Ironically, just as I was about to remind readers that we are entering the peak period of polar bear births around the Arctic (see previous post, “December is polar bear nativity month”), I came across an article about breeding polar bears in captivity — getting the bears to give birth in zoos.
Hudson the polar bear cub is a zoo-born polar bear. He moved in January 2013 from the Toronto Zoo, where he was hand-raised after being rejected by his mother, to the Assiniboine Park Zoo, Winnipeg. The Assiniboine Park Zoo were also the recent recipients of a cub orphaned when its mother was shot after a polar bear attack in Churchill. Photo from Toronto Zoo.
The newspaper article I saw was all about how technically difficult the generation of polar bear cubs has been for the Toronto Zoo (Canada) but it was the premise for the breeding program itself that caught my attention: to save them from extinction.
The zoo is not waiting until the bears are down to the last few hundred (or even thousands) – no, the zoo is starting now, while polar bears are as plentiful as they have been in the last 40 years, to prepare for their demise.
Posted in Advocacy, Population
Tagged animal activists, Assiniboine Park Zoo, captive breeding, captivity, Hudson, polar bear, polar bear births, polar bear cubs, polar bears in winter, pregnancy, Stanley Park Zoo, Toronto Zoo
In a previous post (“Polar bears in winter: insights from Behouden Huys, 1596-1597”) I discussed the chronicle of Gerrit De Veer, who documented polar bear activity during the winter that William Barents’ crew spent on northern Novaya Zemlya more than 400 years ago. De Veer noted that the crew did not see or hear polar bears during the time that the sun was below the horizon, a period that did not correlate with the period of most intense storms and cold (De Veer 1609). However, the bears were active (and often causing trouble!) before and after that time.
De Veer’s account suggests the possibility that polar bears spend the darkest part of the winter curled up in a sheltered spot regardless of whether this is the coldest or stormiest period or not.
However, the experience of Barents and his men occurred over a single season and may not be representative of polar bear winter activity in general. As promised, in this post I’ll discuss the evidence collected by polar bear biologists and Inuit hunters relevant to the question of what polar bears do during the cold and dark of an Arctic winter.
Figure 1. Effective advertising and amusing though it may be, this image also depicts a true Arctic phenomenon – during the winter above the Arctic Circle, when the sun does not rise above the horizon, the moon is visible on its usual cycle. Moonlight and northern lights (aurora borealis) – plus a few hours of dusk at mid-day – provide relief from total darkness. See other images of an Arctic moon and northern lights here, here and here.
As a follow-up to my previous post on polar bears giving birth (December is polar bear nativity month) I thought I’d continue the generalized theme of “polar bears in winter.”
While we don’t really know for sure what non-pregnant polar bears do during the depth of the Arctic winter, we have bits of evidence – some from modern hunters and polar bear researchers but also from Arctic explorers. One explorer in particular comes to mind: William Barents [Willem Barentsz] of Holland, who attempted to reach China via the Arctic Northeast Passage in the late 16th century. On their third voyage (1596-1597), Barents and his crew were forced to spend the winter on the northern tip of Novaya Zemlya (latitude 760N, see Fig. 1) when their ship became trapped in the sea ice. Crew member Gerrit De Veer (1609) kept a journal account of the long, horrifying winter they spent on shore, in a shelter they built with materials salvaged from the ship. They called their winter home Behouden Huys (“the saved house”).
Figure 1. Location of Novaya Zemlya, in the Barents Sea. On the map at left (a), the black square marks the location of Behouden Huys, the over-winter home of William Barents and his crew (1596-97) on Novaya Zemlya (the “track of boats” noted marks the return journey of Barents in the summer of 1597). This is modified from Zeeberg et al. (2002:331). The map on the right is from Wikipedia, for perspective. click to enlarge.
An English translation of De Veer’s journal is now available online and it offers a fascinating glimpse of what it meant to live through that long dark winter under almost-constant fear of attack by polar bears. The Dutchmen were plagued by polar bears almost the entire time they were on Novaya Zemlya (see Fig. 2). De Veer’s notes on these encounters provide a unique perspective on polar bear activities over the Arctic winter – ironically, it is not the havoc the bears caused that provides the most important clue but rather, the timing of when they left Barents and his crew alone.
Figure 2. An engraving from De Veer’s journal conveys the struggle the crew faced in warding off polar bears during their winter stay at Novaya Zemlya. The bears not only stalked and attacked the crew, they got into the food stores on the ship.
Polar bears are generally out of sight at this time of year and will be for several more months. Pregnant females will be snug in maternity dens giving birth and all others will be out on the sea ice looking for seals to eat – if they can find them in the dark.
In most areas of the Arctic, December is when polar bear cubs are born, although in southern regions (like Western and Southern Hudson Bay), some may be born in late November and in the far, far north, a few may be born as late as early February.
The actual “date of birth” for polar bear cubs is often back-calculated from when they emerge with their mothers in the spring, because they are born well away from our prying eyes in the dark of the Arctic winter, deep with a snow or soil den dug for that purpose (see previous post here). So our knowledge of the “true” dates of birth in various regions is limited. We have some evidence from native Canadian hunters prior to 1968, when it was both legal and common practice in Canada for Inuit to hunt bears in their dens (Van de Velde et al. 2003), and from a few scientific research expeditions (Amstrup and Gardner 1994; Harington 1968; Ramsay and Stirling 1988; Derocher et al. 1992).
Polar bear cubs, like all bears, are born tiny and rather undeveloped (see Figs 1 and 2 below). Their eyes do not open until about one month after birth. By the time they are 63 days old (two long months after birth, see Toronto Zoo photo here ), their eyes are wide open and they are well furred. Keep in mind, for perspective, that domestic dogs are born after a 63 day gestation period and their eyes open at about 12 days.