The polar bear problem no one will talk about – the downside to large populations

A large polar bear population with lots of adult males – due to bans on hunting – means more survival pressure on young bears, especially young males. To blame more problems with young male bears on lack of sea ice due to global warming ignores the downside to the reality Norway asked for when it banned hunting more than 40 years ago.

More hungry young males coming ashore looking for food is one of the potential consequences of living with a large, healthy population of polar bears. Biologist Ian Stirling warned of such problems back in 1974.

UPDATE: added below 6 Oct. 2016, statistics of defense of life shootings of polar bears in Svalbard since 1973.

svalbard-more-visitors-more-bears-shot_28-sept-2016-yahoo

Svalbard area polar bear numbers have increased 42% since 2004 and more hungry young polar bears almost certainly mean more polar bear problems, as folks in Svalbard (see map and quotes below) have experienced this year.

According to a Yahoo News report this morning (28 September 2016, As Norway’s Arctic draws visitors, more polar bears get shot):

“Halfway between the northern tip of Europe and the North Pole, the Svalbard archipelago of snow-capped mountains and glaciers is home to 2,654 people and 975 polar bears, according to a 2015 tally by the Norwegian Polar Institute.

“Four polar bears have been shot so far this year,” Vidar Arnesen, a chief police inspector for the governor of Svalbard, told Reuters. “In a normal year, one or two would be shot.”

“There are more contacts between humans and the animals,” he said aboard the Polarsyssel, the governor’s ship, used for inspections and rescue operations.”

[Added: More photos here, from another rendition of the same Reuters report]

Independent young male polar bears (2-5 years) are less experienced hunters and at the bottom of the social hierarchy. Older, bigger bears often take their spring kills of young seals away from them (Stirling 1974:1196) – potentially leaving the teenagers without enough fat to see them through until fall.

The bear pictured above that was removed from Longyearbyen should not have been onshore in April posing a threat to people. April is the prime feeding season for polar bears and there was lots of sea ice available on the east coast, as the sea ice map below shows:

svalbard-capital-and-ice-at-22-april-2016

Competition with bigger, stronger bears likely drove the young male ashore looking for food that another bear wouldn’t take from him.

Such issues were almost certainly among the problems Ian Stirling had in mind back in 1974 when he commented about the total ban on hunting in Norway (which I discussed in an essay about human/polar bear conflicts, with references):

“Dr. Stirling felt that complete cessation of hunting, such as exists in Norway, may increase bear-man conflicts. Dr. Reimers replied that the careful harvesting of polar bears was probably desirable, but the total ban now in effect was largely an emotional and political decision rather than a biological one. Last year four bears were killed in self-defense.” [1974 PBSG meeting “Norway – progress reported by [Thor] Larsen”; Anonymous 1976:11]

It also puts this year’s self-defense kills in Svalbard in historical perspective.

In the polar bear entry for the encyclopedia, “Wild Mammals of North America,” Steven Amstrup wrote (2003:602):

“… Age structure data show that subadults aged 2-5years survive at lower rates than adults, probably because they are still learning hunting and survival skills.”

“I once observed a 3-year-old subadult that weighed only 70 kg in November. This was near the end of the autumn period in which Beaufort Sea bears reach their peak weights, and his cohorts at that time weighed in excess of 200 kg. This young animal apparently had not learned the skills needed to survive and was starving to death.” [my bold]

All this means the last line of this article is indeed true:

“The possibilities of a hungry bear encountering a human being are increasing,” said Lambertini.

More problems with young males is what living with a healthy population of polar bears looks like, which means more bears will have to be shot in self-defense.

UPDATE 6 Oct. 2016: An alert reader (Ole Jørgen Liodden) as pointed out that the statistics for kills of polar bears in Svalbard in defense of life are online at MOSJ (Norway). You can see (below) that it was indeed usual for only one or two bears per year to be shot (as per the statement by the Governor of Svalbard quoted above), but only since 2005:

killed-in-svalbard-1973-to-2015_mosj

However, for most of the winter since 2005 (and all of the winters since 2006), there has been no sea ice in western Svalbard, where most of the population lives (Gjertz and Persen 1987) and few polar bears make their dens. That accounts for the sharp decline in defense kills since 2005, since people out enjoying winter sports are unlikely to encounter polar bears. Prior to 2005, as Ian Stirling suggested, conflicts indeed seemed to increase as polar bear numbers increased – although what is missing are the statistics of conflicts from the pre-1973 period (when polar bear numbers were low).

This data leads to the suggestion that lack of sea ice is likely the primary cause of the decline in human-bear conflicts since 2005 but that increased numbers of tourists visiting eastern Svalbard – with polar bear numbers at high levels – may indeed account for the increase noted in 2016.

In other words, not global warming and increased tourism, as the journalist stated  – just increased tourism.

References
Amstrup, S.C. 2003. Polar bear (Ursus maritimus). In Wild Mammals of North America, G.A. Feldhamer, B.C. Thompson and J.A. Chapman (eds), pg. 587-610. Johns Hopkins University Press, Baltimore.

Gjertz, I., and Persen, E. 1987. Confrontation between humans and polar bears in Svalbard. Polar Research 5:253-256. [the index for this issue lists “Marine bivalve molluscs of Svalbard” for pgs. 253-256 but the abstract and pdf provided are for the Gjertz and Persen paper] http://onlinelibrary.wiley.com/doi/10.1111/j.1751-8369.1987.tb00626.x/pdf

Stirling, I. 1974. Midsummer observations on the behavior of wild polar bears (Ursus maritimus). Canadian Journal of Zoology 52: 1191-1198. http://www.nrcresearchpress.com/doi/abs/10.1139/z74-157#.VR2zaOFmwS4

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