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Expedition report: Beautiful brown bears: Studying bears in the quintessentially Scandinavian woodlands of Dalarna county, Sweden (June/July 2019)

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Abstract This is a report about the first year of collaboration between Biosphere Expeditions and Björn & Vildmark with the overall purpose of researching the behaviour of free ranging brown bears (Ursus arctos) in central Sweden for the Scandinavian Brown Bear Research Project (SBBRP). This collaboration investigates, amongst other topics, how climate change as well as human activities affect the brown bear behaviour and population, and provides managers in Sweden with solid, science-based knowledge to manage brown bears. From 24 June to 1 July 2019, ten citizen scientists collected data on bear denning behaviour and feeding ecology by investigating the 2018/2019 hibernation season den sites of GPS-marked brown bears and by collecting fresh scats from day bed sites. All field work was performed in the northern boreal forest zone in Dalarna and Gävleborg counties, south-central Sweden, which is the southern study area of the SBBRP. After two days of field work training, citizen scientists were divided into three to four sub-teams each day. All study positions were provided by the expedition scientist and only data and samples from radio-marked bears with a VHF or GPS transmitter were collected. Citizen scientists defined den types (anthill den, soil den, rock den, basket den or uprooted tree den), recorded bed material thickness, size and content, as well as all tracks and signs around the den sites to elucidate whether a female had given birth to cubs during hibernation. All first scats after hibernation and hair samples from the bed were collected, and the habitat type around the den and the visibility of the den site were described. 27 winter positions of 20 different bears were investigated. Four bears shifted their dens at least once during the hibernation season. In total, the expedition found 17 dens; five soil dens, three anthill dens, two anthill/soil dens, two stone/rock dens, one uprooted tree den and four basket dens. In four locations only smaller day beds were present. Unusually, one pregnant female hibernated in a basket den where she gave birth to cubs during winter. At one position the expedition found the remains of a dead bear. Analysis showed the animal had died of natural causes. Excavated bear dens had an average outer length and outer width of 2.2 m and an outer height of 0.8 m. The entrance on average comprised 10% of the open area. The inner length of the den was on average 1.5 m and the inner width was 1.3 m. The inner height of the dens was on average 0.6 m. Bears used mainly branches (33%), berry foliage (22%) and mosses (32%) as nest material in their dens, which reflected the composition of the field layer and ground layer that was present at the den site. The expedition found six first post-hibernation bear scats at the den sites and collected hair samples from all beds inside the den. One scat of an adult female bear contained small bear claws and baby bear hair at the edge of the scat. This was a sign that the female bear had given birth to cubs during hibernation, but had consumed the cubs for unknown reasons. Eleven bears selected their den sites in older forests and six bears hibernated in younger forest. Only one bear built a den in a very young forest with an average tree height below 1-3 m. The habitat around the dens was dominated by Scots pine (Pinus sylvestris) 43%, spruce (Picea abies) 37%, and birches (Betula pendula, Betula pubescens) 20%. The expedition investigated about a third of all winter den positions that the SBBRP recorded in 2018/2019 and collected six scats at eight cluster positions, which represents half of the scat samples that the SBBRP normally collects during a time period of 10 days. A detailed food item analysis will be performed in 2020 and the data will be published. Through all of the above, the expedition made a very significant contribution to the SBBRP’s field work in a showcase of how citizen science can supplement existing research projects run by professional scientists. Climate change alters the bear denning behaviour and may reduce food resources that they need for fat production. Overharvest (hunting) of bears and habitat destruction are the major reasons why brown bear populations have declined or have become fragmented in much of their range. In Scandinavia, human activity around den sites has been suggested as the main reason why bears abandon their dens. This can reduce the reproductive success of pregnant female brown bears and increases the chance of human/bear conflict. Understanding denning behaviour is critical for effective bear conservation. Further research is needed to determine whether good denning strategies help bears avoid being disturbed. Additionally, enclosed dens offer protection and insulation from inclement weather. A continued fragmentation of present bear ranges, inhibiting dispersal, together with an increasing bear population, might lead to bears denning closer to human activities than at present, thereby increasing human/bear conflict. The dens that were investigated by the expedition were visible from 22 m on average. Cover opportunities and terrain types not preferred by humans are thereby presumably important for bears that are denning relatively close to human activities, but further research needs to be done to validate this theory. Sammandrag Det här är en rapport gällande det första året av samarbete mellan Biosphere Expeditions och Björn & Vildmark med det övergripande syftet att forska på beteendet hos vilt levande brunbjörnar (Ursus arctos) i Mellansverige för det skandinaviska björnforskningsprojektet (SBBRP). Samarbetet undersöker bland annat hur klimatförändringar och mänsklig aktivitet påverkar brunbjörnens beteende och population vilket i sin tur ger myndigheter i Sverige en gedigen vetenskapligt baserad kunskap för att förvalta brunbjörnstammen. Från den 24 juni till den 1 juli 2019 samlade tio expeditionsdeltagare in data om björnens idesval och födoval. De undersökte idesplatserna där björnar har legat i vintersömnen under säsongen 2018-2019 och samlade även färsk spillning vid daglegor från GPS-märkta bruna björnar. Allt fältarbete utfördes i norra boreala skogszonen i Dalarna och Gävleborgs län, mellersta Sverige, som är SBBRP:s södra studieområde. Efter två dagars utbildning inom fältarbete delades expeditionsdeltagaren in i tre till fyra grupper. Alla studiepositioner tillhandahölls av expeditionsforskaren och endast data och prover från radiomärkta björnar med en VHF- eller GPS-sändare samlades in. Expeditionsdeltagaren definierade idestyper (myrstackide, jordiden, steniden, korgiden eller iden under en rotvälta), undersökte bäddmaterialets tjocklek, storlek och innehåll samt kollade efter spår och tecken runt idet som tydde på att en hona hade fött ungar där under vintern. Första spillningar samlades in och även hårprover från bäddmaterialet togs. Dessutom beskrevs habitatet runt om idet och hur dolt idet var placerat i terrängen. 27 vinterpositioner från 20 olika björnar undersöktes. Fyra björnar flyttade från sina iden minst en gång under vintersömnen. Totalt hittade expeditionsdeltagaren 17 iden; fem jordiden, tre myrstackiden, två myrstackide / jordiden, två steniden, ett ide under en rotvälta och fyra korgiden. På fyra platser fanns endast mindre daglegor. Ovanligt nog övervintrade en dräktig björnhona i ett korgide där hon födde sina ungar under vintern. Vid en position hittade expeditionsdeltagarna resterna av en död björn. Obduktionen visade att djuret hade dött av naturliga orsaker. Utgrävda björniden hade en genomsnittlig yttre längd och yttre bredd på 2,2 m och en yttre höjd av 0,8 m. Ingången utgjorde i genomsnitt 10% av den öppna ytan. Den inre längden på idet var i genomsnitt 1,5 m och den inre bredden 1,3 m. Den inre höjden på idena var i genomsnitt 0,6 m. Björnar använde främst grenar (33%), bärris (22%) och mossor (32%) som bäddmaterial, vilket återspeglade sammansättningen av fältskiktet och markskiktet som fanns vid idesplatsen. Expeditionsdeltagare hittade sex första björnspillningar efter vintersömnen och samlade in hårprover från alla bäddar inne i idet. En spillning från en vuxen björnhona innehöll små björnklor och baby björnhår i kanten av spillningen. Detta var ett tecken på att den björnhonan hade fött ungar under vintern, men hade ätit upp ungarna av okänd anledning. Elva björnar valde att bygga sina iden i äldre skog och sex björnar övervintrade i yngre skog. Endast en björn byggde ett ide i en mycket ung skog med en genomsnittlig trädhöjd under 1-3 m. Habitated runt idesplatsen dominerades av tall (Pinus sylvestris) 43%, gran (Picea abies) 37%, och björk (Betula pendula, Betula pubescens) 20%. Expeditionen undersökte ungefär en tredjedel av alla vinterpositioner som SBBRP registrerade under 2018/2019 och samlade in sex spillningar på åtta klusterpositioner, vilket motsvarar hälften av de spillnings-prover som björnprojektet normalt samlar in under en tidsperiod på 10 dagar. En detaljerad spillnings analys kommer att genomföras under 2020 och uppgifterna kommer att publiceras efteråt. Genom allt ovanstående gav expeditionen ett mycket viktigt bidrag till SBBRP: s fältarbete som visade hur expeditionsdeltagare kan komplettera befintliga forskningsprojekt som drivs av professionella forskare. Klimatförändringar förändrar björnens beteende och kan minska födotillgången. Intensiv björnjakt och förstörelse av habitat är de främsta orsakerna till att populationer av brunbjörnar har minskat eller blivit fragmenterade i stora delar av världen. I Skandinavien är mänsklig aktivitet kring idesplatser troligtvis det främsta skälet till varför björnar byter ide under vintern. Detta kan minska reproduktionen bland dräktiga björnhonor och ökar risken för konflikt mellan människor och björnar. Förståelse av vinterbeteende är avgörande för ett effektivt bevarande av björnen. Ytterligare forskning behövs för att avgöra om goda vinterstrategier hjälper björnar att undvika störningar. Dessutom erbjuder väl isolerade iden skydd från dåligt väder. En fortsatt fragmentering av den nuvarande björnstammen, som hämmar spridning, tillsammans med en ökande björnpopulation, kan leda till att björnar kommer närmare mänsklig bebyggelse, vilket ökar konflikterna mellan människor och björnar. De iden som undersöktes av expeditionen var synliga från 22 m i genomsnitt. Täta terrängtyper som inte föredras av människor är därmed förmodligen viktiga för björnar som bygger sina iden relativt nära mänsklig bebyggelse, men ytterligare forskning måste göras för att validera denna teori.
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EXPEDITION REPORT
Expedition dates:
24 June
1 July 2019
Report published:
March
2020
Beautifu
:
Studying bears in the quintessentially
Scandinavian woodlands of Dalarna
county, Sweden
©
Bj
ö
rn & Vildmark
1
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
EXPEDITION REPORT
Beautiful brown bears:
Studying bears in the quintessentially Scandinavian
woodlands of Dalarna
county
, Sweden
Expedition dates:
24 June
1 July
2019
Report published:
March
2020
Authors:
Andre
a Friebe
Björn & Vildmark
Scandinavian Brown Bear Research P
roject
Matthias Hammer (editor)
Biosphere Expeditions
2
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Abstract
This is a report about the
first year of collaboration between Biosphere Expedition
s
and Björn & Vildmark
with the overall purpos
e
of
research
ing
the behaviour of free ranging brown bears
(
Ursus arctos
)
in
central
Sweden
for the Scandinavian Brown Bear Research P
roject
(SBBRP
). This collaboration
investigates
,
among
st
other topics
,
how climate change as well as human activities affe
ct the brown bear behaviour and
population
,
and
provide
s
managers in S
weden with solid, science
-
based knowledge to manage brown bears
.
From 24 June to 1
July 2019,
ten
citizen scientists
collected data on
bear
denning behavio
u
r
and
feeding ecology by inve
stigating the
2018/2019
hibernation season
den sites
of
GPS
-
marked brown bears
and by collecting
fresh
scats from
day bed sites
.
All field work was performed in the northern boreal forest
zone in Dalarna and Gävleborg counties, south
-
central Sweden, which
is the southern study area of the
SBBRP
.
After two days of field work training,citizen
scientists were divided into three to four
sub
-
teams
each
day.
All study positions were provided by the expedition scientist
and o
nly data and samples from radio
-
marked
bears with a VHF or GPS transmitter were collected.
Citizen scientists defined
den
types (anthill den, soil den, rock den, basket den or uprooted tree
den), recorded
bed material
thickness, size and
content
, as well as
all t
racks and signs around the den
sites
to elucidate whether a female had
given birth to cubs during hibernation.
All first
scat
s after hibernation and
hair samples from the bed were collected
,
and t
he habitat
type
around the den
and the visibility of the den
site
were
described
.
27
winte
r positions of 20 different bears
were investigated
.
Four bears shifted their dens at least
once during the hibernation season.
In total, the expedition
found
17 dens;
five soil dens, three anthill dens,
two anthill/soil dens, two stone/rock dens, one upro
oted tree den and four basket dens.
In four locations only
smaller day beds were present.
Unusually, o
ne pregnant female hibernated in a basket den where she gave
birth to cubs during winter.
At one position the expedition found the remains of
a
dead bear
.
Analysis showed
the animal had died of natural causes.
Excavated bear dens had an average outer length and outer width of 2.2 m
and
an
outer height of
0.8
m
. The entrance on average
comprised
10% of the open area. The inner length of the den was on
averag
e 1.5 m and the inner width was 1.3 m
.
The inner height of the dens was on average 0.6 m
.
Bears
used mainly branches (33%), berry foliage (22%) and mosses (32%) as nest material in their dens
,
which
reflect
ed
the composition of the field layer and ground l
ayer that was present at the den site.
The expedition found
six
first
post
-
hibernation
bear scats
at the den sites and collected hair samples
from all beds inside the den. One scat of an adult female bear contained
small
bear claws and baby bear
hair at t
he edge of the scat
.
This was a sign that the female bear had given birth to cubs during hibernation,
but had consumed the cubs for unknown reason
s
.
Eleven bears selected their den sites in older forests and six bears hibernated in younger forest
.
Only one
bear built a den in a very young forest with an average tree height
below
1
-
3 m.
The habitat around
the den
s
was dominated by Scots pine (
Pinus sylvestris
) 43%, spruce (
Picea abies
) 37%, and birches
(
Betula pendula, Betula pubescens
) 20%.
The expedition
investigated
about a third of all winter den positions that
the
SBBRP
recorded in
2018/2019
and
collected
six scats at eight
cluster positions, which
represents
half of the scat samples that
the
SBBRP
normally collects during
a time period of 10 days
.
A d
e
tailed food item analysis will
be performed
in 2020
and the data will be published.
Through all of the above, the expedition made a very significant contribution to the SBBRP’s field
work in a showcase of how citizen science can supplement existing resear
ch projects run by professional
scientists.
Climate change alters the bear denning behaviour andmay reduce food resources that they need for
fat production. Overharvest
(hunting)
of bears
and habitat destruction are the major reasons why brown bear
popula
tions have declined or have become fragmented in much of their range. In Scandinavia, human
activity around den sites has been suggested as the main reason why bears abandon their dens. This can
reduce the reproductive success of pregnant female brown bear
s and increases the chance of human/bear
conflict.
Understanding denning behaviour is critical for effective bear conservation
.
Further research is
needed to determine whether good denning strategies help
bears
avoid
being disturbed
.
Additionally
,
enclosed
dens offer protection and ins
ulation from inclement weather.
A continued fragmentation of present
bear ranges
,
inhibiting dispersal, together with an increasing bear population, might lead to bears denning
closer to human activities than at present
, there
by increasing human/bear conflict
.
The
dens that were
investigated by the expedition
were visible from 22 m on average.
Cover opportunities and terrain types not
preferred by humans are thereby presumably important for bears that are denning relatively clo
se to human
activities
, but further research needs to be done
to validate this theory
.
3
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
S
ammandrag
Det här är en rapport gällande det första året av samarbete mellan Biosphere Expeditions och Björn &
Vildmark med det övergripande syftet att forska på bete
endet hos vilt levande brunbjörnar (Ursus arctos) i
Mellansverige för det skandinaviska björnforskningsprojektet (SBBRP). Samarbetet undersöker bland annat
hur klimatförändringar och mänsklig aktivitet påverkar brunbjörnens beteende och population vilket i
sin tur
ger myndigheter i Sverige en gedigen vetenskapligt baserad kunskap för att förvalta brunbjörnstammen.
Från den 24 juni till den 1 juli 2019 samlade tio expeditionsdeltagare in data om björnens idesval och
födoval. De undersökte idesplatserna där b
jörnar har legat i vintersömnen under säsongen 2018
-
2019 och
samlade även färsk spillning vid daglegor från GPS
-
märkta bruna björnar.
Allt fältarbete utfördes i norra boreala skogszonen i Dalarna och Gävleborgs län, mellersta Sverige,
som är SBBRP:s södra
studieområde.
Efter två dagars utbildning inom fältarbete delades expeditionsdeltagaren in i tre till fyra grupper. Alla
studiepositioner tillhandahölls av expeditionsforskaren och endast data och prover från radiomärkta björnar
med en VHF
-
eller GPS
-
sän
dare samlades in.
Expeditionsdeltagaren definierade idestyper (myrstackide, jordiden, steniden, korgiden eller iden
under en rotvälta), undersökte bäddmaterialets tjocklek, storlek och innehåll samt kollade efter spår och
tecken runt idet som tydde på att
en hona hade fött ungar där under vintern. Första spillningar samlades in
och även hårprover från bäddmaterialet togs. Dessutom beskrevs habitatet runt om idet och hur dolt idet var
placerat i terrängen.
27 vinterpositioner från 20 olika björnar undersökte
s. Fyra björnar flyttade från sina iden minst en
gång under vintersömnen. Totalt hittade expeditionsdeltagaren 17 iden; fem jordiden, tre myrstackiden, två
myrstackide / jordiden, två steniden, ett ide under en rotvälta och fyra korgiden. På fyra platser f
anns endast
mindre daglegor. Ovanligt nog övervintrade en dräktig björnhona i ett korgide där hon födde sina ungar
under vintern. Vid en position hittade expeditionsdeltagarna resterna av en död björn. Obduktionen visade
att djuret hade dött av naturliga o
rsaker.
Utgrävda björniden hade en genomsnittlig yttre längd och yttre bredd på 2,2 m och en yttre höjd av
0,8 m. Ingången utgjorde i genomsnitt 10% av den öppna ytan. Den inre längden på idet var i genomsnitt 1,5
m och den inre bredden 1,3 m. Den inre hö
jden på idena var i genomsnitt 0,6 m. Björnar använde främst
grenar (33%), bärris (22%) och mossor (32%) som bäddmaterial, vilket återspeglade sammansättningen av
fältskiktet och markskiktet som fanns vid idesplatsen.
Expeditionsdeltagare hittade sex först
a björnspillningar efter vintersömnen och samlade in hårprover
från alla bäddar inne i idet. En spillning från en vuxen björnhona innehöll små björnklor och baby björnhår i
kanten av spillningen. Detta var ett tecken på att den björnhonan hade fött ungar u
nder vintern, men hade
ätit upp ungarna av okänd anledning.
Elva björnar valde att bygga sina iden i äldre skog och sex björnar övervintrade i yngre skog. Endast
en björn byggde ett ide i en mycket ung skog med en genomsnittlig trädhöjd under 1
-
3 m. Habita
ted runt
idesplatsen dominerades av tall (Pinus sylvestris) 43%, gran (Picea abies) 37%, och björk (Betula pendula,
Betula pubescens) 20%.
Expeditionen undersökte ungefär en tredjedel av alla vinterpositioner som SBBRP registrerade
under 2018/2019 och saml
ade in sex spillningar på åtta klusterpositioner, vilket motsvarar hälften av de
spillnings
-
prover som björnprojektet normalt samlar in under en tidsperiod på 10 dagar. En detaljerad
spillnings analys kommer att genomföras under 2020 och uppgifterna kommer
att publiceras efteråt.
Genom allt ovanstående gav expeditionen ett mycket viktigt bidrag till SBBRP: s fältarbete som
visade hur expeditionsdeltagare kan komplettera befintliga forskningsprojekt som drivs av professionella
forskare. Klimatförändringar fö
rändrar björnens beteende och kan minska födotillgången. Intensiv björnjakt
och förstörelse av habitat är de främsta orsakerna till att populationer av brunbjörnar har minskat eller blivit
fragmenterade i stora delar av världen. I Skandinavien är mänsklig
aktivitet kring idesplatser troligtvis det
främsta skälet till varför björnar byter ide under vintern. Detta kan minska reproduktionen bland dräktiga
björnhonor och ökar risken för konflikt mellan människor och björnar. Förståelse av vinterbeteende är
avgö
rande för ett effektivt bevarande av björnen. Ytterligare forskning behövs för att avgöra om goda
vinterstrategier hjälper björnar att undvika störningar. Dessutom erbjuder väl isolerade iden skydd från dåligt
väder. En fortsatt fragmentering av den nuvara
nde björnstammen, som hämmar spridning, tillsammans med
en ökande björnpopulation, kan leda till att björnar kommer närmare mänsklig bebyggelse, vilket ökar
konflikterna mellan människor och björnar. De iden som undersöktes av expeditionen var synliga från
22 m i
genomsnitt. Täta terrängtyper som inte föredras av människor är därmed förmodligen viktiga för björnar som
bygger sina iden relativt nära mänsklig bebyggelse, men ytterligare forskning måste göras för att validera
denna teori.
4
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Contents
Abstract
2
Sammandrag
3
Contents
4
1. Expedition review
5
1.1. Background
5
1.2. Research area
5
1.3. Dates
6
1.4. Local conditions & support
6
1.5. Expedition scientist
7
1.6. Expedition leader
7
1.7. Expedition team
8
1.8. Partners
8
1.9.
Acknowledgements
8
1.10. Further information & enquiries
8
1.11. Expedition budget
9
2.
Winter den sites & scat sampling of Scandinavian brown bears
10
2.1. Introduction
10
2.2. M
aterials and m
ethods
16
2.3. Results
31
2.4. Discussion & con
clusions
36
2.5. Literature cited
40
Appendix I: Den mapping protocol
47
Appendix II: Scat sampling protocol
49
Appendix
II
I: Expedition diary & reports
50
5
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
1. Expedition review
M. Hammer
(editor
)
Biosphere Expeditions
1.1. Background
Biosphe
re Expeditions runs wildlife conservation research expeditions to all corners of the
Earth. Our projects are not tours, photographic safaris or excursions, but genuine research
expeditions placing ordinary people with no research experience alongside scien
tists who
are at the forefront of conservation work. Our expeditions are open to all and there are no
special skills (biological or otherwise) required to join. Our expedition team members are
people from all walks of life, of all ages, looking for an adve
nture with a conscience and a
sense of purpose. More information about Biosphere Expeditions and its research
expeditions can be found a
t
www.biosphere
-
expeditions.org
.
This expedition report deals with
an expedition to
Sweden
that ran from
24 June to 1 July
2019
.
The expedition was part of a l
ong
-
term research project
in
Dalarna
county
in
Sweden to help study and protect the local brown bear
(
Ursus arctos
)
population.
More
about the local brown bear pop
ulation and the history of the research project that the
expedition assisted with is in chapter 2.
1.2. Research area
Sweden is a Scandinavian country in Northern Europe
(Fig 1.2a)
. It is a member of the EU
(but not of NATO or the Eurozone) and the thir
d largest country of the Union. It is a
constitutional monarchy and parliamentary democracy, with a monarch as head of state,
like its neighbour Norway. It is one of the safest countries in the world.
Germanic peoples have inhabited Sweden since prehisto
ric times, emerging into history
as the Geats (Swedish Götar) and Swedes (Svear) and constituting the sea peoples
known as the Norsemen.
Sweden’s capital city is Stockholm, which is also the most populous city in the country.
The country’s total populati
on is about 10 million, with a low population density of 22
inhabitants per square km. Approximately 85% of the population lives in urban areas in the
south. Further north, where the expedition
took
place, there are few people, thousands of
inland lakes, a
long with vast boreal forests and glaciated mountains.
The expedition study site
was
in Dalarna, one of the
25
Swedish
counties
. Dalarna seems
to get first dibs on imagery that is considered more Swedish than ABBA and IKEA
combined (a red
-
coloured cottag
e, glimmering lake in the foreground, deep forest in the
background; Swedes sporting traditional dress, celebrating midsummer, dancing around a
maypole, etc.).
Besides moose, reindeer,
roe
deer and various birds, which you can spot without too
much effort
, Sweden is also home to predators such as the bear, wolf, lynx and wolverine.
6
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Dalarna is also the county exhibiting the widest range
of physical geography: deciduous and coniferous
forests, plains, foothills and alpine regions. Lakes and
rivers occup
y approximately 8% of its surface area,
with around 6,300 lakes larger than one hectare.
Dalarna is roughly the same area as Belgium, but far
more sparsely populated. Fewer than 300,000
inhabitants live in Dalarna compared to more than 10
million living in
Belgium. Some of the world’s oldest
living trees have been discovered on Mt. Fulufjället in
northern Dalarna. The oldest of these Norway spruces
dates back around 9,550 years.
Figure 1.2a.
Flag and map of Sweden,
base (red dot) and study area (red ci
rcle).
An overview of Biosphere Expeditions’ research sites,assembly points,
base camp and office locations is at
Google Maps
.
1.3. Dates
The expedition ran
from
24 June until 1 July 2019.
Dates
were chosen so that the expedition could
visit the bear dens early in the season
when tracks and signs
were
still fresh (bears usually
leave their den sites from
mid
-
April
until the end of May).
1.4. Local conditions & support
Expedition base
The expedition base
was
a remote and rustic research station set in the middle of beautiful
countryside
at Kvarnberg, Dalarna
.
There were
several
traditional red wood cabins for
sleeping in, as well as shared bathroom and shower houses. There
was
also a large
wooden house with comfortable rooms for meeting and relaxing in.
Team members share
d
cabins on a twin basis and there
were
modern showers a
nd
toilets. Breakfast and dinner
were
provided at base
by the expedition cook Elfriede Weber
and a lunch pack
was
supplied for each day spent in the field. There
was
220 V mains
electricity with p
lug type European type E.
There was also intermittent mobile
phone
coverage at base.
7
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Weather
The average ambient temperature
during the expedition
varied between 6 and 13
ºC
at
night
and 20 and 26
ºC
during
the
day
.
The average duration of sunlight was
approximately 19 hours (sunrise 03
:20
and sunset
22
:
4
0), as
the
expedition took place
during the Swedish midsummer period.
Field communications
There
was
patchy mobile phone coverage around base and
often
very little
or
no mobile
phone coverage
around
the study sites.
Two
-
way radios were also used for short dist
ance
communication between research teams.
The expedition leader posted a
diary with multimedia content on Wordpress
an
d
excerpts
of this were mirrored
o
n
Biosphere Expeditions’ social media sites
.
Transport, vehicles & research vessel
Team members made their own way to the assembly point
in Mora
. From there onwards
and back to the assembly point all transport, vehicles and
water
craft
were provided for the
expedition team
for expedition
support and emergency evacuations.
Medical support & insurance
The expedition leader was a trained first aider, and the expedition carried a
comprehensive medical kit. The standard of medical car
e in
Sweden
is
very
high and
medical support was available
via the
ambula
nce services,
a hospital in the
nearby town of
Mora
(55 km from base) or the university medical centre in Örebro (310 km from base). In
case of immediate need of hospitalisation, and
weather permitting, helicopters of the
rescue services
were
available. Safety and emergency procedures
were
in place
, but did
not have to be invoked as there were no medical or
other emergencies
.
1.5. Expedition scientist
Dr.
Andrea Friebe was born in G
ermany and studied biology at the Goethe University in
Frankfurt. She has worked in the Scandinavian Brown Bear Research Project since 1998
and wrote her master
’s
thesis and dissertation about brown bear hibernation and ecology
in Sweden. In 2001 she found
ed the company Björn & Vildmark, which is an interface
between bear research and information for the public and for
wildlife
managers. Andrea is
the
database manager and field technician of the
Scandinavian
B
rown
Bear Research
P
roject
and she is
responsibl
e
,
among
st
other
things,
for all den descriptions
of
all
radio
-
collared
brown bears in Sweden
.
1.6. Expedition leader
Biosphere Expeditions was founded in 1999 by Dr. Matthias Hammer. Born in Germany,
he went to school there, before joining the Army, and
serving for several years amongst
other units with the German Parachute Regiment. After active service he came to the UK
and was educated at St Andrews, Oxford and Cambridge. During his time at university he
either organised or was involved in the running
of several expeditions, some of which were
conservation expeditions (for example to the Brazil Amazon and Madagascar), whilst
others were mountaineering/climbing expeditions (for example to the Russian Caucasus,
8
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
the Alps or the Rocky Mountains). With Bios
phere Expeditions he has led teams all over
the globe. He is a qualified wilderness medical officer, ski instructor, mountain leader,
divemaster and survival skills instructor. Once a rower on the international circuit, he is
now an amateur marathon runner
and Ironman triathlete.
1.7. Expedition team
The expedition team was recruited by Biosphere Expeditions and consisted of a mixture of
ages, nationalities and backgrounds. They were (with country of residence):
Jan Biekehoer (Germany), Cyril Feuerriege
l (Germany), Linda Hall (USA), Judyth Hill
(USA), Paul Joiner (USA), Annabel Marriott (UK), Ben Rees (UK), Anne Schroedter
(Germany), Gerald Turner (USA),
Elfriede Weber (Germany)*,
Chris Zacharia
*
*
(UK).
* expedition cook |
*
*
blogger / member
of the medi
a.
1.8.
P
artners
Biosphere Expeditions’ main partner on this expedition is
Björn & Vildmark
(Bears &
Wilderness in Swedish), a company responsible for science communication, information
and guided tours in
the
Scandinavian Brown Bear Research Project
. Björn & Vildmark was
established in 2001 with the purpose of distributing information about bear research and
bear behaviour to the local population and managers.
Dr.
Andrea Friebe of
Björn &
Vildmark
is also a
researcher in the
Scandinavian
B
rown
B
ear
Research
P
roject
and the
expedition followed the project’s methodologies and shared its data with it.
1.
9
. Acknowledgements
This study was conducted by Biosphere Exped
itions which runs wildlife conservation
expeditions all over the globe. Without our expedition team members (listed above) who
provided an expedition contribution and gave up their spare time to work as research
assistants, none of this research would have
been possible. The support team and staff
(also mentioned above) were central to making it all work on the ground
, most of all our
superb expedition cook Elfie
. Thank you to all of you and the ones we have not managed
to mention by name (you know who you
are) for making it all happen. Biosphere
Expeditions would also like to thank the Friends of Biosphere Expeditions for their
sponsorship and/or in
-
kind support.
The expedition was embedded within
the
Scandinavian
B
rown
B
ear
Research
P
roject
and
we would l
ike
to
thank the Norwegian Environment Directorate, the Swedish
Environmental Protection Agency and the Swedish Association for Hunting and Wildlife
Management for funding.
1.10
. Further
i
nformation &
e
nquiries
More background information on Biosphere E
xpeditions in general and on this expedition
in particular including pictures, diary excerpts and a copy of this report can be found on the
Biosphere Expeditions website
www.biosphere
-
expeditions.org
.
E
nquires should be addressed to Biosphere Expeditions at
info@biosphere
-
expeditions.org
.
9
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
1.11
. Expedition
b
udget
Each team member paid towards expedition costs
a
contribution of
1,
9
7
0 per
person per
10
-
day slot. The contribution covered accommodation and meals, supervision and
induction, special non
-
personal equipment,
and
all transport from and to the team
assembly point. It did not cover excess luggage charges, travel insurance
, personal
expenses such as telephone bills, souvenirs etc.,
or
visa and other travel expenses to and
from the assembly point (e.g. international flights). Details on how this contribution was
spent are given below.
Income
Expedition contributions
16,5
73
Expenditure
Base camp and food
includes all board & lodging, base camp
services
4,486
Vehicles & fuel
includes fuel,
wear & tear
, car hire charges; ; also includes per km
support payment from Scandinavian Brown Bear Research Project
640
Equip
ment and hardware
includes research materials & gear, etc.
2,651
Staff
includes local and Biosphere Expeditions staff & expenses
5,026
Administration
includes registration fees, sundries, etc.
129
Expedition set
-
up and reconnaissance
4,
156
Team recrui
tment
Sweden
as estimated % of PR costs for Biosphere Expeditions
4,981
Income
Expenditure
-
5
,
496
Total percentage spent directly on project
133
%
*
*This means that in 201
9
, the expedition ran at a loss and wassupported over and above the in
come
from the expedition contributions by Biosphere Expeditions.
10
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
2.
Win
ter den sites and scat sampling
of Scandinavian brown bears in Sweden
Andrea Friebe
Björn & Vildmark
Scandinavian Brown Bear Research P
roject
2.1
.
Introduction
2.1.1.
History,
d
istribution
and population dynamics
of brown bears in Sweden and Norway
The brown bear
(
Ur
s
us arctos
)
is a large non
-
social carnivore that is distributed over much
of the Nort
hern Hemisphere in Europe, Asia
and North America.
Bears
live in a great
variety
of habitats, including treeless arctic tundra, grasslands, boreal forest
, forested and
alpine mountains
and deserts. Overharvest
(hunting)
and habitat destruction are the major
reasons why brown bear populations have declined or
have
become fragmented i
n
much
of their range (Tsubota et al. 1987, Servheen 1990, Zedrosser
et al. 2001
,
Dahle 2003).
Figure 2.1.1a.
Development of the brown bear population in Sweden.
Estimated numbers of bears in different years.
Originally, bears were found throughout Sc
andinavia
(Collett 1911
-
12,
Lönnberg 1929). In
the early and mid
-
1800s the brown bear
was present
through
out the Scandinavian
Peninsula at varying densities.
The highest density
in Sweden was
in the central parts of
the country
,
with
low
er
density in the n
orthern parts
. I
n the
south,
the bear had been
largely extinct since the 18th century. Based on records of
bear hunters
by county, the
Scandinavian population was estimated to have consisted of 4
,700 to
4
,
80
0 individuals
around the 1850s with the majority
of bears (
65%
)
living in Norway (Swenson
et al. 1995).
Between 1856 and 1893, an enorm
ous number of bears were killed:
2,605 in Sweden and
5,164 in Norway
, and the population
declined quickly,
by
about 4.8% annually in Sweden
and 3.2% in Norway
(Swenson
et al. 1995)
.
It was government and society
policy
at the
time to exterminate bears
and strong financial incentive
s
were provided by government or
existed already through the sale of
bear
skins and meat
. As a result
,
b
ears gradually
disappeared from south
to north, and survived only in a few mountainous areas in northern
and central Sweden.
11
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
As the 19
th
turned into the 20
th
century, many realis
ed that the situation
had become
critical for brown bears in Norway and Sweden.
As a result, b
rown bears were prote
cted in
national parks in Sweden in 1
910, and on Crown land in 1913. In Norway
the brown bear
only
received protection in the wh
ole of Norway in 1973 (Swenson
et al. 1995). The low
point for the brown bear population in Sweden was
a
round
1930, when about 1
30 bears
were left in four populations. The last population in Norway became functionally extinct in
1931, although brown bears were sti
ll observed throughout the 1980
s.
Figure 2.1.1b.
Map showing
bear population density in 2017 in Sweden and Norway
(
from
Kindberg
&
Swenson 2018).
The darker the colour, the higher the density.
Blue rectangle = southern study site of the
Scandinavian Brown Bear Research Project
=
expedition study site.
12
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
In 1942
the
Swedish bear
population was estimated at 294 and
an
a
utumn
hunting
season
for bears was introduced in 1943.
The hunting quota was strict
and geographically limited
during the following year
s
and averaged 5.5% of the calculated population size.
Population
r
ecover
y
in Sweden continued
at a rate of about 1.5%
p
er year until
199
5
. In
199
3
estimates showed that the Scandinavian population consisted of around 700 individuals.
Calculations previously carried out
on
marked bears
by the Scandinavian
Brown
Bear
Research
Project indicated a growth rate in the southern
part of the Swedish bear
population
during the 1990s of about 16
%
. The
total number of individual bears was
estimate
d to be about 3,200
in 2008 (Kindberg and Swenson 2014),
with
a minimum of
120 ind
ividuals in Norway (Wartiainen
et al. 2009). A new estima
te in 2013 showed a
contraction
an
d
estimated
about 2
,
800 bears in Sweden (Kindberg and Swenson
2014).
The 2017 inventory showed
no statistically sign
ificant growth compared to 2013
(Kindberg
and Swenson 2018).
2.1
.2. The Scandinavian Brown Bear R
esearch
Project
The Scandinavian Brown Bear Research Project started in 1984 to collect and evaluate
facts about the
ecology of the brown bear. The p
roject is a co
-
opera
tion between Sweden
and Norway with
a
number of different goals such as studying the
bear’
s c
hoice of food,
weight developmen
t, patterns of movement, colonis
ation of new areas, choice of den,
social behavio
u
r, morta
lity and reproduction. Even interactions
with other species, such as
moose and domestic livestock
have
been investigated, as well as t
he sensitivity of bears
to
human disturbance and human
-
bear conflict
. Since 1984, the Scandinavian Brown Bear
Research Project has published more than 280 scientific articles, reports and popular
science publications.
Up to this day more than 700 bears ha
ve been captured from a helicopter in
spring, shortly
after the animals emerge
from their dens. Spring provides the best conditions, when
remaining snow cover and minimal ve
getation make it easier to find
bear
s
, open water in
the terrain is limited, and am
bient temperature is relatively low.
Captured b
ears
are fitted
with
a GPS
collar containing integrated activity acceleration sensors, which provide very
accurate and frequent information
points
about
the
bear
’s
activity and movements
,
and a
VHF implant. G
P
S location data are then
transmitted via the GSM network to a base
station from which they can be downloaded remotely. The GPS collars
are
programmed to
collect GPS location fixes at 1
-
hour intervals during the period
of
1 April until 30 November
and once
per day (at noon) from 1 December until 30 March.
2.1.3.
B
ear b
iology
Brown bear weight and body size vary geographically and depend on food availability.
North American brown bears, which have access to a high
-
protein diet, often have a larger
body size
and the shape of the skull is narrower than in European animals (Hörning 1992).
Brown bears are sexually dimorphic. Males are up to 2.2 times larger than females and the
spring body mass of adult individuals averages 115 kg for females and 248 kg for ma
les in
central Sweden (Swenson
et al. 2007).
A
nnual home ranges
in Sweden
overlap and male
bears typically have larg
er home ranges (median: 1055 square km
) than females (median:
124
-
217
square km
, depending on reproductive status) (Dahle and Swenson 2003).
13
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Brown bears are omnivorous and their diet varies among populations and seasons. In
Scandinavia, the diet is mainly composed of graminoids, forbs, berries, ants, and
ungulates (Dahl
e et al. 1998, Persson
et al. 2001). During spring and early summer, adul
t
brown bears accumulate l
ean mass reserves (Hilderbrand
et al. 1999) from
foods rich in
protein (Swenson
et al. 2007). The period of fat accumulation (hyperphagia) starts in
August, when the bears in Sweden consume mainly berries rich in carbohydrates to
gain
adipose fat tissue before entering the winter den (Dahleet al. 1998).
Bears are the only mammals with delayed implantation, gestation, parturition
(birth)
, and
lactation during hibernation. The mating season of brown bears lasts approximately 2
-
2.5
m
onths in Sweden, from mi
d
-
May to early July (Dahle 2003,
Steyaert 2012).
Y
oung
bears
in Sweden
reach sexual maturity at
an age of three to five years (Swenson
et al. 1995),
whereas
in North America
they
are
usually older
(McLellan 1994,
Hilderbrand
et al.
1999).
Brown bears are promiscuous, both males and females mate with different partners
(Bellemain
et al. 2006, Spady et al. 2007, Zedrosser et al. 2007, Steyaert
et al. 2012).
Fertilized eggs undergo diapause
at the blastocyst stage for four to five
month
s until
delayed implantation occurs in November
-
December (Wimsat
t 1963, Foresman and
Daniel 1983. Sato et al. 2000, Iibuchi
et al. 2009). A minimum amount of body mass and
fat content (about 19% in brown bears) prior to hibernation is necessary
for reprod
uction
(Rogers 1976, Beecham 1980,
Elowe and Do
dge 1989, Atkinson and Ramsay 1995,
López
-
Alfaro
et al. 2013). Dates of birth are independent of the dates of
o
estrus, mating
and dennin
g (Dittrich and Kronberger 1963, Sandell 1990, Spady et al. 2007, Friebe
et al.
2014). Brown be
ars commonly give birth to one to three
cubs, which
are born in the den in
January/February (Friebe
et al. 2013, Friebe
et al. 2014). The neonates, which weigh
about 500 g, are naked at birth, and are nursed by their mother with fat
-
and protein
-
rich
milk in the wint
er den (Farley and Robbins 1995, López
-
Alfaro
et al. 2013). Gestation in
ursids lasts app
roximately 56
-
60 days (Tsubota et al. 1987, Quest 2001, Spady et al.
2007, Friebe
et al. 2014). Lactation in brown bears lasts about 1
.5
-
2.5 years (Farley and
Robbins 1995) and the mean litter interval varies among populations and lasts on average
2.8 years
in European brown bears (Nawaz et al. 2008, Zedrosser et al. 2011, Steyaert et
al. 2012). Longevity of free
-
ranging brown bears is 2
5 to 30 years, and reproductive
senescence in females oc
curs around 27 years (Schwartz
et al. 2003).
Hibernation is one of the most efficient energy
-
saving mechanisms, which is regularly
activated early in advance of the beginning of winter (Nelson 1973).
In contrast to other
hibernating species, the body temperature of bears drops only 2 to 6 °C below the summer
core temperatu
re of 37
-
38
°C, (French 1986, Hissa
e
t al. 1994, Tøien
et al. 2011). Heart
rate during hibernation can be as low as 8
-
10 beats per
minute (bpm), compared to the
heart rate of 30
-
50 bpm of
sleeping bears in summer (Folk et al. 1972, Nelson et al. 1973,
Folk
et al
. 1976
,
Folk et al. 1980, Nelson et al. 2003, Folk
et al. 2008). During hibernation,
bears are largely inactive
. T
hey do not
eat, drink, urinate, or defecate, but subsist on the
energy resources they gained during the active season. Their basal metabolic rate
decreases by 40%, and their oxygen consumption by about 50% of normal levels
(Hellgren 1998). During hibernation, bears l
ose between 20
-
45% of their body weight,
depending on several factors, e.g., duration of denning, sex, age, a
nd reproductive status
(Nelson et al. 1973, Nelson 1973, Kingsley et al. 1983, Swenson et al. 2007, López
-
Alfaro
et al. 2013).
14
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
In Sweden all bro
wn bears hibernate and spend
five to seven
months in their dens,
depending on
sex, reproductive status, age and latitude (Friebe et al. 2001,
Manchi and
Swenson 2005). The process when bears enter their dens is called denning. Denning is an
essential part
of the ecology and reproduction of brown bears, because pregnant females
give birth to cubs during winter. The male bears leave their dens at the beginning of April,
some males as early as March. Female bears rest until the middle of April. Normally bears
leave their den sites directly after the end of the hibernation. However, females that have
given birth to cubs during hibernation often stay close to their dens for another
two to three
weeks, sometimes until the end of May, because dens offer protection
against the cold
and
predators
.
Bears prefer different types of dens depending on the ground
characteristics and the surrounding area,
but there are also individual preferences. Bears
in Sweden normally do not reuse their dens, but dig a new den
every year
.
Most bears
hibernate alone; only females with cubs share their den for
one or two winters.
Bears have
the in
stinct to dig dens from birth.
In Sweden brown bears mainly hibernate in excavated
dens
such as
anthill or soil dens. Brown bears select denning h
abitats on the landscape
scale by avoiding water and intermediate
-
sized roads and by denning mor
e at lower
altitudes (Elfström et al. 2008,
Elfström and Swenson 2009).
2.1.4.
Background
to den site
survey
s
Bears normally avoid human infrastructure when d
enning, but due to an expanding bear
population some bears den relatively close to humans. Hibernating bears survive on the
energy stores they have accumulated during the
autumn
hyperphagic
(fattening)
period.
Thus, the denning period is a vulnerable time
for bears
,
because they are unable to
escape from disturbances without losing valuable amounts o
f energy (Elowe and Dodge
1989, Welch et al. 1997, Ordiz
et al. 2008). Well
-
nourished females have larger litter sizes
and shorter litter intervals (
Bunnell and
Tait 1981, Rogers 1987, Stringham 1990, Ryan
1997, Welch et al. 1997,
McLellan 2011) and disturbances of pregnant female brown
bears during the winter can reduce their
reproductive success (Swenson et al. 1997
b
).
E
specially after females give birth, the c
ost of den relocation rises dramatically, because
young cubs
will
be exposed to thermal stress. Thus, the choice of a safe place for the den
appears
to be of vital relevance, particularly for reproducing females.
In Scandinavia, human activity around the
den site has been suggested to be the
main
reason why bears abandon their dens (Swenson
et al. 1997
b
). And indeed, several
researcher
s
have suggested that bears select their den sites to reduce such risks of
disturbance
(Ciarniello et al. 2005, Elfström e
t al. 2008, Elfström and Swenson 2009,
Goldstein
et al. 2010). Many wildlife species use co
ver to avoid human disturbance,
presumably because of the reduced detection risk. During the non
-
denning period, brown
bears select resting sites that are more conce
aled when the risk of human encounters is
higher and when resting clos
er to human settlements (Ordiz
et al. 2011).
The moose
-
hunting season
in Sweden
starts at the end of September and is most intense
during Oct
ober and beginning of November. F
orestry ac
tivities
also occur
year
-
round
. Both
activities have great potential for disturbing bears during hibernation, especially moose
hunting, which often involves unleashed baying dogs (Sahlén 2013). Although brown
bears in Sweden generally are not aggressive, t
hey do sometimes injure humans. The
period of highest risk coincides both with brown bear den entry and the moose hunting
season, when large numbers of hunters and their hunting dogs are presen
t in the forest
(Friebe et al. 2001,
Manchi and Swenson
2005, M
oen
et al. 2012).
15
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
In order to understand how to reduce the rate of injury, it is important to learn more about
bear choice of denning habitat, but thus
far, very little informa
tion about brown bear
denning behavio
u
r and
den site selection is available. T
herefore the results of this study
will
help managers to improve the safety of both humans and bears, e.g. by developing
appropriate hunting restrictions; informing forest managers about brown bears
denning
habitat selection in order to preserve areas tha
t brown bears visit during winter; and
informing the public
on how to minimis
e disturbances
,
whic
h can lead to injuries (Sahlén
et
al. 2011).
Dens built in old anthills appear to be the most common de
n type in Scandinavia
(Swenson et al. 1999, Manchi and
Swenson 2005,
Nowack 2015)
,
especially among
females which are more selective than males in den type selection, considering that they
have greater costs related to disturbance during hibernation (Elfström and Swenson
2009). Nowack (2
015) found that anthill
denning
does result in bigger litter size. Therefore,
we suggest that pregnant females hibernating in anthill dens can save a significant amount
of energy in comparison to hibernating in other den types. Nowak
(
2015
) also
reported that
clear
-
cutting fores
try may have negative effects on the brown bear reproduction and thus
population dynamics. Thus, it is important to gain more detailed knowledge of the den site
selection of free
-
ranging brown bears in Sweden and to evaluate how environmental,
behavio
ural
and individual factors
,
as well as climate change
,
influence the den site
selection.
2.1.5.
Background
to
scat
inventory
survey
s
Understanding a species’ feeding ecology is essential for successful management and
conservation, because food abundance can
influence body mass, survival, reproductive
success, movements, and habitat use. One of the “missing links” in the bear project is that
we have no good understanding of the foods bears depend upon.
We monitor the effects
of climate change
, but have no data
or only very little data about the changes across time
and space of essential food resources and how bears use those resources. We also
have
only
a
very little understanding
around
if
and how bears switch between major food
sources in relation to environm
ental conditions or anthropogenic changes in the habitat.
Most of our knowledge is based on short
-
term studi
es carried out in the late 1990s and
very early 2000
s. Bear densities have likely changed since then, and the bear population
is now
likely
to be
at
carrying capacity. If we want to understand how climatic and
anthropogenic changes in the habitat affect bears, their ecology, fitness and reproductive
output, and population development, then we must start monitoring how bears use their
food resources ov
er time. The purpose of the scat collection that started in 2015 is to
establish and test a long
-
term routine monitoring program
me
of bear nutrition/foods based
on scats from known individuals.
16
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
2.2
. M
aterials and m
ethods
Human disturbance often
has a n
egative effect on bears such as
den abandonment,
stress, habitat loss, fragmentation of habitat including alterations in food availability and
reduced reproductive success.
Information
about den site selections and the bears’ choice
of food will be helpful
for managers when making decisions for brown bear conservation.
The two main tasks of the expedition were
to investigate the den sites where radio marked bears of the
Scandinavian Brown
Bear R
esearch
Project
have hibernated
in order to gain more knowle
dge about
denning behavio
u
r and
to
find and collect
scats for future
analysis
about the bear feeding ecology.
2.2.1.
Study area and population
This study was conducted in the northern boreal forest zone in Dalarna and Gävleborg
counties, south
-
central
Sweden (~61°N, 15°E), which is the southern study area of the
Scandinavian Brown Bear Research Project. The area comprises about 13,000
square
km, is hilly, and is covered with coniferous forests with interspersed lakes and bogs.
Altitudes range from 200
m in the southeast to 1,000 m in the west but are mostly (>90 %)
below
the treeline
, which is
at
about 750 m (Dahle and Swenson 2003). The forest is
dominated by Norway spruce (
Picea abies
), Scots pine (
Pinus sylvestris
), and birches
(
Betula pendula
and
Be
tula
pubescens
). Ground vegetation includes a variety of species
of mosses, lichens, grass, heather and berries. Bilberries (
Vaccinium myrtillus
) and
crowberries (
Empetrum hermaph
r
oditum
) are the main autumn food resource of brown
bears in this area (Opset
h 1998).
The landscape is intersected by a dense network of logging
tracks
(0.7 km/
sqkm
) and a
few high
-
traffic asphalted roads (0.14 km
/
sqkm
) (Martin
et al. 2010). The
human
population density is low
and only a few small v
illages exist in the study area
(Swenson
et
al. 1999).
Snow cover lasts from the end of October until late April and mean daily temperatures
range from
7 °C in January to 15 °C in July (Swedish Meteorological and Hydrological
Institute).
The study area of the Scandinavi
an Brown Bear Research Project
(Fig. 2
.1.
1b
)
is part of
the southernmost core reproductive area for Scandinavian brown bears, with a population
density of about 30 individuals per 1000
sqkm (Bellemain et al. 2005, Solberg et al. 2006,
Kindberg
et al. 2011). The brown bear is a game species and
legal hunting is the single
-
most important cause of mortality for
brown bears in Sweden (Bischof
et al. 2009
). The
annual brown bear hunt
runs
from 21 August until quotas are
reached
(45
75 bears are
harvested per year in the study area),
but stops by no
later than 15
October, in order to
protect hibernating bears from disturbance.
17
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
2.2.2.
Training
and deployment of citizen scientists
The
expedition team comprised ten citizen scientists recruited by Biosphere Expeditions,
one expedition leader from Bios
phere Expeditions and the expedition scientist (and lead
author of this report).
During the
first two days
of the expedition,
citizen scientist
s
were introduced to the field
work (
no prior knowledge was required
before arrival)
.
T
raining
was a mixture o
f
presentations
(Fig. 2.2.2a)
,
classroom lessons
and outdoor practice sessions
(Fig. 2.2.2b)
to become acquaint
ed
with
daily routines, safety aspects, field
protocols
, datasheets, data
entry, sample collection and storage, as well as equipment use and hand
ling.
The first two
den
and cluster sites
were
investigated
as one large group
(Fig. 2.2.2c)
under the
supervision of the expedition scientist.
Figure 2.2.2a.
An indoor presentation as part of the citizenscientists training sessions.
18
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Figure 2.2.2
b
.
An
outdoor
equipment training session
.
Figure 2.2.2c
.
The whole expedition group
recording
a bear den
in the field
.
19
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
After the training
days
, citizen scientists were divided into sub
-
groups
of three to four.
Sub
-
groups differed on purpose in how long
and difficult the tasks for the day were so that
citizen scientists of varying ability and fitness could decide on which sub
-
group to join.
Each
sub
-
group
was briefed
at the expedition base
on the
weather, safety, den positions
assigned to it for the day,
as well as other tasks and points of note
(Fig 2.2.2d)
.
Figure 2.2.2d
.
Briefing at the beginning of the working day
.
The sub
-
group
received a backpack with the equipment
required
for the den study and for
scat sampling including: a
road map, a handhel
d GPS with a camera and reserve
batteries, the
field
prot
ocols and manuals, pens, a paper
map with the daily positions of
the dens/scats, a communication radio, plastic bags, hand disin
fection, gloves, sample
labels
,
den
measuring tools
such as
a measuring
tape, a torch, a densiometer, a
relascope, and a cylinder for the habitat measurements.
Sub
-
groups then navigated by vehicle to the road points nearest to their assigned study
positions
(Fig. 2.2.2e)
and continued on foot to them
cross
-
country and guide
d by a GPS
(Fig 2.2.2f)
, performed their
research
tasks, returned to their vehicles and repeated the
process for the next position until their work was done or they had run out of time.
20
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Figure 2.2.2e
.
Navigating
by vehicle to the road points nearest to
the
assigned study position
.
Figure 2.2.2f
.
Continuing on foot cross
-
country to a bear den site, guided by a GPS.
21
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
All
study
positions were provided by the
expedition scientist
.
D
en locations had been
identified with telemetry by triangulation from the
ground during the winter or by
coordinates obtained from GPS
-
collared bears. Based on the observed movement data,
cluster sites corresponding to bed sites of bears were located. A cluster site was defined
as a minimum of three consecutive locations within
a circle of 30
m radius, i.e. an area
where
a
bear
had
spent
more than two
hours, suggesting resting time.
D
aily
research
routes
for sub
-
groups
were planned each evening for the next day and the positions were
inserted into the handheld GPS and then visite
d in the field. Because bears have l
arge
home ranges,
it was necessary
for the sub
-
groups
to drive on small forest roads to come
as close as possible to the
study
positions. The remaining
walking
distance from the
closest forest road position to the den or
cluster position was on average 300
to
1
,
200
m.
All measurements and observations were noted
i
n
to
the field protocols
(Fig. 2.2.2g)
. The
completed protocols received a unique protocol
ID
to ensure
link
age between
collected
data/sample
s
and
a scanned fie
ld protocol sheet. The protocol ID contained the name of
the study, the year of the data collection, initials of the observer and a running number
(e.g. DENS_2019_MaHa_001).
Figure 2.2.2g
.
Recording data into the field protocol.
Only data and samples
f
rom radio
-
marked bears with a VHF
or GPS transmi
tter were
collected. The bear ID
, age, sex and reproductive status
were
added
to
the protocol,
because denning and foraging strategies often vary among bears in different age, sex, and
reproductive classes. T
he reproductive status contained information if the bear was
solitary, accompanied with cubs
born in
the
same year or by older offspring.
22
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
2.2.3.
Field work
Den sites
When
a
den was found
at or around the study position given (this was not always the
case)
, the actual coordinates of the den position
were noted
on the protocol, including the
time range the bear had been in the den. Some bears shift their dens during winter. If the
reason why the bear abandoned the den was known (e.g. forest fe
lling, hun
ting activities,
etc.),
the information about the type of disturbance was noted.
Den type
All dens were examined and the den types were defined. In Sweden bears
mainly
use
the
following different types of dens:
Anthill den
: T
he most commo
n den
ty
pe is t
he anthill den. This den
type is significantly
more often used by females than by males (Elf
ström and Swenson 2009). Female
preference for specific den
types is probably related to the higher degree of insulation and
protection from disturbance in anthill
dens, especially compared to
basket
dens, which are
almost exclusively used
by large adult males (Elfström
et al. 2008). The anthill den seems
to combine all important attributes to function as optimal shelter. It is composed of thick
walls that often are
overgrown by bilberries (
Vaccinium myrtillus
), providing good stabi
lity
in comparison to other den
types, which are to varying degrees reliant on a closed snow
layer for insulation.
Soil den: Soil dens are often built at
or into
slopes. It is easier to d
ig horizontally rather
than vertically, and has the advantage of the opening facing to the side. This keeps the
warmth inside the den and does not expel the heat upwards. Additionally, the den is better
protected from snow and rain if the entrance faces to
the side of the den. The difference
between the anthill den and the soil den is mainly
in the
composition of the walls. The
walls of an anthill den consist of relatively loose organic m
aterial interspersed with roots,
creating an add
itional
insulating air
layer. Soil dens usually miss this insulating air layer
and may also contain more moisture.
Anthill/soil den: This is basically an
anthill
den that is dug
into the ground
soil also
. For a
combination of anthill/soil den the following
apply: 1. If the de
n consists of >80% anthill
material
= the den
is defined as an anthill den; 2. if the den consists of >80% soil material
= the den
is
defined as a soil d
en; 3. if the den consists of 20
-
80% anthill with
the rest soil
material = the den
is defined as an a
nt
hill/soil den.
For dens of this type t
wo digital
pictures, one fro
m the front and one from the sid
e
are always taken. Some dens collapse
during or after hibernation, in
which case
no measurements
were taken
.
Stone/r
ock den: The rock den
cannot be adjusted
in space and fit,
but is the typical bear
den that is pictured in many books. The many rocks that remain from the wi
thdrawal of the
most recent ice
age offer the bear a suitable place to rest during wint
er. Rock dens only
constitute
7
% of dens in Sweden
(
Elfström and Swenson 2009).
Basket den: Only 9
% of dens in Sweden are so
-
called
basket
dens
(Elfström and
Swenson 2009).
These dens look like giant bird nests made from branches and twigs,
without a roof. When it snows, the bear
inside the nest is then
c
overed by
snow as the
only insulating layer
. Bears therefore sleep protected as if in an igloo, on top of their beds.
Mostly male bears hibernate in this manner
,
however, it has happened that females give
birth to their young in open dens
(Elfström and Swe
nson 2009).
23
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Uprooted tree den: A few bears use uprooted trees as a cover during hibernation. Those
dens,
just like
the
basket
dens are open and not totally covered during winter if very little
snow falls during winter.
Den measurements
The direction of
the den entrance was taken with a compass in degrees according
on the
360
º scale.
Figure 2.2.3a
.
Measuring the
outer height
(top) and
inner height
of a bear den.
24
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
To estimate
insulation properties, we estimated the proportion (in %) of the inner
surface
area of the walls and ceiling
that was open
. A basket den typically has 100% open area. If
a den had several openings, e.g. an entrance that accounted for e.g. 15%, plus a hole that
accounted for 5% of the open area, the total proportion was 20%.
Bears usually
collect
den
bed material that mainly contains moss, berry shrubs, heather
lichens or grass. The amount of bed material varies among dens. The thickness and the
size of the bed, including the material of the bed
,
were
measured and
recorded. So
me
females with new
-
born cubs (who
stay longer at the den site
)
often remove the bed from
the den in order to rest outside of the den. If the bed
was
removed from the den, we
estimate
d
content of the bed material, but did not take bed size
measurements
.
All other measurements were taken with a measuring tape
in accordance with Fig 2.2.3b
(see also Fig. 2.2.3a).
Figure 2.2.3b
.
Den measurement as per the field protocol.
25
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Tracks and signs at den sites
Tracks and signs around the den sites
(Fi
g. 2.2.3c)
can provide
important information
about winter behavio
u
r,
as well as provide hints
as to
whether
a female has given birth to
cubs during hibernation. The reproductive success of female bears is often documented
by direct observation after a fema
le has left the
den
with or without offspring. Infanticide is
common during the mating season that starts early after the denning season is over.
Primiparous female brown bears
(bears that give birth to cubs the very first time)
lose their
cubs often di
rec
tly after den emergence and as such can
be classified into the wrong
reproductive class, because no cubs
are
observed after den emergence. Bear cu
bs are
very curious and active. As such
they leave many signs at t
he den sites, such as scratch
marks on trees
after climbing.
There marks are
easily recognized on birch trees, as the
ir
bark is very sensitive.
Where cub signs were found, they were
noted on the protocol.
Figure 2.2.3c
.
Bear signs: Top left
-
c
limbing marks
of a bear cub
on bir
ch tree, top right
-
b
ear cub
in
tree.
Bottom left
-
c
limbing marks of adult bear
, bottom right
-
gnaw
marks of adult bear
.
26
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
In
addition,
all signs of food intake, such as opened tree stumps, where bears
had
eaten
carpenter ant
s, excavated anthills of
F
orm
ica
spp.,
which is often the first food resource for
bears in spring, as well as kill remai
ns from mooses and their calves, were recorded.
Samples
The first scat: Bears do not defecate during hibernation and the first scat is most often
found around the
den. This scat is very large and heavy and easy to distinguish from other
scats
(Fig. 2.2.3g)
. It contains concentrated waste products that have accumulated inside
the intestines during
hibernation. B
ear cu
b claws inside first scats have been reported
from
North American black bears,
which indicates that the mother has eaten its cub during
hibernation, probably because the bear cub died
(
Scanlon et
al. 1998)
. We examined all
first scats in the field, and collected them in a plastic bag, to freeze them for f
uture
analysis.
Hair:
Bear
s
have two different type
s
of hairs. The fur is covered by a top
coat that is up to
10 cm long. The
hair of the
dense
undercoat is thinner, curly and shorter. Both hair types
can be found in the bed inside the den. We collected a
minimum of 10 hairs from the bed
inside the den, which will be used for future studies for stress and genetic analysis. The
hair was packed and stored in a paper envelope at the base. All samples
were marked
with the Protocol_ID
_number, the Bear_ID, and t
he date the sample was collected.
Habitat descriptions
The habitat
around the den
was described on two different levels
: large and small scale.
The large
-
scale level habitat within a 50
m radius around the den was investigated to
obtain
more information
about the forest category that bears
select
for denning in general.
Sometimes, several habitat types existed within this 50
m radius.
In that case only
the
habitat where the den was situated
was described (f
or detailed information about the
habitat and fo
rest categories
,
see
the
den protocol
in Appendix I
).
We measured the size
of the habitat where the den was located to get an idea about the habitat structure and
how
limited/extensive the habitat was
. In Sweden, intensive forestry is carried out
,
but
some
times small patches of dense habitat that have been spared from logging remain on
the edges of some habitats. A pa
tch size was defined as follows: small <0.1 ha, medium
0.1
-
1 ha, large
>1 ha.
If the den was located in a habitat with elevation, we measure
d the bearing and the incline
of the terrain with the compass, recorded in degrees on the 360º scale. Additionally, we
counted the
proportion of all tree species that comprised
the forest
within the defined
habitat
. Only trees >1 m
in
height were count
ed a
nd all recorded tree species
(usually only
pine, spruce and birch)
should add up to 100% in total.
The small
-
scale level habitat
within
a
10
m radius around the den site was investigated i
n
order to gain more knowledge about the habit
at requirements at t
he den site. W
e
studied
the ground vegetation within a 10
m radius around the den site. First, we measured the
proportion
of the area without vegetation (e.g.
if the area was covered by rocks or sand
where n
o vegetation was present). Then
we divided the gr
ound vegetation in
to
a ground
layer (moss and lichens) and a field layer (berry foliage, heather, grass, herbs). The total
proportion
of
ground layer and total proportion
of
field layer
could
exceed 100% as
different vegetation categories can grow over eac
h other (e.g. berry shrubs often grow
in a
field layer
above a ground layer of
moss
es
or lichens).
27
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Tree density measurements (number and
size)
:
We
also
counted the number of each tree
species (>3
m
in height
) within 10
m from the den entrance. Then
we mea
sured the
average tree height
of all tree species (pine, spruce
and
birch
) present
with the
habitat
with
a relascope (Fig.
2.2.3
c)
.
Fig
ure 2.2.3c.
Relasco
pe (Ludde) m
ethod to measure tree h
e
ight:
When the relascope is placed against one eye as
shown
and the top and the bottom of the tree are aligned with the measuring pins A and B by walking away from or
towards the tree, then the distance D, which can be measured on the ground easily
by
a measuring tape, equals the
height of the tree H.
In order t
o
elucidate
forest density, we counted the number of tree stems for each tree
species th
at f
e
ll outside the upper relascope
gap at breast
height level in a circle of 360°
around the den entrance. Tree stems that were smalle
r than the gap were not counted
(
Fig 2.2.3d).
Figure 2.2.3
d
.
Relasco
pe (Ludde) m
ethod to
score
tree
stems. Stems that fall inside the relascope gap
are not scored (such as the pine tree shown)
; those that are equal to or larger than thegap are scored.
28
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Visibility and canopy cover
:
Be
ars abandon their first dens in 22% of denning events
(Sahlen
et al. 2015)
. Thus
,
a
site with good canopy cover
might be
an important factor
when selecting a den site for hibernation. There are two
main
factors that
characterise a
forest site:
the vegetati
on and the terrain. Both have an effect on the concealment of a den
to a varying extent. The horizontal cover represents the visibility of
the den from ground
level. This
was measured by placing a
red and white
cylinder
-
shaped device (60 cm high,
30 cm wid
e
, see Fig. 2.2.2g
) at the entrances of the dens. We
then
walked in
all
four
cardinal and one random direction and measured the minimum distance required for the
device to be completely hidden
from view
. Thus, the shorter the sighting distance, the
more ho
rizontal cover the den had.
Canopy cover (crown cover) was measured with a spherical convex or concave mirror
known as a densiometer (Lemmon 1956). The mirror is divided into 24 fields
with
each
field contain
ing four
points (see
Fig. 2.2.2e
). We
performed
four
measurements (in each
cardinal direction) and counted the number of dots that were not covered by vegetation
(when
the
sky reflected in the mirror). The lower the canopy openness, the more canopy
cover the den had.
Figure 2.2.3
e
.
Densiometer m
et
hod to
score
canopy cover by counting dots not covered by tree canopy. Shown are the
densitometer in use and a typical view of the densitometer mirror with trees covering some dots and leaving others clear.
Scat sampling at cluster sites
The
Scandinavian
Brown Bear Research Project
collect
s
scats from GPS
-
collared bears
fro
m late May until late September
. One scat of every GPS
-
collared individual should be
collected on a bi
-
weekly basis. The expedition
assisted with this project by collecting
s
cats
from
p
reviously identified
bear clusters
from 23 to 29
June 2019
(see
below
for cluster
identification and location)
.
29
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Finding
scats and
day beds
Bear clusters are places wher
e bears remain for longer than two
hours, such as day and
night beds (resting site
s tha
t contain some bear hairs)
and
as such
have a high probability
of containing
scats.
B
ear positions were do
wnloaded and visualis
ed every morning on a
daily basis. For the bear of interest, all clusters for a given day were filtered out and plotted
on a map.
Each day a sub
-
group of citizen scientists
sta
rted with the cluster that seemed
most pro
mising for finding a scat, i.e.
the cluster where a bear
had
remained the longest.
In case no samples
were
found or
could be collected at
the first
site,
the next clus
ter
was
visited until a scat was found or other tasks were more important
.
Scats found were
documented using the scat collection protocol (see Appendix II).
A bed site
is
defined
as
a
bear bed only if it contains bear hairs (Ordiz
et al. 2011). Some
bears
collect mosses, shrubs or other material and build a nest that they use as a day bed.
However, sometimes bears do not make much effort to build
such a resting place; they
just lie
down and those resting sites
are
more difficult to detect
for a citizen sci
entist with a
relatively untrained eye (Fig. 2.2.3f)
.
Bear scat
was only collected if only one bed was
present at a site, to avoid collecting samples from unknown individuals accompanying a
radio
-
collared bear during the mating season. Whenever possible, t
he scat closest to the
bed site was collected. Additionally, we noted if a carcass was present at the day bed.
Scats were stored individually in plastic bags, marked with
a unique identification number
and stored
in a freezer
at
-
20
°C for later analyses.
Figure 2.2.3f.
Bear day beds
. Some
bears collect much bed material for building a resting site (left
), other bears just lie
on the ground. The latter
beds are more difficult to detect. On the right picture, a bear has rested for some hours on a
stone
. No bed material was collected, but signs from the weight of the bear
are
visible and hair is present.
30
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Figure 2.2.3g.
Bear scats
look very different
, depending
on the bear’s diet
. First (top): The first bear scat after
hibernation is large, hea
vy and very dense. Second: Typical bear scat in spring when b
ears often forage
li
ng
on
berries
from the last season a
nd plenty of grass and herbs. Third:
Typical bear scat in May/June
when bears hunt moose calves;
p
ieces of bones and a lot of hair
are visibl
e in the scat.
Fourth
(bottom):
T
ypical bear scat in autumn when
bears forage a
lot of blue
,
crown and lingonberries. They eat approximately 30% of their body weight in berries per day. In autumn, often
several scats are found around the resting places.
31
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
2
.3.
Results
Den sites
Ten citizen scientists and two staff
investigated 27 winter positions
of
20 different bears
from 25 to 30 June 2019.
All positions
investigated
were recorded during the winter
2018/2019, except two positions that were recorded durin
g the hibernation season
2016/2017.
Den
positions
are shown in Fig
. 2.3b
.
Four bears shifted their dens at least
once
during the hibernatio
n season (see Den Nr. in
Table 2.3a
). At 17
out
of
the
27 positions the
expedition
found bear dens and
in
four
locat
ions only smaller day beds were present. However, all locations with only day beds
were
in
places that bears had used after they
had
abandoned their first dens. One female
that hibernated together with two yearlings built her den on a little island i
n a la
ke. The
expedition used stand
-
up paddle boards to reach the island. At another winter position,
the
expedition did not
find a den, because the forest was
clear cut
after the bear
had
left its
den site. The den position was in the middle of a fresh clear cu
t and it was not possible to
detect any bear signs.
Figure 2.3a
.
Reaching a lake island den site.
At one position
the expedition
found the
remains of
dead bear
(Fig 2.3c)
. The VHF implant
was still active when
an expedition sub
-
group visited the locat
ion. The bear
had died close
to a small water
-
rich bog and
skeletal remains
as well as the VHF transmitter were found
about 50 cm
deep
in the mud. Judging by the nature of the bones, the bear
had died a
while
previously
,
probably summer 2018.
A
s many bones
as possible
were removed
from
the mud, including the cranium
,
and investigated
for
bullet
holes
.
None were found, but
we
found bite marks in the cranium, which were
probably
caused by another bear. We could
not
determine whether
the bite marks were caused
by a fight
that led to death
, or
whether
the
y
occurred post
-
mortem through
bear
-
on
-
bear scavenging
. Cannibalism
in bears
is
common, although food shortage is not reported to be the reason of intra
-
specific killing
(Swenson et al. 1997
a
; Steyaert et al. 20
12
)
. Sexually selected infanticide is the main
reason for intra
-
specific predation among brown bears
(Steyaert 2012)
.
32
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Figure 2.3
b
.
Map of
the
Orsa Finnmark
study site. Red dot = winter positions, green star = expedition
base.
10 km
33
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Figure 2.3c
.
Recove
ring bear skeletal remains from a bog.
A number of mammals with particularly high natural value
,
such
as
brown bears in
Sweden
,
are included in the state's game
list
. If
these
are found dead in the wild, it should
be reported t
o the police. The Scandinavi
an Brown Bear
Research
P
roject has an
agreement with the SVA (statens veterinärmedicinska anstalt)
the national veterinary
institute
that all dead radio
-
collared bears
can be sent di
rectly to the SVA, if no crime
(
e.g. illegal hunting
)
is suspected. We
took all the
bear
bones to the
expedition
station in
order to send them to the SVA for further inspections
into
the
cause
of death
, which was
specified as unknown, but without suspicious signs of illegal killing.
Den type
In total, the expedition
invest
igated five soil dens, three anthill dens, two
anthill
/soil dens,
two stone/rock dens, one uprooted tree den and four
basket dens. One pregnant female
hibernated in a basket den where she gave birth to cubs during winter
(Table 2.3.a)
. All
dens were constr
ucted inside, rather than
at
the periphery, of the home range.
Den measurements
Excavated bear dens
such as
anthill and soil dens had an average outer length of 2
.
2
m
(range
1
.
7
m
-
3
.
1
m)
,
outer width of 2
.
2
m (range
1
.
5
m
-
2
.
8
m) and outer height of 0
.
8
m
(range
0
.
2
m
-
1
.
3
m). The den that
had
an outer
height
of 0
.
2
m was a soil den that was
dug
0
.
6
m deep in the ground.
Den
entrance
s were
on average 0
.
5
m high (range
0
.
2
m
-
0
.
6
m) and 0
.
6
m wide (range
0
.
4
m
-
1
.
0
m). The entrance represented on ave
rage 10%
of the open area. The inner length of the den was on average 1
.
5
m (range 1
.
3
m
-
1
.
8
m)
and the
inner width was 1
.
3
m (range
0
.
8
m
-
1
.
8 m). The inner height of the den
s
was on
average 0
.
6
m (range
0
.
3
m
-
0
.
9
m).
34
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Table 2.3a.
Details of
bear
dens investigated by the expedition.
(NF= not found)
Hibernation
season
ID
number
Bear
na
me
Den nr.
Sex
Age
Reproductive
status
Den
found
H
air
sample
F
irst
scat
D
en type
2018_2019
W0104
Abborrgina
1
F
19
3 2
-
year olds
yes
yes
NF
basket
2018_
2019
W0605
Sälga
1
F
14
2 yearlings
yes
yes
NF
anthill
2016_2017
W0720
Rådika
1
F
13
2 yearlings
yes
yes
NF
rock/stone
2018_2019
W1011
Lillunn
1
F
10
2 yearlings
yes
yes
NF
soil
2018_2019
W1203
Pengel
1
F
11
pregnant
yes
yes
yes
anthill/soil
2018_2019
W1205
Klummy
1
F
8
2 yearlings
yes
yes
NF
uprooted tree
2018_2019
W1205
Klummy
2
F
8
2 yearlings
yes
yes
yes
bed
2018_2019
W1304
Bergsloga
1
F
7
pregnant
yes
yes
yes
basket
2018_2019
W1319
Snygga
1
F
11
pregnant
no
none
NF
NF
2016_2017
W1416
Lutane
1
M
solitary
no
none
NF
NF
2018_2019
W1417
Brunna
1
F
pregnant
yes
yes
NF
anthill
2018_2019
W1505
Gymåsa
1
F
pregnant
yes
yes
NF
rock/stone
2018_2019
W1512
Latola
1
F
5
pregnant
yes
yes
yes
anthill/soil
2018_2019
W1605
Tando
M
4
solitary
dead bear
non
e
NF
NF
2018_2019
W1608
Majko
1
F
4
solitary
yes
yes
NF
soil
2018_2019
W1701
Älma
1
F
3
solitary
yes
yes
NF
basket
2018_2019
W1701
Älma
2
F
3
solitary
yes
yes
yes
bed
2018_2019
W1701
Älma
3
F
3
solitary
no
none
NF
NF
2018_2019
W1701
Älma
4
F
3
solitar
y
no
none
NF
NF
2018_2019
W1701
Älma
5
F
3
solitary
no
none
NF
NF
2018_2019
W1702
Gädda
1
F
3
solitary
yes
yes
yes
basket
2018_2019
W1707
Tinnanso
1
F
3
solitary
yes
yes
NF
soil
2018_2019
W1806
Tronda
1
F
2
solitary
yes
yes
NF
anthill
2018_2019
W1812
Råsten
1
M
2
solitary
yes
yes
NF
soil
2018_2019
W1812
Råsten
2
M
2
solitary
yes
yes
NF
bed
2018_2019
W1812
Råsten
3
M
2
solitary
yes
yes
NF
bed
2018_2019
W1813
Gutmyra
1
F
2
solitary
yes
yes
NF
soil
35
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member of the United Nations Environment Programme, the International Union for the
Conservation of
Nature and the European Citizen Science Association.
Bed material
Bears used mainly branches (33%), berry
foliage (22%) and mosses (32%) as
nest
material in their dens (Fig
.
2.3e
). These results reflect the composition of the field layer
and ground layer th
at was present at the den site
. Heather, grass and lichens was rarely
used as nest material.
Figure
2.3e.
Left
: Composition of the bed material from hibernating bears in Sweden.
Right
: Available ground layer and field layer vegetation in a radius of 10
m around the winter dens.
Habitat
None of t
he 17 bears hibernated in water
-
rich areas
such as
bogs
or swamps. Eleven
bears selected their den sites in older forests (type G1: medium tree > 10 cm diameter at
breast height) and six bears hibernated in younger forest
(type R2: medium tree
>
1.
3 m
but < 10 cm in diameter at breast height (1.3 m)). Only one
bear built a den in a very
young forest with an average tree height smaller than 1
-
3 m.
The habitat in a radius of 50
m around the den was dominated by Scots pine (
Pinus
sylvestris
;
43%
)
, followed by spruce (
Picea abies
;
37%
)
, and birches (
Betula pendul
a
,
Betula pubescens
;
20%
)
. However,
at a
smaller scale (10
m radius around the den)
spruce was the dominant tree species (43%), followed by pine (40%) and birch (17%). The
sighting distance to the den was on average 22
m. In 85%
of cases
, it was the vegeta
tion
that limited the visibility to the den, in 15% the landscape terrain was the reason.
36
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member o
f the United Nations Environment Programme, the International Union for the
Conservation of Nature and the European Citizen Science Association.
Samples
The expedition group found six
first
post
-
hibernation
bear scats at the den sites and
collected hair samples from all 17 beds inside the den. We examined t
he scats, packed
and
labelled
them
and stored them afterward in a
-
20°
C
freezer for further analysis
,
tentatively projected to happen in August 2020
. One scat of an adult female bear
contained tiny bear claws and baby bear hair at the edge of the scat
(Fig
2.3f)
. This was a
sign that the female bear had given birth to cubs during hibernation, but
had consumed the
cubs for an unknown reason, probably because the cubs had died. The scat and the claws
were later sent to a lab for genetic analysis and in order
to estimate the age (in days) of
the cubs.
No results have come back at the time of writing.
Figure 2.3f.
Baby
bear hair (left) and claws were found in one scat.
W
e detected
signs of cubs at six
den sites. Climbing marks of cubs and scats from cubs
w
ere found, as well as several day beds around the den.
Scat sampling at cluster sites
The expedition group found 6 scats at 8 cluster positions. At 2 clusters sites the expedition
group found remains of kills. At one cluster moose cal
f
bones were found a
nd at another
cluster the bones and a cranium of a beaver were present. All scats were half dry and had
a solid formed shape and contained mainly grass, herbs, ants, or meat/hair. Detailed food
item analysis of the scats will occur
in 2021
and the data wil
l be published after all analysis
are done.
2.4. Discussion
& conclusions
The expedition
visited 27 winter positions and investigated 17 dens
,
which represent about
a third of
all winter positions that the
Scandinavian Brown Bear Research Project
recorde
d
in 2019. Additionally, the
expedition
collected
half of the scat samples
that the
Scandinavian Brown Bear Research Project
normally collect
s
during this time period.
As
such the expedition’s citizen scientists made a very significant
contribution to the
Scandinavian Brown Bear Research Project
’s
field work and we thank all the participants
and Biosphere Expeditions for
their excellent work.
37
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member o
f the United Nations Environment Programme, the International Union for the
Conservation of Nature and the European Citizen Science Association.
Den abandonment
and
disturbance
Understanding
denning behavio
u
r
is critical for effective
bear conservation,
for
example by
minimising
human disturbance during the critical hibernation period. During
the
field
season
of
2019,
the
Scandinavian Brown Bear Research Project
recorded
three cases in
which
bears
shifted dens during hibernation. I
n one case the bear
needed
five attempts
before successfully locating a place that was used for the rest of the denning period. Onl
y
open beds, but no winter dens,
were found at
new
positions
after disturbance
. Thi
s
suggests that the quality of
hibernation
location
decreases immense
ly
if a bear gets
disturbed during winter and abandon
s the
original den. Brown bears select their den sites
shortly before starting to hibernate
, typically at least 1
2 km fro
m human activity (Friebe et
al. 2001).
Sahlén
(2013) and
Sahlén
et al.
(
2015) doc
umented high den abandonment
rates (22%) in our study area. The majority of documented den abandonments appeared
to be the result
of human disturbance (Swenson et al. 1997
b
, Linnell
et al. 2000). Several
studies have shown that bears try to avoid human dis
tu
rbance during hibernation, e.g.
by
selecting den sites far from roads or in conceale
d and rugged terrain (Elfström et al. 2008,
Goldstei
n et al. 2010
,
Ordiz et al. 2011, Sahlén et al. 2011, Ordiz et al. 2012
,
Ordiz
et al.
2013). Additionally, pregnant fe
males
select
better concealed den types,
such as anthill,
soil
and rock dens, than male bears (Elfström and Swenson 2009). Bears tha
t hibernate in
open “
basket
dens”
are probably more vulnerable to disturbance.
The bears must trade
off between the energy
costs and benefits to decide on an optimal
denning strategy.
A
study of reproducing females is particular
ly
important, because they
play a crucial role
in population dynamics (Sæther
et al. 1998). Previous studies have
shown that disturbance during hyperp
hagia and hibernation has a negative effect on the
bear
’s
fitness and reproductive success (Elowe and
Dodge 1989, Swenson et al. 1997
b
,
Welch et al. 1997, Linnell et al. 2000, Ordiz
et al. 2008). Free
-
ranging female brown bears
in central Sweden select pre
determined places for denning by visiting their den areas on
average more than once a month during
the season (Friebe
et al. 2001). Thus, they
ch
o
ose a known place for the winter den.
As such they may
be aware of some of the
regular disturbances that occur
there and are therefore either accustomed to them, or
have already selected against such disturbances when c
hoosing their den site (Friebe
et
al. 2014).
Further research is
needed
to determine whether
good
denning strategies help pregnant
females avoid
disturbance.
The
Scandinavian Brown Bear Research Project
’s
study of
pregnant females showed that 47% of the females started hibernation before 15 October,
the last day hunting is permitted if the quota has not been filled. Therefore, an early start of
hib
ernation
and the construction of a well
-
protected
den in
suitable
habitat could also be a
strategy to avoid disturbance and loss of energy during the hunting season. Restricted use
of their home range, combined with reduced movements, are known strategies
of female
brown bears with
small
cubs to avoid male bear encounters during the mating
season
(Dahle and Swenson 2003,
Martin
et al. 2013, Steyaert
et al. 2013).
More detailed information about den site selection may also improve the safety of humans
and
bears. Although the Scandinavian brown bear is not an aggressive bear as long as it
is not wounded, bears at dens are associated with higher
levels of aggression (Swenson
et al. 1999, Linnell et al. 2000, Moen
et al. 2012). Human encroachment, habitat
frag
m
entation, resource exploitation
and hunting can affect the presence (Fahrig 1997),
habitat use, behavio
ur (Swenson
et al. 1999) and population dy
namics of wildlife
(Cartwright
et al. 2014). As villages expand and new roads are built
in Sweden
, human
activ
ity relentlessly expand
s
into formerly undisturbed areas, affecting bear behavio
u
r.
38
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member o
f the United Nations Environment Programme, the International Union for the
Conservation of Nature and the European Citizen Science Association.
A continued fragmentation of present bear ranges inhibiting dispersal, together with an
increasing bear population, might lead to bears denning closer to human activities
than at
present. Cover opportunities and terrain types not preferred by humans are thereby
presumably important for bears that are denning relatively close to human activities. This
can alter the fine
-
scale den site selection for these bears, and therefore
also their naturally
evolved behavio
u
r to endure unfavo
u
rable conditions during winter (Mannaart 2016).
Therefore, undeveloped forest regions along with corridors for dispersal are probably
important to decrease anthropogenic effects on bear denning behav
io
u
r. The dens that
were investigated in this study were visible
from
22
m
on average
.
Therefore
,
it is possible
that b
ears that
are
forced to
build their
den
s
closer to
human
activities
may need to select
for better cover.
Den type
The amount of protect
ion and i
nsulation provided by a den varies depending on the den
type. D
ifferences
are likely to
influence the amount of heat loss and vulnerability to
disturbances. Enclosed dens offer protection and insulation from inclement weather.
Especially in excava
ted dens, which can be adjusted by an individual in relation to its body
size, radiant heat from the soil and metabolic heat from the bear can be trapped within the
den and keep the den temperature higher than the a
mbient temperature
(Shiratsuru et al.
202
0
).
These authors also observed
that bears excavate a den cavity
in relation to their
body size and that
older bears tend to excavate better
-
fitting den cavities compared to
young bears. Additionally, bedding materials on the ground enhance insulation, by
forming
a microclimate between the bear and the soil.
All this means that
enclosed dens provide
bears with a microenvironment where temperatures are relatively warm and stable.
It is more common
that adult male
bears select basket dens than sub
-
adult mal
es or
females (Elfström and Swenson 2009). The sex
-
specific differences in the use of den
types may be explained by the generally smaller surface area:volume ratio of male bears
that also allows them to hibernate for a shorter time without excessive energy
loss.
Additionally, male bears can store fat and lose proportionally less weight per day than
smaller bears (Manchi and Swenson 2005). The tendency of female bears to
prefer
anthill
or soil dens can be explained by the high energy demand
o
n
females for bi
rth and
lactation during the den
ning period. Female bears utilis
ing excavated anthill dens have
higher reproductive success compared to those using other den types (Nowack 2015).
However, during the
2019/2020
hibernation season,
the
Scandinavian Brown Bear
Research Project
observed one female that gave birth to cubs in a basket den
,
which is
very unusual.
Furthermore, female brown bears depend even more on the occurrence of anthills than
males do, by excavating more anthills per km² for reasons
of nutriti
on
(Elgmork and
Unander 1998). However, there appears to be a decline in the use of anthill dens by brown
bears in our study area, which might indicate a decline in the availability of anthills. Our
study area is
under intensive, highly destructive forestr
y use with quick plantation and
clear
-
cutting cycles
, which
may well
be a reason for th
e possible anthill decline. This
type
of forestry
creates monospecific, small
and even
-
aged
pine
sta
nds with short rotation
periods, which have little or nothing in comm
on with natural forests
; they are simply pine
growth and cutting fields in areas where there was once natural forest.
This
has
had
a
strong influence on the Swedish flora and fauna
,
and
has
caused a decrease of many
species that rely on
true forest habitat
s (Berg
et al. 1994).
39
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member o
f the United Nations Environment Programme, the International Union for the
Conservation of Nature and the European Citizen Science Association.
Also
,
mound
-
living ants (
Formica
spp.), which function as key
stone species and are widely
spread in the boreal forest, are negatively affected by forestry manag
ement in Scandinavia
(Gösswald et al. 1965, Kilpeläinen
et al. 2008
,
Nowa
ck 2015). Their nests suffer from
mechanical damage as well as from changes within the microclimate that occur through
removal of aphid
-
containing trees (V
epsäläinen and Wuorenrinne 1978, Rosengren
et al.
1979). Hence, clear
-
cutting likely increa
ses the ab
andonment of anthills.
It is thus of immense importance to perform
a long
-
term study of brown bear
denning
behavio
u
r, in order to
elucidate
if clear
-
cutting forestry may have negative effects on
brown bear reproduction and thus population dynamics. We sug
gest that forest
management units consider such
effects in their management to minimise their impact
on
wildlife and biodiversity. Future research could be targeted to investigate whether certain
den or denning habitat types result in less den abandonment.
Signs and s
cats
In central Sweden, adult female bears normally either give birth to cubs during hibernation
or hibernate together with offspring. In general, we presume that females that have
separated from their cubs and mate afterwards during the spri
ng, and hibernate
alone
in a
den
,
are pregnant. However, in previous studies,
the
Scandinavian Brown Bear Research
Project
observed that 60% of the females
presumed pregnant
emerged from their
new
dens without cubs (Swenson
et al. 1997
b
). Analysis of activ
ity data dur
ing hibernation
however, showed
that about 35% of those females in fact had been pregnant
,
but lost their
cubs directly after denning. This shows how
tentative
conclusions based only on cub
observations are. For this reason, we note all signs o
f cubs at den sites to gain information
about reproduction. During the
2019
field season,
the
Scandinavian Brown Bear Research
Project
in three instances
detected signs of cubs at den sites from females
that were not
observed with offspring
later. The fema
le “Pengel”, who
dropped a first scat containing
baby bear claws, was observed with one cub in July and October. Although we have no
knowledge
as to
why the female
consumed some of her cubs, we know
that the litter size
was
originally
bigger than only one
cub.
Food availability
and climate change
Scandinavia is one of the areas
that is likely to be most affected by climate change
(Walther et al. 2002, Stenset et al. 2016), which in turn
will
affect the abundance and
variation in food resources for bears (
Bojarska and Selva 2012). Unlike other bear
populations in Europe or North America that have access to several different food
resources in
autumn
, bears in northern Europe rely almost exclusively on berries during
hyperphagia. The bears in this study are a
ble to adapt to annual changes in the availability
of berry species by switching between
berry species. F
or example, in years of failure of
the bilberry crop, bears rely
heavily
on lingonberries instead. However, brown bears in
Scandinavia depend almost ex
clusively on berries to gain body mass prior to hibernation
and have few other abundant and carbohydrate
-
rich foods available (Stenset
et al. 2016).
Food availability has been shown to affect yearling offspring size (Dahle and Swenson
2003) and r
eproductiv
e success (Zedrosser
et al. 2007). Therefore, changes in climatic
conditions that affect the abundance of berry species
will
be especially problematic for
bears in Scandinavia (Stenset
et al. 2016). The present study is important for the
documentation and
understanding of feeding habits of brown bears, to understand the
potential responses and adaptations of bears to climatic changes, and ultimately, for the
effective management and conservation of the species.
40
© Biosphere Expeditions, a not
-
for
-
profit conservation organisation registered in Australia, England, France, Germany,
Ireland, USA
Officially accredited member o
f the United Nations Environment Programme, the International Union for the
Conservation of Nature and the European Citizen Science Association.
The 2020 expedition should:
C
ontinue to inves
tigate den sites of brown bears
to document e
ffects of climate
change and human activity
on
brown
bear
den site selection
C
ontinue to collect
bear
scat and hair samples in order to gain more knowledge
about the seasonal differences in
choice of food
Star
t
to examine first scats of female brown bears after hibernation
more detail in
order
to gain more information about
the virtually unknown areas of
cub loss or
f
o
et
us
abortions during hibernation
.
Continue to document signs of cubs at den sites
to elucida
te
brown bear
reproduction
parameters
, such
as age of
primiparity, cub survival or repr
oduction
rates
Help
the project
to search for
GPS
collars that
have fallen off
bears in the woods
Help
the project
to find
remains
of
dead bears
to elucidate
reasons o
f death such as
illegal
or intraspecific killing
.
2.5
.
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