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Why Do Sika Deer Head for the Alpine Zone in Japan?
Shigeyuki IZUMIYAMA
Institute of Mountain Science, Shinshu University
Minamiminowa 8304, Kamiina, Nagano 399-4598, Japan
Email: izumiys@shinshu-u.ac.jp

Abstract
We captured sika deer in the Northern and Southern Japanese Alps and monitored their seasonal movement
patterns in the surrounding area. The daily air temperature in early June reached 5°C and the plants’ growing
period persisted for four months. Alpine sika deer are thought to stay in the alpine zone from the plants’ earlygrowing period. The alpine sika deer observed stayed in the alpine zone to feed on alpine vegetation and Betula
forest understory. The autumn migration of these alpine sika deer started in September. These adult sika deer
repeated the same seasonal migration pattern each year. One sika deer exhibited a long-distance dispersal
movement, with a straight-line distance and actual distance between its natal range and post-dispersal range of
74 km and 131 km, respectively. This evidence of long-distance dispersal of sika deer may explain the
expanding distribution of sika deer in central Honshu.
Key words: alpine meadows, natal dispersal, Northern Japanese Alps, seasonal migration, sika deer

1. Introduction
The attractions of the Southern Japanese Alps include
dense evergreen coniferous forests where the primal
breath can be felt, and “alpine meadows” full of Trollius
japonicas blooming, which have been likened to an
earthly paradise. In recent years sika deer (Cervus nippon)
have penetrated into this alpine zone, and with themgrazing the rare Alpine plant community, there is a danger
that these “alpine meadows,” a symbol of the rich
mountain environment, will disappear (Fig. 1).
In only 10 years after 2000, the brightness of thealpine meadows was lost. From a questionnaire survey

Fig. 1

conducted in 1984, it was found that there were virtuallyno sika deer breeding in the northern part of the Southern
Alps. From the 1990s the sika deer quietly started to use
the evergreen coniferous forests of Veitch’s silver fir andAbies mariesii in the subalpine zone, as well as the Betula
ermani (Erman’s Birch) forests and herbaceous
communities. From the early 2000s sika deer encroachedfurther into the subalpine zone and settled there, and in
about 10 years the brightness of the “alpine meadows”
disappeared.
It was generally thought that the alpine environment,
featuring many steep slopes, was too harsh anenvironment for the sika deer to breed. However the

Alpine meadow of Trollius japonicas in Kusasuberi of Mount Kitadake in 1980 (left) and forest floor with no flowers on
Mt. Senjogatake in 2006 (right).

Global Environmental Research
26/2023 97-102
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hooves of sika deer living on steep slopes have worn
down, and are like the hooves of serow that perch on
cliffs. Why have the sika deer encroached into the alpine
zone where the breeding conditions are consideredsevere? Where do sika deer that appear in the Japanese
Alps during summer come from and how did they getthere? Why do sika deer come to the Japanese Alps.
Research on the movement of sika deer was
conducted by tracking them with GPS collars in thenorthern part of the Southern Japanese Alps. Their
movement in spring from their winter habitat at elevations
below 1,800 m to their summer habitat was observed inJune. This movement occurred over a long period of time,
and was great both in terms of difference in elevation andin distance. This spring movement was observed alongwith the ascent of the foliation front from the upper partsof the subalpine zone to the alpine zone, when the plants
started to grow and green shoots appeared, extending
from the lower elevation towards the higher elevation. In
summertime, from early June until early October, the sika
deer made use of the alpine environment, including alpine
meadows, from the upper subalpine zone to the alpine
zone. During summer, the positions of the individual
tracks and vegetation in the Mt. Senjogatake (3,033 ma.s.l.) region revealed that the places where the sika deergrazed excessively on the rare alpine vegetation
communities consisted of Erman’s Birch forests andherbaceous species of altherbosa (alpine plantcommunities) in the upper subalpine zone. After reaching
the main ridge lines, which are the environment they usedin summer, no large movements were observed. Their useof the surrounding alpine environment continued until
September. The individuals’ fixed positions wereconcentrated in Erman’s Birch forests and altherbosa. The
sika deer kept continuously grazing on the alpine
meadows throughout the summer (Fig. 2).
Only recently have sika deer begun to use in thecirque near the summit. At the bottom of the Ko-senjo
cirque, we could see the mesh-like paths that sika deer
had worn across it in all directions. These gave evidenceof the movement of bucks which had stayed there for twomonths or in the O-senjo cirque. A protective fence
installed on Mt. Senjogatake (3,033 m a.s.l.) and fences
damaged during winter were repaired in early June.
Before the repair the sika deer were already reaching thesurrounding area and using the areas inside and outside
the protective fence. However, after the repair they could
not use the area inside the fence. Comparing photographs
inside and outside the fence after only two weeks reveals
flowers starting to bloom on the inside of the protective
fence, while on the outside none can be seen. This shows
how great the effect of the protective fence is. It also
shows how severe the browsing pressure of the sika deeris (Fig. 3).
It is thought that the movement to their summer
habitat is motivated by a need to move to areas with morefavorable grazing conditions. The expanding distributionof the sika deer is the result of movement from regions
where the breeding density is high and the grazing
conditions have become poor to regions where thebreeding density is low and the browsing pressure is less.
It is thought that as a result of repeated movements
constantly seeking locations with good grazing conditions,favorable for birthing and raising young in the case of thedoes and for development of physical size in the case of
the bucks, they have encroached into the upper parts ofthe subalpine zone. This is thought to have produced thepressure for expansion of distribution that has caused thedeer to emerge from the foot of the mountains of theSouthern Japanese Alps, where the breeding density of thesika deer is now high, and ascend towards the alpine zone
(Fig. 4).
Sika deer are now heading towards the Northern
Japanese Alps. Ahead lies Mt. Shiroumadake (2,932 ma.s.l.) and other places with plentiful flowers of richdiversity. The sika deer have come through the dangers of
extinction since the Stone Age, barely surviving. They are
tough creatures that have survived disturbances fromhumans nearby. In the future we must continue to livewith these sturdy neighbors. We must utilize experiencefrom the past in the Southern Japanese Alps so that the
problem will not be repeated in the future.

Fig. 2 Sika deer equipped with a GPS collar (left) and a hoof worn down (right).

Why do sika deer head for the alpine zone in Japan?

Fig. 3

Movement of sika deer in the Southern Japanese Alps.

Fig. 4Inside and outside the fence.

2. Study Area and Methods
To study the seasonal migration and natal dispersal of
the sika deer in the Northern Japanese Alps, we captured
deer in the southern part of the Northern Japanese Alpsand monitored their seasonal movements in thesurrounding area. The elevation there ranges from 0 to
3,190 m, exhibiting the greatest altitudinal gradient in
Honshu. This area has many peaks with altitudes of≥3,000 m a.s.l., including Mt. Hotaka (3,190 m a.s.l.; thethird tallest mountain in Japan). Contrasting with therolling terrain of the ridgelines and valley floor, most of
the area is characterized by a complex terrain with steep
slopes and deep valleys.
The vegetation changes distinctively with elevation.
The ridgelines >2,700 m a.s.l. mark the forest limit, where
Pinus pumila (Japanese stone pine) and alpine meadow(including snowbed grasslands, windblown meadows andwindblown heath) dominate. Betula (Betula ermanii)
forests are distributed mainly in the subalpine to alpine
zones (2,000–2,700 m a.s.l.). Tall grasslands are also
distributed in this area. Natural evergreen coniferous
forests (mainly composed of Tsuga diversifolia, Abies
veitchii, and A. mariesii) are found widely in thesubalpine and alpine zones (1,800–2,700 m a.s.l.).
Deciduous broad-leaved forests (mainly composed ofbeech and Japanese oak) and Japanese larch plantations

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are distributed mostly in the upper montane zone
(1,000–1,800 m a.s.l.). In the lower montane zone(<1,000 m a.s.l.), evergreen coniferous plantations,P. densiflora (Japanese red pine) forests, and deciduous
broad-leaved forests are distributed in patches (Ministryof the Environment, 1997).
The climate is characterized by high precipitation insummer and relatively low precipitation in winter. In thecity of Omachi (726 m a.s.l.), at the foot of the mountains,the mean annual temperature is 9.6◦C, and the mean
temperatures in the warmest and the coldest months are
22.2◦C (July) and –2.9◦C (January). On Mt. Nishidake(2,680 m a.s.l.), along a mountain ridge, the mean annual
temperature is –0.2◦C, and the mean temperatures in thewarmest and coldest months are 13.3◦C (July) and–13.3◦C (January), respectively. In the city of Omachi(726 m a.s.l.), at the foot of the mountains, the meanannual precipitation is 1,395 mm and maximum snow
depth is 38–101 cm (Omachi City; Japan Weather
Association, 2011; Nishidake, unpublished data).
The study area was designated as Chubu-Sangaku
National Park by the Ministry of the Environment in 1934.
Most of the sites above 1,500 m a.s.l. are either
designated “special protection zones” or “special zones,”consisting of highly vulnerable vegetation. The
deer-capture site was situated in the eastern foothills of
the Northern Japanese Alps in the Kita-Azumi district ofNagano Prefecture, Japan (Fig. 5).
We captured deer using a dart gun with a ketamine–
xylazine mixture as a tranquilizer. The ages of all of thedeer were determined from tooth replacement and tooth
wear. We received an academic capture permit from
Nagano Prefecture to capture the deer. We captured 72
deer around Omachi City from April to November 2012–2022. We attached GPS collars (VECTRONIC Aerospace
GmbH, Berlin, Germany) that were programmed with
2-hour relocation schedules on the deer.

Fig. 5 The study area.

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3. Results and Discussion
We analyzed the movement patterns of theGPS-collared deer. Almost of all the deer were migratory,
with migration distances of 10 to 25 km. The
non-overlapping winter home ranges of all of the
migratory deer indicate relatively little snow in the study
area. Thus there may be a wide range of areas suitable tothe deer for wintering. The alpine deer demonstrated
remarkable altitudinal differences between their summer
and winter home ranges, ranging from 750 to 1,800 m.
They summered in the alpine zone (2,200–2,900 ma.s.l.) and wintered in the montane to subalpine zones(750–1,700 m). Regardless of the wintering area, thealpine deer’s upward altitudinal movements took place inJune and brought them to their summer home range.
Alpine plants initiate plant growth when air temperatures
are above 5°C (Kudo and Suzuki, 1999; Wipf, 2010). The
daily air temperature reached 5°C in early June and theplants’ growing period persisted for four months. Hence,
the alpine deer are thought to relocate to the alpine zone
from the plants’ early growing period. The alpine deerpreferred vegetation mainly found above 2,500 m a.s.l.
(i.e., alpine pine forests, alpine meadows, tall grasslands,
and Betula forests). Moreover, the alpine deer avoided
evergreen coniferous forests, which exhibited the highest
proportional availability. This finding demonstrated thehigh availability and utilization of palatable plants in
Betula forest understory. Thus, the alpine deer stayed in
the alpine zone to feed on alpine vegetation and Betula
forest understory.
The alpine deer’s autumn migration started from
September. They all initiated their autumn migration
before snowfall in the alpine zone (the first snowfall wasin mid-October, according to notes at one mountainlodge). All of the alpine deer were male and had autumn
home ranges. Considering that the breeding season of thesika deer starts in September, the alpine deer’s autumn
migration is considered a response to the shortage of foodavailability and a movement toward their breeding area.

The adult deer repeated the same seasonal migration
pattern each year (Takii and Izumiyama, 2022).
So, what is happening that results in new deer
populations appearing in areas they previously did not
inhabit? The females (does) give birth to their fawns inJune. The sex ratio of the fawns born is 1 to 1. The fawns
grow up in groups with their mothers (female group). All
male individuals (bucks) and some female individuals are
known to leave their natal group when they grow up. In
understanding the reasons for the expansion of the sika
deer distribution, determining the movements of one
young deer can provide much information.
To determine the long-distance dispersal of a sika
buck, we captured a five-month-old sika buck andconducted GPS tracking for 20 months in the eastern
foothills of the Northern Japanese Alps. The buck showed
the same seasonal movement pattern as a GPS-collared
doe in the same group until 11 months of age. The buck
departed from its natal group in May 2015, and after fourmonths, the buck settled in the neighboring mountains,
where deer are scarce. This buck exhibited a long-distancedispersal movement: the straight-line distance and actual
distance between his natal range and post-dispersal range
were 74 km and 131 km, respectively. He used four
stopover sites (i.e., staying ≥3 days) during his dispersal
movement, including in the alpine zone, where he stayed
during summer. The evidence of long-distance dispersalof sika deer may explain the expanding distribution ofthese deer in central Honshu (Takii et al., 2019).
How did the buck leave his natal group and find a
new home range? By direct observation, a GPS collareddoe (body mass: 73 kg, ≥3 years old) was found to be themother of GPS collared juvenile male deer (body mass:
39 kg, 5 months old). We were able to obtain GPS fix dataon the doe and the young buck for 21 months and 20
months, respectively. The doe migrated between her
summer and winter home range during spring and autumn.
The five-month-old buck exhibited seasonal migration
along with the doe during his first autumn and spring (Fig.
6a). The buck moved along with his mother, and utilized

Fig. 6a Pre-dispersal home range (50% fixed kernel) of a juvenile sika buck and his mother’s home range,
monitored in Omachi City, Nagano, central Japan, 2014–2016. The juvenile buck and his mother’s homerange are outlined by solid and dotted lines, respectively. The red line shows their seasonal migration route.

Why do sika deer head for the alpine zone in Japan?

the same summer and winter home range until May 2015.
The elevations of their summer and the winter homeranges were 1,186 ± 140 m and 718 ± 127 m, respectively.
On 18 May 2015, at 11 months of age, the buck
departed from his summer home range and entered thevagrant stage of his dispersal. The buck had gone missing
after his dispersal started, but a camera trap set by the
Kiso Forest Office captured a photograph of theGPS-collared sika buck in May 2016, and we could obtaindata from this buck after that. The buck moved
southwards, and after four months (6 September 2015) hesettled in the eastern foothills of Mt. Ontake (3067 ma.s.l.). The buck exhibited a long-distance dispersal
movement: the straight-line distance and actual distance
between his natal range and post-dispersal range were
74 km, and 131 km, respectively.
He used four stopover sites during the vagrant stageof his dispersal, and the duration at each stopover siteranged from three to 40 days. The buck utilized higher
elevations during his migration, compared to at his
stopover sites (Fig. 6b; Tukey HSD, p>0.05). It isnoteworthy that the buck utilized the alpine zone(≥2,500 m a.s.l.) of Mt. Norikura (3,026 m a.s.l.), on
30–31 July and 19 August. After the buck had settled into
his post-dispersal home range, he exhibited an exploratory
movement 12 km eastwards and stayed there during
12–26 October, coinciding with the sika deer rutting
season (Takii et al., 2019).

Fig. 6b Post dispersal movement of a juvenile sika buck.
Stopover sites (i.e., staying > 3 days) are shown in
the 50% fixed kernel with the solid pink line. The
area shown in Fig (a) is outlined as a square inFig (b). (Based on Takii et al., 2019)

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Although the dispersal movement of male sika deerin Japan is poorly understood, two studies have indicatedthat male deer disperse at the age of 12 to 30 months(Yamazaki and Furubayashi, 1995, Takii et al., 2012a).
We found that our GPS-collared juvenile buck dispersed
at a younger age, 11 months. The buck dispersed in midMay. Takii et al. (2012a) also documented that three outof four juvenile bucks dispersed in spring. The buckdispersed for a straight-line distance of 74 km. To ourknowledge, this is the longest known dispersal distance ofthe sika deer.
In other research on a polygynous deer species,
dispersal distances were found to be longer at highpopulation density than at low density, and the emigrating
bucks that dispersed from their natal range settled in areasof lower density than expected by chance (Loe et al.,2009). In our study, the deer density was relatively low at
the capture site (Nagano Prefecture in 2016), but the deer
dispersed and settled in a much lower density area.
During the pre-dispersal period, the buckdemonstrated the same seasonal movement as his mother.
Since the maximum snowfall is relatively high in Omachi
City (784 m a.s.l.; 56–93 cm, 2013–2015), the deer likely
exhibited seasonal migration to lower elevation areas
during the winter to avoid deep snow (Igota et al., 2004;
Takii et al., 2012b).
Takii et al. (2012b) also reported that one dispersedbuck exhibited the same philopatric movement as his
mother. Although the post-dispersal tracking period lasted
for 10 months in our study, the young buck did not exhibit
migratory movements, but was sedentary, except for an
exploratory movement during the rutting season. Our
observation showed that post-dispersal movement is notalways associated with the mother's movement. Since theestimated deer density was very low in the post-dispersal
area (Nagano Prefecture in 2016), the juvenile buck likely
exhibited his exploratory movement during rutting season
to seek mating does. The actual dispersal distance of thisbuck was greater than the straight-line distance. This
indicates that the dispersal path was non-linear. However,the buck never returned to his prior stopover sites, always
heading southwards.
The buck utilized higher elevations for his movement
paths compared to his stopover sites. Anthropogenic
structures, such as roads represent barriers to animal
movement. Also in our study, the deer did not utilize
urban areas for their movement paths but utilized muchhigher mountainous areas. Thus, it is likely that deerutilize higher elevations for movement paths to increase
their survival rate.
The deer stayed in the alpine zone during the summer
for a few days. There had been no evidence of sika deerutilizing the alpine zone of Mt. Norikura, so ourobservation is the first report of sika deer utilizing thisarea. In the Northern Japanese Alps, camera trap surveys
in recent years have revealed that most of the deer

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captured in the alpine zone were bucks (Hotta and Ozeki,
2014; Hotta, 2016), and most deer were captured between
July and August. Our data might explain this phenomenon,
since dispersing bucks demonstrate vagrant movements
prior to immigration. Furthermore, the deer likely utilize
the alpine zone during summer to access better forage,
because of the higher nutritional value of plants at higher
elevations (Albon and Langvatn, 1992).

4. Conclusions
We captured sika deer in the Northern and Southern
Japanese Alps to monitor their seasonal movement
patterns using GPS collars. Alpine sika deer are thought tostay in the alpine zone from the plants' early growing
period. The alpine sika deer stay in the alpine zone to feedon alpine vegetation and Betula forest understory. The
autumn migration of the alpine sika deer starts from
September. Adult sika deer repeat the same seasonal
migration pattern each year. One sika deer was found to
exhibit a long-distance dispersal movement, with astraight-line distance and actual distance between the
natal range and post-dispersal range of 74 km and 131 km,
respectively. This evidence of long-distance dispersal ofsika deer may explain the expanding distribution of thesika deer in central Honshu.

Nagano Prefecture (2011) The Third Plan for Conservation andManagement of Sika Deer in Nagano Prefecture. Nagano
Prefecture, Nagano, 48 pp.
Takii, A., Izumiyama, S., Mochizuki, T., Okumura, T. and Sato, S.
(2012a) Seasonal migration of sika deer in the Oku-Chichibu
Mountains, central Japan. Mammal Study, 37: 127–137.
Takii, A., Izumiyama, S. and Taguchi, M. (2012b) Partial migrationand effects of climate on migratory movements of sika deer in
Kirigamine Highland, central Japan. Mammal Study, 37:
331–340.
Takii, A., Izumiyama, S. and Mochizuki, T. (2019) An initial recordof a long-distance dispersal route of a male sika deer in central
Japan. Mammalia, 84: 63–68.
Takii, A. and Izumiyama, S. (2022) Movement patterns of sika deerin the mountainous regions of central Honshu. Sika deer: Life
History Plasticity and Management, Chapter 10. Series:
Ecological Research Monographs. Springer.
Uno, H. and Kaji, K. (2000) Seasonal movements of female sika
deer in eastern Hokkaido, Japan. Mammal Study, 25: 49–57.
Wipf, S. (2010) Phenology, growth, and fecundity of eight subarctic
tundra species in response to snowmelt manipulations. Plant
Ecology, 207: 53–66.
Yamazaki, K. and Furubayashi, K. (1995) A record on dispersal of ayoung sika stag in western Tanzawa, central Japan. Journal of theJapanese Forestry Society, 77: 305–313. (in Japanese withEnglish abstract)

References
Albon, S.D. and Langvatn, R. (1992) Plant phenology and thebenefits of migration in a temperate ungulate. Oikos, 65:
502–513.
Hotta, M. and Ozeki, M. (2014) First record of the sika deer Cervus
nippon by camera traps near the Mt. Iwakoyazawadake of Hida
Mountains, Japan. Bulletin of Nagano Environmental
Conservation Research Institute, 10: 33–36. (in Japanese)
Hotta, M. (2016) First record of the wild boar Sus scrofa and somerecords of Sika deer Cervus nippon by camera traps on the alpine
zone near the Mt. Jiigatake and Mt. Iwakoyazawadake of
Hida Mountains, Japan. Bulletin of Nagano Environmental
Conservation Research Institute, 12: 51–54. (in Japanese)
Igota, H., Sakuragi, M., Uno, H., KajiI, K., Kaneko, M., Akamatsu,
R. and Maekawa, K. (2004) Seasonal migration patterns offemale sika deer in eastern Hokkaido, Japan. EcologicalResearch, 19: 169–178.
Kudo, G. and Suzuki, S. (1999) Flowering phenology of Alpine
plant communities along a gradient of snowmelt timing. Polar
Bioscience, 12: 100–113.
Loe, L.E., Mysterud, A., Veiberg, V. and Langvatn, R. (2009)
Negative density-dependent emigration of males in an increasing
red deer population. Proceedings of the Royal Society
B-Biological Sciences, 276: 2581–2587.
Ministry of the Environment (1997) Japan Integrated Biodiversity
Information System (J-BIS). http://www.biodic.go.jp/index_
e.html (accessed 4 June 2023)
Nagano Prefecture (1976) Vegetation of Nagano Prefecture. Nagano
Prefecture, Nagano, 137 pp.

Shigeyuki IZUMIYAMA
Dr. Shigeyuki Izumiyama is a professor at
Shinshu University. He has been director of theInstitute for Mountain Science at the university
since 2015. He was awarded a PhD in Agriculture
from Gifu University in 2006. His recent researchinterests include ecological research andconservation management practices for large
mammals in Japan’s central mountain region and in Kyrgyzstan. He
received an Ecological Research Award from the Ecological Society ofJapan in 2003 and Mammal Study Award from the Mammal Society ofJapan in 2013.

(Received 4 June 2023, Accepted 11 October 2023)