HOPE Report No.33' 2004-11-03
Dr. Struhsaker's trip to Yakushima and Koshima
Date: July 2, 2004
Ryutaro Goto (sophomore, Kyoto University)
This summer, I was given the chance by Dr. Matsuzawa to travel to
Yakushima and Koshima with Dr. Struhsaker as his guide. Below is a report
of this trip.
Before the trip
I looked through two books written by Dr. Struhsaker, The Red Colobus
Monkey and Ecology of an African Rain Forest, and learned a little about
his work in Africa.
The First Meeting
Dr. Struhsaker was the main guest lecturer at this year's annual
conference of the Primate Society of Japan. After the conference, he
planned to travel to Koshima and Yakushima. The conference was to be held
in Inuyama City; therefore, I left Kyoto for Inuyama to join him.
I first met him at a seminar room at the conference hall. He was engaged
in a discussion with Japanese researchers, so we only shook hands and
greeted each other briefly. But I was glad to find that he was a friendly
tall gentleman. His beard suited him well.
Dr. Struhsaker's lecture
Dr. Struhsaker was the guest lecturer for the second "Imanishi-Itani
Memorial Lecture," held to honor the late Kenji Imanishi (1902-1992)
and Junichiro Itani (1933-2001). He talked about his conservation efforts
in Africa, especially at Kibale forest in Uganda. I had the opportunity to
learn about what he had been doing in Africa and about the importance of
After the lecture, someone from the audience asked him why he chose to
observe without feeding the monkeys to get them used to humans, as is
common in other field sites. He said that feeding wild animals creates an
unequal and unnatural relationship between us and the animals, and
therefore, we cannot observe their natural behaviour. He also pointed out
that feeding them may bring human illnesses into the colony. I decided to
keep this issue in mind as we visited Koshima and Yakushima, the two main
field sites in Japan for studying monkeys.
Visiting the Japan Monkey Center
The next morning, Dr. Struhsaker and I visited the Japan Monkey Center in
Inuyama. This center has a large variety of primates. Under the hot sun,
we observed the monkeys and apes. From his experiences in Africa, Dr.
Struhsaker had a vast body of knowledge about the various species of
primates we observed; it was as though he was guiding me through the
center instead of the other way around.
He noted the cages of the Monkey Center were too small, with which I
agreed. We unfortunately saw many abnormal behaviours, characteristic of
primates kept in captivity. I strongly felt that enrichment of zoos is an
important issue that must not be neglected.
At the Koshima Hotel "Tagiri-So"
After visiting the Monkey Center, we flew to Miyazaki. Mr. Suzumura (a
technician at the Koshima Monkey Research Station) met us at the Miyazaki
airport and took us to the Koshima hotel "Tagiri-So." It rained
heavily in Miyazaki.
Mr. Suzumura told to us about Koshima Island in the car.
1. The distance between Koshima Island and the mainland is very short
(about 300m). In recent years, sand was beginning to collect in the sea in
between. Therefore, many people were starting to worry about what would
happen if eventually, Koshima and the mainland became connected and
monkeys came into the mainland. What would become of potato-washing?
2. Koshima monkeys are famous for potato-washing. But, Mr. Suzumura told
us that the technicians gave potatoes only in special occasions, such as
filming. Therefore, unfortunately, we would not have the chance to see the
famous potato-washing behaviour. I found it interesting that monkeys
remember how to wash potatoes though they are not fed potatoes regularly.
3. There were 9 baby monkeys at Koshima when we visited, and the youngest
baby had been born only 2 weeks before. I was looking forward to seeing
We arrived at the hotel "Tagiri-So." Dr. Struhsaker had last
been to Koshima in 1968. He told me that the roads had improved
We had planned to meet Mito Satue, the discoverer of the cultural
potato-washing behaviour and the owner of "Tagiri-So," at the
hotel. Dr. Struhsaker had met her in 1968, and we were looking forward to
seeing her. Unfortunately, she was currently visiting her son in Sante Fe,
New Mexico, so we could not see her. But we met an interesting couple
working at "Tagiri-So," Mikio Ikai and his wife, Midori. Mrs.
Ikai had been working at an NGO in Ghana for 2 years, so her English was
good, and Dr. Struhsaker enjoyed talking about Africa at dinner with her.
Mr. Ikai was good at playing the African piano, and we listened to his
music during dinner.
We had heavy rain that night, and the sea was stormy. It looked as though
we would not be able to visit Koshima island the next day. I asked the
fishermen whether they could sail across to the island tomorrow morning,
and they replied bluntly that there was little hope of sailing in this
weather. I negotiated with the fishermen and managed to have one of them
promise take us to the island if the weather was good the next morning.
Everything depended on the weather, and I must admit that I spent an
I woke up at 5:50am and found the bad weather had passed. I called the
fisherman and asked how the sea condition was, and he said that we would
be able to go to the island. I was excited and wanted to inform Dr.
Struhsaker about the good news, so I went to wake him up, but he was not
in his room. Wondering where he had gone, I asked Mr. Ikai. He told me
that he was taking a walk. Soon, he returned to the hotel and told me that
we could go to the island. He had gone to the docks to ask the fishermen
whether we could go to the island. How active he is!!
Column 1 "What is the Koshima Island?"
Koshima is a small island of 30ha, surrounded by beautiful sea and covered
with an evergreen broad-leaved forest. Various studies have been conducted
there since 1947, when research of Japanese macaques began here. Since
1952, all individuals have been identified and their personal histories
have been recorded, especially in their family trees with dates of their
birth and death. Other information, such as socially pertinent incidents
like changes in high-ranking males and females, individual transfer
between groups, and their body weight has also been recorded. Many studies
have been conducted on Koshima monkeys. The findings of cultural behaviour
like potato-washing, especially, were an outstanding product of Japanese
primatology in their early time, and as a result, Koshima is known
Visiting Koshima Island
At breakfast, I handed the schedule I had written in English during the
night before to Dr. Struhsaker. I hoped that this schedule would help my
inexperienced tour-guide skills. We left for Koshima soon after breakfast,
and we took a short boat ride. Because of the tides, we had only 1 hour in
Koshima until the fisherman came back to pick us up.
When we got off the boat, we found monkeys gathering around the beach. The
monkeys on the island are not weary of humans, so we could observe them
from a close distance. We saw some that were grooming each other and
mothers giving milk to their infants. Dr. Struhsaker filmed some of the
monkeys and the beautiful beach.
After we came back to the mainland around 9:30am, we visited the Koshima
Field Station. Because I had thought that we would not be able to visit
Koshima, I wanted to ask the technician to take us to Sakurajima. They
told us that they had plans with another group until noon, but that we
would have a second chance to visit Koshima again with them in the
afternoon. So, we changed our plans once again and went to Koshima once
more on the Center's boat.
On the way, Dr. Struhsaker asked them about the accident of Kenji Yoshiba.
Kenji Yoshiba was a researcher and had met Dr. Struhsaker before. He was
killed in an accident in the sea near Koshima when he was still very
young, as a result of a series of unfortunate events, such as bad weather
and the boat engine malfunctioning.
Visiting Koshima again
We visited Koshima for the second time with Mr. Kanji and Mr. Suzumura
(both technicians at the Field Center). This time, there were more monkeys
than we saw in the morning. The technicians fed them some wheat and
checked each monkey, identifying them by face. They also found a new baby,
just born last week.
When Mr. Kanji and Mr. Suzumura gave the monkeys some wheat, the monkeys
ate directly from the ground by flexing their forearms and bending down to
lick the grains. Dr. Struhsaker told me that in the old days, the monkeys
would throw the grains into the water and separated the wheat grains from
the sand. This behaviour is called "wheat placer mining." During
my visit, I never saw the monkeys washing the wheat grains this way. Had
they lost their cultural behaviour?
I also heard that the monkeys used to sometimes swim from Koshima to other
islands, but recently, this behaviour was rarely seen. I thought that this
tendency might be related with the loss of the culture of wheat placer
I learned much about the monkeys from Mr. Kanji while at Koshima.
Column 2 "Mr. Kanji's Explanations"
1. Boss monkeys do not exist
These days, groups that do not have "boss monkeys" are common in
Japan. When we feed monkeys for observation, many individuals gather
together, and there are more frequent fights for food than in the wild.
Therefore, the social hierarchy can be seen more clearly, perhaps
suggesting the presence of an especially dominant monkey. Feeding does
make observation of the monkeys easier, but on the other hand, it makes
for an unnatural circumstance.
2. About male monkeys
When male monkeys are about 5 years old, they become stronger and start to
threaten low-ranking females. These conflicts become more serious as they
age further, and young males often leave their natal troop and become
In the fall during mating season, they briefly return to their troop.
When males are about 10 years old, they return to their troop as
low-ranking members. This time, they are kind to the female monkeys,
participating in grooming and playing with children, and through these
behaviours, they slowly rise in social rank.
3. About female monkeys
Female monkeys become more aggressive after giving birth to a child. They
have to be assertive in securing food for their offspring; they can no
longer afford to yield to others. Other monkeys abstain from attacking
mother-infant pairs as well.
Also, female monkeys choose their male partners to their advantage. During
mating season, they spend a lot of time with high-ranking males, enjoying
their protection to avoid attacks from other males. However, recent
research has shown that the offspring of these females are not necessarily
fathered by the dominant males. Apparently, females are wise in their use
4. Recent problems in Koshima?
Beginning in the 1980s, monkeys have started to eat raw fish after being
exposed to the taste through stealing from fishermen, a previously
The bait that fishermen leave behind causes problems as well. These
contain high amounts of preservatives, causing the monkeys that ingest
them to first become so well-muscled and deformed that even the
technicians cannot recognize them by face, and then suddenly emaciated.
After visiting Koshima Island, we were taken to Sakurajima by Mr.
Kanji. We enjoyed seeing the Sakurajima volcanoes from the car.
We arrived at the Sakurajima hotel late in the afternoon. Dr. Struhsaker
said that his back and shoulders had become stiff from the long hours of
sitting during the conference and traveling, so we decided to take a walk
along the shore before dinner. During the walk, I asked him how I could go
study in Kibale next summer, and he told me about the research going on
there. I realized that I would have to work hard to earn enough money to
be able to study there, and that I would have to refine my interest in the
relationship between plants and chimpanzees even further, to find
specifically what kind of questions would be suitable for me to pursue.
At dinner, we talked about the food in Africa, and Dr. Struhsaker also
praised his wife's cooking at home. We drank a little liquor that was made
of sweet potatoes, and he was surprised at the taste, saying that it
tasted like alcohol from a lamp!
Leaving for Yakushima
We left the hotel for Yakushima early in the morning. After being on the
ferry for 3 hours, we arrived at Yakushima at 12:00pm.
On the ferry, we saw blood-type fortunetelling on TV. According to that, B
had the best luck. Dr. Struhsaker's blood type was B, and he exclaimed,
"B is positive!"
Column 3 "What is Yakushima?"
Yakushima Island is the southern limit of where Japanese macaques can be
found, and a subspecies, Yakushima macaques (Macaca fuscata yakui), is
unique to the island. Monkeys are distributed from the subtropical forest
along the shores to the subalpine forest, close to 2,000m above sea level.
In this area, a variety of field studies have been conducted, such as
ecological and genetic studies on various kinds of species, including
mammals, insects, turtles, and snakes.
Visiting the Forest of Ancient Cedars
We took a taxi from the port at Yakushima and went to Yakusugi Cedar Land.
We saw hydrangeas by the road. Dr. Struhsaker commented that his wife
We arrived at Yakusugi Cedar Land and took a walk through the forest,
where we found a lot of endemic plants along the path. Yakusugi Cedar Land
is an old forest of ancient cedars and hemlocks. Some of the cedars in the
forest are over 2000 years old. These ancient trees had innumerable
wrinkles and various aerophytes that looked like real cedar branches, and
the diversity of aerophytes made it look like there was a garden on the
tree. These giant trees made me think of the insignificance of human
beings within the context of the larger picture.
For lunch, we ate sushi by the riverside, where it was cool and fresh. Dr.
Struhsaker wondered why we did not find any fish in this beautiful river.
Afterwards, we walked along the trail and came across a troop of monkeys.
We were excited for the unexpected meeting, which was our first contact
with monkeys in Yakushima. The troop disappeared into the forest.
We went to see the Kigen cedar, the second oldest cedar in the forest
at 3000 years. We were amazed at the diversity of aerophytes.
The taxi driver, Mr. Kamata, had a lot of knowledge about Yakushima's
environment and plants. Dr. Struhsaker said that he was not only a taxi
driver but also a first-class naturalist.
I was glad that the knowledge of plants I had gained in Borneo was useful
in talking about the plants of Yakushima in English.
Observing sea turtles
After leaving Yakusugi Cedar Land, we went to see the big waterfalls. From
the car, we were lucky to see a deer, a snake, and many troops of monkeys
along the road. When we were looking at the waterfalls, we were caught in
a shower. The annual rainfall in Yakushima is 8000~10000 mm.
We arrived at the hotel, "Yakunoko," and met Tessei (the owner
of the hotel), who took an active part in the conservation efforts of
Yakushima forest. We also met Tomoyuki, who was attending school in the
United States and thus spoke English well.
After dinner, we went to observe the nesting loggerhead turtles on Nagata
beach. There, volunteers work to help the nesting turtles by cleaning the
beach and preventing people from walking onto the beach when the turtles
are there. Tomoyuki's father, Mr. Ohmuta, was a leader of this volunteer
group and explained their efforts to us. Dr. Struhsaker was moved by their
activity and efforts.
Bird watching at Yodogo River
In the morning, we went to Yodogo River with Tomoyuki for some bird
watching. Yodogo River was beautiful and cool, and the sound of the river
was relaxing. We walked on the trail along the river. But we could not
find any birds; I thought that perhaps we would have had better luck
earlier in the morning.
Dr. Struhsaker was hiking briskly along the rocky areas, and Tomoyuki
asked how old he was, amazed at his agility.
Mieko joined us
At noon, we met Mieko, a graduate student researching about how monkeys in
Yakushima catch insects, at Yakushima Cultural Village. She and I had both
participated in researching Yakushima monkeys last year, so we knew each
other. At lunch, Dr. Struhsaker and Mieko talked about her research.
In the afternoon, we went to the west side of Yakushima Island with Mieko,
where there is a good place for observing wild monkeys. We stayed there
for short time, watching the monkeys that came by. Mieko told us about the
conflicts between the local people and the monkeys, who often come by
orchards and fields and eat the fruits and vegetables there. The local
people are trying to prevent damage by installing electric fences, but
this was unsuccessful because of the high cost, partially caused by vines
becoming entangled in the fences. Each year, 400 monkeys are killed by
farmers. While this island is blessed with a large population of monkeys,
we must also recognize the problems that it causes for the farmers here.
I was excited to be given a DVD of red colobus monkeys by Dr. Struhsaker.
Thank you very much!
In the early morning, Mieko came by the hotel and brought us to the west
side of Yakushima.
Early in the morning is the best time for finding monkey troops, since
monkeys start to forage for food soon after getting up. We can follow the
calls they make while eating to find the troops. After eating, however,
they rest silently, making it difficult for us to find them.
We saw a few monkeys from the car and followed them on foot. They were
eating leaves of ako (Ficus superba), yamamomo (Myrica rubra), and hime
yuzuriha (Daphyniphyllum teijsmanii). Dr. Struhsaker videotaped some of
the monkeys while they were eating, and I tried chewing on some of these
leaves. Yamamomo was easy to eat, perhaps good for a salad. On the other
hand, hime yuzuriha was bitter because of its high tannin content, making
me think of chewing tobacco plugs in Borneo.
We followed the monkeys into the forest and found a troop eating mushrooms
on a tree. Neither of us had seen this behaviour before.
When we were observing the monkeys, we heard the cry of a deer. It is a
well-known fact in Yakushima that deer often follow monkey troops, looking
for the fruit that they drop from trees.
Mieko went deeper into the forest in order to find the troops she usually
observed. Dr. Struhsaker and I waited for her until she came back at 10.
At 10, Mieko came back and we had an early lunch in the car. Mieko had
brought us rice balls and sandwiches, which were delicious.
After lunch, we went into the forest again. Mieko led us to the point
where she had found some monkeys. Once we arrived, we looked for the
monkeys by using a detector that reacts to the collar of the α
female, and we were soon able to find the troop. There were many adult and
juvenile monkeys on the opposite side of the river.
Why did the mother monkey neglect her baby?
When we were observing the monkeys, we saw a shocking sight. A baby monkey
was following its mother and screaming for help. However, the mother
completely neglected her baby. It seemed that the infant was unable to
drink the mother's milk. Dr. Struhsaker said that he had never seen
something like this before and was greatly concerned. Mieko also said that
she had never seen such behaviour. After the trip, I received an e-mail
from Mieko that said that the baby had later died. What made the mother
neglect her baby?
After observing monkeys, we were thirsty and rather tired. Therefore,
we went to drink some fruit juice at the Tropical Fruits Garden. The juice
made us feel refreshed once again!
That night, we had originally planned a dinner party with some of the
local people. But Dr. Struhsaker and I were both exhausted and
unfortunately had to cancel our plans. Instead, Tessei cooked a small
dinner for us, and the sukiyaki that he made was very delicious.
After dinner, Dr. Struhsaker suggested that we going turtle watching on
the beach, so we visited Nagata beach again. There were many more visitors
than when we visited before. This made me worried about the turtles, but
Dr. Struhsaker said that it was good to have so many people interested in
the turtles and that it would also help with the volunteering efforts.
Dr. Struhsaker saw the light of some fishing boats on the sea and asked
whether they were using fishing nets. He said that more than 90% of turtle
fatalities are cause by fishing nets. I asked the volunteer guides, and
they said that in Yakushima, fishermen mainly use poles and spears and
rarely use nets, especially when turtles are around. Even after I told
this to Dr. Struhsaker, he seemed a little worried.
Dr. Struhsaker does not eat shrimp, since they are bred in breeding farms
that are made by killing mangroves. Shrimps are also caught using fishing
nets, which kill many sea turtles. I thought he was a true
conservationist, considering all aspects of the environment.
At the beach
In the morning, Dr. Struhsaker and I walked along the beach. We found
beautiful seashells and many sea turtle tracks on the sand. Dr. Struhsaker
and I both picked up some seashells for his son.
Visiting the Recycling Center
We visited the Recycling Center directed by Tessei, the owner of our
hotel, where we learned about their work to protect the environment. Extra
wood is collected from all sawmills, and garbage from half of the island
comes to the Center, where both of these are composted. This compost is
then used by farmers and gardeners all over Yakushima, and the Center
remains popular because of the constant demand for fertilizer.
Goodbye to Dr. Struhsaker
After we visited the Recycling Center, we went to the airport and said
goodbye to Mieko. During our flight from Yakushima to Osaka, we were able
to see Koshima and the beautiful Sakurajima volcanoes from our airplane
When we arrived at Osaka, we drank some beer and celebrated the completion
of our trip. We left for Kansai International Airport Hotel by bus, and on
the way, Dr. Struhsaker gave me some advice about my future, what I should
do in order to accomplish my goals. He said that he would try to introduce
me to the people at Kibale and tell them that I was interested in
researching there. We said goodbye at his hotel.
During this trip, I was exposed to many kinds of interactions between
humans and monkeys: researchers and monkeys, fishermen and monkeys,
farmers and monkeys. Often, foods such as potatoes, fish, fishing bait,
and fruit influence this relationship. I also learned about the various
types of food monkeys eat in the wild, such as ficus and myrica leaves. It
was interesting to know what kinds of plants they preferred and what
chemicals these leaves contain.
I came to understand that while feeding makes observation easy, it also
makes the behaviours of the monkeys unnatural. Without the help of food,
we could never have achieved the deep level of understanding of their
behaviours and society that we currently do. However, we sometimes mistake
our current understanding as being complete. For example, until recently,
we believed that each troop had a "boss" monkey. Therefore, we
have to study their behaviour in the wild as well; both methods are
On this trip, I was most surprised by the mother that completely neglected
her baby. I also know of a mother that carried around the body of her dead
baby for 2 months after its death. I had always thought that protection
for offspring was a natural instinct. What causes the difference between
the caring mother and the negligent one?
Dr. Struhsaker was a first-class naturalist who gave me important advice
about my future. He is a true pantheist, admiring everything in the wild,
and his concerns about environmental problems and conservations were
contagious, motivating me to consider them as well. Thank you so much for
being patient with my tour-guiding skills.
Dr. Matsuzawa gave me this precious chance. Thank you very much.
To Dr. Yamagiwa, Dr. Maruhashi, and Dr. Michael Huffman, Mr. Kanji, Mr.
Suzumura, Mr. Tessei, and Ms. Mieko Kiyono, and to the people of Tagiri-So
and Yakunoko, I express my gratitude. Thank you very much.