The Guardian today expanded on a story published in the Moscow Times that quotes a Russian scientist claiming cannibalism among polar bears is on the rise in the Russian Arctic. However, the scientist offered no numbers to support this claim and there is no suggestion he had done a study on this phenomenon.
As I’ve said before, incidents of cannibalism cannot be said to be increasing because there is no scientific baseline for which recent occurrences can be compared. Scattered anecdotal reports of any behaviour cannot be touted as evidence for a trend even though they may be of interest and worth recording.
There is also no suggestion that the person quoted in the Russian newspaper, Ilya Mordvintsev, is a polar bear expert (he is called simply a ‘scientist’) and it appears to be his personal opinion that cannibalism is on the rise. Here is what the Moscow Times had to say (‘Polar Bear Cannibalism On the Rise in Russia’s Arctic, Scientists Say‘):
Polar bears in Russia’s Arctic are increasingly turning to cannibalism as growing human activity and development in the region shrinks their hunting grounds, scientists at the Russian Academy of Sciences said Wednesday.
While cannibalism is a recognized part of polar bears’ natural behavior, its frequency has climbed sharply in recent years, Ilya Mordvintsev, a senior researcher at the Academy’s Severtsov Institute of Ecology and Evolution, told Interfax.
According to Mordvintsev, increased development of the Yamal Peninsula and the Gulf of Ob by oil and gas companies have fueled the degradation of polar bear hunting grounds and disrupted the animals’ feeding habits. The region is a hotspot of development for major gas and oil producers like Gazprom and Novatek.
“The signals are coming not just from scientists, but also from the growing contingent of employees of oil and gas companies and the Defense Ministry,” he said.
Polar bear cannibalism most often happens when a malnourished male bear attacks a female and her cub, eating the cub, he said. The phenomena gained widespread attention when members of a 2017 [sic] National Geographic expedition captured it in a graphic video.
Cannibalism happens when adult male polar bears are thin but also when they are fat: it is not a reliable sign of ‘desperation’. The link provided in the story above to a cannibilism video from a ‘2017’ expedition for National Geographic was actually shot in August 2015 off Baffin Island. It shows a male bear in fairly good condition running down a female with a young cub, not a starving bear on the attack. Watch it below:
I’ve discussed the topic of cannibalism previously in some detail.
The literature shows the only observation known for a fact to have involved a cannibal bear in poor condition (starving), in the fall (when the ice was low), occurred in 1984 (Lunn and Stenhouse 1985). Several recent incidents involved adult males in good or excellent (very fat) condition (Stirling and Ross 2011).
Other papers on the topic discussed in my 2013 post are listed below (Amstrup et al. 2006; Derocher and Wiig 1999; Dyck and Daley 2002; Stone and Derocher 2007; Taylor et al. 1985) and I suggest you read it if you are interested in this topic of cannibalism blamed on climate change.
The Guardian story adds a quote from another Russian researcher, Vladimir Sokolovwho, is quoted as saying:
…this year polar bears had been mainly affected by abnormally warm weather on Spitsbergen Island to the north, in Norway’s Svalbard archipelago, where there had been no ice floes and little snow.
Really? He doesn’t say when this ‘abnormally warm weather’ on Spitzbergen was recorded but sea ice around Svalbard was shockingly thick over the summer of 2019 and extent remained fairly high this winter (it varies quite a bit day to day as the graph below shows):
‘No ice floes’? Svalbard has had more ice floes this year than it’s seen in decades. Longyearbyen on the west coast of Spitzbergen has been plagued by polar bear problems this winter because there has been much more ice than usual offshore (the historical sea ice extent discussed in that post).
Amstrup, S.C., Stirling, I., Smith, T.S., Perham, C. and Thiemann, B.W. 2006. Recent observations of intraspecific predation and cannibalism among polar bears in the Southern Beaufort Sea. Polar Biology 29, no. 11:997–1002. Pdf here.
Derocher, A.E. and Wiig, Ø. 1999. Infanticide and cannibalism of juvenile polar bears (Ursus maritimus) in Svalbard. Arctic 52: 307-310.
Dyck, M.G. and Daley, K.J. 2002. Cannibalism of a yearling polar bear (Ursus maritimus) at Churchill, Canada. Arctic 55: 190-192.
Larsen, T. 1985. Polar bear denning and cub production in Svalbard, Norway. Journal of Wildlife Management 49: 320-326.
Lunn, N.J. and Stenhouse, G.B. 1985. An observation of possible cannibalism by polar bears (Ursus maritimus). Canadian Journal of Zoology 63:1516-1517.
Stirling, I. and Lunn, N.J. 1997. Environmental fluctuations in arctic marine ecosystems as reflected by variability in reproduction of polar bears and ringed seals. In Ecology of Arctic Environments, Woodin, S.J. and Marquiss, M. (eds), pg. 167-181. Blackwell Science, UK.
Stirling, I. and Ross, J.E. 2011. Observations of cannibalism by polar bears (Ursus maritimus) on summer and autumn sea ice at Svalbard, Norway. Arctic 64:478-482.
Taylor, M., Larsen, T. and Schweinsburg, R.E. 1985. Observations of intraspecific aggression and cannibalism in polar bears (Ursus maritimus). Arctic 38:303-309.