||80˚39.6' N / 017˚23.5' E
||wind from SE, Force 3
We woke up this morning exactly where one should be on a “Polar Bear Special”: in the drifting pack ice near the Seven Islands (Sjuøyane), with more than 6-8/8 ice cover and pretty much unlimited visibility.
Actually, it is not so much just that the bears “like” that specific amount of ice cover but rather that their primary prey, the ringed seals do. Aerial surveys of ringed seals done in many parts of the circumpolar Arctic have shown that the seals show the highest preference for sea ice cover in the range of 6/8 to 8/8, probably because, in turn, such habitat has substantial populations of arctic cod living beneath the ice itself. Although you can find some bears in almost any kind of hab
itat in Svalbard at one time or another, the very best places to search are in areas of high ice cover over the biologically productive continental shelf, or in the bays and fiords of the archipelago that are still covered by the fast ice that formed in winter, precisely because those are the favoured habitats of the ringed seals and their availability is greatest.
By shortly after breakfast, three bears had already been spotted and we headed for the nearest, which turned out to be a 3-4 year old subadult male who came right up beside the ship. He was very curious and went back and forth on the ice by the bow while investigating us at close range until he concluded we were not very interesting, i.e. there was nothing to eat so he headed away across the ice. Our collective appreciation was underlined by the deafening roar of camera shutters! The next bear was a large fat adult male which, like the majority of older males, was not frightened of the ship but simply did not wish to be nearby. Thus, he simply kept steadily walking away from us so we let him continue in peace, undisturbed.
A little later, we watched another bear eating a small ringed seal which, judging from its size, was a newly weaned pup. This was an interesting dietary example because it is the big flush of young ringed seals born in early April that provides the most important single food resource for the bears. They begin to accumulate fat from their mother’s milk within days. By the time they are weaned at about 6-7 weeks of age, they weigh 20-25 kg, are 50% fat, and not very experienced with predators. From the time they are weaned, to when open water predominates in early summer and the seals become pelagic and thus inaccessible, the bears must accumulate about 2/3 of the energy they will need for the entire year. Thus, staying focused on seal hunting is critical. The continued effort necessary for the population of polar bears to survive is underscored by the realization that each bear in the population requires an average of about 43 ringed seals (big bears more and smaller bears less) or “ringed seal equivalents” each year (e.g., one bearded seal might be the equivalent of 2-5 ringed seals, depending on size). Then consider that the Svalbard population of polar bears, presently estimated to number about 2,700, requires roughly 116,100 ringed seals (or ringed seal equivalents) per year and you realize how critical and demanding hunting seals is for polar bears.
Through the day, we also had demonstrations of different hunting techniques used by the bears to hunt ringed seals. The most common methods were variations on the basic theme of “still-hunting” which means remaining motionless for long periods of time by a crack in the ice or a breathing hole, and hoping to catch an unsuspecting seal when it surfaces. The breathing holes in large floes of annual ice were self-maintained by the seals themselves through the winter so they could breathe when the water was completely covered by ice. However, by this time of year, most of the snow that covered and hid the breathing hole during winter has melted, exposing the water at the surface. At this time of year, “still-hunting” may be done by lying, sitting, or standing motionless, so as to not transmit any noise into the water below that might frighten a seal away when it returns to breathe. Energetically, still-hunting is probably most biologically important because the bear is not unnecessarily wasting energy while waiting for the packets of energy (seals) to come to it. Even so, the success rate of lying still hunts (the most common form) documented in one study was only 1.5% of 223 attempts observed. The average length of a lying still-hunt undertaken by an adult male was about 68 minutes compared with 37 and 41 minutes for females accompanied by cubs of the year or yearlings respectively.
The most exciting hunting method to watch though is the “walking stalk”, in which a bear tries to sneak up on a ringed seal hauled out to bask on the surface of the ice. When doing the bear walks slowly and steadily toward the seal, and holds its head low, likely to make its black nose and eyes less noticeable. Again, the actual success rate is low, only 1.8% of 65 hunts in one study.
Although we didn’t see any walking stalks of ringed seals today, we did get to watch a spectacular tension-filled stalk by an adult male bear on a large bearded seal. The bear had been walking away from the ship when it spied the bearded seal hauled out at the edge of a lead a hundred or so meters off to one side. The bear instantly froze so as not to draw attention to itself while it carefully determined its hunting plan which would combine a gripping and precisely executed walking stalk, followed by slipping into the water and swimming both on the surface and underwater for the last few metres to the seal (an “aquatic stalk”). At the last instant, the bear tried to exit the water and seize the seal by the head in a single motion but there was too much rotten ice near the seal which would not support the bear. In a flash, the bearded seal rolled and spun itself off the ice edge and into the water and, by doing so, successfully escaped an incredibly close brush with death. In what might have appeared to be a somewhat philosophical response to missing the seal, the bear floated in the water looking about briefly, after which it simply climbed back out onto the ice to resume his relentless search for the next seal. Although there are no good statistics on the success of aquatic stalks on bearded seals, the success rate appears to be low although, when successful, the rewards are bigger because bearded seals are so much larger than ringed seals. The large size of bearded seals, at 250-350 kg, means that most can only be successfully hunted by adult male polar bears, while the much smaller 35-45 kg ringed seal can be killed by polar bears of all ages.
Today we also identified something not often seen or recognized in the natural behaviour of polar bears – the final stages of breakup of a breeding pair of adults. Polar bears have induced ovulation, which means that usually a week or more of intense behavioural interactions between the male and female are required before their normally antagonistic behaviour has become sufficiently subdued to make it possible for them to mate. Since normally, a female would be terrified of an adult male and avoid him if at all possible, a great deal of behavioural change is required before the female is sufficiently trusting of an adult male to allow him to mate. Once ready, they mate several times a day for several days in a row. By the time that is finished, there is then a spell of slow behaviour with only a small amount of passive and gentle interactions while the bears go through the psychological process of separating while still not interacting in any way that might be potentially harmful to the other. Because of long-term studies done of the complete pattern of breeding behaviour of polar bears in Canada, it was possible to recognize the behavioural stage the bears were in. This was also an important bit of documentation for the scientific record because, although most breeding of polar bears takes place in April and the first half of May, recent analyses of behavioural observations made in Svalbard in recent years has confirmed that a small amount of mating continues here until the end of June or possibly early July.
All in all, by the end of today we have seen 20 polar bears on this trip, several of which have provided both excellent viewing of hunting and other behaviours at a distance as well as several close opportunities for photography – a true Polar Bear Special!