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Home range of feral house cats(Felis catus L.) in forest of the Orongorongo Valley, Wellington, New Zealand.

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The home ranges of four male and five female feral house cats (Felis catus) were studied by radio- telemetry. In the narrow, steep-sided valley the home ranges of cats were linear, with an average length of 6.34 km for males and 3.83 km for females; only large males crossed the river. Females with kittens had small home ranges of 0.84 to 2.0 km. Home ranges of animals of the same sex, including breeding females, overlapped considerably. The social organisation of feral cats at low density differs little from that of higher-density free- ranging domestic cats.
Aerial view down the Orongorongo Valley to the sea, from point marked with arrow in Fig . 1 Photo: N.Z. Geological Survey, D.S.I.R. truncata) or black beech (N. solandri). Higher on steep slopes on the east side of the river is a zone of scrub and above 600 m chiefly silver beech (N. menziesii) forest. A detailed description of the vegetation is given by Campbell (1984). The two main prey species, rats (Rattus rattus) and rabbits (Oryctolagus cuniculus), are distributed patchily. We snap-trap quarterly for rodents (Fitzgerald, 1978; Fitzgerald and Karl, 1979) and in trapping over 5 years near the floor of the valley and in silver beech the overall capture rates in lowland beech and silver beech forest were 0.65 and 0.76 rats/loo trap nights respectively, about one-quarter the capture rate of 2.57 rats/100 trap nights in lowland mixed rata/podocarp/broadleaf forest. Rabbits are mainly restricted to patches of grass, low vegetation and scrub on the floor of the valley. Some of these areas support only one or two pairs of rabbits separated from other rabbits by the river or by steep forested slopes. Rabbits live above-ground in dense scrub but dig short burrows (stops) for breeding. Mice (Mus musculus) are fairly evenly distributed through forest near the floor of the valley and at about similar densities in the silver beech forest, but their numbers fluctuate considerably from year to year (Fitzgerald, 1978). Adult possums (Trichosurus vulpecula) are eaten as carrion, and young are probably killed by cats at the age when they leave their mothers' backs. Possum trappers operated in parts of the study area and skinned possum carcasses were sometimes available to cats. Birds are a small part of the diet of cats in the Oron g oron g o Valle y and those eaten are mainl y
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B.M. FITZGERALD and B.J. KARL
Ecology Division, Department of Scientific and Industrial Research, Private Bag, Lower Hutt, New Zealand.
71
HOME RANGE OF FERAL HOUSE CATS (FELIS CATUS L.) IN FOREST
OF THE ORONGORONGO VALLEY, WELLINGTON, NEW ZEALAND.
Summary: The home ranges of four male and five female feral house cats (Felis catus) were studied by radio-
telemetry. In the narrow, steep-sided valley the home ranges of cats were linear, with an average length of 6.34
km for males and 3.83 km for females; only large males crossed the river. Females with kittens had small home
ranges of 0.84 to 2.0 km. Home ranges of animals of the same sex, including breeding females, overlapped
considerably. The social organisation of feral cats at low density differs little from that of higher-density free-
ranging domestic cats.
Keywords: Feral cat, domestic cat, Felis catus, radio-telemetry, territory, social organisation, home range.
Introduction
We have studied the home range of feral house cats
(Felis catus L.) in forest of the Orongorongo Valley,
Wellington, using radio-telemetry, as part of studies
of the ecology of feral cats in New Zealand (Fitzgerald
and Karl, 1979; Karl and Best, 1982; Fitzgerald and
Veitch, 1985); with the long-term aim of better
management of predators and conservation of native
fauna.
Current information from other sources is sparse,
or may not be applicable. Domestic cats, associated
with man in cities, dockyards and on farms, have
overlapping ranges and are sociable to some degree
(LaundrÈ, 1977; Macdonald and Apps, 1978; Dards,
1978; Corbett, 1979; Liberg, 1980; Panaman, 1981;
Izawa, Doi and Ono, 1982; Natoli, 1985), though they
have been considered as essentially solitary because
they hunt alone (Kleiman and Eisenberg, 1973).
However, their behaviour might be affected by their
dependence on man for food and shelter. Studies of
home range and social interactions of feral cats so far
are inconclusive (Corbett, 1979; Jones and Coman,
1982; Konecny, 1983; Brothers, Skira and Copson,
1985).
Study Area
The Orongorongo Valley is a long, steep-sided valley
on the west of the Rimutaka Range, east of
Wellington. The ridges rise to 160-442 m a.s.l. on the
west side of the valley and to 700-941 m a.s.l. on the
east (Figs 1 and 2). The D.S.I.R. Research Area of
about 1200 ha, extending over 4 km of the valley floor
and to the crest of the ridge on either side, was the
site of our earlier study of the food habits of cats
(Fitzgerald and Karl, 1979). However, several cats that
we trapped and radio-tagged within the Research Area
travelled well beyond it and they determined the size
of the study area, i.e. from near the mouth of the
Oron
g
oron
g
o River to about 16 km u
p
the valle
y
.
Figure 1: The lower Orongorongo Valley, showing the
D
.S.I.R. Research Area (hatched). Dotted lines show major
ridges.
The valley floor consists largely of a stony
riverbed over which the river frequently changes
course; recently flooded areas consist of bare gravel,
and the older, more stable areas are covered with
grass, low vegetation and scrub. In the northernmost
1-2 km the river is narrow with large boulders and
deep pools but downstream the river widens,
meandering with many riffles.
The southern third of the study area is in rough
pasture and scrub and the northern two-thirds in
forest. Most of the forested lowland terraces and
gentler slopes have mixed rata/podocarplbroadleaf
forest and the ridges have hard beech (Nothofagus
New Zealand Journal of Ecology 9: © New Zealand Ecological Society
72
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 9, 1986
Figure 2: Aerial view down the Orongorongo Valley to the
sea, from point marked with arrow in Fig.1 Photo: N.Z.
Geological Survey, D.S.I.R.
truncata) or black beech (N. solandri). Higher on
steep slopes on the east side of the river is a zone of
scrub and above 600 m chiefly silver beech (N.
menziesii) forest. A detailed description of the
vegetation is given by Campbell (1984).
The two main prey species, rats (Rattus rattus)
and rabbits (Oryctolagus cuniculus), are distributed
patchily. We snap-trap quarterly for rodents
(Fitzgerald, 1978; Fitzgerald and Karl, 1979) and in
trapping over 5 years near the floor of the valley and
in silver beech the overall capture rates in lowland
beech and silver beech forest were 0.65 and 0.76
rats/loo trap nights respectively, about one-quarter
the capture rate of 2.57 rats/100 trap nights in
lowland mixed rata/podocarp/broadleaf forest.
Rabbits are mainly restricted to patches of grass, low
vegetation and scrub on the floor of the valley. Some
of these areas support only one or two pairs of rabbits
separated from other rabbits by the river or by steep
forested slopes. Rabbits live above-ground in dense
scrub but dig short burrows (stops) for breeding.
Mice (Mus musculus) are fairly evenly distributed
through forest near the floor of the valley and at
about similar densities in the silver beech forest, but
their numbers fluctuate considerably from year to year
(Fitzgerald, 1978). Adult possums (Trichosurus
vulpecula) are eaten as carrion, and young are
probably killed by cats at the age when they leave
their mothers' backs. Possum trappers operated in
parts of the study area and skinned possum carcasses
were sometimes available to cats.
Birds are a small part of the diet of cats in the
Oron
g
oron
g
o Valle
y
and those eaten are mainl
y
ground-feeding introduced species, such as blackbird
(Turdus merula), thrush (T. philomelos), chaffinch
(Pringilla coelebs) and hedgesparrow (Prunella
modularis) (Fitzgerald and Karl, 1979).
Methods
Cats were caught using drop-door cage traps
(illustrated by Veitch, 1985) baited with fish heads.
We operated two trapping regimes: (1) general
trapping, on the eastern side of the river with traps set
along the vehicle track, foot tracks and bush edge (the
number set and their sites varied between trapping
periods); and (2) specific trapping, with a few traps set
close to (usually within 200 m of radio-located cats.
Because of the size of the traps, difficult terrain and
dense vegetation, only 3-6 traps could be set near an
animal. Specific trapping was carried out when the
transmitter battery began to fade, and continued until
the animal was caught or the transmitter ceased
functioning.
Trapped cats were run into a retaining sleeve,
weighed, and anaesthetised intramuscularly with
ketamine hydrochloride at a rate of 10 mg per 1 kg
body weight. Each cat was fitted with a radio
transmitter and ear-tagged with a numbered metal tag.
They were held in the trap for about an hour after
dosing, to recover sufficiently to be released.
The radio transmitter emitted a pulsed signal on
160 MHz, as used by Ward (1985) and had an
effective life of about 3 months. The transmitters
weighed about 25 g which represented, on average,
less than 1% of the cat's body weight. The transmitter
chip, battery and reed switch were set in a moulded
hard plastic case with SYLGARD 184 encapsulating
resin. A transmitter, with a loop aerial, was put over
the cat's head and the excess aerial was taken up by
doubling it on to itself and crimping a "D" size bird
band at each end of the doubled up aerial.
The signals were received on an A VM LA12
receiver and hand-held, 3-element yagi directional
aerial. Because of the steeply dissected nature of the
country strong signals could be picked up at distances
varying from 2.5 kilometres to only a few hundred
metres. Cats were located during daylight, and we
endeavoured to obtain a morning and afternoon fix
on each cat. The intervals between radio-fixes varied
because of the distances involved and the difficulty of
locating animals regularly. Some animals were located
on most attempts but others, especially those furthest
north from the Field Station, were often not found.
Cats were usually located to within an area of about
10 m diameter but because of the dense ve
g
etation
FITZGERALD and KARL: HOME RANGES OF FERAL CATS
73
were not often seen. Attempts to fix their position
more accurately or to see the cats usually ended in
them being disturbed and moving away.
The cats mainly used the riverbed, and the
forested terraces and lower slopes, so home ranges
tended to be linear. Conventional analyses using either
non-statistical polygon techniques or statistical models
based on the assumption that the data conform to a
probabilistic distribution (Smith, 1983; Rhoades and
Langham, 1984) are not applicable to such ranges. We
have therefore expressed home ranges chiefly in terms
of cumulative length of home range, but because
ranges that are described as linear do have some width
we have included, as two other measures of range size,
the cats' shortest distance from the centre of the
riverbed, and height above the riverbed. The very
steep hillsides, deeply dissected by side streams, make
reliable estimates of area of home range almost
impossible; however, to get an approximate idea of
the area of home ranges we have multiplied range
length by the average of the distance from the cat to
centre of the riverbed at each fix.
Results
Nine cats (four male, five female) were trapped and
fitted with radio transmitters between April 1981 and
May 1983. The periods for which cats carried active
transmitters, and the weights of cats, are shown in
Fig. 3. Three females had been trapped and tagged
previously. Lena was first trapped as a kitten weighing
0.8 kg on 19 March 1976, Nanny as an 0.8 kg kitten
on 15 February 1979, and Lucy as an adult weighing
2.0 kg on 16 November 1979. During the present
study Lena was 6 years old, Nanny was 2 years old,
and Lucy was at least 2 years old. Some time between
March 1976 and February 1982 Lena's right front foot
had been amputated above the wrist, probably by a
gin trap set for possums. The injury had completely
healed, she walked on it, and ran with a slightly
rolling gait. Despite the disability she was in good
condition and in autumn 1982 reared two kittens.
None of the males had been trapped before.
Records on two cats ceased when they shed their
transmitters, on five when the batteries expired and
they could not be recaptured, and on four cats when
they died (two of unknown causes, one in a gin trap
and one was shot).
Cats were difficult to recapture; when the
transmitter batteries weakened we made considerable
effort to re-trap cats but only three out of seven were
recaptured. Females seemed to be more trappable
when they were feeding kittens; four of the five
females were lactating when trapped and two whose
transmitter batteries expired were lactating when
recaptured one to nine months later (Fig. 3). Of the
lactating females, Lena had small kittens still in the
natal den and the others had larger kittens at heel.
Sandy was possibly the father of Lena and Mini's
kittens because both litters included a tortoiseshell
female kitten.
R
ange length
All the radio-tagged cats spent most of their time in
the valley floor but sometimes moved up the gullies of
side streams. Because the Orongorongo Valley is
narrow and steep-sided, the cats' home ranges were
linear: ranges of females were about 18 times longer
than wide, and of males about 28 times longer than
wide. Maximum range lengths, in a straight line, for
the five females ranged from 1.89 km to 6.40 km and
for the four males from 4.75 km to 8.60 km (Table 1).
Ranges of both females and males were largely
revealed within 10 records taken irregularly over 20-40
days (Figs 4a-c). The major exception was that
females with kittens moved over a smaller area and
the lengths of their ranges were then 0.25-0.5 the
length without kittens. Mini, radio-tagged in
November 1981, revealed her range of 4.0 km with
five records over 11 days and her recorded range did
not increase substantially over the next 80 days (Fig.
4a). When retrapped in November 1982 she was
lactating, and subsequent sightings of her kittens
suggested that they had already left the natal den.
With kittens, her recorded range was restricted to just
over 2.0 km lon
g
(the northern half of her ran
g
e) for
Figure 3: Periods of radio-tracking cats, with weight in kg at
capture and fate (D = died. X = shed transmitter, Z =
battery faded).
74
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 9, 1986
at least 65 days. Eleven days later she was found shot
near the south end of her range, giving a recorded
range 3.85 km long during the second radio-tracking
period.
Similarly, Lena had two kittens about seven days
old in the natal den when she was trapped; they left
the den 22-26 days later and were seen with Lena until
day 43 of radio-tracking (Fig. 4c). Lena's range
throughout this period and until day 73 was 0.84 km
long. Over the next five days her range increased to 4
km long and she remained within that range for the
next 120 days. Two other females, Nanny and Jenny,
both lactating when trapped, had ranges of 1 to 1.5
km for about 60 days; their ranges then began to
increase (Fig. 4a) but Nanny was caught in a gin trap
and Jenny slipped her transmitter before their ranges
stabilised again.
Lucy's range reached a plateau after 10 records in
the first 44 days and remained stable for the next
three months. In spring (mid September) she moved
considerably south of her usual range and well up one
of the side streams and spent at least three days there.
A
fter this excursion she returned to her previous range
and remained largely within it for the remaining 70
days of her life. She may have moved out of her usual
ran
g
e to mate, because when retra
pp
ed 64 da
y
s later
at the end of November she was lactating. Lucy's
cumulative range length from the time she was
retrapped in June was very similar to that determined
when the transmitter was first fitted.
All four males had long home ranges, between
4.75 km for Thunder and 13.92 km for Sandy. The
differences in range size probably reflect age and
social status. Sandy was the largest adult male; his
range length increased rapidly to 8.2 km by day 35
and then gradually to 8.6 km at day 74 by which time
the battery was weakening. He could not be retrapped
but his transmitter was found on day 163 near a
farmhouse at the mouth of the Orongorongo River. If
he shed his transmitter there, this would increase his
range length to 13.92 km. A large ginger cat fitting
Sandy's description was seen on 5 January 1984
(almost 5 months later) about 0.75 km north of where
the transmitter was found. He has been seen several
times since, within his radio-revealed home range and
was still present in March 1986. Blackie's range
increased to 6.4 km over two months and we then lost
contact with him as the batteries weakened. Thunder,
weighing 2.8 kg when tagged, was located on only
three days before he was found dead on day 41.
Another young male, Eddie, weighing 2.75 kg when
first trapped, had a maximum cumulative range of 5.6
km. After he was first trapped his range quickly
reached 3.9 km and he remained within this range for
more than five months before extending his range
northward.
R
iver-crossings
All the records for the females and Thunder were on
the east side of the river. Eddie was found only on the
east side of the river for the first 5.5 months that he
was radio-tracked. He then moved north where the
river is narrow and crossed to the west side of the
river. In contrast, the two larger males (Blackie, 3.2
kg; Sandy, 4.75 kg) frequented both sides of the river
about equally; Sandy was found 13 times on the east
side and 12 times on the west, and Blackie was found
nine times on each side of the river.
These two cats crossed the river most often in the
northern part of the study area. We have compared
the number of times on successive fixes within
tracking sessions that Blackie and Sandy were found
on the same or opposite sides of the river in the north
and south part of the ranges (using Big Bend as the
dividing point, Fig. 1). They crossed on four out of
seven occasions in the north section and only once out
of twenty-three occasions in the south section. The
difference between the two areas is highly significant
(Fisher's exact test
p
= 0.006) and su
gg
ests that the
Table 1: Home range size of cats in the Orongorongo Valley.
R
ange widths calculated for Blackie and Sandy include both
sides of the river.
Maximum Average Approximate
range length range length area
(km
2
)
Females
Lucy 6.40 264.1 1.7
Nanny 2.75 283.0 0.8
Mini 4.08 205.3 0.8
Lena 4.02 178.2 0.7
Jenny 1.89 110.3 0.2
Average 3.83 208.2 0.8
Males
Thunder 4.75 114.3 0.5
Eddie 5.60 176.6 1.0
Blackie 6.41 245.6 1.6
Sandy (radio) 8.60 358.0 3.1
Sandy (sighting) 13.92 5.0
Average
(radio only) 6.34 223.6 1.4
FITZGERALD and KARL: HOME RANGES OF FERAL CATS
75
Figure 4: Cumulative home range lengths with time. Symbols indicate days on which fixes were obtained. (a) females with
records 3 months, (b) males with records 3 months, (c) females and male with records > 6 months.
76
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 9, 1986
cats may be crossing the river mainly by rock-hopping
or on fallen logs, which is only possible in the
northern part of the study area.
R
ange width and height above riverbed
We have used two measures of the width of the home
range and, indirectly, of habitat use. For each fix we
recorded the shortest distance from the cat to the
centre of the riverbed, and the cat's height above the
riverbed. Combining the fixes for cats of the same
sex, the females were always recorded within 1150 m
of the centre of the riverbed and males within 600 m
(Fig. 5a). The cats rarely moved far up the hilbides.
Females were recorded no more than 280 m above the
riverbed, and males no more than 160 m (Fig. 5b).
Females spent significantly more time (as measured by
the number of fixes) further from the riverbed, and
higher above the riverbed than did males
(Kolmogorov-Smirnov two-tailed test p < 0.005 and p
< 0.001 respectively). The males, who spent more of
their time close to the riverbed than did females, may
have been feeding more on rabbits along the riverbed,
but we have insufficient information on the food of
individual cats to confirm this. We recorded eight
individual prey, mainly at dens of kittens; prey at dens
were three young rabbits (one whole rabbit weighed
315 g), a rat and a blackbird. In addition Nanny was
seen carrying a bird, probably a blackbird, and
remains of two small rabbits were found at a site
where Sandy was recorded for two days.
We located four cats (Mini, Lucy, Lena and
Eddie) sufficiently often that their results can be
compared. In addition, fixes of the two males (Blackie
and Sandy) with rather similar ranges using both sides
of the river have been combined so they can be
included in the analysis (Table 2). Lucy was found
further from and higher above the river than the
males; Lena was found hi
g
her, but because much of
Figure 5: (a) Distance of cats from the centre of the riverbed
at each radio-fix (all females and all males combined).
(b) Height above the riverbed of cats at each radio-fix (all
f
emales and all males combined). males N = 115, females N
= 216.
Table 2: Differences between cats for height above river (figures above the diagonal) and distance from centre of riverbed (figures
below the diagonal) at radio-fixes (* p < .05, ** P < .01; Kolmogorov-Smirnov 2-tailed test D values).
Sandy &
N Blackie Mini Lucy Lena Eddie
Height above river
Sandy &
Blackie 43 0.207 0.536** 0.390** 0.211
Mini 55 0.326* 0.424** 0.365** 0.152
Lucy 68 0.479** 0.248* 0.169 0.374**
Lena 65 0.196 0.151 0.304** 0.219
Eddie 66 0.200 0.158 0.311** 0.041
Distance from river centre
FITZGERALD and KARL: HOME RANGES OF FERAL CATS 77
her home range was in steep country, not further from
the river than Sandy and Blackie. In contrast, Mini
tended to frequent forest on old fans of sidestreams,
which spread out giving wide areas that did not rise
very high above the river. Eddie occupied the same
home range as did Lena.
R
ange overlap
The ranges of most of the cats overlapped
considerably with the ranges of at least one neighbour
of the same sex. To compare the ranges of concurrent
animals the study was divided into two periods, from
April 1981 to January 1982 (Lucy, Nanny, Mini,
Blackie and Thunder) and from February 1982 to May
1983 (Mini, Lena, Jenny, Eddie and Sandy) (Fig.
6a-b). During the first period the ranges of the two
breeding females, Lucy and Nanny, overlapped
somewhat, but Mini, whose range overlapped
extensively with Lucy's, was radio-tracked only after
Lucy had died. In the second period the ranges of all
three breeding females overlapped, and that of Lena
completely covered that of Jenny. Although Mini was
radio-tracked after the other two females, her range in
this period was similar to that in the first, and there is
no reason to suppose that it differed in the intervening
months. Similarly, Lena, who was the oldest of the
females, was probably present in her revealed home
range during the first tracking period and would have
overlapped extensively with Lucy and Nanny. The
high proportion of fixes in one locality for Nanny,
Lena, and Jenny (Fig. 6) reflect periods when these
females had young kittens with them and did not
move far.
Two cats, Lena and Eddie, held almost identical
home ranges for much of the study (Fig. 6b) and were
sometimes found close together; Eddie may have been
one of Lena's offspring from a previous litter. They
were both trapped on 24 February 1982, 170 metres
apart, and both retrapped on 20 May sixty metres
apart. Eddie was found inside Lena's home range
throughout the first five months they were radio-
tracked; only in the sixth month did he move north
outside Lena's range.
A
ctivity and den sites
Cats were active by day and by night but also spent
long periods resting. Sometimes a cat moved almost
from one end of its home range to the other in a few
hours but at other times it remained in the same
locality for several days. The greatest distances moved
per hour during the day were 478 and 418 m/h by
Lucy and 260 m/h by Mini; most of the other
movements recorded were of less than 200 m/h. Over
Figure 6: Distributions of cats along the Valley, based on
radio-fixes and captures. (a) records for animals April
1981-January 1982, (b) records for animals February
1982-February 1983. Valley subdivided at 0.5 km intervals.
24 hours, females without kittens moved on average
about 750 m and the subadult male Eddie about 1.3
km.
In the Orongorongo Valley, cats did not have
permanent dens but could be found resting in any part
of their home range. Sandy was once disturbed from a
dry, sheltered 'nest' in a leaning, hollow stump but
was not found there again. However, females kept
their young kittens in one den, usually in the hollow
base of a tree, until they weighed about 450-500 g
(about 7 weeks old). Lena had young kittens when she
was trapped and radio-tagged. She was at the den with
the kittens whenever we checked from 0820 h to 1745
h over the next 22 days. On 18 March 1982 the kittens
weighed 440 and 445 g; four days later they had
moved to another hollow tree about 140 m away and
weighed 510 and 485 g. From then on Lena and the
kittens moved about fre
q
uentl
y
, usuall
y
to
p
laces
78
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 9, 1986
where they could hide in holes in tree stumps, fallen
logs, or in dense thickets of kiekie (Freycinetia
baueriana). All the other lactating females that were
trapped had larger, active kittens that moved
frequently from one sheltered place to another.
Discussion
The behaviour of cats in the Orongorongo Valley was
probably influenced by the distribution of their prey,
giving results that differed somewhat from those of
other studies. Firstly, because the cats fed chiefly on
rats and rabbits (Fitzgerald and Karl, 1979) which
were plentiful only in the bottom of the long, steep-
sided valley, the cats' home ranges were rather linear
and more akin to the ranges of carnivores living in
streams and rivers, e.g. mink (Gerell, 1970; Birks and
Linn, 1982) and otters (Erlinge, 1968), than to feral
cats in less rugged habitats. Secondly, the cats were
hunting dispersed prey rather than taking concentrated
food supplies from houses or garbage dumps and did
not have permanent dens (c.f. Laundre, 1977;
Panaman, 1981; Izawa et al., 1982; Natoli, 1985).
However, our results on the cats' use of home ranges
and their social organisation are generally consistent
with other studies. Also, the few animals we studied
were a large proportion of the population; we did not
catch additional adults despite considerable trapping,
and most cats seen on the research area were
identifiable as radio-tagged cats.
The range lengths of most females and of a
sub adult male were reliably estimated but those of
some lactating females and the adult males were
probably underestimated. Bekoff, Daniels and
Gittleman (1984) suggest that 100-200 fixes are needed
for reliable estimates of the size of home ranges of
large carnivores, but that for smaller species fewer
fixes suffice. Range length of our cats was usually
revealed with 10 fixes taken over 20-40 days; more
fixes would probably be needed to measure area
instead of length.
The size of home ranges of house cats in different
habitats varies about 200-fold. Home ranges of female
cats associated with man vary from an average of 0.84
ha to 112 ha (Dards, 1978; Macdonald and Apps,
1978; Corbett, 1979; Liberg, 1980; Warner, 1985).
Among feral cats, females in the Galapagos Islands
had home ranges of 82 ha (Konecny, 1983), those in
the Orongorongo Valley about 80 ha (this study) and
in semi-arid Victoria, Australia, 170 ha (Jones and
Coman, 1982). Densities are even more varied; from
23.5 cats/ha on a Japanese island where cats fed on
fish wastes (Izawa et al., 1982), to about 2 cats/ha in
the Portsmouth dockyards (Dards, 1983), 1.2 cats/ha
on uninhabited Herekopare Island, New Zealand
(Fitzgerald and Veitch, 1985) and about 0.025 cats/ha
in Victoria, Australia (Jones and Coman, 1982).
The home ranges of adult male cats in the
Orongorongo Valley, like those elsewhere, were much
larger than those of adult females and the subadult
male (Dards, 1978; Macdonald and Apps, 1978;
Corbett, 1979; Liberg, 1980; Jones and Coman, 1982;
Konecny, 1983; Warner, 1985). The ranges of adult
males in the Orongorongo Valley also differed from
those of females in two other respects; the adult males
frequently crossed the river whereas females did not,
and the adult males were usually recorded closer to
the river than the females were (Fig. 5a & b). The
concentration of activity close to the river by adult
males may reflect more hunting on rabbits. Gibb,
Ward and Ward (1978) found that a large male was
more successful at killing adult rabbits than were
females. Females scavenged off the male's kills, and
on 3 occasions when they did kill adult rabbits
themselves they were supplanted by the male.
The home ranges of young males may be more
similar to those of females than to those of adult
males. Eddie, first trapped at 2.75 kg, lived within the
same home range as Lena for 5.5 months before
expanding his range northwards and hunting on both
sides of the river. Other studies show that young
males do not disperse from their mothers' home
ranges until they are 1-3 years old (Liberg, 1980;
Dards, 1978; 1983), and then may be forced out by
other cats in the group (Liberg, 1980; Warner, 1985).
The description of behaviour and social
organisation of cats given by Leyhausen (1965; 1979),
derived chiefly from domestic cats, also largely applies
to feral cats. He described cats as having a 'first-
order home', usually a room, and a home range
consisting of a 'varying number of more or less
regularly visited localities connected by an elaborate
network of pathways'. The home ranges of
neighbouring cats usually overlap, with both animals
using the same pathways and hunting grounds, but at
different times. Leyhausen (1979) used the terms
'home range' and 'territory' interchangeably, but
emphasised (p. 218) that "territory" must be
understood in terms of space and time. However, the
cat's home range is not a territory in the strict sense
of a fIXed area that is defended, and from which rivals
are excluded (Brown and Orians, 1970), as the home
ranges of both feral and domestic cats overlap
considerably.
Although our cats did not have permanent dens
or 'first order homes', feral cats in other studies ma
y
79
FITZGERALD and KARL: HOME RANGES OF FERAL CATS
have had them (Jones and Coman, 1982; Brothers et
al., 1985). Nor do we have evidence for or against the
suggestion that cats avoid each other by using areas of
overlap at different times.
In the Orongorongo Valley the females held
overlapping home ranges. All three females studied
during the second period were probably present during
the first period and their inclusion would further
increase the degree of overlap. We radio-tracked only
one adult male at a time but Sandy was probably
present when Blackie was radio-tracked and their
ranges may have overlapped considerably.
In other studies of feral cats, Corbett (1979)
found from radio-isotope tagged faeces that the range
of one female included the range of the other but
concluded, contradictorily, that 'cats of both sexes
tended to live in separate ranges'. In southern
Sweden feral males were 'evenly distributed, and
usually had large.........., partly overlapping home ranges'
(Liberg, 1980, p. 344), but Liberg (p. 347) also
described their ranges as 'more or less exclusive'. In
the Galapagos Islands, of two dominant males one
shared 51% of his home range with the second, and
the second shared 76% of his range with the first
(Konecny, 1983). In southeastern Australia the home
range of two adjacent males and two adjacent females
did not overlap, but other adults (not radio-tagged)
were seen occasionally in their ranges (Jones and
Coman, 1982).
Free-ranging domestic cats usually live in groups
centred on farmhouses and associated buildings, and
their home ranges overlap (Laundre, 1977; Macdonald
and Apps, 1978; George, 1978; Corbett, 1979; Liberg,
1980; Panaman, 1981; Warner, 1985), though
individuals within a group concentrate their hunting
into areas where other individuals of the group rarely
hunt (Panaman, 1981). However, the combined range
of a group of females does not overlap that of any
other group of females (Liberg, 1980). This pattern is
found even at the highest densities of cats. In the
Portsmouth dockyards most adult females lived in
groups, sharing their ranges with one or more females,
while adult males had large, overlapping ranges that
covered the ranges of several groups of females
(Dards, 1978; 1983). Likewise, in a Japanese village
where cats fed on fish wastes at a few sites the home
ranges of members of the same feeding group
overlapped considerably (within and between sexes),
but the ranges of cats belonging to different feeding
groups overlapped very little (lzawa et al., 1982).
Cats with overlapping home ranges living in a
group at a farmhouse are closely related (Laundre,
1977; Macdonald and A
pp
s, 1978; Liber
g
, 1980;
Panaman, 1981). In one case where they were not,
they had been introduced into the group as 2-3
month-old kittens (George, 1978). We do not know
the relationship of the cats in the Orongorongo Valley
but the oldest cat, Lena, may have been the mother of
some of the others.
Although cats have been described as solitary
animals (Kleiman and Eisenberg, 1973), Leyhausen
(1965, p 257) emphasised that solitary animals are not
necessarily asocial, or socially indifferent; 'the only
mammal one could conceivably speak of as being
socially indifferent is a dead one'. For cats are
neither solitary and asocial nor territorial, but have a
social structure that appears to be intermediate
between that of some of the larger carnivores which
hunt in packs, e.g. lion Panthera leo, hunting dog
L
ycaon pictus and spotted hyena Crocuta crocuta
(Bertram, 1979), and that of the solitary, territorial
leopard Panthera pardus (Bertram, 1982) and wild cat
Felis silvestris (Corbett, 1979).
The sociality of house cats is seen in their
overlapping home ranges and group living, and in
breeding females nursing and guarding each other's
kittens (Macdonald and Apps, 1978; Macdonald,
1983). Sociality seems to be strongest where man
provides food and shelter and weakest among feral
cats having dispersed prey and plentiful shelter. Liberg
(1980) suggested that domestication of cats increased
selection for grouping; if so this characteristic has
been retained in populations of feral cats.
Acknowledgements
We are indebted to G.D. Ward for preparing radio
transmitters, for advice on radio-tracking, and for
help in the field, and to J .A. Gibb for help in the
field and his active interest and discussion throughout
the study. H.A. Robertson gave statistical advice and
J.A. Gibb and N.P. Langham gave constructive
comments on the manuscri
p
t.
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... Previous analysis using a Bayesian approach dependent on spatial correlation of camera trap detections failed to converge due to lower rates of clustered detections than anticipated given the close spacing of~500 m. Although there may be observational spatial independence of detections, abundance estimates at Site 1 are potentially inflated as cats are expected to travel further than 500 m within their home range according to the literature [34]. The RN model relies on the premise that detection probability is mostly driven by abundance at a location. ...
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... Although home ranges of feral cats have been studied from rural and urban areas across the globe, these studies are mainly from the USA (Hall et al. 2000), UK , Australia (Edwards et al. 2001;Molsher et al. 2005) and New Zealand (Fitzgerald and Karl 1986;Langham and Porter 1991;Harper 2007;Recio et al. 2010). Use of global positioning systems (GPS) has simplified wildlife radio-tracking to be effective and with minimal researcher disturbance to the animals (Hansen and Riggs 2008;Recio et al. 2010). ...
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Impact scoring schemes are useful for identifying to what extent alien species cause damage. Quantifying the similarity and differences between impact scoring schemes can help determine how to optimally use these tools for policy decisions. Using feral mammals (including rats and mice) as a case study, environmental and socio-economic impacts were assessed using three schemes, namely the Generic Impact Scoring System (GISS), Environmental Impact Classification for Alien Taxa (EICAT) and Socio-Economic Impact Classification for Alien Taxa (SEICAT). The results show that socio-economic impacts scores differ between the respective schemes (GISS and SEICAT) possibly because they assess different aspects of social life and economy. This suggests that both scoring schemes should ideally be applied in concert to get a complete picture of socio-economic impacts. In contrast, environmental impact scores are correlated between GISS and EICAT assessments and this similarity is consistent over most mechanisms except for predation and ecosystems, suggesting that one scoring scheme is sufficient to capture all the environmental impacts. Furthermore, we present evidence for the island susceptibility hypothesis as impacts of feral mammals were found to be higher on islands compared to mainlands.
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Overall sex ratio was in favour of males 1:0.80, and coat colour was tabby (74%), orange (26%) and black (2%). The breeding season extended from October-March (peak November-December). Mean number of embryos was 4.7 per female. Evidence of females producing 2 litters was found. Mortality in kittens increased as they grew older, with litters of kittens >1.8 kg containing 2 or fewer animals. Most cats lived in herbfield or tussock grassland, with very few if any in feldmark. The total population was estimated at 169-252 adults. One adult male's home range covered 41 ha, but this appeared not to be maintained during winter. Its daytime activity varied greatly, much time being spent foraging for food. -from Authors
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The range was composed of 3 characteristic components such as a feeding site, resting sites and paths. Each cat used only one feeding site and did not switch it seasonally. The cats utilizing the same feeding site organized 'feeding group'. Synchronization of feeding activity and overlapping ranges of the members of the same feeding group were observed. These features of feeding group show the amicable relationship among the members. This probably results from adaptation to a clumped distribution of abundant food resource. -from Authors
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Otters were studied by reading tracks and signs in fresh water habitats in Southern Sweden, in 1958-1966. 1. The populations in winter consisted of 30-40% resident territory holders, about the same proportion of temporary residents or transients and 25-38% young of the year. The rate of reproduction of otters is low. Most probably some females do not breed every year. The density of otters in the areas studied was one otter per 0.7-1.0 km2 area of water or one individual per 2-3 km length of lake shore, and one otter per 5 km length of a stream. 2. Otters display territorial behaviour which is shown by signal activity, dispersion pattern and movements of the otters. 3. The adult dog otters maintain territories which have an individual character, their size and location depending on the qualities of the dogs. The boundaries are overlapping zones where territorial conflicts occur continuously. 4. The females with cubs (family groups) exploit territories separately. The areas are probably fixed and situated within the dog otters' territories. Territorial conflicts between the family groups are rare, after the areas have been settled. 5. Otters - apart from territory-holding dog otters and females with cubs - behave as temporary residents (mainly during summer and winter) or transients. 6. Territorial behaviour primarily appears between individuals of the same sex. The behaviour has a pronounced individual character. The individuals behave according to their status in a hierarchic system. 7. The territories are primarily maintained by threatening signals. Avoidance plays a larger part than pursuits. 8. The territories of the family groups are feeding areas, securing the young access of food all the first year of their lives. The dog otters' territories primarily have sexual significance. /// Исследовали популяции выдр в пресноводных водоемах Южной Швеции в 1958-1966 гг. 1. Популяции выдр зимой состоят на 30-40% из постоянных обитателей участков, примерно того же количества временных и кочующих обитателей и 25-38% молодых особей, родившихся в том же году. Скорость размножения у выдр очень низка. Некоторые самки очевидно не приносят потомства ежегодно. Плотность популяций выдр в исследованных участках составляла І экз. 0,7-1,0 KM2 водной поверхности или Іэкз. на 2-3 погонных км берега озера либо на 5 погонных км берега реки. 2. Выдры имеют индивидуальные участки, что доказывается характером их распределения и передвижения. 3. Взрослые самцы занимают определенные территории, являющиеся их индивидуальными участками. Территории соседних участков перекрываются у границ, и здесь постоянно возникают конфликты. 4. Самки с детенышами (семьн) занимают отдельные территории, расположенные внути индивидуальных участков. После заселения участков территориальные конфликты между семьями возникают редко. 5. Остальные представители популяции (исключая упомянутых выше самцов и самок с детенышами) ведут себя как временные или кочующие посетители участков, особенно летом и зимой. 6. Территориальная приуроченность проявляется сначала у представителей одного пола. Поведение выдр в отношении территории носит индивидуальный характер и зависит от положения каждого животного в иерархической системе. 7. Выдры охраняют свои участки от других особей, применяя сигналы угрозы. 8. Территории семейных групп - это места, хорошо обеспеченные пищей, где имеется возможность прокормить детенышей в течение первого года их жизни. Выбор участков взрослыми самцами связан с их половой активностью.
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I propose a goodness-of-fit test to evaluate compliance of the spatial distribution of activity with bivariate normality. Home-range data for 2 Columbian white-tailed deer fawns (Odocoileus virginianus leucurus) were subjected to this test. The distribution for 1 fawn departed significantly from the expected; the distribution of the other fawn did not.
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Free-ranging domestic cats on farmsteads were censused annually in August 1977-81 within a 5,182-ha area typical of the cash-grain region in central Illinois. The estimated average number of cats on the area in late summer was 326 (6.3/100 ha). Annual recruitment of immature cats into the late summer population averaged 1.5/adult female. Survival beyond 3-5 years of age was rare; <1% survived 7 or more years. Eleven adult cats were radio-monitored during a 30-day period in summer; four males ranged over larger areas (P < 0.01) than seven females (228 ± 100 ha and 112 ± 21 ha, respectively). When cats were not on farmsteads, approximately 73% of their radiolocation points (N = 1,227) were in edge or linear configurations of cover. Cats made disproportionately high (P < 0.05) use of farmsteads and perimeters, roadsides, and field interfaces and disproportionately low use (P < 0.05) of fields of corn and soybeans. Domestic cats on the area were well fed by humans but routinely deposited prey at their residences.