79

Population Trend, Habitat Change and Conservation of
the Unique Wildlife Species on Amami Island, JapanKen SUGIMURA1*, Fumio YAMADA2 and Asako MIYAMOTO1
1

Department of Forest Management, Forestry and Forest Products Research Institute (FFPRI)
P.O. Box 16, Tsukuba Norin Kenkyu Danchi-nai, Ibaraki, 305-8687 Japane-mail: kensugi@ffpri.affrc.go.jp
2
Department of Wildlife Biology, FFPR
P.O. Box 16, Tsukuba Norin Kenkyu Danchi-nai, Ibaraki, 305-8687 Japan*corresponding author

Abstract
Amami Island has many terrestrial wildlife species and subspecies that are endemic to the Nansei
Archipelago. Many of them live in the forest ecosystems, while young secondary forests have
replaced the majority of the original forests due to the past clear-cutting forestry. Of those species, thegreat scaly thrush Zoothera dauma major, Owston white-backed woodpecker Drendrocopos leucotos
owstoni, long-haired rat Diplothrix legata and Amami pygmy woodpecker Dendrocopos kizuki amamii,
appear to be so dependent on the mature forests (uncut for at least 50 years after selective felling) that
their numbers must have decreased at least for the last few decades. On the other hand, the populations of Amami rabbit Pentalagus furnessi, purple jay Garrulus lidthi, Amami woodcock Scolopax mira,
Ryukyu robin Erithacus komadori and spinous rat Tokudaia osimensis have decreased in the central partof the island, where mongoose numbers have skyrocketed in recent years. In the mean time, forestry
practices that turned out to be economically unprofitable have resulted in a precipitous decline inproduction in the early 1990s. Mongoose control has also encountered critical financial problems dueto the ignorance of the local community. These situations are rooted in a local economy that has been
deeply dependent on government subsidies, which facilitated various development activities.
Key words: endemic species, forestry, invading predators, local economy, mature forests

1. Introduction
Amami Island, located at 28°N, 129°E, belongs to
the Nansei Archipelago (the Nansei Islands), a chain
extending from the south of Kyushu to the east of
Taiwan (Fig. 1). Island populations are the mostvulnerable to extinction (Williamson, 1981), and thisis also true for the Nansei Archipelago and the
Ogasawara Islands. They are smaller than theJapanese Islands and have many endemic species thatare included in the red list of the IUCN or the Ministryof the Environment (former Japan Environment
Agency). Stattersfield et al. (1998) nominated bothof these islands as the most urgent among the 76 areasin the world for the conservation of the endemic bird
species. WWF International also ranks the Nansei
Archipelago as one of the “critical or endangered”
terrestrial ecoregions.
The forest ecosystems on Amami Island as well as
in Yambaru (the northern part of Okinawa Island) (Fig.
1), in particular, sustain a large number of endemic
species of the Nansei Archipelago. Yet, less than 1%of the forests on Amami Island have been protectedfrom such development activities as logging, constructing large entertainment parks, vehicle roads, etc.
Extensive clear-cut forestry has been conducted primarily for pulpwood production from the 1950s
through early 1990s, so mature forests remain small(Sugimura, 1988; Sugimura, 1995) (Fig. 2). In addition, Java mongooses Herpestes javanicus that werereleased in 1979 for the purpose of controlling a venomous snake, the habu Trimeresurus flavoviridis, hasbeen expanding its distribution from the site of release(Fig. 1) (Yamada et al., 2000).
Thus, the endemic species in the forest ecosystems
have been threatened by habitat changes and introduced predators. Nevertheless, there are few long-term
studies that deal with their population trends andimpacts of these changes on them (Sugimura, 2002).
On the other hand, government subsidies have playeda critical role in the local economy and facilitatedvarious kinds of development activities (Sugimura,1988).
The objectives of the present paper are as follows:

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K. SUGIMURA et al.

Fig. 1 The location of Amami Island in southwestern Japan. (adapted from Sugimura et al., 2000)

Fig. 2 Typical forest habitat. (left: mature forest, right: cutover area)(1) to get an overview of the characteristics of theterrestrial vertebrate fauna, (2) to examine thepopulation trends of the wildlife species endemic to
the Nansei Archipelago, (3) to speculate on somefactors that appear to be the major causes of the trend,and (4) to propose effective conservation measures
taking the social background into account.

2. Geographical BackgroundAmami Island is the second largest island in the
Nansei Archipelago: 819.5 km2 including three othersmaller islands in the vicinity. All the statistics givenin the present paper include these three islands unlessspecified. It is the largest island in the Amami
Insular Group that is located in the southernmost partof Kagoshima-ken (one of the 47 prefectures or admi-

nistrative districts of Japan). The island is mountainous with a forest cover of 85%, and its highest
peak is 694 m. Precipitation is abundant throughout
the year (2,871 mm average over 30 years(Kagoshima-ken, 2002)) creating densely distributed
tributary systems (Fig. 3). The soil is generally notvery suitable for agriculture due to abundant rainfallthat often laterizes it (Oshiro, 1984). Besides, typhoons occasionally cause great damage to the soil
with strong winds and high salinity (Ishijima &Itokazu, 1980).
The middle and southern parts of the Nansei
Archipelago (south of the Tokara Strait) became isolated permanently from Kyushu about 1.5 million
years ago - long before the islands north of the Tokara
Strait (Fig. 1) were separated from the continent - andhave a number of endemic species and subspecies ofPopulation Trend and Habitat Change on Amami Island

Fig. 3 Abundant precipitation throughout the year creating
densely distributed tributary systems.

terrestrial animals that are not found elsewhere(Kizaki & Oshiro, 1980; Otsuka & Takahashi, 2000).
About ten thousand years ago the Okinawa Insulargroup was separated from Taiwan and the southern

81part of the Nansei Archipelago. No land bridge hasformed over the Kerama Strait (Fig. 1) since then(Otsuka & Takahashi, 2000). As a result, the faunaand flora of the Okinawa and Amami insular groups
are distinctive not only by virtue of endemism but also
some primitive types of species whose closest phylogenic relatives are found in Southeast Asia or Tibet,
while the biota of the Japanese Islands is closely
associated with that of the Asian Continent lying
northwest of Japan.
Accordingly, Amami Island has a number of endemic species and subspecies of terrestrial vertebrates.
They are listed in Table 1 along with some subspeciesof particular concern. Particularly noted is a large
number (17 species) of endemic reptiles and amphibians, reflecting a long geological period of isolationfrom the continent and their poor dispersal ability.
The Nansei Archipelago has as large a number ofendemic species as the Japan Islands for these groups,
indicating a high level of endemism despite of its
small geographical area.

Table 1 Species of terrestrial vertebrates on Amami Island that are endemic to the Nansei Archipelago(subspecies of particular concern are also depicted).
Common nameMammals
Amami rabbit
Long-haired rat
Spinous rat
Watase’s shrew
Orii’s shrew
Ryukyu bent-winged bat
Birds
Purple jay
Amami woodcock
Ryukyu robin
Great scaly thrush
Owston white-backed woodpecker
Amami pygmy woodpecker
ReptilesTree-climbing lizard
Green kanahebi
Dark-edged hime lizard
Barbour lizard
Oshima lizard
Amami Takachiho
Riukiu green snake
AkamataGlass hibah
Hyan
Hime hab
Habu
Amphibians
Hallowel green frog
Riukiu red frog
Ishikawa frog
Amami tip-nosed frog
Otton frog
Amami green frog
Anderson’s crocodile newt
Sword-tailed newt

Scientific nameDistribution

Pentalagus furnessi
Diplothrix legata
Tokudaia osimensis
Crocidura watasei
Crocidura orii
Miniopterus fuscus

AO, TS
AO, TS, OH
AG, OHAG, OG
AO, TSNS south of TR

EN
EN
EN
NT
EN
EN

Garrulus lidthi
Scolopax mira
Erithacus komadori
Zoothera dauma major
Dendrocopos leucotos owstoni
Dendrocopos kizuki amamii

AOAG
NS, DG
AO
AO
AO

VU
EN
VU
CR
EN
VU

Japrula polygonata
Tokydromus smaragdinus
Ateuchosaurus pellopleuru
Eumeces barbouri
Eumeces marginatus
Achalinus werneri

VU

Dinodon semicarinatus
Amphiesma pryeri
Calliophis japonicus
Trimeresurus okinavensis
Trimeresurus flavoviridis

NS south of TR
TR, AG, OG, MG
NS
AG, OG
TR, AG, OG
AG, OG
TR, AG, OG
AG, OGNS south of TR
AG, OG
AG, OG
AG, OG

Hyla hallowelli
Rana okinavana
Rana ishikawae
Rana amamiensis
Babina subaspera
Rhacophorus viridis
Tylototriton andersoni
Cynops ensicauda

AG, OG
AG, OG
AG, OG
AO, TSAG
AG, OG
AO, TS, OG
AG, OG

Entechinus semicarinatus

RDB category

VU
NT

NT

EN
VU
VU
VU
NT

Distribution: DG (Danjo Insular Group); TR (Tokara Insular Group); AG (Annami Island Goup), AO (Amami Island), TS(Tokuno Island); OG (Okinawa Insular Group); OH (Okinawa Island); MG (Miyako Insular Group); NS (Nansei Archipelago)
RDB category (in Japan): CR (Critically Endangered); EN (Endangered); VU (Vulnerable); NT(Near Threatened)
Source: WWF Japan Scientific Committee (1984), Ito et al. (2000), Japan Wildlife Research Center (2000).

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The mammalian fauna of Amami Island includes
six endemic species. There are no species on the
East Asian Continent closely related to them except
Orii’s shrew Crocidura orii and the Ryukyu bentwinged bat Miniopterus fuscus (Motokawa, 2000).
The two species of rats have their closest relatives in
Sumatra and Celebes (Tokuda 1969, p. 120). Theirappearance and habits are unique because of the manyspines (modified hairs) on the body of the spinous rat
Tokudaia osimensis and because of the large size andpreference for arboreal habitats of the long-haired rat
Diplothrix legata (Fig. 4). The Amami rabbit Pentalagus furnessi (Fig. 5) is one of the most remarkablein terms of primitive morphological characteristics(Chapman & Flux, 1990). Yamada et al., (2002) estimated that the lineage of Pentalagus diversified during the generic radiation of the leporids in the middleof the Miocene based on molecular phylogeny.
Of particular concern among the birds are thepurple jay Garrulus lidthi, Amami woodcock Scolopax mira and great scaly thrush Zoothera dauma
major (or amami) because of their small range ofdistribution. The purple jay (Fig. 6) used to live on
Tokuno Island (personal communication with Mr.

Fig. 4

Arboreal long-haired rat, total length of an adultis over 50 cm. (Yoshitaka Takatsuki)

Fig. 5

Amami rabbit, retaining primitive morphologicalcharacters. (Yoshitaka Takatsuki)

Tsuneda), but there is no recent record of its survival(Ishida et al., 1990). Because of its conspicuousness,this must mean it is extinct there. The great scaly
thrush is generally regarded as a subspecies that is
endemic to the Amami and Kakeroma Islands.
Ishida et al. (1998) thought that it should be identified
as a species based on its geographical isolation,
distinctive territorial song and morphological characteristics. Monroe and Sibley (1993) also classified
it as a species according to a phylogenic analysis.
On the other hand, the Ryukyu robin Erithacus komadori is noted in particular for its aesthetic value.
Even during the feudal period before the Meiji
Restoration of 1868, the feudal clan of the current
Kagoshima presented it alive to the shogun, hereditarygeneralissimo of the central government in Edo(present Tokyo) because its warble was so beautiful.

3. Population Trends of the Unique Wildlife
Species
3.1 Mammals
There have been few population surveys except for
the Amami rabbit. Monitoring pellet count is normally the only viable approach and it has been usedfrequently, although various census techniques havebeen applied to lagomorph populations (Seber, 1982).
The first Amami Island rabbit-pellet count was
conducted in 1976 (Anon, 1977). They reported thatpellets were numerous on every forest road they
visited on the island. During the two periods, 19851986 and 1989-1990, pellets were counted along
forest roads in regions B to F (Fig.1) (Sugimura, 1988;

Fig. 6

Purple jay endemic to Amami, Kakeroma and
Uke Islands.

Population Trend and Habitat Change on Amami Island

Sugimura, 1998). These studies indicated that the
rabbit most heavily used secondary forests, 10 to 40
years after clear-felling. Yet, in spite of an increasein the area of young forests due to continuous cutting,they indicated a significant decline in the distribution
and abundance between the two periods. Later,
Sugimura et al. (2000) estimated the distribution andabundance of the Amami rabbit, counting their fecalpellets along streams and forest roads.
Theyestimated the distribution area as around 370 km2 on
Amami and 33 km2 on Tokuno Island. Some
populations were completely isolated and thought tobe very small. They compared the results of thisstudy with those of previous studies and indicated that
the Amami rabbit’s total population had declined overthe last two decades.
The study in 1976 suggested 233 pellets km-1 day-1
as the average number on three forest roads visiteddaily. In the central part of Amami Island theaverage fecal abundance decreased from 47.2 in
1985-1986 to 13.3 pellets km-1 day-1 in 1989-90(Sugimura, 1987; Sugimura, 1993). In the 19931995 studies the figures were 15 pellets km-1 day-1 forthe same area and 19 pellets km-1 day-1 for the whole
range. Thus, the population seems to have declined
significantly after 1976.
As to the change indistribution area, Anon (1977) estimated the range
based on a questionnaire, interviews and pellet
searches on some forest roads. When the past range
was compared with the fecal distribution in the
1993-1994 studies, it appeared to have retreated in thenorthern part (Fig. 7). A study conducted in 2002

Fig. 7

Change in the estimated distribution range from1976 (a) to 1993-1994 (b) on Amami Island.
(modified from Sugimura et al., 2000)

83

revealed further decrease in the distribution area inregions B and D possibly due to the invading mongoose as described later.
The Amami spinous rat is found on Amami andTokuno Islands (Motokawa, 2000; Japan Wildlife
Research Center, 2000). The forest area of Tokuno
Island is much smaller than that of Amami, and the rat
is found almost exclusively in forested areas(Sugimura, 1987). Therefore, the populations on
Amami Island may be essential for the survival of thespecies. According to Sugimura (1987), 5.9 rats
were trapped alive per 100 trap-nights in the winter of
1985-1986 in various ages of stands in regions B to E
(Fig. 1). No rat was caught in the same area in thewinter of 1994, while 1.9 rats were caught per 100
trap-nights in the winter of 1995 in regions farther
south (Japan Environment Agency, 1995). Yamada(unpublished) has recently identified many black rats
Rattus rattus in automatic flash photographs taken in
the areas where none of the spinous rats was caught in
1985-1986. These findings, along with the frequent
observation of black rats by other field researchers(personal communication with Ishida, K. and Takashi,M.), suggest that the black rat might have replaced thespinous rat in regions B to E.
The long-haired rat is primarily arboreal and acavity nester in relatively large trees (Ikehara et al.,
1981; Suzuki, 1985). It is found on Amami, Tokuno
and Okinawa Islands (Motokawa, 2000; Japan Wildlife Research Center, 2000), and Ikehara et al. (1981)
suggested that the population size on Okinawa would
be much smaller than that on Amami Island. Yet,even on Amami Island this species appears to be muchless frequently observed than it was before the PacificWar, since Suzuki (1985) and T. Nakamura (personalcommunication), a former forester at the Amami
National Forest Office, noted that local people used toobserve groups of individuals living together inmature forests moving around inside the canopy layer.
When the distribution is compared between before andafter 1980 according to information collected througha questionnaire and interviews, it was found that thearea decreased and fragmented after 1980 (Japan
Wildlife Research Center, 1994).
3.2 Birds
In the breeding and wintering seasons of 19851986 numbers of 19 species of birds were recorded
according to the sample-count method (Bond, 1957),
establishing over 50 sampling stations along logging
roads in regions B and E (Fig. 1) (Sugimura, 1988).
The same species of birds were enumerated by thesame method in April 1993, February 2001 and April
2001 in order to compare changes in abundance.
Selecting five unique species and comparing theiraverage numbers observed at each sampling station
per visit, all of them were found to have decreased in
number during the fifteen-year interval (Fig. 8). In
particular, the purple jay and Japanese wood pigeon

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K. SUGIMURA et al.

Fig. 8Comparisons of the average number of birds observed at a sampling station per visit
among the 1986, 1993 and 2001 censuses.

Columba janthina were much less abundant in 2001.
The Ryukyu robin appeared to have increased in 1993,
but declined in 2001. Sugimura (2002) compared theabundance of the jay and the robin between regions B
and E. He found that the abundance did not differ
significantly between the two regions in 1986 and1993 for either species. However, both species wereless numerous in regions B than E in 2001. In contrast, the numbers of the two woodpecker species,
white-backed woodpecker Dendrocopos leucotos andpygmy woodpecker Dendrocopos kizuki, did not differ
much between the two periods or between the tworegions (Sugimura, 2002).
Regarding the other species of concern, the Amami
Ornithologists Club conducted a survey on the great
scaly thrush over its distribution range in 1990 and has
continued it annually since 1994. They estimate thatthe surviving number is quite small, possibly around
100 individuals, and indicate that there has been no
obvious increasing or decreasing trend during the past
several years. As for the Amami woodcock there has
been no effective method of monitoring its population,
since it has no territorial song and seldom makes
conspicuous sound. Counting those that appear on
forest roads at night is the only viable method. Yet
they were observed in regions B, C and D in 1985 and1991, while no birds were counted in the same regionsin 1994 (Sugimura, 1987; Kanai & Ishida, 1995).

In addition, comparing other species between
1985-1986 and 2001, only three among 14 species
were found to be more abundant, namely the ashy
minivet Pericrocotus divaricatus, great tit Parus
major and varied tit Parus varius (Sugimura, 2002).
Three species, the brown-eared bulbul Hypsipetesamaurotis, Japanese white-eye Zosterops japonicus
and narcissus flycatcher Ficedula narcissina, showed
no great changes in number. The other eight species
revealed a decline, namely the whistling green pigeon
Sphenurus formosae, Oriental turtle dove Streptopelia
orientalis, Japanese paradise flycatcher Terpsiphone
atrocaudata, jungle crow Corvus macrorhynchos,Japanese bush warbler Cettia diphone, pale thrush
Turdus pallidus, black-faced bunting Emberizaspodocephala and grey-faced buzzard Butastur
indicus. In summary, 12 of the 21 bird species described in this section decreased in number, seven
showed no great changes and only three species
showed an increase in number.

4. Habitat Changes and Their Effects on
Unique Wildlife Species
4.1 Forests and forestry
Broad-leafed evergreen forests (particularly of
evergreen oak Castanopsis sieboldii and Iju Schima

Population Trend and Habitat Change on Amami Island

wallichii) dominate the islands. Perennial grasses
Miscanthus sinensis and ferns Dicranopteris pedata
predominate in cutovers (Shimizu et al., 1988), in
which forests will eventually recover with naturalregeneration from shoots of the dicotyledonous species that formerly prevailed. The afforested area is
not large (less than 20% of the entire forest area),
which is mostly occupied by Ryukyu pine Pinus
luchuensis and a relatively small area of Japanesecedar Cryptomeria japonica. Plantation forestry has
not yet proven to be commercially profitable and mostplantations have been abandoned after receiving subsidies from the government.
Before the Second World War, forests wereselectively logged and most of the forests in thecentral mountains suffered little human disturbance.
Sugimura (1995) and Sugimura et al. (2000) defined
both these and uncut forests as mature forests thatmust have covered the mountains extensively. It is
generally thought that all of those threatened taxa had,in the past, been dependent on mature forests ofbroad-leafed evergreen trees. Forest trees had notbeen heavily utilized before the national government
started the Amami Insular Group Recovery Project in1954. Since then, a number of logging roads havebeen built with a large amount of financial aid.
Timber production on Amami Island peaked in 1963
and again in 1972, but declined suddenly within a few
years after reaching the second peak (Fig. 9). The
decrease was particularly marked for saw-lumber
relative to pulpwood due to a decrease in the area of
mature forests. The total area of mature forest in2000 was estimated to be about 40% of that in 1970,
accounting for about 9.1% of the forest area on theisland (Table 2). Extensive young secondary forests,
observed all over the island, are the consequence ofwhole-tree harvesting, which cleared forests completely, without leaving a single tree or snag on thesite.
Table 2

Change in the area of mature forests on Amami Island.

Year
Area（thousand ha）

1970
15.66

1980
9.78

1990
7.28

2000
6.33

The areas were estimated from aerial photographs, groundobservations and forestry statistics (Sugimura, 2002).

Fig. 985

Most of the trees that are ready to be cut at present
have low commercial value, as young broad-leaved
trees and pines, which are currently overwhelmingly
dominant on Amami Island, can be processed only for
pulpwood. Forestry on Amami Island yields only anegative ‘profit’ as a whole when financial aid fromthe government is taken into account (Sugimura,1988), as is also suggested in Fig. 9. Thus, logging
may be economically feasible only by means ofgovernment subsidies, most of which have been
granted for construction of logging roads, reflecting
large demand for public engineering works as a sourceof employment for the local society. The subsidies
for forestry development amounted to 2,645 million
yen (ca. $22 million), of which 60% was spent forroad construction in the fiscal year 2000 for the whole
Amami Insular Group (Kagoshima-ken, 2002). In
spite of such a large amount of subsidies the amountof cutting decreased drastically in the early 1990s.
4.2 Effects of forestry
Sugimura et al. (2000) attempted to illuminate therelationship between the impact of clear-cutting
forestry and the population of the Amami rabbit.
They divided the whole distribution range arbitrarily
into 39 sub-regions (average 770 ha) using ridge lines,
vehicle roads and rivers. Each sub-region borders ona few to several adjacent sub-regions. Then, they
analyzed the rabbit abundance in each sub-region
statistically and obtained the following equation.
ln P = 1.3ln N +0.0019 * (68 – M ) *M + 0.057L + 1.0(R2 = 0.61, p < 0.001)(P: the number of pellets observed per km; M:
percentage of mature forest; L: percentage of cutover;
N: the average number of pellets observed per km in
the neighboring sub-regions weighted by the length of
the border with each sub-region).
Descriptions of mature forests and cutover are
given in the previous section. Young secondary
forests covered the largest area on the island, and thepercentage of mature forests (M) was below 34% for
the majority of sub-regions. Therefore, this equationsuggests that the rabbit’s abundance is positively
correlated with M. That is, the larger the area of
mature forests, the higher was the rabbit’s abundance.

Amount of output of primary forest products and government subsidies for forestry in the Amami
Island Group.

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K. SUGIMURA et al.

It also suggests that opening up a forest may
contribute to an increase in the abundance of theAmami rabbit by providing herbaceous food sourceson the ground. Sugimura (1988) also suggested thata mixture of mature and young forests would make up
a suitable habitat for the rabbit over the long term.
He found more pellets in young secondary forests
close to mature forests than in young secondary
growth further from mature forests.
As to the spinous rat, Sugimura (1988) suggested
that it would be negatively affected by logging for awhile until young secondary forests cover the area.
The same genus on Okinawa Island was trapped inevergreen forests of Castanopsis trees but not in
agricultural fields (Mitsui & Ikehara, 1979). In
addition, Suzuki (1985) indicated that the acorns ofCastanopsis trees in winter were a major food source.
Therefore, the spinous rat may be negatively affectedby the loss of mature forests, since they yield a larger
amount of acorns than younger stands. On the other
hand, the decline in the area of the mature forests
since 1990 has not been as large as before (Table 2).
So the recent population decline reported by the Japan
Environment Agency (1995) would have been causedby some other factors.
In contrast, it is obvious that extensive clearcutting forestry has had a great negative impact on thelong-haired rat, because their habitat is primarily
arboreal and they use relatively large trees withcavities in the trunk as nest sites. Although available
information is scarce, their distribution area has
decreased and has become more fragmented, as noted
before.
As for the birds endemic to the Nansei Archipelago,comparing their abundance among logged areas,
young secondary forests and mature stands in thecentral part of Amami Island, Sugimura (1987) andSugimura (1988) found that four of these, the Ryukyu
robin, white-backed woodpecker, great scaly thrush
and Amami pygmy woodpecker, exhibited substantial
population declines when mature forests were clear
cut. Only the purple jay was found frequently inyoung forests. Ishida et al. (1995) also indicated thatthe habitat preference of the great scaly thrush was
primarily mature forests of broad-leafed trees, where
the soil was relatively wet. According to Ishida et al.
(1998) the Amami woodcock also prefers mature
forests to young stands in which pioneer pine trees
coexist. Therefore, the majority of the endemic
species would be negatively affected by clear-cuttingof mature forests.
There are some species of birds that appear toprefer young forests, such as the Japanese wood
pigeon, brown-eared bulbul and buntings Emberizaspp. (Sugimura, 1987). The same study suggested
that the Japanese bush warbler, Japanese white-eye,jungle crow and Oriental turtle dove would not be
negatively affected by the loss of mature forests, but
13 out of 20 species would be negatively affected.

Among these, the Japanese wood pigeon revealed a
precipitous population decline in the winter and spring
censuses of 2001, compared with the censuses 15
years before (Sugimura, 2002). It is not clear how
forest habitat change is related to population decline.
4.2 Invasive predators
Those who are concerned about the unique wildlife
on the island have indicated a need to control feral
cats and dogs since the 1970s. Sugimura (1994) reported that 11 out of 15 feces of dogs he found on forest roads contained rabbit hairs. He has found a few
pieces of cat feces only once on a forest road, whichcontained abundant rabbit hairs, in an area where rabbit density was supposed to be one of the highest.
Nakano and Murai (1996) reported that they foundsigns of predation by feral dogs on the spinous rat andthe long-haired rat. Mr. Minami (personal communication), a late professional habu hunter, observed aferal cat killing a rabbit that was climbing up a slope.
He suggested that the rabbits would be more vulnerable to cats than dogs, since dogs would not be able toclimb up the slope. Anyway it is certain that they
may threaten the survival of some rabbit populations.
Another piece of evidence is that there is an inverse
relationship between the population density of theAmami rabbit and the human population in the close
vicinity (Sugimura, 2002). The population size offeral cats and dogs is potentially large in areas where
the human population is large. The human population has gradually declined since the end of the Pacific
War (Sugimura, 1987) to about a half its past level,
and it is still decreasing. So the number of cats anddogs they keep may also have decreased, as long as
the average family keeps nearly the same number ofcats and dogs. Besides, forest road construction decreased in the 1990s to about one third of the level inthe 1970s and about a half of that in the 1980s. Feral
cats and dogs travel along the roads, which expanded
into the interior of the island in the 1970s and extended more densely in the 1980s. Yamada (unpublished) has recently recorded the presence of manycats and dogs in the forest of the interior part of theisland by automatic flash photography. Therefore,
even though they may still threaten the survival ofsome local populations of the unique wildlife species,
they do not explain the recent population decline of
the Amami rabbit and spinous rat that has taken placeover a wide range of their distribution.
In contrast, the mongoose has rapidly increased its
population size (Yamada et al., 1999). It was probably released at Akasaki in Naze around 1979
(Fig. 1). Since then, it has expanded its distribution
range from region B towards regions E and F by 10
km in ten years and later over 20 km in 18 years. It
preys on the Amami rabbit, spinous rat, purple jay,
Ryukyu robin and other endemic species (Abe et al.,
1991; Abe, 1992; Yamada et al., 2000). Because thetotal mongoose population has increased rapidly andPopulation Trend and Habitat Change on Amami Island

they prey on rabbits, they have probably contributed
to lowering the rabbit’s population. Figure 10
indicates that the rabbits decreased from 1985-1986 to
1993-1994 in every region surveyed. Subsequently,
their pellet numbers decreased in regions B, C and D,
where the mongoose has a higher population density,
while they increased in the other regions except region
H (Sugimura, 2002). Also, rabbits were less abundant in the vicinity of cities and towns, where feral
dogs and cats are more frequently observed (Sugimura
et al., 2000). These observations imply that predation may be an important factor in the decline of the
rabbit on Amami Island.

Fig. 10 Change in the number of fecal pellets of the Amami
rabbit observed in recent years on Amami Island.

More recently it has been indicated that black rats
are observed frequently in the interior of the island,
where Sugimura (1987) was not able to trap any ofthem. Ishida (personal communication) suggested
that they might climb up trees and raid bird nests.
The rat was introduced to the island long time ago.
They have been abundant in sugar cane fields as the
major prey for the habu. It is not clear why they
suddenly increased their population in the interior of
the island. The coincidence with the precipitousdecrease in spinous rat populations implies that there
may have been competition for food sources between
the two rat species.

5. Steps toward Reasonable Conservation
Planning
5.1 Local economy
The textile industry has been the most importantamong the productive industries, as it produces
expensive market wares, i.e., pongee fabric with a
special texture for making Japanese kimonos. However, it has suffered a serious depression especiallysince 1985 (Kagoshima-ken, 2002). Besides, thisprimary industry of Amami Island is small for a ruralarea in terms of the percentage of people employed init, which is, roughly speaking, one fifth of that of theother islands in the Amami Insular Group and about ahalf of that of Kagoshima-ken. Thus, every self-supporting productive industry in the island economy issmall, so that it is inevitable that the local society has
been largely dependent on financial support from the87national and prefecture governments to the Amami
Insular Group, of which Amami Island contains 56%of the total population. As a result, the secondary
industry, in which construction for public enterprises
is most important, has the largest number of people
employed.
Based on statistics provided by Kagoshima-ken(2002), the prefectural and national governments contributed in total 144,928 million yen (ca. $1,200
million) to the local governments in the 2000 fiscal
year. This enormous amount of funds suggests how
important government subsidies were not only tosustaining the industries but also to creating jobs forthe 73,896 people living on the islands in the year
2000. Estimating from the statistics provided by
Kagoshima-ken (2002), public engineering works
accounted for more than 50% of the jobs.
5.2 Forest management
As suggested previously, the great scaly thrush,
Owston white-backed woodpecker and long-haired rat,
must have all suffered substantial population declines
because of extensive clear-cutting.
They willprobably not be able to maintain their populations if
no mature forests (primary forests and old secondary
forests) are retained. Small populations of the
Ryukyu robin may be able to survive in young secondary forests, but population decline will be substantial
because of the decrease in the area of mature forest.
Mosaics of young and mature forests are still abundant in the central and the southern parts of Amami
Island. Therefore, primary conservation measure insuch areas would be to limit forest road construction.
This measure would restrict the logging of moremature forests and help prevent the isolation of somelocal populations.
Forestry has been subsidized by the national andprefectural governments to a large degree, and has
provided construction companies with a considerable
amount of work. As a result, most of the mature
forests have been replaced by young secondary forestsand logged areas (Sugimura, 1988). The governments involved have planned to manage those youngforests for pulpwood, even though it is of low commercial value. Yet, the economic inefficiency of theforestry industry has helped most of the young forests
to recover for these ten to twenty years in the central
part of the island. Therefore, it would be wise topursue a forest management policy of stopping theloss of mature forests and encouraging long- rotation
management of less mature forests (Harris, 1984).
One possible procedure would be a shift in the useof government subsidies to aim at a longer rotationcycle and a shift from construction of logging roads tosilvicultural experiments for forest conservation andmore efficient use of mature forests. At the sametime, the subsidies could provide jobs for local people
so as to maintain the current contribution of theforestry industry to society.

88

K. SUGIMURA et al.

5.3 Controlling predators
Information on feral cats and dogs is so limited
that their effects cannot be ascertained. Researchers
have indicated the importance of their control since
the late 1970s, while they recognized the problem of
the mongoose to be serious in the 1990s (Sugimura,2002). The Japan Environment Agency started investigating the ecology and the status of the mongoosein 1994. At present the same agency (promoted to aministry in 2001) and the local governments are
involved in capturing mongooses and attempting toeradicate their populations.
However, Yamada(2002) doubts the effectiveness of these projects.
First, they have been trapping mongooses mainly nearresidential and agricultural areas far from the core
distribution areas of the indigenous species. Second,
the trapping period does not coincide with the breeding season, so the population may recover soon.
Therefore, it is essential to investigate the effects ofthe mongoose on the indigenous species, endemic
species in particular. This should make it clear
which species is to be protected as the first priority
and in which area.
A budget can be allocated from the large amount ofgovernment subsidies. Even a small portion of thebudget that has been used for public engineering
projects would be sufficient to provide economic
incentives for trappers to catch a larger number ofmongooses.

Concluding Remarks
Although most of the endemic species that thepresent paper deals with may not yet be on the brinkof extinction, it is most likely that their populations
have been declining (Table 3). Therefore, certain
measures do need to be taken if they are to beconserved. Sugimura et al. (2000) suggested thatthree measures would be effective for the Amami
rabbit, and this would also be true for the other speciesof concern. They are (1) to restrict extensive logging
Table 3of mature forests to maintain a widespread mosaic of
cutover and mature forests; (2) to control predators(feral cats and dogs and introduced mongooses); and(3) to cease forest road construction that may
encourage further expansion of predators in forests.
One of the major obstacles facing policy decisionmakers with regard to bringing these measures into
practice will be that the value of these species isintangible and difficult to quantify when they have togive it priority over a human activity, such as road
construction, whose benefits are visible and readily
quantifiable. Yet, construction of a forest road itself
does not yield sufficient economic benefits, so reducing the number of roads to be built could save asubstantial amount of subsidies. Then, the amount ofsubsidies saved could be invested in predator controls
and monitoring the populations of some uniquespecies. Once it has been shown that a particular
human disturbance (logging or the invading mongoosein the present study) can be mitigated, the benefits ofspecies preservation do not have to be stated precisely
in contrast with those of development activities. It
will become apparent that the cost of this kind ofpreservation is small relative to the amount of subsidies to be saved.

Acknowledgements
A number of people living on Amami Island supported our surveys that extended over 15 years. To
name a few, Dr. M. Hattori provided us some researchequipment; Mr. M. Tsuneda helped identify bird
species; S. Abe, Y. Abe, Y. Handa, Y. Takatsuki, M.
Takashi and H. Kawaguchi joined our field surveys.
Also, biology students from Kagoshima University
and Kanagawa University assisted in some of the
fieldwork. We also thank the Ministry of theEnvironment (former the Japan Environment Agency)
the Japan Wildlife Research Center and the World
Wildlife Fund Japan for financial support.

Population trends of the unique wildlife species of concern in the present paper.

Common nameMammals
Amami rabbit
Long-haired rat
Spinous rat
Birds
Purple jay
Amami woodcock
Ryukyu robin
Great scaly thrush
Owston white-backed
woodpecker
Amami pygmy woodpecker

Population trend

Most probable or likely causes

Decline in area and density
Decline in area and density
Decline in area and density

Logging, predators*
Logging
Logging, predators

Decline in density
Decline in area and density
Decline in density
Decline in area and density
Decline in density

Predators
Logging, predators
Logging, predators
Logging
Logging

Decline in density

Logging*Predators are mainly mongooses and feral cats and dogs

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(Received on 13 March 2003, Accepted on 4 July 2003)