Recently, several polar bear biologists have teamed up with photographers to get pictures of starving bears into the scientific literature ‚Äì and picked up by the media, with mixed results.
For the second time in five years, polar bear biologist Ian Stirling has teamed up with a photographer to give unwarranted scientific credence to an anecdotal account of polar bear behaviour. It included a picture of a pitifully thin animal (classic animal tragedy porn) and was framed to increase alarm over predicted effects of global warming. It got little media attention.
His Norwegian colleagues Jon Aars and Magnus Andersen have just done the same with a bear caught eating a white-beaked dolphin (photo above) ‚Äì but this time the media took the bait.
Update 13 June 2015 ‚Äì Information added on white-beaked dolphin distribution, sea ice conditions in 2014 and a correction. See below.
Longest-ever underwater swim by a polar bear
A few years ago, Stirling co-authored a paper with photographer Jenny Ross (Stirling and Ross 2011) about an incident of cannibalism in Svalbard she captured on film (discussed here). This year, he has co-authored a paper with photographer and Arctic expedition organizer Rinie van Meurs, which came out a few weeks ago.
It’s about a polar bear that hunted three bearded seals by swimming underwater (an “aquatic stalk”) for just over three minutes, the event captured on video by an ecotourism boat captain (cruising north of Svalbard, Norway) ‚Äì see van Meurs photo below (Fig. 1), from the paper.
Figure 1. The polar bear who made the longest underwater dive while hunting bearded seals. Fig. 1 from the Stirling and van Meurs 2015 paper. Click to enlarge.
Apparently, no one had ever seen a polar bear dive for more than a minute or so, which meant the two additional minutes of breath-holding was presented as truly extraordinary!
Since the paper is about an underwater swim,1 it’s rather odd that the only photograph included in the paper (Fig. 1) is one of the bear out of the water, his soaking-wet condition emphasizing his thinness. That’s what makes this animal tragedy porn.
Perhaps the bear’s poor condition made him a bit more motivated to try and catch a seal, but the authors don’t suggest that possibility. It’s also likely that the reason he didn’t catch a seal using this method is the reason he was so thin in the first place ‚Äì a bear with good hunting abilities would normally be close to its heaviest at this time of year, after feeding heavily during spring (April-June) when sea ice and fat young seals are plentiful.
In other words, the fact that this bear was so thin suggests other issues in effect (sickness, old age, injury), such as likely befell Ian Stirling’s “polar bear that died of climate change” in the same general area in 2013. None of those possible factors are mentioned in this academic paper: it only states the animal was a “large adult male.”
Instead, the authors attempted to put this single underwater stalk into an evolutionary context, but in my opinion the strategy fails miserably. It simply displays their superficial understanding of rapid evolutionary change ‚Äì about which books, papers, and dissertations have been written, including my own (Crockford 2004, 2006, 2009).
In fact, what the authors have done is shamelessly exploited the concept of evolution in order to frame a tabloid-worthy bit of behaviour as a pseudo-scientific morality tale about global warming.
Despite acknowledging that almost nothing is known about the diving abilities of polar bears past or present, and the rather enormous range in estimated age for the origin of polar bears as a distinct Arctic species (5 million to 400,000 years), the authors chose to conclude:
“…increased diving ability cannot evolve rapidly enough to compensate for the increasing difficulty of hunting seals because of the rapidly declining availability of sea ice during the open-water period resulting from climate warming.” [my bold]
How is it that such a statement passed peer review?
First-ever record of polar bears eating white-beaked dolphins
The other paper came out earlier this week, by Jon Aars and Magnus Andersen of the Norwegian Polar Institute and what appear to be several photographers ‚Äì Agn√®s Breni√©re and Samuel Blanc ‚Äì about an incident of polar bears feeding on white-beaked dolphins (Lagenorhynchus albirostris) trapped in shorefast ice near Svalbard.
One of Blanc’s photos (Fig. 2) of another bear feeding on a dolphin carcass later that year has been useful for publicizing the incident. This photo was taken later than the incident described in the scientific paper but has been the photo preferred by journalists, culminating with a story in the Guardian today (12 June, Polar bears eat dolphins as Arctic warms), after a warmup by New Scientist two days ago (more on that below).
[Here are some other gems: Thanks, global warming: Now polar bears are devouring dolphins (Washington Post); Grisly images show polar bears eating DOLPHINS for the first time ‚Äì and scientists say global warming may be to blame (Daily Mail); Arctic Polar Bears Now Eating Dolphins for First Time Ever (Revolution News)]
Figure 2. Polar bear feeds on the carcass of a white-beaked dolphin trapped in sea ice near Svalbard in July 2014. This is Fig. 3 from the Aars et al. 2015 paper, photo by co-author Samuel Blanc. Click to enlarge.
The primary incident described in the second paper involved a thin adult male polar feeding on the carcass of a white-beaked dolphin (see photo at the top of this post).2 The “…tooth wear yielded an estimated age of about 16-20 years.” [correction from original ‚Äì my apologies, I missed the age estimate somehow]
Sixteen to twenty years is old for a male bear, and puts this animal in the same age category as the carcass of the old male found by Stirling and others in August of 2013 in the same general area. Old males have trouble defending their kills from younger, stronger bears ‚Äì which means they have trouble getting enough to eat.
White-beaked dolphins are regular visitors to the Svalbard area in summer and fall ‚Äì the only thing slightly unusual about this incident is their presence in spring and the fact they were subsequently trapped by ice:
“Prior to this report, no recording of the species has been made in winter or spring this far north in Svalbard. The fjords and around the coast of northern Spitsbergen, an area normally covered by annual ice, were ice-free in winter 2013/14.”
Update 13 June 2015 (added material here to Fig. 2a): As Fig. 2a below shows, it appears the fjord where the old bear was found feeding on white-beaked dolphins on 23 April had been ice-free for only a few weeks (between 11 March and 7 April), although the area to the north had been ice-free for months (you’ll have to click on the figure to enlarge). That suggests the trapped dolphins had been in the area for about 2 weeks before the bear was spotted feeding on the second one he’d killed.
The range map for white-beaked dolphins shows that this region of Svalbard is only slightly beyond their usual range. Exploring beyond such boundaries when conditions permit is not an unusual behaviour for any animal (especially young ones). Did movements of their usual food at this time of year lure them into the area, at a time of year when it was dangerous to do so? Are white-beaked dolphin population numbers up, encouraging some small pods to explore available adjacent territory?
It seems not much is known about the population size of this species (see IUCN status), so it’s hard to say. It certainly seems imprudent to me to conclude that the presence of a few individuals of this species only 6 weeks or so before, and only slightly east of where they would normally been seen, can be blamed exclusively on global warming.
Figure 2a: Range of white-beaked dolphin (IUCN) compared to sea ice on the date Raudfjorden (arrow) was ice-free (11 March) and when it again became ice covered (7 April), according to NSIDC MASIE charts. Trapped dolphins were about 6 weeks earlier than their usual June arrival. Click to enlarge.
[Note that beluga “whales” are actually members of the dolphin family ‚Äì they routinely live in areas covered with sea ice and are therefore experienced with the need to stay close to open water in order to breath. Yet, even they get trapped in the ice on occasion. I described the carnage that went on a few years ago in Hudson Bay in this post]
Oddly, there is no mention at all in this paper about the well known effects of the Atlantic Multidecadal Oscillation (AMO) on the amount of sea ice in spring in the Barents Sea (discussed most recently here), despite the fact that co-authors Aars and Andersen discuss the effects on polar bears due to changes in the state of the AMO on the website of the Norwegian Environmental Monitoring of Svalbard and Jan Mayen (MOSJ) ‚Äì see my previous discussions here and here.
There’s no doubt that sea ice conditions have been challenging for Barents Sea polar bears over the last few years due to the state of the AMO (a recurring phenomenon not related to global warming). Some bears have undoubtedly suffered as the bears described here (especially young, experienced bears, old bears, and bears that have made bad decisions and ended up in the wrong place at the wrong time). It seems, however, that a number of them have figured out a solution ‚Äì hang out to the east in Franz Josef Land in the North Kara Sea.
In the recent New Scientist article (10 June 2015: “Polar bear caught eating dolphins and freezing the leftovers”), the authors are quoted as being surprised by seeing dolphins in that area (see Fig. 3, location #1), and that the bear appeared to have been “caching” one of the dolphins for later consumption.
I’m surprised at the admission in the paper itself (see footnote 2 below) that the bear was feeding on ice that was only 20 cm thick (about 8‚Ä≥). That’s what sea ice folks call “thin ice.”
Figure 3. This is Fig. 3c from Aars et al. 2015. It shows sea ice conditions for April 2014 (when dolphin-feeding incident described took place, located at #1). #2 and #3 indicate regions where two bears were feeding on a dolphin carcass in July 2014. Bears were also seen feeding on dolphin carcasses at location #1 in July (see photo in Fig. 2 above) and in September. Click to enlarge.
The conclusion reached by Aars and colleagues about this incident? Here is their final sentence:
“An increase of white-beaked dolphins in areas where the sea ice shifts northward may, given the significant size of these animals, offer a new prey or carrion food source to bears in an environment where access to ringed seals and bearded seals may decline in future years.”
My conclusions: The pictures of thin bears were not necessary to tell these stories, if the facts of the anecdotes really had scientific merit. And since these two polar bear incidents were considered worthy of publication in scientific journals, then I expect these other recent media-worthy animal exploits will eventually be given the same treatment:
15 May 2014Beaver walks into Fairbanks hardware store [text account]
21 April 2015 Python climbs a tree with a curious technique in Thailand [picked up by the Daily Mail here]
10 May 2015A leopard climbs a tree with a zebra in the mouth
Footnote 1.Details from the underwater swim paper (Stirling and van Meurs):
This is the total sum of knowledge so far regarding polar bear dives:
“Stirling (1974) reported polar bears diving for 34, 40, 55, and a maximum of 72 s to feed on kelp. L√∏n√∏ (1970) reported polar bears diving to depths of 3‚Äì4 m to retrieve ”seaweed,” but no dive durations were given. Dyck and Romberg (2007) observed a subadult polar bear diving for fish in a river near its mouth and staying under water for between 3 and 29 s on a total of 17 dives. Over the past 10 years, we have observed both adult male and female polar bears in Svalbard, diving to feed on the remains of whales in a few meters of water, for untimed durations estimated to range between about 15 and 30 s.” [my bold]
From pg. 2:
“In mid-afternoon, August 19, 2014, one of us (RVM) observed a large adult male polar bear (Ursus maritimus) lying and looking around on a large flat annual ice floe several hundred meters across at 800 23.46_ N, 0130 13.09_ E, 20 km north of the north coast of Spitsbergen, the main island in the Svalbard Archipelago. The adult male bear was exceptionally thin (Fig. 1): body condition one out of five, the lowest category (Stirling et al. 2008)….the 3-min 10-s duration of this long underwater swim to stalk a bearded seal far exceeds anything previously reported.” [my bold]
Concluding paragraph (pg. 3):
“As the climate continues to warm and the amount of sea ice in the circumpolar Arctic continues to decline (Stroeve et al. 2012), access to seals on ice floes may become progressively more difficult owing to the presence of more water between floes and earlier seasonal disappearance of ice altogether. Although our observations demonstrate polar bears possess strong subsurface swimming and navigating abilities, previous observations confirm that the success rate of aquatic stalks of seals haul out on the ice surface where they are vulnerable to predation from the water is low (Stirling 1974). Therefore, we suggest that polar bears cannot evolve increased diving ability rapidly enough to compensate for greater difficulty of hunting seals because of the rapidly declining availability of sea ice during the open-water period resulting from climate warming.” [my bold]
Footnote 2. Details from the white-beaked dolphin feeding paper (Aars et al. 2015)
“At 16:37 on 23 April 2014, we encountered an adult male polar bear at the carcass of a white-beaked dolphin in Raudfjorden, at 79¬∞45’1‚Ä≥ and N 11¬∞56’28‚Ä≥. The carcass (dolphin A) was on the sea ice about 5 m from shore. The remains of a second dead white-beaked dolphin (dolphin B) were observed on land, about 50 m farther south and 5 m from the shore. Tracks from the bear showed he had also been feeding on dolphin B. About a metre from dolphin A was a hole about 60 by 75 cm in diameter, covered with ice slush (Fig. 1). The surrounding sea ice was about 20-cm thick. This was the only location in the fjord without solid ice, and appeared to be a breathing hole kept open by the dolphins. We therefore considered it likely that dolphin B was also taken by the bear at this hole. Little more than the spine, rib cage and skull of dolphin B remained when we found it. Dolphin A was more or less intact, as only the outer fat layer was removed from parts of the dorsal side and no meat was taken (Fig. 1).
Among six species of dolphins in the genus Lagenorhynchus, only white-beaked dolphin and Atlantic white-sided dolphin (L. acutus) have been observed in the waters of Svalbard. For white-beaked dolphins, Reeves et al. (1999) reported a range in body length of 154‚Äì278 cm and 55‚Äì309 kg among individuals measured. The white-sided dolphin has not been recorded in the more northern areas of the archipelago (Reeves et al. 1999). Earlier observations of white-beaked dolphins as far north as northern Spitsbergen have all been made in summer and autumn (June‚ÄìNovember; Fig. 2. Prior to this report, no recording of the species has been made in winter or spring this far north in Svalbard. The fjords and around the coast of northern Spitsbergen, an area normally covered by annual ice, were ice-free in winter 2013/14. It is likely that the presence of the dolphins in early spring was due to the lack of sea ice in the period prior to our observation. Ice maps indicated open water as late as 28 March, but dense ice in Raudfjorden from 4 April. In the period 17‚Äì18 April, strong northerly wind packed drift ice into the fjords. We speculate that this event led to the entrapment of white-beaked dolphins, including the two we found dead. Entrapment, and later suffocation, of white-beaked dolphins in areas with heavy pack ice has earlier been reported along the coast of Newfoundland (Sergeant & Fisher 1957; Hai et al. 1996).” [my bold]
Aars, J., Andersen, M., Breni√©re, A. and Blanc, S. 2015 in press. White-beaked dolphins trapped in the ice and eaten by polar bears. Polar Research. Open access http://www.polarresearch.net/index.php/polar/article/view/26612 Pdf here.
Polar bears (Ursus maritimus) depend on sea ice, where they hunt ice-associated seals. However, they are opportunistic predators and scavengers with a long list of known prey species. Here we report from a small fjord in Svalbard, Norwegian High Arctic, a sighting of an adult male polar bear preying on two white-beaked dolphins (Lagenorhynchus albirostris) on 23 April 2014. This is the first record of this species as polar bear prey. White-beaked dolphins are frequent visitors to Svalbard waters in summer, but have not previously been reported this far north in early spring. We suggest they were trapped in the ice after strong northerly winds the days before, and possibly killed when forced to surface for air at a small opening in the ice. The bear had consumed most parts of one dolphin. When observed he was in the process of covering the mostly intact second dolphin with snow. Such caching behaviour is generally considered untypical of polar bears. During the following ice-free summer and autumn, at least seven different white-beaked dolphin carcasses were observed in or near the same area. We suggest, based on the area and the degree to which these dolphins had decayed, that they were likely from the same pod and also suffered death due to entrapment in the ice in April. At least six different polar bears were seen scavenging on the carcasses.
Crockford, S.J. 2004. Animal Domestication and Vertebrate Speciation: A Paradigm for the Origin of Species. PhD dissertation, University of Victoria, B.C. (filed at the National Library under “Zoology)
Crockford, S.J. 2006.Rhythms of Life: Thyroid Hormone and the Origin of Species. Trafford, Victoria.
Crockford, S.J. 2009. Evolutionary roots of iodine and thyroid hormones in cell-cell signaling. Integrative and Comparative Biology49:155-166.
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. http://arctic.journalhosting.ucalgary.ca/arctic/index.php/arctic/article/view/4147 Open access. Pdf here.
Stirling, I. and van Meurs, R. 2015 in press. Longest recorded underwater dive by a polar bear. Polar Biologyhttp://link.springer.com/article/10.1007/s00300-015-1684-1
The maximum dive duration for a wild polar bear (Ursus maritimus) of any age is unknown, and opportunities to document long dives by undisturbed bears are rare. We describe the longest dive reported to date, by a wild undisturbed adult male polar bear. This dive was made during an aquatic stalk of three bearded seals (Erignathus barbatus) lying several meters from each other at the edge of an annual ice floe. The bear dove for a total duration of 3 min 10 s and swam 45‚Äì50 m without surfacing to breathe or to reorient itself to the locations of the seals. The duration of this dive may be approaching its maximum capability. Polar bears diverged from brown bears (Ursus arctos) about 4‚Äì500,000 years ago, which is recent in evolutionary terms. Thus, it is possible that the ability to hold its breath for so long may indicate the initial development of a significant adaptation for living and hunting in its marine environment. However, increased diving ability cannot evolve rapidly enough to compensate for the increasing difficulty of hunting seals because of the rapidly declining availability of sea ice during the open-water period resulting from climate warming.