3rd Revised

For restoring forest ecosystem andnative animals in Yambaru

1Animals Only Found in Yambaru
In Yambaru, there live many endemic animals which cannot befound anywhere else in the world.

About Yambaru
Yambaru, which means the northern mountainous area of Okinawa Island, had referred to
the region of Onna-son and northward before.
Recently, the word is more commonly used to
the region further north, which might be caused
by improved transportation facilities.
Yambaru will, hereafter, refer to the SF Line,a fence line which extends from Shioya to
Fukuji Dam, and the area northward.

ShioyaYambaru
Fukuji Dam

SF Line

Okinawa rail
CR

NEWF

NNM

CR

NEWF

SNM

Forests inhabited byendemic species
Amami and Okinawa Islands are considered to be isolated from the continent
at least 1.7 million years ago. Such longtime and further repeated isolation and reunion of the islands have caused speciation and phylogenetic diversification ofterrestrial organisms. As a result, the islands are currently inhabited by higher
proportion of endemic species. In the Okinawa Island, a lot of endemic species inhabit Yambaru in which Fagaceous forests extend.

1

Okinawa woodpecker

Endemic to the Amami andOkinawa Islands

Endemic to Yambaru
CR

Critically endangered

EN

Endangered

VU

NEWF National endangered species of wild fauna and flora
SNM Special natural monuments of JapanNNM National natural monuments of JapanPNM Prefectural natural monuments

Vulnerable

Okinawa spiny rat
CR

Okinawa Ishikawa’s frog
EN

NEWF PNM

Yambaru long-armed scarab beetle
EN

Ryukyu long-haired rat

NEWF NNM

EN

NEWF NNM

Amami woodcock

Ryukyu robin（※Endemic
subspecies）

EN

VU

NEWF NNM

NEWF PNM

Ryukyu black-breasted
leaf turtle

Kuroiwa’s ground gecko※Endemic species of the
VU
Okinawa Islands（those that cannot befound on Amami Oshima）※Endemic
subspecies of
the Okinawa
Islands

NNM

VU

NEWF PNM

NEWF NNM

A Vulnerable Ecosystem
The Yambaru ecosystem which lacks carnivorous native mammals have caused
unique adaptations to the native fauna andflora, such as non-volant Okinawa rails andOkinawa woodpeckers which forages on the
ground. A unique ecosystem of Yambaru has
been formulated by the interaction amongsuch organisms.
Since the Yambaru ecosystem has beendeveloped in an isolated environment, it isvery vulnerable to the impact by invasive
species, especially carnivorous mammals.

Namie’s frog
EN

Anderson’s crocodile newt
NEWF PNM

Ryukyu tip-nosed frog
VU

VU

NEWF PNM

Holst’s frog※Endemic species of
the Okinawa Islands EN（those that cannot befound on Amami Oshima）

NEWF PNM

2

2

Introduction of Mongooses
Mongooses brought from the Gandis Delta werereleased on the Okinawa Island in 1910.

About the mongoose

English name：Small Indian Mongoose
Scientific name：Herpestes auropunctatus*Recently the Javan mongoose was scientificallyclassified into two species: the Javan mongooseand small Indian mongoose. The mongoose introduced into Okinawa Island is the small Indian mongoose.
Tail length is nearly half
the size of total body length.

Weight: Males：0.5 to 1kg;
Females：0.3 to 0.6kg

Total body length：50 to 60 cm.

Distribution

Hawaiian Islands
Okinawa Island

West Indies

Fiji
Mauritius

The original distribution (yellow) and introduced
regions (red allows)

Ecology

3Life History
c.
De
v.
No
t.
Oc
p.
Se
g.
Au
l.
Ju
n.
Ju
y
Ma
r.
Ap
r.
Ma
b.
Fe
n.
Ja

・They are diurnal and rest under rocks orin hollows at tree bases at night.
・They are solitary and their home range
size is 3–9 ha.
・They are good jumpers and can jumpover a fence up to 80cm in height andclimb over a fence. However, theyrarely climb up trees in the wild.
・Although the life span of mongooses in
Okinawa Island has yet to be known, it
is estimated as one to three years, five
years at the longest in other areas.

Original distribution of small Indian mongooses is very wide from Western Asia to
Southeast Asia. They were introduced into
about 70 islands in tropical areas, including
the Hawaiian, Fiji and West Indies Islands,
during the late 1800s, in order to control rat
and poisonous snake populations.

MatingGestation
Bearing
Lactation

Mongooses reach sexual
maturity in 180 days after
birth. Once to twice a year,
they bleed 2-3 pups with 49
days gestation period.

Independenceof sub-adults

Diet
Mainly feeding on insects and reptiles but
they eat a variety of food items：mammals,
birds, amphibians, arthropods, and even plants
and fruits.

I love to e
at avariety of food!

Why mongooses came to Okinawa?

N

1993

Seventeen mongooses were released in Naha and Nishihara, southern part of Okinawa Island in 1910, in order to control
the number of rats which ate sugar canes, and venomous Habu
snakes which harmed humans.

Fukuji Dam

1978

A couple of fencelines preventing
mongooses fromentering the
Yambaru region

1978

The only 17 mongooses has increased their population and expanded their distribution to the northward of the island.

Mongoose distribution
reached to Ogimi-son by theearly 1990s, then expanded
to the Yambaru forests inhabited by threatened animals.

2000
2006
2004

Just 17 mongooses spread
across Okinawa Island.

Invasion into Yambaru

Prefectural road No.2

Northern front line ofmongoose distribution

Released in Naha City andNishihara-cho in 1910.
0

Mongooses disturb
a forest ecosystem
in Yambaru.
Okinawa habu
Native rats andfrogs, etc.
Insects, etc.

Plants10

20km

Mongooses have entered aforest ecosystem in Yambaru inwhich the Okinawa Habu snake
is the top predator. Native animals in Yambaru are suitablepreys for mongooses, because
they have never adapted to protect themselves from carnivorous
mammals.

Will native animals in Yambaru
be extinct?

Stomach and fecal contents analysis made it clear thatmongooses fed on more than 30 animal species in Yambaru, including insects, lizards, frogs, birds and mammals.
Endemic animals to Yambaru, such as Okinawa rails, Okinawa woodpeckers and Okinawa spiny rats were also
found in them. In particular, Okinawa rails have been foundless and less in the area where mongooses have invaded.
Their distribution range has been decreased to 60% fromthe range when they were first discovered in 1981. If weleave mongooses in Yambaru, there would be extinction
crisis for the native animals.

Stomach contents of mongooses(Left : Okinawa rail; Right : Okinawa spiny rat)

Don’t mongooses eat
Okinawa Habu snakes?

Animals forced to be extinct bymongoose predation.

Despite the fact that mongooses were introduced to control
Habu snakes, they don’t actually prefer to eat the snakes. It isbelieved that these two animals rarely encounter, becausemongooses are diurnal but Habu snakes are nocturnal.

In the West Indies, Hawaiian Islands, Fiji
and Mauritius, many native animals including
small mammals, birds, snakes and frogs areforced to be extinct or declined by introducedmongooses. If we don’t take measures, thesame thing will happen in Yambaru.

4

3

To Restore Forest Ecosystem
in Yambaru
Central and prefectural governments launched mongoose
capturing projects in 2000s.

1985〜

History of measures tocontrol mongooses

In 1985, University of the Ryukyus ( UR ) started its basic research.
In1993, the Northern Dams Office, Okinawa Development and Promotion
Bureau (NDO) started capturing mongooses. In 1999, “Council for Measures to Invasive Animals of Okinawa” was organized by relevant organizations including Ministry of the Environment (MOE), the Northern Dam
Office, Okinawa Prefectural Government ( OPG) and UR. OPG in 2000
and MOE in 2001 started mongoose capturing projects across the Yambaru area.

Mongooses designated as “Invasive Alien
Species (IAS)”

In 2005, the Invasive Alien Species Act was enforced to prevent IAS fromharming ecosystem, human health, and agriculture, forestry and fishery industries. Feeding, bleeding, keeping, transporting and importing IAS are prohibited
under the act. The mongoose was designated as IAS, since they damage ecosystems and agricultural industry.
In accordance with the act, MOE and OPG drew up “Mongoose Eradication
Action Plan” aiming to eradicate mongooses from Yambaru in 10 years,
strengthen their projects with enormous capturing efforts.

Prevent mongooses from invading Yambaru
Barrier fence against mongoose invasion

Basic Research(UR and NDO)

2000

OPG started capturingmongooses.

2001

MOE started capturingmongooses.

2005
Invasive Alien Species Act
enforced.
M ong o ose Eradic at i on
Action Plan drawn up.

2006
The 1st Fencecompleted along SF Line.

2008

Yambaru Mongoose
Busters organized.

2013 〜

The 2nd Term Mongoose
Eradication Action Plan developed and The 2nd Fencecompleted along ST Line.

1st Fence (SF Line)

2nd Fence (ST Line)

In order to prevent mongooses from invading Yambaru, OPG and NDO constructed
the 1st Fence (4.13km in length) between Shioya, Ogimi-son and Fukuji Dam,
Higashi-son in 2006. To enhance effectiveness of the barrier, OPG, furthermore, completed the 2nd Fence (7km in length) between Shioya and Taira, Higashi-son in 2013.
The height both of the fences is 1.2m. Metal plates are attached at the top of thefences, and the fences under the metal plate have vertically longer mesh structure,
which make mongooses unable to climb over them. In addition, the fences are bent inL-shape at their bottom on the ground so as to prevent mongoose from digging holes.
The 2nd Fence has, furthermore, narrower mesh structure and is attached metal
plates at its bottom to prevent invasive snakes from passing through.Moreover, OPG
installed the 3rd Fence between Genga, Nago-city to Arime, Higasi-son, to strengthen
effort to prevent invasion of mongoose.

5

2013

Mongoose Proof Fence
No. 2 completed.

2016

Yambaru National Park
designated.

2017 〜

The 3rd Term Mongoose Eradication Action Plan developed
and The 3rd Fence completed.

The Yambaru Mongoose
Busters
The Yambaru Mongoose Busters(YMB) organized in 2008 plays a key roleat the frontline of the mongoose eradication project. Since the project has now
declined the number of mongooses,
hit-or-miss trapping could no longer succeed in the capturing. YMB is working
harder for more effective and efficient
capturing through daily observation andlong experience, and by analysing hugeamount of accumulated data.

●Trapping and monitoring methods
Only a single method is not enough to eradicatemongooses. We combine a variety of tools andmethods in order to implement the project more
effectively. We are also conducting surveys to investigate remnant mongoose and the recovery of native
animals.

Detecting remnant
mongooses

The Mongoose Busters use a variety of methods todetect remaining mongooses.

Capturing tools
Mongoose sniffer dogs
Kill trap

Live trap

Steel mesh frame box
traps are used for the capturing in the area which native rare animals inhabit.
The trap must be checked
everyday to avoid killing
native animals.

Cylindrical kill traps arechecked once a month,
therefore, can be set more
traps and are much more
efficient than live traps. We
limit the area and period touse kill traps taking into account by-catch of native
animals.

A handler instructs
a sniffer dog to detectmongooses. They arealways together andforming trusting relationship.

This trap puts the legs between jaws covered withrubber so as to capturemongooses alive without
injured.

Mongoose Busters not only capture mongooses but also monitor native animals
using a variety of methods, e.g. recording their witness, feces and voice, etc.

Dog Team :Search for mongoose traces.

Sniffer dogs and handlers search formongooses and their feces and informtheir detection to the trapping team.

pare for trapping tomorrow.

Training.

The dogs are trained
to keep their capacityand get higher skill.

Evening
Meetingarea. They check on the condition of thetraps, replace the bait, and check whether any animals have been captured.

2:30 Recording and preparation.
5:00
p.m. Record results of today’s works and pre- p.m.

Finallylunch time!

Head forthe forests.
Morning
Meeting

9:00 9：10 Trapping Team: Set up and check on traps.
a.m. a.m. Each member heads for their assigned

Roll call foreach team andconfirming
today’s work.

Hair trap
A sticky sheet set on
the trap collects mongoose hairs.

Sniffer dogs and their handlers

Soft catch●One day of
Mongoose Busters

A pair of a sniffer dog andhandler detects a mongoose
itself and its feces and smell.

Camera trap
A camera with a passive infrared sensor
takes pictures of animals
when they pass in frontof the camera trap. It
can monitor not only
mongooses but also native animals.

Roll call for eachteam and confirming
the works tomorrow,
finally sharing and reviewing
today’s activities.

6

4

Mongoose population decline
The effects of the project are becoming evident.

The number of mongooses has
extremely declined.

?

? What does this mean??
This result suggests thatthe mongoose population
is decreasing.

● Trapping efforts is expressed as “trap days” = the number of traps x trapping days. For instance, if 100 traps are set for two (2) days, “trap days” is
200 trap days.

Mongoose-captured sites and trapping sites
The more traps were set up, the moremongooses were captured, during thefirst several years.

F Y 2000

Despite increased trapping efforts (trap days),
the number of captured mongooses has been
declining since 2009.

F Y 2005

Trap days：78,576
Number of captured
mongooses:：123

F Y 2010

Trap days：279,896
Number of captured
mongooses:：575

F Y 2016

Trap days：1,303,149
Number of captured
mongooses:：230

Trap days：1,681,314
Number of captured
mongooses:：78●Capturing points of mongooses

Number of captured mongooses and trapping
efforts (trap days)
Number of captured mongooses
600

2,000,000

0.45

1,800,000

0.40

1,600,000

0.35

500

1,400,000

400

1,200,000

300

800,000

1,000,000
600,000

200

400,000

100

200,000
2000

2002

2004

2006

2008

2010

2012

2014

Number of captured mongooses per1000 trap days
0.50

Trap days

700

0●Trap locations

2016

0

Despite less than 400,000 trap days, more mongooses
had been captured until 2007. However, the number of captured mongooses has declined since 2008 though much
more trapping efforts have been done.

0.30
0.25
0.20
0.15
0.10
0.05
0.00
2000

2002

2004

2006

2008

2010

2012

2014

2016

The number of captured mongooses per 1000 trap
days reached its peak in 2003, then turned to declining. It has been further declining with very low value
since 2010. This shows that the density of mongooses in Yambaru has now got to extremely low.

?
?

? As mongoose population has declined, can we decrease trapping effort?

No! The hard works are still ahead. The capturing works are more difficult after the density gets lower. Even though an experienced staff of the Busters fully works out, it becomes very difficult to capture only a mongoose. However, once we loosen thecapturing, all efforts we have made would go to waste.
Remember that only 17 mongooses first released have spread throughout Okinawa
Island. We have to continue the capturing effort until mongooses in Yambaru get tozero in order to restore Yambaru to such forests as native animals live safely.

7

Okinawa rails are coming back tothe south area of Yambaru!
Monitoring survey on Okinawa rails
To monitor the population and distribution of Okinawa rails, since 2007, Ministry of the Environment has been conducting playback surveys, which soundthe rail’s calls with a speaker, thencount call-back from wild rails respondto the sound.
When first discovered in 1985, Okinawa rails were found in the area between
Shioya and Taira. Their distribution area had, however, been smaller toward thenorthern area with invasion of mongooses.

FY2007In FY 2007 when the number of captured mongooses reached its
peak and exceeded 600, we couldn’t confirm Okinawa rails in thesouthern part of Yambaru.

ShioyaIn FY2010, the number of captured mongooses drastically declined and reached to the 200s.
However, few rails have confirmed in the southern part.

Taira

detected
not detected

FY2010uninvestigatedSince 2012, adult andyoung rails were found in
the southern part of Yambaru, which indicated thatthe rail recovered its distribution.
A chick of Okinawa rail

In these days, the rails were found in many
areas and their distribution expanded to thesouth area of Yambaru.

FY20168

5

Action Plan of the Mongoose
Eradication Project in Yambaru
Ministry of Environment and Okinawa Prefectural
Government drew up the 3rd term Action Plan of theMongoose Eradication Project in 2017 and are
implementing the plan

Project Goal

In order to restore the forest ecosystem in Yambaru
inhabited by a number of endemic and threatened
species, eradicate mongooses from the Shioya-Fukuji
line and northward area by FY 2026 and prevent theirre-invasion into the area.
TargetTarget１
１

Eradicate mongooses
from Yambaru.

TargetPrevent re-invasion ofmongooses into Yambaru.

2

Target3

4

Enhance effectiveness ofthe project by developing
new techniques.
Collaborating with research institutes, wewill develop more effective traps, mongoose
prevention fences, and monitoring tools.

Target5

Target

6

9

Ⅱ

Ⅴ
Ⅶ

Ⅷ

Ⅰ
Ⅳ

Ⅲ

Ⅵ

Restore native animals.
Conducting monitoring surveys on
threatened animals.

TargetWe divided Yambaru area
into eight zones, and will
eradicate mongooses fromthe north in order.

Increase public awarenessthrough various publicity
activities.
Evaluate implementation andeffectiveness of the projectand improve the action plan
and activities when necessary.

Using the twofences to block out
mongooses

Shioya (S)SF Line(Fence+dam lake)

ST Line(Fence)Taira (T)A buffer zone forpreventing the invasionof mongooses.
Apart from "The 3rd Term
Mongoose Eradication Action
Plan", OPG is conducting its
own plan "Action Plan of themongoose Eradication Projectof Okinawa" ,in order to reduce
their population and habitat
significantly until FY 2026.
That Action Plan is conductedin the area between south of
ST line to prefectural road 14,
called as "priority measures
region.

Steps for Eradication

1 Reduce the density
As a first step, reduce thedensity in a zone inhabited by anumber of mongooses.

If no mongoose informationfor over a year

3 Eradication check

Target areasfor eradicatingmongooses

Verify eradication of mongooses
in the zone using concentratemonitoring by sniffer dogs,
camera traps and hair traps.

2 Remove remnants
In a low density zone where
capturing efficiency has reduced,
we also concentrically set traps
in the area where more information on mongoose existence has
been gathered from trapping andsniffer dog’s surveys.

If no mongoose information
for another year and more

eradicated
4 Keepstatus
Continue trapping and monitoring to keep eradicated status
in the zone.

Eradication
completed!

GOAL!!
Fukuji Dam (F)Amami-Oshima Island, Tokunoshima Island,
the northern part of Okinawa Island and Iriomote Islandis candidate for world natural heritage registration.
Two important points to be registered in the World Natural Heritage are “to exist outstanding and universal value” and “to protect its value in the future” . We will continue preparing
for registration the fifth world natural heritage in Japan, including measures of mongoose at
Yambaru
10

It s not the mongoose s fault

Do not bring any
invasive species into
YambaruThis forest belongs to
Yambaru’s native species…

Although mongooses are treated as pests
disturbing the ecosystem in Yambaru, they
are an essential component of the ecosystem in their original habitats like in India. The
introduction of mongooses by humanscaused them to disturb the ecosystem in Okinawa Island. Therefore, we have to recognize that it’s our fault. In order to conserve
native animals in Yambaru, it’s absolutely indispensable to eradicate mongooses fromthe region.
It is important for us to be aware of invasive species in our daily lives. We need to remember three principles for measuresagainst invasive species: “Do not
let them in”, “Do not release them”,
and “Do not them spread”.

Visit the following websites for information on invasive species
About the Invasive Alien Species Act……………………… ht t p : / / w w w . e n v . g o . j p / n a t u r e / i n t r o /About measures against invasive species in the……………………………………… http://kyushu.env.go.jp/naha/wildlife/gairai.html
Ryukyu Islands
Database of invasive species, National Institute forEnvironmental Studies ……………………………………… http://www.nies.go.jp/biodiversity/invasive/

Mongooses are “Invasive Alien
Species” designated by the law
Transporting and keeping living mongooses is prohibitedby the Invasive Alien Species Act. In addition, mongooses
are not purchased by governmental bodies. “Mongoose
Busters” is capturing mongooses with special permission,.

What you can do for Yambaru s future.

It is not just mongooses. Please don t abandon your pet.
Abandoned dogs and cats will turn to feral and eat native endemic and rare animals. Living withhumans is what makes pets happy. ……
Making your pets happy will make wild animals in Yambaru happy.
If abandoned pets turn to feral, they will attack native wild animals.
Regulations for handling a house cat
enacted by municipal governments inYambaru, Kunigami, Higasi and Ogimi● A microchip shall be implanted in a pet cat.
● Application for the registration shall be submitted
within 30 days after acquisition of the cat.
● The owner who doesn’t want breeding of his/hercat shall endeavor the breeding control.
● Feeding stray cats is prohibited.
※The above dog and cat are both feral ones taken pictures in Yambaru.

※Abandoning pets is prohibited by law.

Municipal governments in Yambaru: Kunigami, Ogimi and Higashi, enforced the “Ordinance on Welfare and Management ofCats” on 1 April, 2005.

Ministry of the Environment
Naha Nature Conservation Office

Okinawa Prefecture,Environmental
Department, Nature Protection Section

1F Naha first local government Bldg.,
1-15-15 Higawa, Naha City, Okinawa Prefecture,
900-0022
T E L：098-836-6400 ／ FAX：098-836-6401

1-2-2 Izumizaki, Naha City, Okinawa Prefecture
900-8570
TEL：+81-98-866-2243 ／ FAX：+81-98-866-2240

Edition: Nansei Environmental Laboratory Co., Ltd.

Design: Hirayama Printing Co., Ltd. Issued December, 2017