares died during the study periods and one transmitter failed, so data of six hares
were eventually used in the analysis. All positions found further than 1 km from a receiver were
marked as errors and were excluded, as it exceeded the range of the transmitters used. In total, 1224
positions (fixes) were used in the analysis. Home ranges were constructed using the Adaptive Kernel
method (Worton 1989). To allow comparison with other studies also the Minimum Convex Polygon
method (Mohr 1947) was used.
The data were divided into three time periods: April, May and December/January. To overcome the
methodological problem of increasing estimates of home range size with the number of fixes used
(
Broekhuizen 197ꢀ, Marboutin and Aebischer 1996), data for each hare were subdivided into units of
0 fixes per time period. For each unit of 40 fixes the size of the home range and core range were
4
determined, and for each period, the averages of these estimates were taken. Home range size was
estimated on 90% and core ranges on ꢀ0% of the fixes excluding the outermost points first. The time of
sunrise and sunset was used to separate day-time locations from night-time only.
The vegetation in the study area was mapped in the field in June 1996, aided by false-colour
photographs. Six different vegetation types were recognised, ranging from frequently inundated lower
salt marsh communities to elevated dune vegetation. The map was made in a Geographical Information
System and the percentage of all radio fixes of hares in each vegetation type was determined by
making an overlay of the hare data on the vegetation map. The study area is described in more detail
in Van der Wal et al. (1998).
Results
Average home range size for the total study period was 27.3 ha (SD = 9.0) when
using the Minimum Convex Polygon method, and 28.7 ha (± 8.ꢀ) when using the
Adaptive Kernel method on 90% of all fixes (Table 1). Home range size did not differ
between sexes (Mann Whitney U-test: Adaptive Kernel U = 6, n = 3, n = 3, p >
1
2
0
.2; MCP U = ꢀ, n = 3, n = 3, p > 0.2). The home ranges of the six hares showed
1 2
considerable overlap (mean ꢀ1 ± 9% on an area basis).
Home range size did not differ significantly across seasons (Fig. 1; Kruskal-
2
Wallis: c = 2.0ꢀ, df = ꢀ, p = 0.36). However, the size of the core range varied from
-
Table 1. The home range size of the six hares followed throughout the research period.
Home range size is calculated on 90% of the fixes following the Mimimum Convex Polygon
(
MCP) and Adaptive Kernel method.
Home range size (ha)
Hare
Sex
Body mass
Fixes (n)
(
MCP)
(Ad. Kernel)
1
2
3
4
ꢀ
6
M
F
3100
4030
30ꢀ0
3100
3100
3100
27.9
34.8
3ꢀ.2
24.6
30.1
10.9
32.7
29.1
39.8
29.4
27.4
14.0
227
187
224
20ꢀ
143
238
M
F
F
M
Mean
SD
32ꢀ0
380
27.3
9.0
28.7
8.ꢀ
204
3ꢀ

290
P. Kunst et al.
1
1
1
4
2
0
8
6
4
2
0
Home range
Core range
a
a
a
b
bc
c
April
May
December/
January
Fig. 1. Average size of home range (± SE) and core range for hares during the three time periods of the
study. Adaptive Kernel method based on 90% (home range) and ꢀ0% (core range) of the fixes,
respectively. Bars with different letters differed significantly from each other.
2
.6 ha in winter to 3.7 ha in April (Fig. 1; Kruskal-Wallis: c = 6.ꢀ4, df = ꢀ,
1
p < 0.0ꢀ). During night time, hares had home ranges and core ranges the size equal
of those in day-time (Mann Whitney U-test: home range U = 20, n = 6, n = 6, p >
1
2
0
.2; core range U = 21, n = 6, n = 6, p > 0.2).
1 2
No large-scale movements of radio-tagged hares were observed; individuals were
faithful to their home ranges throughout the year. However, the centre of activity
moved for all six hares between spring and winter in N to NE direction towards the
dunes by 108 m (± 12.9) on average. Females showed a relatively large shift based
on night time observations (248 ± 81 m), and almost no displacement on the basis
of fixes in day time (24 ± 2 m; Mann Whitney U-test: U = 9, n = 3, n = 3, p < 0.1).
1
2
Males had comparable shifts in their activity centre between spring and winter
based on either day-time (104 ± 31 m) or night-time (149 ± 29 m) observation.
Habitat use of hares as based on the proportions of fixes in the different
2
vegetation types did not differ significantly across seasons (c = 12.31, df = 8, p =
0
.2ꢀ). Also, no significant differences in habitat use between day and night were
2
found (c = 7.19 df = ꢀ, p = 0.20).
Discussion
No large-scale movements of radio-tagged hares were observed over the 9-month
study period despite large changes in food availability due to both flooding and
seasonality. Biomass of the grass Festuca rubra, which is an important food item for
2
hares throughout the year (Van der Wal et al. 2000), was 43.1 ± ꢀ.7 g/m in May

Hare home ranges in natural salt-marsh habitat
2
994 and dropped to 11.6 ± 1.4 g/m in December 1994 (R. Van der Wal, unpubl.
291
1
data). This study supports the view that hares have a non-migratory way of live
Broekhuizen and Maaskamp 1982, Pépin and Cargnelutti 198ꢀ). Large-scale
movements have been observed elsewhere following periods of heavy snowfall
Grzimek 1972), which is likely to be linked to a poor accessibility of food. Large
(
(
parts of our study area are regularly flooded by the sea, which impedes foraging
opportunities for a period of hours up to several weeks. During extreme high tides,
hares have been observed to gather on the tops of nearby dunes, rather than
migrate to areas where the overall probability of inundation is lower. However, for
all six hares the activity centre had shifted N to NE towards the dune ridge between
spring and winter. This shift might be induced by floodings which are most
dramatic during winter.
Home range size of hares in the natural salt-marsh system was found to be
comparable to those in agricultural areas (Table 2). Only in the most large-scale
agricultural area of all studies (Table 2, study no. 7), Marboutin and Aebisher
(
1996) report home ranges which seem greater than average. It appears that most
variation in the size of home ranges is due to the proportion of fixes taken into
account when calculating home range size, as the size of the home range of an
animal is strongly influenced by occasional sallies. In our study, home range size
was linearly related to the percentage of fixes included in the calculation, but this
relationship turned exponential when more than 90% of the fixes were included. By
following Burt (1943) and defining home range as that area where the majority of
the activities take place, we excluded the outermost 10% of the fixes when
calculating home range size. In our study, estimated home range size using
Adaptive Kernel was ꢀꢀ ha when 100% of the valid fixes were included, and dropped
to 44 ha and 29 ha when calculated on the basis of 9ꢀ% and 90% of the fixes
respectively. Reitz and Léonard (1994) indicate an even more extreme drop in home
range size when reducing the number of fixes included (Table 2). Similar to studies
in agricultural areas (Broekhuizen and Maaskamp 1982, Kovacs and Buza 1992)
home ranges of the hares in the salt marsh greatly overlapped, which indicates a
high degree of tolerance.
In our study, home range size did not differ across seasons. However, we found
the size of the core range (ꢀ0% of the fixes) smallest in winter, when food
availability is lowest due to natural dieback (R. Van der Wal, pers. obs.). Similarly,
Reitz and Léonard (1994) found that average home range size tended to be smallest
in winter, which is contrary to expectation if food availability is determining home
range size (Hulbert et al. 1996). Large core ranges in April may be related to peak
sexual activity, since ‘March madness’ is delayed by about a month in the
salt-marsh system. Alternatively, small core ranges during winter might reflect low
activity as a strategy to save energy when food is in short supply, and weather
conditions often poor. By minimising movements and maximising the time in
shelter (Thirgood and Hewson 1987), wind chill and associated high energetic costs
are likely to be kept low.

2
92

Hare home ranges in natural salt-marsh habitat
293
We did not find differences in the size or location of home ranges between night
and day, suggesting weak differences in habitat use between day and night. Habitat
use, as based on the number of fixes in the various vegetation types, also did not
differ across seasons. This is in contrast to the general patterns observed in
agricultural areas and indicate a different use of natural habitat. In their classical
study, Tapper and Barnes (1986) showed that hares shifted their activities between
fields according to crop development, usually preferring the early stages of
development. Similarly, hares in France were shown to incorporate stubble fields
successively in their home range after harvest (Reitz and Léonard 1994), and in
New Zealand rangeland there were distinct seasonal differences in the use of
different vegetational units by hares (Parkes 1984). Generally, night-time ranges of
hares in agricultural area are significantly larger than day-time ranges (Reitz and
Léonard 1994, Marboutin and Aebisher 1996), reflecting a wider area for foraging
(
Homolka 1986, Tapper and Barnes 1986). The diet of hares in the salt marsh of
Schiermonnikoog changes over the season, with large amounts of the lower salt
marsh shrub Atriplex portulacoides consumed in winter, at the expense of the grass
Festuca rubra, which grows in higher parts of the marsh (Van der Wal et al. 2000).
However, this major switch in the use of food plants did not lead to detectable
changes in spatial use of the salt marsh, which probably reflects the patchy
structure of the system. Without extending their home ranges, hares have access to
most of their food plants in a relatively small area. In agricultural areas the daily
resting areas are often clearly separated in space from the nightly feeding areas
(
Tapper and Barnes 1986, Reitz and Léonard 1994), leading to differences in the
size of night and day range and contrasting habitat use. This salt marsh offers
foraging and resting places in close vicinity. Throughout the year, home range size
has frequently shown to increase as fields with different crop species or management
regime are included sequentially. We hypothesize that due to the heterogeneity of
the salt-marsh vegetation, use of space by hares within a day and throughout the
year are relatively invariable. The fact that the average home range size in our
study is among the smallest of all studies, suggests that this high level of patchiness
guarantees food availability and shelter throughout the year in an area of limited
size.
Acknowledgements: We thank T. Baarspul, M. Bestman, R. Keizer, R. Slot, E. Timmerman, and J. Wolf
for their tremendous help in carrying out the radio telemetry work often under harsh working
conditions. We are indebted to S. Broekhuizen and R. Drent for transfer of knowledge and valuable
discussion. The Institute for Forest and Nature Management (IBN-DLO Arnhem) kindly provided us
800 metres of hare catching net. We thank C. Van der Wal for his crucial support with catching hares
and are grateful to Natuurmonumenten for their permission to carry out the work.
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Received 5 June 2000, accepted 27 March 2001.