Sika Deer in Nara Park: Unique Human-Wildlife Relations

Abstract

Sika deer have had a long history of cultural importance in Nara Park, beginning in the eighth century with a legend that a god rode into the park on the back of a white deer. With protection for religious reasons, the population built up and became tame because of its frequent interaction with people visiting the religious shrines at the park. The interface of sika and humans at such close proximity over the years inevitably led to harmony or conflict depending on the goals and motivations of people. Nara Park in its modern form was established in 1880, and these conflicting values of sika deer in the park have continued into modern times. However, the long history of known numbers, and approachable tame deer, have yielded an unusually long and detailed record of population dynamics, ecology, and behavior. It has also led to high populations of deer with consequent impacts on their habitat. In this chapter we review and summarize this unique record of cultural and biological interrelations between sika deer and humans.

Full text

Chapter 25
Sika Deer in Nara Park:
Unique Human-Wildlife Relations
Harumi Torii and Shirow Tatsuzawa
Abstract Sika deer have had a long history of cultural importance in Nara Park,
beginning in the eighth century with a legend that a god rode into the park on the
back of a white deer. With protection for religious reasons, the population built up
and became tame because of its frequent interaction with people visiting the reli-
gious shrines at the park. The interface of sika and humans at such close proximity
over the years inevitably led to harmony or conflict depending on the goals and
motivations of people. Nara Park in its modern form was established in 1880, and
these conflicting values of sika deer in the park have continued into modern times.
However, the long history of known numbers, and approachable tame deer, have
yielded an unusually long and detailed record of population dynamics, ecology, and
behavior. It has also led to high populations of deer with consequent impacts on
their habitat. In this chapter we review and summarize this unique record of cultural
and biological interrelations between sika deer and humans.
Introduction
Nara Park is located adjacent to the urban area of Nara city, which is one of the most
beautiful old cities in Japan and contains many historical places and much cultural herit-
age that attract two million tourists from abroad every year. Nara Park covers approxi-
mately 6.6 km2, including flat areas where tourists visit temples and other attractions
and the adjacent mountains (Fig. 25.1), such as Mt. Kasuga that, thanks to their long
history of protection, contain unique ecosystems. Sika deer have lived in Nara Park
through the ages and have shaped the specific ecosystem and scenery of the park.
Sika deer are symbols of Nara Park. They are widely accepted as essential to the
park, and in 1957, they were designated a national natural treasure, the “Deer of Nara.”
The deer, as main subjects in many historical artworks, have long been tamed to human
presence, but basically they are free-ranging. They continue to be a major source of
attraction to tourists, and this has not motivated people to control the population of deer.
In Japan where forests are very dense, sika deer are difficult to observe for more than a
fleeting moment. This has made the tame deer at Nara good subjects for long-term
population censuses and behavioral studies by direct observation at close range.
D. R. McCullough et al. (eds.), Sika Deer: Biology and Management of Native 347
and Introduced Populations,
DOI: 10.1007/978-4-431-09429-6_25, © Springer 2009
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348 H. Torii, S. Tatsuzawa
On the other hand, the sika deer at Nara Park have been in close relationship
with the local people both in a positive and negative way. Today the population of
deer in Nara Park has increased to around 1,200, and they have caused increases in
traffic accidents and damage to crops. Discussions about the management of these
animals are needed to face the problems of not only damage to agriculture and for-
estry, but also the serious effects on the habitat of the area. In this chapter, we will
review the history and current circumstances of Nara sika deer.
History of Deer and People in Nara Park
Ancient Times to the Edo Era
The following history is taken from Fujita (1997). The first record of the idea of
“Shin-Roku” (deer as messengers of God) is found in the year 1006. After that,
several old documents from the eleventh and twelth centuries show deer in Kasuga
area were not hunted, for the place was a holy land, and some of them tell a legend
which said a god from the Kashima shrine entered Mt. Kasuga riding on a white
deer in the year 768 (Fig. 25.2).
Fig. 25.1 Map of Nara Park. Tourists encounter several hundred deer in the daytime in the area
surrounded by the black line. Adapted from the CD map, 1/25,000 [Nara] published by the
Geographical Survey Institute.
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25 Sika Deer in Nara Park: Unique Human-Wildlife Relations 349
Fig. 25.2 Painting showing the legend that a
god came to Mt. Kasuga riding a white deer
from Kashima Shrine (provided by Nara
National Museum).
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350 H. Torii, S. Tatsuzawa
After the thirteenth century, Nara deer were protected by Kofuku-ji Temple,
which controlled the whole Yamato district, including Nara, from any hunting or
capturing. At this time killing of deer was consider the same as killing of priests.
This helped the population of deer to increase and, at the same time, forced people
to contain their frustrations about damage to their crops and other deer-human
conflicts.
In 1602, Tokugawa Ieyasu, the first shogun of the Edo Era, clearly designated
Nara deer as “Shin-Roku” and prescribed punishments for persons killing them.
This ordinance assured deer of protection with the government’s approval. However,
in 1671, antler-cutting (ceremonial sawing off the antlers of males) was started to
prevent accidents with people and destruction of night lanterns by antler trashing.
This indicates that times were starting to change, and governments could no longer
ignore public outcries. Because one or two hundred male deer were antler-cut annually
for 46 years from 1672, the deer populations of those times can be estimated roughly
from expected sex ratios to range from a few hundred to one thousand.
From the above history it is apparent that deer were deified from ancient to
modern times and were used politically by authorities. As Fujita (1997) notes, this
unique relationship between deer and people did not derive from beliefs of local
people, nor adoration of deer in the real sense of the term; nevertheless, it is clear
that protection for religious reasons was the main cause of the increase in the popu-
lation of deer, with resultant damage to crops and other human-deer conflicts.
From the Meiji Era until before World War II
Nara Park was established in 1880, and this spelled the end of the “Shin-Roku”
myth. With the restoration period (the Meiji Era starting from 1868), the general
trend of thought in Japan was modernization, and little further credence was given
to traditional religion which was considered only superstition. Deer were regarded
as just one more species of wild animal, and not sacred. Adding to this, guns
became available in large quantities to the public, so wild animals faced hard times.
Nara deer were not an exception and they lost their special religious status, denoted
by a record that government officials ate deer meat in a stew.
In 1873, the local government confined 700 deer in an enclosure to prevent
damage to crops. However, in only a few years the population in the enclosure
decreased to 38 due to overcrowding. However, some deer remained free in the
fields, and the Kasuga area, including Kasuga Shrine and Mt. Kasuga, was desig-
nated a conservation area. This made it difficult to distinguish between wild deer
and protected “Shin-Roku.” Deer crossed into areas of human habitation and
caused agricultural damage.
To prevent this, the Kasuga Shin-Roku Preservation Society (“Kasuga Shin-Roku
Hogo Kai;” later the name was changed to the Foundation for the Protection of
Deer in Nara Park) was organized by 1897. The local government paid a subsidy to
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25 Sika Deer in Nara Park: Unique Human-Wildlife Relations 351
the society from 1902 to 1918. Private lands were surrounded by deer-proof fences
and ditches, and the society paid compensation for crop damages. Moreover, the
society started to herd and protect deer at night to decrease crop damage and pre-
vent poaching and wild dog attacks. However, damage kept on increasing, resulting
in the ongoing capture of deer in crop fields, to be held permanently in captivity.
This method is still used today.
After World War II until the Present
As World War II intensified, conservation became more difficult, and it was
neglected as labor and funds were redirected to the war effort. Consequently, the
deer population decreased rapidly. By the end of the war in 1945 the population was
as low as 79 individuals.
In the years following the war the population recovered under rigorously
enforced protection. In 1957 “Deer of Nara” were recognized as a national natu-
ral treasure as they “blend in with the appealing scenery of the park and provide
the most beautiful natural scenery of Japan with wildlife.” In addition, the con-
servation area was expanded to the whole of Nara city. The law for protection of
cultural properties designates an administrator, but the sika deer was left without
a designated administrator for many years. In the meantime, the Foundation for
the Protection of Deer in Nara Park (the Nara Deer Fund) had been working for
their conservation.
Nara city government had been making partial payment for the crop damage, but
in 1979, the farmers brought a lawsuit to get complete compensation for damage.
This action resulted in an arbitrated settlement which designated a smaller protected
area and allowed the control of deer outside the protected area. Nevertheless, in
30 years after the arbitration nothing changed in practice; local authorities contin-
ued only the capture of deer in crop fields. No population control was done, and the
level of crop damage did not decrease. This is probably because people have the
deep-seated idea that deer are a protected species, and the local authorities fear
damaging the tourist’s image of deer at Nara, which might impact negatively on
visitation.
Major management actions include keeping pregnant females in captivity to
prevent accidents at the time of birth and cutting males’ antlers at the end of sum-
mer. Males with larger antlers are chosen and isolated until the beginning of
October to cut their antlers at an event for tourists. Deer captured in crop fields are
kept in permanent captivity. Moreover, injured or sick individuals are confined until
they are recovered and released, or die.
Studies on behavior and ecology of Nara deer began quite early in the history
of Japanese mammalogy. The most impressive was the study of social behavior
done by Kawamura (1950, 1957) right after World War II. Kawamura used an
individual-identification method and did behavioral experiments in Nara Park
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352 H. Torii, S. Tatsuzawa
from 1948 to 1950. He demonstrated the basic social structure and habitat use
patterns of the deer. In addition, annual population censuses of deer numbers were
conducted by the Nara Deer Fund. This is one of the rare instances in which the
same census method was applied over a long time period, thus yielding a long
record of numbers.
Further ecological research of the deer was done in Nara Park in the 1970s, such
as socio-biological studies (e.g., Miura 1976; Takaragawa and Kawamichi 1977),
the study of age determination methods and population structure of deer (Ohtaishi
1978), and analysis of food habits and effect of deer browsing on the vegetation
(Takatsuki 1980). These pioneering research projects established the dynamics of
the deer population and the relationship between deer and vegetation, not only
in the flat areas of Nara Park, but also the adjacent mountainous area including
Mt. Kasuga (Fig. 25.1).
Behavior of Nara Deer and Their Social Structure
Grouping, Social Rank, and Leaders
According to Kawamura (1950, 1957) at the time he began research in 1948, about
140 deer were using the flat grass land (32 males above the age of one year and 110
females and fawns), and females and fawns formed 12 groups based on blood rela-
tionships. Each of these groups had its own well-organized home range. A few
groups gathered at daytime and fed together in the fields of Tobihino and
Asajigahara, but at night each group rested in its own resting sites (Kawamura
1950). Some individuals were seen to move away from their home range in mating
seasons; compared to the loose-bond male groups, however, female groups were
quite stable (Kawamura 1950, 1957).
Kawamura (1957) studied experimentally whether the female groups were struc-
tured under a ranking system and whether there was any individual group leader.
He threw a piece of sweet potato in the middle of two targeted individuals and
observed their agonistic behaviors to determine their rank order. To determine the
leader of the group, he disguised himself as a horse and approached the group to
observe which individuals gave the alarm call (“pya!”) first. As a result, he showed
that: (1) a specific individual always gives alarm calls first, and (2) the same spe-
cific individual usually leads the group when they move. He concluded, therefore,
that female groups have a specific leader.
On the other hand, males seemed to join groups of females readily, and males above
the age one year possessed home ranges that overlapped those of females. Their
interests towards female groups were subtle, and except for mating seasons, they
usually formed groups consisting of only males. However, in the mating season,
males’ home ranges changed and boundaries between mountains and the flat lands
disappeared. The number, location, and configuration of male territories where
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25 Sika Deer in Nara Park: Unique Human-Wildlife Relations 353
mating took place did not change during the five years of Kawamura’s study
although their occupiers switched once in a while.
Territory and Home Range
Following Kawamura’s (1950, 1957) pioneering work, Miura (1983) continued
social structure studies. After two years of direct observation with individual iden-
tification, he pointed out four types of male social structure and noted that the ten-
dency for males to gather with each other was the highest in spring and summer and
the lowest in autumn during the mating season. The 82 known individual males
were divided into territorial or non-territorial individuals. The former were all over
five years old. The home ranges of territorial males were smaller and non-overlap-
ping compared to those areas occupied by non-territorial males. Territories were
divided into two areas: the core area where males showed exclusive behaviors and
the surrounding area (Miura 1984).
Miura (1984) also found that territorial males showed 57.4% of sexual behavior,
and 76.2% of mating behavior. Thus, territorial males had a better chance of mating
than non-territorial males and territoriality contributed to higher mating success.
Moreover, he showed that: (1) the location and configuration of territories were
stable; (2) the dominant individual of the year occupied a given territory; (3) domi-
nance and ranking was positively correlated with the size of antlers; and (4) there
was a positive correlation between the length of antlers and body weight.
Miura (1984) also analyzed the male vocal repertory and categorized vocaliza-
tions into six types. Minami and Kawamichi (1992) subsequently reported 13
vocalization in five groups of Japanese sika deer. Minami (1993) noted the similar-
ity of deer calls with the sounds of traditional Japanese deer calling instruments,
which mimic the natural calls.
Other Social Behaviors
Because close direct observations are possible, other notable behavioral studies
have been done in Nara Park that would have been difficult elsewhere. Inoue and
Kawamichi (1976) studied the development of social behavior by observing fawns
from birth to five months of age. They noted that (1) suckling lasts six months; (2)
fawns join the female group during the suckling period; and (3) contacts with
human during this time affect later habituation to humans. Other relationships
between individuals have been studied, such as (1) resting time of females becomes
relatively shorter during mating seasons due to many disturbances by males (Yabu
and Wada 1996); (2) allogrooming behavior is more likely to be initiated by
females (Matsuno and Urabe 1999); and (3) the frequency of behavior between
both sexes is not affected by their mating relationships or the rank of the male
(Yamada and Urabe 1998; Matsuno and Urabe 1999).
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354 H. Torii, S. Tatsuzawa
Population Trend Dynamics of Nara Deer
Population Trends
In the flat plain of Nara Park, a population census is taken every summer by the Nara
Deer Fund (Fig. 25.3). These counts, combined with historic estimates, indicate that
a population recorded at above 700 individuals in Meiji Era dropped to 79 at the end
of World War II, and with conservation efforts recovered up to 1,000 by 1965. After
some fluctuations, the population became stable around 1,200 (Nara Deer Fund
2005) (Fig. 25.3). This gives an incredibly high density calculated at 1,000 individu-
als per km2 in the 120 ha plain. Tatsuzawa et al. (2002), who studied daily activity
and its seasonal variation for 10 years (1990 through 1999), showed that the popula-
tion was steady at high density: mean = 961.1 per km2 (SD = 60.0) in summer and
907.7 (SD = 62.8) in autumn. In addition, the summer population density showed a
strong negative correlation with the rate of population increase in the following year.
In other words, a negative density-dependent relationship was confirmed. Yearly
fluctuation of the number of fawns (birthrate, early mortality, or dispersal rate)
seemed to contribute most to the density effect (Tatsuzawa et al. 2002).
Nara Park deer mainly feed on short-grass vegetation (mainly Zoysia japonica).
Calculated from the productivity and digestibility of Z. japonica, the deer capacity
of Nara Park grassland is 12–14 per ha in the growing season of this plant (April to
September). Thus, a population of 1,100–1,200 per km2 (Miyazaki 1980; Miyazaki
et al. 1984) suggests that the Nara deer are at or near their maximum number based
on food resources. Food habits will be covered in greater detail in a later section.
From at least the end of the 1940s (Kawamura 1950) to the end of the 1980s
(Tatsuzawa and Fujita 2001) hundreds of Nara deer continued daily dynamic
movements back and forth across the flat from the base of Mt. Kasuga to around
Koufuku-ji Temple (Fig. 25.1). However, developments in the flat (for instance,
Fig. 25.3 Population trend of Nara deer based on yearly censuses by the Nara Deer Fund.
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25 Sika Deer in Nara Park: Unique Human-Wildlife Relations 355
installation of railings and fences, shrinkage of the woodland area) terminated this
movement. Although about 20–50% of the population traversed the flat even in the
1990s, the percentage has decreased every year (Tatsuzawa et al. 2002). Infrastructure
of the park has become a physical barrier and caused cautious females to stay in the
woodland, speeding the increase of the population in the woodland area.
Early Mortality and Life Expectancy
In Nara Park pregnant females are captured from the end of March to April and kept
in captivity until the middle of July after they deliver fawns. The estimated mortal-
ity of young animals during this period can be derived from the records kept by the
Nara Deer Fund. The average mortality of young of the year over a five-year period
was 40.9% (±3.9%), and for one-year-olds 22.4% (±4.1%). Because the bodies of
dead fawns disappear soon after death it is possible that fawn mortality was higher
than estimated. An analysis by Ohtaishi (1976) of individuals buried after death led
to an estimate of 50% fawn mortality.
We constructed a the life table of Nara Deer by age determination of individuals
found dead (unpublished), and it showed that the mean life expectancy at birth was
4.0 years for females and 3.8 years for males. Deer that lived to one year of age had
a longer life expectancy for both sexes, again reflecting a high mortality in early life.
Both mean life expectancy and the greatest length of life were higher in females; thus,
females had greater longevity than males.
Age-Specific Pregnancy Rate
We calculated the pregnancy rate of 235 females that died between February and May
(unpublished). There was only one pregnant individual out of 22 one-year-olds, giv-
ing a pregnancy rate of 4.2%. The pregnancy rates of two- and three-year-olds were
52.6% and 86.7% respectively. The highest rate was achieved by three-year-olds. The
average rate for females over the age of three was 73.7%, and rates decreased rapidly
after age 12; however, one pregnancy was noted even in a 23-year-old female.
However, pregnancy rates were calculated from the recovered bodies of individ-
uals that died from accidents occurring during capture of pregnant individuals in
spring, so they may be overestimated. Because pregnant females are targeted by
this capture, the actual pregnancy rate across all females is probably around 50%.
From the censuses of the Nara Deer Fund over the last several decades there was
a total of approximately 1,200 individuals; 300 were males, 700 were females, and
200 were fawns (Fig. 25.3). As stated earlier, the survival rate at the end of age one
is about 40% and 20% at age two. This indicates that the population of females of
age one and two is 140 in total, and, therefore, there are about 560 fawn-bearing
females. Every year, around 200 females in captivity and 50 females in the wild are
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356 H. Torii, S. Tatsuzawa
estimated to give birth (Nara Deer Fund, personal communication). If these esti-
mates are correct, it means that more than 250 individual females give birth every
year; thus almost half of females above the age of three years give birth, which is
not so different from the 50% pregnancy rate estimated above for the total female
population (both in captivity and free-roaming).
Feeding Habits and Nutritional Status
Food Habits
In the 1970s, Takatsuki and Asahi (1977) examined deer droppings at Nara Park
using microhistological techniques and found that deer feed mainly on monocotyledon
plants, such as graminoids, indicating they were grazers. Zoysia japonica and
Miscanthus sinensis (silver grass) covered the whole area of Nara Park at that time.
After 30 years of extremely high population density, the vegetation changed. Miscanthus
sinensis decreased in Mt. Wakakusa, whereas tourists and the local people who
artificially fed deer increased, therefore changing the feeding environment of deer.
Visitors and tourists feed deer routinely at Nara Park (Fig. 25.4). Still, from the
rumen content analysis by Torii et al. (2000) deer were still using the same food
plant categories as reported by Takatsuki and Asahi (1977).
Fig. 25.4 Tourists at Nara Park feeding deer rice crackers.
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25 Sika Deer in Nara Park: Unique Human-Wildlife Relations 357
From examining the rumen contents of dead deer we also found that Nara deer
feed mainly on graminoids (mostly Z. japonica) and broad-leaved trees. They also
fed on herbaceous plants, coniferous leaves, seeds, and nuts. We also found Sasa
spp. bamboo leaves in the rumen contents, although there is little Sasa left around
Nara Park due to the continuous feeding by deer on these highly preferred species.
Bamboo leaves in the rumen probably come from deer eating fresh bamboo fronds
set out as decorations during religious events at temples or shrines.
Because Nara Park deer feed mainly on short-grass vegetation they face food
shortage in winter when the short-grass withers. Thus, for example, the percent of
crude protein in rumen contents increased in spring, stabilized in summer and
autumn, and then decreased in winter. In winter deer mainly feed on vegetables
provided by humans. Nara deer are not completely dependant on food provided by
humans; but such foods partially compensate for food shortages which are espe-
cially severe in winter. Clearly, artificial feeding, and also feeding on farmers’ crop
fields, help support the continuous high density of deer at Nara.
Nutritional Status
We collected the femur bones from dead deer found around Nara Park and evaluated
the color and material of the bone marrow in accordance with the categories of
Takatsuki (2001). In this analysis, we were able to separate the marrow into five
types, including a yellow gelatinous texture that was not observed by Takatsuki
(2001). The content of fat in this yellow gelatinous texture averaged 6.3% (SD = 2.9);
this was similar to deer that starve to death in spring in northeastern Japan and
Hokkaido. This indicates that Nara deer are in extremely in poor condition, and many
of them would not be able to survive in a truly wild situation. Certainly survival of
less well-nourished individuals is largely due to the active involvement of the Nara
Deer Fund and supplemental feeding by visitors. Also, the more benign conditions
for Nara deer include being spared stresses such as predation and migrations.
These findings all indicate that Nara deer are a high density, low performance
population. Reproduction usually starts at the age three in Nara Park, which is one
year later than in most other areas. The age-specific pregnancy rate is lower and
individuals are in poorer nutritional condition than in comparable populations. Poor
physical condition, which is specific to the end of winter in deer in Hokkaido and
western Japan, is seen all year round in Nara Park deer.
Alteration of Park Vegetation by the High-Density Population
It has been 1,300 years since deer protection started in Nara and the deer population
has been very dense for at least a few hundred years. This has had a great effect on
the vegetation of Nara Park and surrounding areas. The most obvious feature is a
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358 H. Torii, S. Tatsuzawa
pronounced browse line. There are very few branches of favorite tree species below
the height of 2 m, which is the upper limit of deer reach. Podocarpus nagi and
Pieris japonica (andromeda), plant species that deer do not eat, cover the land
around the Kasuga grand shrine. The well-known short grass vegetation covers the
ground of many areas and, of course, is maintained as a lawn under the high grazing
pressure of deer.
Takatsuki (1980) classified the vegetation of Nara Park into three types. The first
type is vegetation unpalatable to deer. It occurs on the flat, but unpalatable vegeta-
tion grows abundantly on the uplands of Mt. Kasuga and Mt. Wakakusa (Fig. 25.1)
as well. Unpalatable vegetation is typified by Podocarpus nagi and Sapium seb-
iferum (Chinese tallow), both alien invasive species. Podocarpus nagi was first
brought into the Kasuga grand shrine in the ninth century as a sacred tree. Notably,
there now are pure P. nagi forests in Tobihino. Sapium sebiferum was planted in the
park because deer do not feed on it. S. sebiferum grows also in Tobihino and Mt.
Wakakusa. Pieris japonica grows as an understory plant of P. nagi and S. sebiferum
stands. In addition a fern, Hypolepis punctata, that deer dislike, grows on both sides
of the approach to Kasuga grand shrine.
The second type is short-grass vegetation established by deer browsing pressure.
The Z. japonica grass community is a typical short-grass vegetation type. Many
deer forage day and night on these grass communities, virtual lawns, and many
tourists gather at such landscapes, which are the outstanding scenic areas of the
park. Zoysia japonica is the main food item of deer as noted earlier. Poa annua
(bluegrass) and Hydrocotyle maritima (a wetland plant) can also be found in the
area, and occasionally Trifolium repens (white clover), Sisyrinchium angustifolium
(blue-eyed grass), and other species. Of concern is that in some areas Sapium seb-
iferum has started to invade. It is possible that the Z. japonica community vegeta-
tion will be lost in the future if this invasion continues.
The third type is Miscanthus sinensis growing where deer browsing pressure is
low in the upland areas. This community is also shrinking rapidly. Traditionally,
burning was carried out to favor this community, but brackens establish more rap-
idly after fire, so this practice may have to be discontinued. Currently, fences are
being erected to preserve the remaining areas of M. sinensis on Mt. Wakakusa.
Miyazaki (1980) estimated the appropriate population in the flat of Nara Park to
be 1,100–1,200 individuals based on the short-grass production. This was based on
the height of the short-grass, which at the time was higher than 4 cm. However,
present production is lower because the height is less than 4 cm. This estimation is
for the population of spring to autumn, so the forage biomass must be much lower
in winter.
Moreover, just after World War II the height of the plants in the flat was high
enough to hide a rugby ball (Kawamura 1957). This suggests that the vegetation
and biodiversity of the grassland, even in the flat area, was probably much richer
then, and it has changed for the worse over time. From these results it is clear that
long-term deer browsing has established a unique vegetation resistance to deer
feeding. It has evolved to be unpalatable, so it persists despite heavy foraging
pressure.
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25 Sika Deer in Nara Park: Unique Human-Wildlife Relations 359
Conservation of Mt. Kasuga Primeval Forest and Nara Deer
The Effect of Deer Browsing on the Vegetation of Mt. Kasuga
The Mt. Kasuga primeval forest lies next to the flat area in Nara Park. It is one of
the few broad-leaved evergreen forests remaining in Kinki district, which is the
northern limit of such forests. Hunting and logging in the area have been prohibited
since the year 841 and the forest has been left almost untouched by humans. This
virgin forest was designated as a “National Natural Treasure” and as a special
“National Natural Treasure” in 1924 and 1956 respectively. In 1998, it was also
recognized by UNESCO as a World Cultural Heritage Site along with the Kasuga
grand shrine. However, it is known that the forest is affected by deer foraging.
Maesako (2001a) randomly selected 22 study sites, and of 2,351 trees of 56 dif-
ferent species identified, bark stripping marks were found on 251 trees (10.7%) of
36 species (64.3%). In 1986, the Environmental Agency established 20 permanent
meter-square quadrats in the same area within Mt. Kasuga forest. According to the
results, in 1986 there were six species of canopy trees (Castanopsis cuspidata
(chinquapin), Neolitsea aciculata (Lauraceae), etc.), 15 species of shrubby plants
(C. cuspidata, Quercus sessifolia, Eurya japonica, etc.), and 12 species of forest
floor vegetation (C. cuspidata, Pieris japonica, etc.).
Plant composition was measured again in 2003 (Maesako 2004). The species
composition of the canopy trees had not changed, while on the forest floor, six
species, such as Quercus salicina, Q. glauca (blue oak) and holly, disappeared and
five species, including Symplocos prunifolia and Camellia japonica appeared. Four
new species of shrubs, such as C. japonica and Q. sessifolia, appeared in the
intermediate, sub-canopy layer. In total, the number of species observed in the area
decreased from 18 species in 1986 to 15 species in 2003. These findings may show
that the effects of deer browsing began only rather recently.
Four species of trees, C. cuspidata, Q. sessifolia, Symplocos prunifolia, and
Neolitsea ariculata, were the only species larger than 10 cm dbh, and we compared
their diameter distributions. Larger C. cuspidata grew steadily, but below 20 cm dbh
the number of trees decreased. However, S. prunifolia, a species that deer do not
bark, increased. Regeneration is difficult for broad-leaved evergreen forest species,
and this threatens the perpetuation of the pristine natural forest. The next generation
of the forest will likely be largely unpalatable species.
This process is apparent in seedlings also. Shimoda et al. (1994) followed the
survival rate of seedlings and amount of deer browsing inside and outside a deer-
exclusive fence in a new forest gap. The effects of deer browsing on the survival
rates differed among plant species. The foraging rates were high and the survival
rates were low for Mallotus japonicus (Euphorbiaceae), Aralia elata (angelica
tree), and Zanthoxylum ailanthoides (prickly ash). Q. salicina had a marked low
foraging rate and low survival rate while Neolitsea aciculata and Sapium sebiferum
were low in foraging rate and high in survival rate. Moreover, Maesako (2002)
counted 42 seedlings of new species not part of the pristine forest in the area.
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360 H. Torii, S. Tatsuzawa
They are likely to form the canopy of the future. These results show that not only
the natural death of seedlings through competition and crowding, but also deer
browsing on seedlings has a great effect on the regeneration of forests.
The effects of deer are most pronounced in tree-fall gaps. New gaps caused by
typhoons or some other main factor are produced on average once in 6.6 years on
Mt. Kasuga. It takes about 70 years for the gaps to close in and 110 years for the
forest floor vegetation to grow into canopy. The average turnover rate to the next
new gap is estimated to be 180 years (Naka 1994). All these findings indicate that
in any forest gap created on Mt. Kasuga, the next generation of the forest will
regenerate with only species unpalatable for deer.
Yamakura et al. (2001) predicted the future of Mt. Kasuga using the survival rate
and seedling production of Zanthoxylum ailanthoides. According to their results,
the Z. ailanthoides in the area will disappear within 185 years, and most of the
seedling death is due to deer browsing. Seeds buried in the soil will run out before
existing individuals disappear. Furthermore, it is possible that species that do not
produce buried seeds disappear earlier due to the effects of deer browsing. Nanami
et al. (2002) predicted that in 250 years the forests will be formed by only Neolitsea
aciculata, Podocarpus nagi, and Sapium sebiferum with a shrub understory of
N. aciculata. However, recently deer began to forage on Maesa japonica, Urtica
thunbergiana (nettle), and N. aciculata, all of which were thought to be unpalatable
(Maesako 2001b). Deer are known to feed on other species when more favored
plants are used up, so there is fear that the whole forest might disappear.
Deer Density in the Forest of Mt. Kasuga
To protect the vegetation and biodiversity, we must first determine the population
density of deer. In 2005, using a block count method, an estimate of deer density
on Mt. Kasuga was 15.9 and 22.8 per km2 in March and November respectively.
The density in autumn is not so different from that of Odaigahara in Nara where
forest degradation through deer browsing is an issue. Other high density records for
sika deer in Japan are 30–50 deer per km2 on Nakanoshima Island in Lake Toya,
Hokkaido (Kaji 1986), 80 on Nozaki Island, Nagasaki Prefecture (Doi et al. 1985),
and 35 in Nikko, Tochigi Prefecture (Koganezawa and Satake 1996). These areas
have in common a marked alteration and impoverishment of vegetation. It is clear
that further deer population growth must be prevented to protect the precious for-
ests on Mt. Kasuga.
Management of the Nara Deer Population
The present deer management at Nara Park creates many problems. Feeding by
local people and tourists is the most important factor for deer winter survival.
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25 Sika Deer in Nara Park: Unique Human-Wildlife Relations 361
Feeding makes up for the natural food shortage and, at the same time, encourages
deer to remain in the flat areas waiting for the tourists to buy them deer crackers.
This prevents dispersion of the deer to the surrounding areas such as Mt. Kasuga.
Capturing pregnant females and keeping them in an enclosure is probably the
main factor lowering the mortality of newborn fawns, thus weakening an important
regulatory mechanism in wild populations. Group feeding and breeding in captivity
may be causing the attenuation of mother-fawn relationships. After captive females
are freed, they often suckle a few, sometimes even four or five fawns, behavior not
observed elsewhere. Antler-cutting of males in rutting periods might disrupt rank
and mate selection and is likely to disturb territory occupation. This may lead to
less-adaptive individuals being more successful in breeding and, thus, interfere
with natural selection. The effect of antler-cutting on fighting behavior is still
unclear. Moving some antler-cut males to surrounding areas (e.g., Ikoma city,
10 km away) is definitely altering natural dispersal and innate behaviors.
Yamakura et al. (2001) suggested putting up a fence to control deer browsing
and conserve vegetation in the Mt. Kasuga primeval forest. However, Tatsuzawa
and Fujita (2001) pointed out that fencing would lead to more human-deer conflicts
in the flat area and more detrimental effect on the vegetation in Mt. Kasuga area
outside of the primeval forest. What is needed is simultaneous management of the
deer and vegetation of the total park. To recover the biodiversity of the park a sci-
entific and adaptive management plan to control deer is needed.
People of Nara have lived with deer for more than 1,000 years. Although the deer
cause inconvenience in daily life as well as serious damage, people still feel it is natu-
ral that deer live within the same area. It is valuable for both deer and people that Nara
Park be used as a biological study field and environmental education facility, a place
where we can learn to solve people-deer problems to the benefit of both.
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