JAGIELLONIAN UNIVERSITY
FACULTY OF CHEMISTRY
ENVIRONMENTAL PROTECTION - ENVIRONMENTAL BIOLOGY
FOOD HABITS OF POLAR BEAR IN SVALBARD
 EVIDENCE FOR CLIMATE CHANGE
ADAPTATION?
Kaja Chmura
Bachelor done at Institute of Environmental Sciences under the
supervision of prof. dr hab. Henryk Okarma and direct supervision of
dr Nuria Selva, Institute of Nature Conservation,
Polish Academy of Sciences
Kraków 2011
I would like to thank
my direct supervisor dr. Nuria Selva,
Miłosz and Wojtek for all the help.
2
Contents
Abstract ................................................................................................................................................... 4
1 Introduction..................................................................................................................................... 5
2 Materials and methods ................................................................................................................... 8
2.1 Study area................................................................................................................................ 8
2.2 Study species ......................................................................................................................... 11
2.3 Scat collection and analysis ................................................................................................... 12
3 Results ........................................................................................................................................... 14
4 Discussion ...................................................................................................................................... 17
5 References ..................................................................................................................................... 21
Appendix 1: Svalbard archipelago ........................................................................................................ 23
Appendix 2: Exact location of sample collection(marked by star), Hornsund, Gnålodden.................. 24
Appendix 3: Documentation of the study area and the evidence of polar bear .................................. 25
Appendix 4: Distribution of polar bears subpopulations in the Arctic ................................................. 28
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Abstract
Polar bears (Ursus maritimus) are one of the world s largest carnivores. These
mammals are supposed to be one of the species most affected by climate change in the near
future because they are on top of Arctic food chain and they need ice to hunt for seals  their
main prey. Due to earlier ice break-up, polar bears may be forced to move inland to search for
food. I investigated the food habits of a polar bear during the ice-free period in Hornsund,
southwest Spitsbergen in 2004. The bear was observed grazing at the bottom of a seabird
colony, and regularly resting in the area. A total of 43 scats were collected and analyzed
revealing a high frequency of occurrence and relative volume of vegetal matter (83.7% and
76.7%, respectively). The relative volume of terrestrial food items (plants and birds, 83%)
was much higher than that of marine food items (seals, 21%), which were more scarce in the
bear diet. These results, although from a single individual, provide some evidence that polar
bears may be changing their diet as a way to adapt to climate change and emphasize the
important role that terrestrial food items may have for the species. This study is preliminary
and may inspire further research in that direction.
Keywords: Diet, Ursus maritimus, climate change adaptation, Arctic, Spitsbergen
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1 Introduction
Polar bears (Ursus maritimus) are one of the world s largest carnivores. According to
numerous recent investigations, these mammals are supposed to be one of the species most
affected by climate change in the near future; more precisely  global warming. This is
because they are on the top of the Arctic food chain and they need ice to hunt for seals  their
main prey (Derocher & Stirling 1993, Andersen et al. 2002, Andersen et. al. 2003, Derocher
et al. 2004, Derocher 2005, Evans et al. 2006, Amstrup et al. 2007, Aars et al. 2008, Elliott et
al. 2010). Due to increase in temperatures in the areas which they inhabit, sea ice melts earlier
and bears are forced to move inland as early as 23rd of June (Elliott et al. 2010). Therefore,
they have less time to gain sufficient fat stores for winter, which may negatively affect
pregnant females and the condition of their cubs, thus increasing their mortality (Elliott et al.
2010).
There has been a lot of discussion about the adaptation of polar bears to climate
change.A recent publication (Elliott et al. 2010) states that polar bears have been observed
feeding opportunistically on: terrestrial food items like grass (e.g. Elymus arenarius) or
berries (Vaccinium uliginosum, Empetrum nigrum). They also feed occasionally on caribou,
fish, rodents and birds during the ice-free period. However, those food items were noted to
have very little significance for bears in energetic terms. Other authors (Hobson & Ramsay
1991) suggested that some observations show that few polar bears consume small amounts of
sedges (Carex spp.) and berries.
According to the literature, polar bears are strictly meat eaters. Although their diet
depends on the area they live in, their dominant food consists of three species of seals: ringed
seals (Phoca hispida), bearded seals (Erignathus barbatus) and harp seals (Phoca
groenlandica, Andersen et al. 2002). Considering the area of Svalbard archipelago (see point
2.1, study area), some studies show that bears also attempt to hunt on walruses (Odobenus
5
rosmarus) and young Svalbard reindeers (Rangifer tarandus platyrhyncus), as well as
consume their carcasses (Bangjord et al. 2000). Recent publications, revealed that these
carnivores are opportunistic scavengers as well, since they have been observed feeding on the
corpses of two species of whales: white whales (Delphinapterus leucas), and narwhals
(Mondon monoceros, Andersen et al. 2002). A second choice of polar bears are colonial birds.
Polar bears may consume bird carcasses, but they can also attempt to hunt birds, such as
barnacle geese (Branta leucopsis) and glaucous gulls (Larus hyperboreus). A bear was
observed chasing a flock of barnacle geese and three chicks of glaucous gulls in the water;
unfortunately without success. It was found that polar bears hunt chicks or consume eggs,
rather than adult birds because they swim too fast for bears to catch them (Stempniewicz
2006). They have also been observed feeding on seabird colonies of little auk (Alle alle ) in
Franz Josef Land (Stempniewicz 1993). Other birds found to be consumed by polar bears are
pale-bellied brent goose (Branta bernicla hrota) and eiders (Somateria spp). The predation on
birds occurs in the summer months and intensifies as the sea ice melts earlier. During this
time polar bears also consume vegetation but there is no publication which would emphasize
it as an important food source. In fact, there are not many articles about polar bear diet,
especially concerning traditional studies based on scat analysis.
In this paper an attempt is done to describe the diet of one polar bear regularly
observed in Svalbard, in summer 2004. This individual was regularly resting in the same area,
which was covered by bear hair and scats probably from spring- summer seasons. Studies on
polar bear diet in Svalbard are usually based on observations of kill sites done from the
helicopter (e.g. Andersen et al. 2002), but rarely based on traditional analysis of scat contents,
due to the difficulties involved in collecting the necessary material (remote and difficult area,
large home ranges of bears and relative low densities, risk associated to polar bear attacks). I
aimed at estimating the relative contribution to its diet of terrestrial vs. marine food items.
6
Furthermore, the role of terrestrial food items in bears adaptation to climate change in the
Arctic is discussed.
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2 Materials and methods
2.1 Study area
The samples were found in the Svalbard archipelago, island of Spitsbergen, see
Figure1 and for detailed information see Appendix 1). Svalbard is located in the Arctic, about
midway between Norway and the North Pole. It covers an area of 62,000km2 (Ronning 1996).
Spitsbergen is the largest of all the islands in the archipelago, with an area of 37,673km2
(Umbreit 2009).
The climate of Svalbard is extreme due to its location in the high latitude area. In
summer  also called the snow-free period  temperatures are relatively constant between 0
and 10° C with an average temperature of 4-5° C in July, the warmest month. Most mild
climate is found on Bjłrnołya, the southernmost island, and the western side of Spitsbergen
(see Appendix 1). Snow melts there during June, although there were years when snow
remained until July. The ice in the inner parts of the fjords in Svalbard often persists until late
spring or even until beginning of summer, especially in the eastern coast, and its dispersal is
variable from fjord to fjord and from year to year. The snow-free period ends in September,
when it begins to snow. The fjords do not freeze over until winter. Furthermore, the snow and
ice free periods in the eastern and north-eastern regions of Svalbard are shorter. During winter
period, in the coldest months from January to March, the average temperatures (measured in
Isfjord Radio) were -11 or -12° C. Even in winter the climate is not that harsh. This is partly
caused by the influence of mild air masses from the south and by the North Atlantic current,
which brings relatively warm water up to the west coast of Spitsbergen throughout the year.
In Svalbard, the duration of polar nights and days slightly differs in two regions. On Bjłrnłya
polar nights last for 84 days and in northern Svalbard they last for 128 days, whereas there are
polar days for 99 days on Bjłrnołya and 141 days in northern Svalbard.
8
The vegetation in the Svalbard archipelago is quite abundant, even though 60% of the
area is covered with glaciers. Most plants are found from the tidal zone up to 200 meters
above sea level. There are no trees in this area; only shrubs such as the arctic willow (Salix
arctica) and the dwarf birch (Betula nana). The growing season is generally short in the
Arctic and it often starts before the melting of the snow. This is because the sun radiation is
high enough to penetrate the snow covering and initiate photosynthesis (Mehlum 1990). The
places with most abundant vegetation are linked to seabird colonies.
Svalbard is inhabited by polar bears and their number is around 5000-6000 individuals
(Mehlum 1990). During summer 2004, a polar bear was observed in Gnålodden, in the area of
Hornsund, southwest Spitsbergen (Stempniewicz 2006,see Appendix 2 and 3). From field
signs, it seemed that the animal was regularly resting in the area protected from the wind and
exposed to the sun. The site was covered in bear hairs and scats. On August 10th its fresh
tracks were observed on the beach. The animal itself was observed on August 12th around
16:00 sleeping at the mentioned resting site. Ten days later, on August 22nd at 14:40, a polar
bear (probably the one observed before) was observed feeding on the vegetation at the base of
the bird colony (see Appendix 2 and 3).
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Figure 1: Location of the Svalbard archipelago in the Arctic
[Source: http://dombo.be/jw5e/nature.html]
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2.2 Study species
Polar bears can be found in the circumpolar Arctic (Derocher et al. 2004). Their home
range extends from 1000km2 to 600,000km2 (Aars et al. 2008,see Appendix 4 ). The number
of these mammals is not estimated in all populations, nevertheless; the world s population
oscillates between 20,000-25,000 individuals (Evans et al. 2006).
Polar bears are one of the largest mammals on the planet. They exhibit sexual
dimorphism; males are bigger than females, weighing from 350 kg to 450 kg, whereas,
females weigh from 150kg to 250 kg. If pregnant, females can weigh up to 500 kg. The
largest bear weighed in Svalbard was about 700 kg; the largest weighted in the world was
1003 kg (Alaska). Bear fur cover differs from yellow-white in summer to white in winter.
Moreover, it is oily and water repellent which causes the hair not to mat. It is relevant for
polar bears because they can easily shake of the water and ice after swimming. They
completely molt every year in May or June. Furthermore, these carnivores compared to other
ursids have long and powerful neck and more slender bodies. Their head and ears are also
smaller than comparing with other bears. Such physical features allow them to swim in water
and chase their prey. Especially small ears help them to maintain body heat. Other important
characteristics are massive limbs and five-toed paws with non-retractile claws. The soles of
bear feet have thick, black pads and are covered with hair. This helps them to walk and run on
ice and snow without slipping (Mehlum 1990).
The areas which polar bears inhabit in Svalbard are: ice edges, active ice with re-freezing
leads, often solid fjord-ice in later winter and drift-ice in summer. They can also be found on
beaches on land and islands in ice-free periods. Pregnant females often den in areas of Kong
Karls Land and other easterly islands. They may be encountered anywhere in the archipelago
but they are mainly seen in eastern and northern regions. During winter many bears probably
stay in the marginal ice-zone near Bjłrnłya or further south in the Barents Sea. In late winter
11
and spring many animals migrate to the east and north-east region. Many pass through
Hornsund, along the coast of southern Spitsbergen, or round the south coast of Edgełya
(Mehlum 1990, Evans 2006).
2.3 Scat collection and analysis
In August 2004 a total of 43 scats were collected at the place where the polar bear used
to rest in Gnålodden. Scats were of different ages (from about 3-month to 1-2 day old);
however, the weather conditions contributed to the good preservation even of few-months old
scats. They were put into envelopes, labeled and air-dried for transport. Once they arrived to
Poland, they were kept in the freezer until analysis. All samples were soaked in water, washed
on a 4mm strainer and dried in a dryer at 60°C. Food items were identified according to the
food categories in Table 1 (see in Results). Food items were also ascribed to two general food
categories: (i) marine (seals) and (ii) terrestrial food items (the rest). With the help of a
reference book (Mehlum 1990) birds were classified into two families: (i) Uria spp. and (ii)
Larus spp.
Diet composition was described by the frequency of occurrence and the relative
volume. The frequency of occurrence was defined as the percentage of scats containing a
given food item. Relative volume was also described as the percentage each food item
represents in the volume of all samples. First, the partial volume (Vp) of each item in each
scat was calculated as in (1).
(1)
where is the visually estimated percentage volume of a particular food item and
is volume of the scat.
The volume of each scat was measured using a measuring vessel filled with water up to 2000
dm3. Each scat was submerged in water, and then the volume was read off the vessel and the
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number was subtracted from 2000 in order to calculate the scat volume.
Then, for each food item the sum of all partial volumes (Vp) was calculated and
divided by the total volume of all scats in order to estimate the relative volume of that food
item in the bear diet (see Table 1 in Results).
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3 Results
The diet composition of the scats analyzed is shown in Table 1. Almost all scats
contained animal food items. Mammals appeared more frequently in the scats than birds. Two
bird genus were identified: (i) Uria spp. and (ii) more frequent Larus spp. The frequency of
occurrence of vegetal matter was also high, though slightly lower than the frequency of
occurrence of animal matter. However, when taking into account the relative volume, the
vegetation was surprisingly more abundant than animal matter. The relative volume of birds
was lower than that of mammals.Considering the contribution of terrestrial and marine food
items to the diet, the individual bear object of this study definitely foraged much more on
terrestrial food items; terrestrial food represented almost 83% of total scat volume (see Fig.
2).
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Table 1: Diet composition of a polar bear in Svalbard (n= 43 scats). Frequency of occurrence (%) and relative volume (%)
of food categories are indicated
Food items Frequency of occurrence (%) Relative volume (%)
Plant material 83.7 75.6
Mosses 2.3 0.0
Seeds 18.6 1.1
VEGETAL MATTER 83.7 76.7
Birds 41.9 6.1
Uria spp. 7.0 1.4
Larus spp. 23.3 4.4
Eggs 2.3 0.2
Undetermined birds 11.6 0.1
Mammals 95.3 21.5
Seals 76.7 21.0
Polar bear hair 7.0 0.1
Undetermined mammals 11.6 0.4
ANIMAL MATTER 97.7 27.6
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Relative volume(%) of terrestial and
marine food items
90%
80%
70%
60%
50%
40%
83%
30%
20%
10%
21%
0%
Terrestrial (plants & birds) Marine ( seals)
Figure 2: Relative volume (%) of terrestrial and marine food items
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Relative volume(%)
4 Discussion
The present study suggests an important role of terrestrial food for polar bears during
the ice-free period. Vegetal matter was found to be of great importance for the investigated
bear. Most of its scats contained vegetal matter, and the bear consumed it in high quantities,
as the relative volume indicates. Seals constituted only 21% of the total volume of the scats.
Although there are not many scats and they come from a single individual, these results are
interesting enough and provide some evidence supporting the hypothesis of polar bears
switching to a more terrestrial diet as a way to adapt to climate change (Parkinson 2006,
Stempniewicz 2006). Furthermore, the relative abundance of birds in the scats of the studied
bear also provide for the hypothesis. The closeness of bird colonies of two genus (Uria spp.
and Larus spp.) reflects itself in the obtained results. In fact, polar bears have been observed
before preying on birds in the study area and devastating a nest of glaucous gull
(Stempniewicz 2006).
Recently, there have been many studies which indicate that polar bears may be
switching to more terrestrial food. Polar bears attempted to hunt on colonial sea birds and
consume their eggs and chicks (Stempniewicz 1993, 2006, Elliott et al. 2010). Such behavior
may be related to the need that polar bears have to gain sufficient energy for the winter, while
the sea-ice melts earlier and the time and chances to get the necessary food decrease. As they
can get easily accessible food resources, some bears may decide to stay around in areas with
abundant seabird colonies, like Hornsund, instead of traveling to the east coast of Svalbard,
where the ice persists even in summer, to look for seals.
Polar bears have also been observed preying on young Svalbard reindeer and
consuming their carcasses (Bangjord et al. 2000). When polar bears are on land, their
distribution extends along the distribution of Svalbard reindeers. Moreover, since there is an
abundance of glaciers and scarcity of vegetation, these ungulates are mainly found near the
17
coast or in the valleys, where the probability of encountering a polar bear is greater than
inland. All cases of predation of bear on reindeers occurred during winter and spring season,
whereas scavenging occurred during spring when many carcasses from the animals that did
not survive the winter become available. The study by Bangjord et al. (2000) is a clear
evidence of switching to terrestrial food and it might be linked to an adaptation to climate
change.
This extensive plant consumption shown by the analysis of the scat content was
corroborated by the observation of the bear grazing in the study area, under the seabird
colony, where the vegetation was lush (see Fig. 4). In fact, polar bears have been often
observed feeding on tundra vegetation at the Gnålodden seabird colony. This place is
abundant in Cochleria groenlandica, a plant known to be very rich in vitamin C (personal
information from professor Lech Stempniewicz). Whether polar bears consume plants in
order to gain energy, some microelements or both is still an open question. In this sense,
seabird colonies may represent important suppliers of food for polar bears; not only by
providing a nutrient input to the soil and favoring vegetation growth, but also by supplying
eggs and bird carcasses. The remains of Uria spp. and Larus spp. found in the scats probably
come from the Gnålodden colony of these two bird species.
Figure 3 The polar bear object of this study, grazing at the bottom of seabird
colony, Gnålodden, Hornsund, southwest Spitsbergen, Svalbard on August 22th,
14:40; Photo by Nuria Selva
18
During the ice-free period polar bears have more difficulties to hunt on marine fauna,
especially seals. Thus, it is not surprising that they turn to relatively more easy prey and
adapt their foraging to new conditions. Studies in other areas have also found an important
contribution of non-marine food items to polar bear diets. One example is a quit old study
done by Russell in 1975, on both North Twin Island and mainland (James and Hudson Bay in
Canadian Arctic) showed that bears consumed a lot of grass and other vegetation. Polar bears
were seen grazing and also one bear was observed consuming a seal and traveling right away
5 km to eat grass. Scats which were analyzed in this study revealed a relatively high
contribution of vegetation. Grasses occurred in 80 % of samples and made up 41 % of the
total volume. Most abundant grass in the samples was a large, coarse grass Elymus arenarius.
Some faeces where composed only of spikes of this plant in which the amount of nutrients is
higher than in other plant parts. Investigated polar bears also consumed mosses soon after
emergence from their dens in March. Although the frequency of occurrence (36 %) and
volume (4 %) of these plants was quite low, they are probably a good source of vitamins and
minerals. Eating them could be important due to lack of vitamins and minerals in polar bears
bodies after denning. This could be a proof that vegetation is an important food resource for
polar bears. Another investigation from Hudson Bay (Andriashek 2003) argued that
substantial number of bears foraged inland on plant matter, especially two species of berries:
(i) Vaccinium uliginosum and (ii) Empetrum nigrum. Females, mostly pregnant ones and
those with cubs, were more fond of these food items than males. Authors of the study
suggested that pregnant females and females with cubs need more caloric intake and such
consumption also may allow them to elongate the lactation into the ice-free period. This could
positively influence the condition of both polar bears and their cups.
19
This investigation highlights the importance of terrestrial food items for the polar bear.
There is no doubt, that birds and vegetation were important energy sources for this bear in the
ice-free period. This observation can be the result of the foraging habits of that individual
bear, but can be also indicative of diet switching in response to new environmental conditions.
Summing up, consumption of terrestrial food by polar bear may be interpreted as an
adaptation to a climate change in the Arctic. Nevertheless, it is important to conduct further
research on polar bear food habits and terrestrial foraging in relation to climate change
adaptation.
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22
Appendix 1: Svalbard archipelago
[Source: http://www.svalbardrepublic.org]
23
Appendix 2: Exact location of sample collection(marked by star),
Hornsund, Gnålodden
[Source: http://cruise-handbook.npolar.no/en/hornsund]
24
Appendix 3: Documentation of the study area and the evidence of
polar bear
Picture 1: Fresh tracks of polar bear on the beach,
Gnålodden, Hornsund, southwest Spitsbergen,
Svalbard on August 10th, 2004
[Photo by Nuria Selva]
Picture 2: Polar bear in its resting area, after waking up, Gnålodden, Hornsund, southwest
Spitsbergen, Svalbard on August 12th
[Photo by Nuria Selva]
25
Picture 3: Tracks of the polar bear whose diet was studied at Gnållberget, Hornsund, southwest
Spitsbergen
[Photo by Nuria Selva]
Picture 4: View of the study area from the base of seabird colony, Gnålodden, Hornsund, southwest
Spitsbergen, Svalbard
[Photo by Nuria Selva]
26
Picture 6: Polar bear hair in the resting place, the place of scats collection, Gnålodden,
Hornsund, southwest Spitsbergen, Svalbard
[Photo by Nuria Selva]
Picture 7: Cochleria groenlandica at the base of seabird colony,
where the bear was observed grazing, Gnålodden, Hornsund,
southwest Spitsbergen, Svalbard
[Photo by Nuria Selva]
27
Appendix 4: Distribution of polar bears subpopulations in the Arctic
[Source: http://anniekatec.blogspot.com/2010/12/polar-bear-status-pits.htm]
28