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Global Environmental Research ©2004 AIRIES
8(2)/2004: 125-131
printed in Japan
Present Status of Invasive Alien Raccoon and its Impact in Japan
Tohru IKEDA1, Makoto ASANO2, Yohei MATOBA3 and Go ABE1
1Graduate School of Letters, Hokkaido University,
Kita 10 Nishi 7 Kita-ku, Sapporo, Hokkaido 060-0810, Japan
e-mail: tikeda@reg.let.hokudai.ac.jp
2Faculty of Applied Biological Sciences, Gifu University,
Yanagido 1-1, Gifu, Gifu-ken 501-1193, Japan
3Department of Veterinary Parasitology, Rakuno Gakuen University,
Bunkyoudai, Ebetsu, Hokkaido 069-8501, Japan
Abstract
Irresponsible breeding and release of pet raccoons (Procyon lotor) has caused their naturalization
in Japan. The raccoons have already naturalized in 42 of Japan’s 47 prefectures, and there has been a re-
markable increase in agricultural (cattle breeding) and urban areas, where the raccoons can find food
and hide easily. Their home range size varies widely according to the habitat, ranging from 35 ha in
urban areas to 2,219 ha in forests (mean : 299.1 ha). The raccoon avoids energy loss in winter by
semi-hibernation. It has opportunistic and omnivorous feeding habits, taking crops and fruit in agricul-
tural areas and native species in forests. It also preys on indigenous species such as the Japanese cray-
fish (Cambaroides japonicus) and Ezo salamander (Hynobius retardatus). Reproductive observations
have shown high productivity (reproductive rate : 66% in yearlings and 96% in adults, litter size : 3.6 in
yearlings and 3.9 in adults) and a potentially rapid rate of population growth (0.20 to 0.25). Intensive
eradication guided by biological data will be indispensable to controlling invasive alien raccoons.
Key words: impact, invasive alien raccoon, management, naturalization
1. Introduction
After the ratification of the ‘Convention on Bio-
logical Diversity,’ invasive alien species issues be-
came a major concern in Japan. Invasive alien species
are considered to be the one of the most important
causes of extinction and decline of wild native species
(Margin et al., 1994; Williamson, 1999). In particular,
invasive alien mammals are thought to have serious
impacts on native ecosystems because of their high
trophic level.
With Japan’s spectacular economic growth, numer-
ous species of mammals have been imported into
Japan as pets. The number of alien mammals is on the
increase with the increase of imported mammals, and
over 30 species of mammals have thus far naturalized
in Japan (The Committee on Mammal Conservation
and Management, 1999).
Among these alien mammals of Japan, the raccoon
(Procyon lotor) is a representative nuisance. The rac-
coon is very popular not only for its cute appearance
but also its comical behaviors (Zeveloff, 2002). Its
round, funny face with a bandit’s mask across the eyes
and a striped bushy tail create a humorous impression,
and people find its habit of washing of food prior to
eating curious. It prefers waterfronts generally, but is
well known to be highly adaptive to various environ-
ments owing to its omnivorous feeding habits
(Sanderson, 1987).
This species came from North America. In addition
to being introduced to Japan, it was introduced into
the Caribbean islands in 1932 (Sherman, 1953),
Germany in 1934 (Lever, 1985) and the Soviet Union
in 1936 (Aliev & Sanderson, 1966), where it caused
heavy damage to crops or native ecosystems.
In Japan, after the smash hit of the animated car-
toon ‘Rascal Raccoon’ on TV in 1977, the raccoon
became popular as pet animal and many raccoons
were imported (Ikeda, 1999a). The raccoon, however,
is fierce in nature, and comes to show its wildness as
it grows up. It is thought that many raccoon breeders
had troubles with their raccoons and abandoned them.
The raccoon is also clever with its hands, and can es-
cape from simple breeding cages easily. As a conse-
quence of irresponsible abandonment and escapes
from captivity, many raccoons have naturalized in
various regions in Japan (Fig.1). Including temporal
cases, the raccoon has already naturalized in 42 of
Japan’s 47 prefectures. The raccoon has so wide a
food repertory that many native species are exposed to
126 T. IKEDA et al.
the menace of raccoon predation.
This paper is a review of the spread of the invasive
alien raccoon and its impact in Japan. We also attempt
to compare its population trend data with those of the
raccoon dog (Nyctereutes procyonoides) to point out
the former’s impact on native species specifically, and
we attempt to develop effective countermeasures for
its control.
2. History and Process of Naturalization of
the Invasive Alien Raccoon in Japan.
The first naturalization of raccoons in Japan oc-
curred in Inuyama City, Aichi Prefecture, in 1962
(Ando & Kajiura, 1985) (Fig.1). Some raccoons es-
caped from a zoo, then colonized Gifu Prefecture. In
addition, a raccoon breeder abandoned over 40 rac-
coons in Kani City, Gifu Prefecture in 1982. Most of
these raccoons were captured, but the remaining rac-
coons still continue to harm crops.
The next naturalization occurred in Eniwa City,
Hokkaido Prefecture, in 1979 (Ikeda, 1999a) (Fig.1).
About ten raccoons escaped from a breeding cage and
naturalized in a livestock farming area. Owing to mul-
tiple escapes and abandonment, the raccoon has
spread throughout the west-central and eastern part of
Hokkaido at present (Fig.2).
In Hokkaido, the raccoon naturalized in the live-
stock farming area initially (Fig.3). Figure 4 shows
Fig. 4 Damage to livestock farms by invasive alien raccoons in Eniwa City in
1996.
Fig. 1 Distribution of naturalized raccoons in Japan.
: Initial naturalized area
1 in Inuyama City in 1962
2 in Eniwa City in 1979
3 in Kamakura City in 1988
Fig. 2 Distribution of invasive alien raccoons in Hokkaido
Prefecture.
Source: Natural Environment Division, Office of Environ-
mental Affairs, Department of Environment and
Lifestyle, Hokkaido Prefectural Government.
Fig. 3 Raccoon family roaming in a cowshed.
(Photograph by the Raccoon Research Group)
Present Status of Invasive Alien Raccoon and its Impact in Japan 127
damage to the livestock farms by raccoons. It is clear
that the raccoons prefer cattle breeding farms and fish
breeding farms to other livestock farms. At cattle
breeding farms, the raccoons are likely to get plenty of
corn, the raccoon’s greatly preferred food, from the
compound cattle feed throughout the year, and can
find safe cover, such as lumps of dried pasture grass,
for reproduction. As Giles (1940) and Tester (1953)
highlighted the importance of corn in the diet of the
raccoon, the raccoons roaming around the cattle
breeding farm in Eniwa City also showed a high de-
pendence on corn from the compound feed even after
the harvest of corn in the field. In November, 80% of
raccoon feces contained undigested corn (Yoshino,
1994). A fish breeding farm also made fish available
for food, but was not suitable for reproduction. As a
consequence, it seemed that the raccoons reproduced
at the cattle breeding farm, then expanded their distri-
bution mainly along the river.
The third naturalization occurred in Kamakura City,
in 1988 (Fig.1). The process of naturalization in
Kamakura City was different from that in Hokkaido.
The main cause of the naturalization was an escape
from captivity, as with the other places, but the rac-
coon established its habitat in an urban area. There are
many old wooden houses, Buddhist temples and
Shinto shrines in Kamakura City, and these Japa-
nese-style architectures have some air vents under the
eaves and the floors. The raccoon invaded via these air
vents and built nests under the roofs (Fig.5). In urban
areas, the raccoon can access garbage easily, and catch
carp and goldfish from ponds in gardens. The raccoon
can also use drainpipes as safe travel paths that were
used by the raccoon dog before the raccoon invasion.
Urban areas are also available for the raccoon, so it is
expanding its distribution. Figure 6 shows information
on invasions by raccoons in Kamakura City in 2001.
The raccoons have spread out all over the city at this
moment.
In other areas where the raccoon has invaded, the
main causes seem to be escapes and abandonment.
From an ecological point of view, the raccoon can
naturalize in all environments in Japan, but we must
Fig. 5 Raccoon invading a house.
(Photograph by the Raccoon Research Group)
pay special attention to agricultural and urban areas to
prevent more multiplication of the raccoon.
3. Behavior of the Invasive Alien Raccoon in
Japan.
Table 1 shows the home range size of the invasive
alien raccoon in Japan determined by radio telemetry
method. The home range size varies widely according
to its habitat. The largest home range size was 2,219 ha
in forested area, and the smallest was 35 ha in an ur-
ban area. The range size in urban areas (mean: 49.0 ha)
was smaller than those in suburban and rural areas
(mean : 358.0 ha) (p < 0.01, Mann-Whitney’s U-test).
In forested areas of Hokkaido, the home range size
of the invasive alien raccoon tended to diminish re-
markably as the temperature dropped (Ikeda, 1993).
The raccoon used only river sides for its paths in the
snowfall season. It seemed that the raccoon had trou-
ble walking in deep snow coverage according to our
observations. In midwinter, the raccoon avoids energy
loss by remaining motionless in the hollow of a tree or
in a vacant house.
The raccoon is thought to have a polygamous or
promiscuous mating system (Zeveloff, 2002). The
invasive alien raccoon in Japan also showed a polyga-
mous mating system. The male raccoon tended to
keep more than one female in its home range. The
raccoon in Hokkaido mated from January through
March, with a peak in February. In this breeding
period, the male raccoon tended to come and go
among a few females in its home range, while the
female raccoons kept still in their dens.
These activities of the invasive alien raccoon in
Japan are almost the same as its activities in its place
of origin (Zeveloff, 2002). It seems that the invasive
Fig. 6 Entry into houses or courtyards by invasive alien
raccoons in Kamakura City in 2001.
Source: Kamakura City
128 T. IKEDA et al.
alien raccoon can establish its niche in Japan easily.
Furthermore, it has no natural enemies in Japan such
as the bobcat (Felis rufus) or the coyote (Canis
latrans). There is a danger that the invasive alien rac-
coon will continue to increase its numbers throughout
the nation.
4. Reproductive Characteristics of the Inva-
sive Alien Raccoon
Table 2 shows the pregnancy rate and mean litter
size of invasive alien raccoons in west-central
Hokkaido by analysis of placental scars or fetuses in
the uterus (Asano et al., 2003). Juveniles (that year’s
litters) were distinguished from yearlings and adults
(over 2 years of age) by examining tooth eruption and
root foramina closure of the canines. The invasive
alien raccoon showed very high productivity. The
mean pregnancy rate was 66% in yearlings and 96%
in Adults. Litter sizes ranged from 1 to 7 and averaged
3.6 in yearlings and 3.9 in Adults. These reproductive
characteristics are almost the same or slightly higher
than those reported in North America (Ritke, 1990;
Stuewer, 1943; Fritzell et al., 1985). The rate of popu-
lation growth in west-central Hokkaido was estimated
to range from 0.20 to 0.25 without harvest mortality
(Asano et al., 2003). Based on these data, it is clear
that without relevant measures to control the raccoon,
it is capable of population expansion.
5. Feeding Habits of the Invasive Alien Rac-
coon
The invasive alien raccoon shows opportunistic
and omnivorous feeding habits in response to its habi-
tat environment. In general, the raccoon takes animal
Tabl e 1 Home range size of invasive alien raccoons in Japan determined by radio telemetry
method
Each home range size shown is the maximum size in each period. We attached collar transmitters
(Type 8C by ATS Inc., weight:120 g) to raccoons, and plotted locations by triangulation method
with a 3-element Yagi antenna (YA-23L) and mobile receiver (Yaesu FT290mkII).
Home range
size (ha) Sex Period Study area Habitat type
2219 Male Jun.1992-Jan.1993 Eniwa Forest
509 Male Sep.1993-Oct.1994 Eniwa Forest
417 Male Sep.1993-Oct.1994 Eniwa Forest
152 Male Sep.1993-Oct.1994 Eniwa Suburban
184 Male Sep.1993-Oct.1994 Eniwa Suburban
144 Male Mar.2000-May 2000 Nopporo Forest park surrounded by
residences
77 Male Apr.2000-May 2000 Nopporo Forest park surrounded by
residences
40 Male Sep.2000-Oct.2000 Kamakura Urban
47 Male Sep.2000-Oct.2000 Kamakura Urban
648 Female Sep.1993-Oct.1994 Eniwa Forest
313 Female Jun.1992-Jan.1993 Eniwa Forest
310 Female Sep.1993-Oct.1994 Eniwa Forest
278 Female Sep.1993-Oct.1994 Eniwa Forest
207 Female Sep.1993-Oct.1994 Eniwa Forest
195 Female Sep.1993-Oct.1994 Eniwa Forest
138 Female Nov.1999-May 2000 Nopporo Forest park surrounded by
residences
114 Female Nov.1999-May 2000 Nopporo Forest park surrounded by
residences
100 Female Sep.1993-Oct.1994 Eniwa Suburban
81 Female Sep.1993-Oct.1994 Eniwa Suburban
74 Female Sep.2000-Oct.2000 Kamakura Urban
35 Female Sep.2000-Oct.2000 Kamakura Urban
Tabl e 2 Age-related pregnancy rate and mean litter size of invasive alien
raccoons collected in west-central Hokkaido in 1999-2000.
(Asano et al., 2003)
Pregnancies
Age(years) N N %
Mean litter size (±SD)
0 69 0 0
1 71 47 66 3.6±1.3
2 43 41 95 3.7±1.2
3 27 25 93 4.1±1.2
4 18 18 100 3.7±1.5
≧5 14 14 100 3.8±1.3
Total 242 145 84 3.8±1.3
Present Status of Invasive Alien Raccoon and its Impact in Japan 129
fat in summer and vegetable fat in autumn in prepara-
tion for semi-hibernation in winter.
In agricultural areas of Hokkaido, the raccoon
damages crops and fruits such as corn, melons, water-
melons, strawberries, paddy rice, soybeans, potatoes,
beets, oats, and so on in summer and autumn. It eats
livestock feed, feed grain and pasture grasses, too. The
total amount of agricultural damage amounts to
30,000,000 yen every year. The raccoon eats crops
and fruit only in the harvest season, excluding dried
corn in compound cattle feed which is available
throughout the year. The raccoon takes beetles and
hornets (Vespula flaviceps) in summer and autumn
(Murayama, 1991; Yoshino, 1994; Nakamura, 1994).
Research in Nopporo Forest Park surrounded by agri-
cultural and residential areas in Hokkaido showed that
bower actinidia (Actinidia arguta) and arthropods oc-
curred in 90% of raccoon scats in autumn (Yutani,
1999).
In forests, the raccoon preyed on various native
species. So far we have recorded their predation on
small mammals such as the gray red-backed vole
(Clethrionomys rufocanus bedfordiae), snakes, frogs,
dragonflies, damselflies, bees, butterflies, cicadas,
shrimp, shellfish, wild vines and Japanese yew (Ta xus
cuspidata) by dissection of raccoons trapped during a
nuisance control harvest.
6. Impacts of the Invasive Alien Raccoon
Besides damage to crops, the raccoon also poses a
threat of spreading infectious diseases. The raccoon
can transmit raccoon roundworm (Baylisascaris pro-
cyonis) infection (Miyashita, 1993). Raccoon round-
worm has not been detected in naturalized raccoons
yet, but we should be concerned about this infection
because it has been detected in a raccoon in captivity.
Furthermore, raccoons transmit rabies. It is feared that
rabies could spread throughout the nation carried by
raccoons if the disease should invade Japan (Ikeda,
1999a).
As for the impacts on native ecosystems, competi-
tion with some native species is likely occurring.
Resource competition with the raccoon dog and the
red fox (Vulpes vulpes) turned these animals out into
unfavorable habitats (Ikeda, 1999a). In Nopporo
Forest Park, the raccoon occupied the peripheral parts
of the park where animals could access crops easily,
so the raccoon dog was pushed deeper into the forest
(Fig.7). In this area, the number of the raccoon dogs
increased after an active harvest of the raccoon, but
decreased again as the number of raccoons recovered
(Fig.8). Another example of a raccoon impact is a
take-over of a hollow tree from an owl for a breeding
nest, which disrupted the owl’s reproduction (Fig.9).
In addition to resource competition, direct preda-
tion on valuable native species is another serious
problem posed by the invasive alien raccoon. An in-
vestigation by digestive tract analysis made it clear
that the raccoon preys on the Japanese crayfish
(Cambaroides japonicus) (Hori & Matoba, 2001), and
it is likely that the raccoon preys on the Ezo salaman-
der (Hynobius retardatus) and some species of frogs
Fig. 7 Main sites of captures of raccoons and raccoon dogs in
Nopporo Forest Park.
Fig. 8 Fluctuation in number of captured raccoons and
estimated population of raccoon dogs in Nopporo
Forest Park.
Fig. 9 Raccoon taking over an owl’s nest for breeding.
(Photograph by T. Ikeda)
130 T. IKEDA et al.
judging from the shape of leftover carcasses (Ikeda,
2002).
Raccoon predation on birds and eggs is common in
North America (Zeveloff, 2002). In Nopporo Forest
Park, some raccoons attacked a reproductive colony of
grey herons (Ardea cinerea), which subsequently
abandoned their breeding grounds in 1997 (Ikeda,
1999b; Ikeda, 2000).
7. Present Measures against the Invasive
Alien Raccoon in Japan
Nuisance control harvests of the invasive alien rac-
coon were conducted in various places in Japan, but
they amounted to no more than a bandage measure,
because the decrease in damage to crops reduced the
victims’ desire to catch the invasive alien raccoon.
The Hokkaido government made a municipal by-
law to put raccoon breeders under obligation for regis-
tration starting 2001 (Ono, 2002). Under this munici-
pal bylaw, raccoon breeders must notify the governor
of their possession of raccoons. This measure seemed
to be effective at stop irresponsible releases, prevent-
ing new naturalization of the raccoon.
The Hokkaido government formulated basic guide-
lines for the control of the invasive alien raccoon, and
set eradication from the wild as its goal in 2003. The
Hokkaido government also started a scientific action
plan toward eradication of the raccoon. This plan was
intended to eradicate the invasive alien raccoon in the
course of ten years, but faced difficulty due to lack of
budget.
Other prefectures continue to conduct nuisance
control harvests continually. They are expected to
switch from nuisance control harvesting to scientific
control programs based on ecological population data
to eliminate the impacts on native ecosystems.
8. Toward Creation of Effective Manage-
ment Measures
Due to its excellent adaptability to various environ-
ments and its lack of natural enemies in Japan, the
invasive alien raccoon has increased in number and
caused serious damage to native ecosystems and hu-
man economy.
The invasive alien raccoon shows high reproduc-
tive power and a potentially rapid rate of population
growth, thus we certainly will be unable to control the
raccoon if we resort only to nuisance control harvest-
ing. Unfortunately, public awareness of invasive alien
raccoon issues is low, except in some prefectures
where damage from raccoons is serious. It must be
noted that educational efforts will be needed regarding
invasive alien raccoon issues, especially their irre-
versible impacts on native ecosystems.
As for methods of control, intensive extermination
under scientific control programs on the basis of adap-
tive management rather than nuisance control harvests,
will be indispensable to controlling the invasive alien
raccoon. It will be necessary to collect detailed popu-
lation data and reproductive parameters in cooperation
with prefectural governments. These data should then
be used to estimate a culling rate that can reduce or
even eradicate the population.
The Invasive Alien Species Act will be enforced in
2005. We hope that scientific raccoon control pro-
grams will start in many parts of the country.
Acknowledgements
We would like to acknowledge the contributions of
the Raccoon Research Group menbers, Dr. Norio
Ohtaishi, Dr. Masatsugu Suzuki, Laboratory of Wild-
life Biology (Graduate School of Veterinary Medicine,
Hokkaido University) member, Dr. Mitsuhiko
Asakawa, members of the Department of Veterinary
Parasitology (Rakuno Gakuen University) and the
Research Group of Regional Sciences (Graduate
School of Letters, Hokkaido University). Great appre-
ciation is extended to the Natural Environment Divi-
sion (Department of Environment and Lifestyle,
Hokkaido Prefectural Government) and Kamakura
City. Our study was supported in part by a grant from
the Ministry of the Environment as part of the Global
Environment Research Programme.
References
Aliev, F. F. and G. C. Sanderson (1966) Distribution and status
of the raccoon in the Soviet Union. Journal of Wildlife Man-
agement, 30:497-502.
Ando, S. and K. Kajiura (1985) Status of raccoons in Gifu Pre-
fecture. Bulletin of the Gifu Prefectural Museum, 6:23-30. (in
Japanese)
Asano, M., Y. Matoba, T. Ikeda, M. Suzuki, M. Asakawa and N.
Ohtaishi (2003) Reproductive characteristics of the feral rac-
coon (Procyon lotor) in Hokkaido, Japan. Journal of Veteri-
nary Medical Science, 65:369-373.
Fritzell, E. K., G. F. Hubert Jr., B. E. Meyen and G. C.
Sanderson (1985) Age-specific reproduction in Illinois and
Missouri raccoons. Journal of Wildlife Management,
49:901-905.
Giles, L. W. (1940) Food habits of the raccoon in central Iowa.
Journal of Wildlife Management, 4:375-382.
Hori, S. and Y. Matoba (2001) Arthropods recognized from the
contents in the digestive tract of raccoons. Bulletin of the
Historical Museum of Hokkaido, 29:67-76.
Ikeda, T. (1993) Ecological survey of naturalized raccoons in
Eniwa City, Hokkaido. In : H. Higashi, ed., Current Status of
Alien Mammals and Measures in Japan. WWFJ Natural
Conservation project report, Fiscal 1992, pp. 3-11. (in Japa-
nese)
Ikeda, T. (1999a) Progress of naturalization of raccoons and
related problems in Hokkaido. The Annual Report on Cul-
tural Science, Faculty of Letters, Hokkaido University,
47(4):149-175. (in Japanese)
Ikeda, T. (1999b) Invasive alien raccoon issues in Nopporo
Forest Park. Forest Protection, 272:28-29. (in Japanese)
Ikeda, T. (2000) Toward fundamental management of invasive
raccoons. Japanese Journal of Conservation Ecology,
Present Status of Invasive Alien Raccoon and its Impact in Japan 131
5:159-170. (in Japanese)
Ikeda, T. (2002) Raccoon. In : The Ecological Society of Japan,
ed., Handbook of Alien Species in Japan. Chijin-shokan,
Tokyo, 70 p. (in Japanese)
Lever, C. (1985) Naturalized mammals of the world. Longman,
New York.
Margin, S. D., T. H. Johnson, B. Groombridge, M. Jenkins and
H. Smith. (1994) Species extinctions, endangerment and cap-
tive breeding. In : J. S. Olney, G. M. Mace and A. T. C. Feis-
ter, eds., Creative Conservation, Chapman & Hall, London,
pp. 3-31.
Miyashita, M. (1993) Study of larva migrans of raccoon round
worm Baylisascaris procyonis. Seikatsu Eisei (Journal of
Urban Living and Health Association), 37:137-151. (in
Japanese)
Murayama, M. (1991) Study of Naturalization of Raccoons in
Hokkaido. Master’s Thesis, Graduate School of Letters,
Hokkaido University, Sapporo. (in Japanese)
Nakamura, N. (1994) Study of Feeding Habits of Naturalized
Raccoons in Stockbreeding Area of Eniwa City (2). Gradua-
tion Thesis, Faculty of Letters, Hokkaido University, Sap-
poro. (in Japanese)
Ono, S. (2002) Background of measures for invasive alien rac-
coon and related problems in Hokkaido. In : The Ecological
Society of Japan, ed., Handbook of Alien Species in Japan.
Chijin-shokan, Tokyo, pp. 26-27. (in Japanese)
Ritke, M. E. (1990) Quantitive assessment of variation in litter
size of the raccoon Procyon lotor. American Midland Natu-
ralist, 123:390-398.
Sanderson, G. C. (1987) Raccoon. In : M. Novak, J. A. Baker,
M. E. Obbard and B. Malloch, eds., Wild Furbearer Man-
agement and Conservation in North America, Ministry of
Natural Resources, Ontario, pp. 487-499.
Sherman, H. B. (1953) Raccoons of the Bahama Islands. Jour-
nal of Mammalogy, 35:126.
Steuer, F. W. (1943) Reproduction of raccoons in Michigan.
Journal of Wildlife Management, 7:60-73.
Tester, J, R. (1953) Fall food habits of the raccoon in the South
Platte Valley of Northeastern Colorado. Journal of
Mammalogy, 34:500-502.
The Committee on Mammal Conservation and Management.
(1999) Appeal for the emergent measure on naturalized
mammals in Japan. Honyurui Kagaku (Mammalian Science),
39(1):115-129. (in Japanese)
Wiilamson, M. (1999) Invasions. Ecography, 22:5-12.
Yoshino, T. (1994) Study of Feeding Habits of Naturalized
Raccoons in Stockbreeding Area of Eniwa City (1). Gradua-
tion Thesis, Faculty of Letters, Hokkaido University,
Sapporo. (in Japanese)
Yutani, S. (1999) Present Status and Food Habit of Naturalized
Raccoons in Nopporo Forest Park. Graduation Thesis, Fac-
ulty of Science, Hokkaido University, Sapporo. (in Japanese)
Zeveloff, S.I. (2002) Raccoons : a natural history. The Smith-
sonian Institution, Washington, D.C.
(Received 28 December 2004, Accepted 31 December 2004)
