Tag Archives: polar bears

Dangerous animals—bears

Truth is stranger than fiction. The most recent human fatality caused by a bear took place in the wilds of Ohio. Well, sort of the wilds—just outside of Cleveland.

It seems that a young man, Brent Kandra, was tending to a captive bear when the bear attacked and killed him. The bear was owned by a man who has kept exotic animals for display in the past, and the event has sparked debate about the wisdom, and regulation, of large exotic animals being kept by private individuals (Associate Press 2010).

Whether in a cage or in the wild, bears are undeniably dangerous animals. This is the next in our series exploring dangerous animals. Unlike most of the other species we have looked at whose danger to humans is really more imagined than real, bears do come in contact with humans with some regularity, sometimes with unfortunate consequences.

In North America there are three bear species: the black bear (Ursus americanus); the brown bear (Ursus acrtos); and the polar bear (Ursus maritimus).

Black bear

Black bear in the Canadian Rockies

Like so many common names, the name black bear is really not very good since the animals are often many other colors than black. The fur comes in shades of blond, black, brown, cinnamon, and gray. Interestingly, the bears tend to be black in the eastern forests, and more color variation is introduced as you survey the populations to the west, such that in California most of the bears are brown.

The black bear is the smallest of the bear species, and the most common, with the widest current distribution. They are found across Canada and south through New England into the Appalachian Mountains. There are populations in the Ozarks and in the southern states. In the west they can be found through the Pacific Northwest, and through the Rocky Mountains south into Mexico.

Black bears are generally shy and reclusive, but they can become accustom to humans, especially when they learn to associate human activity with food—through trash or handouts. In many backcountry areas where bears are common officials try to keep bears and people separate, but it is not always possible. Food storage is a great concern when camping. For example, while camping at one remote location in the Great Smoky Mountains campers were to hang their food from a cable over a stream.

Hanging a food pack over a stream in bear country

Hanging a food pack over a stream in bear country

Incorrectly hanging your bag could lead to a bad time.

Results of improperly hanging your food pack

Results of improperly hanging your food pack

Brown bears are similarly misnamed, although the color variation is less dramatic than their black bear cousins. There are several subspecies, or races, of brown bears that you may have heard of, dividing them into coastal Kodiak and inland grizzly populations, but they are all the same species.

Brown bear

Brown bear

While once much more wide-spread in their distribution, brown bears are limited today to Alaska and northwest Canada, with several populations in western United States parks such as Glacier and Yellowstone.

Encounters with polar bears are understandably rare given the remoteness of their habitat. (See why polar bears are sensitive to climate change.) Polar bears spend much of their time out on sea ice, hunting seals. However, unlike other bear encounters, most encounters between humans and polar bears seem to be motivated by predation—that is, the bear is looking to eat them.

Bear encounters do sometimes lead to injury or even fatalities, and as people spend more time in bear country, the chances for an encounter naturally go up. In encounters that go badly, injury is more common than fatality as bears most often attack when they feel threatened, and once the threat is over they tend to leave. Rarely do bears prey on humans as a food source, but it does happen. In general there are about 1.8 bear-caused fatalities per year (see Clark 2003, Gunther and Hoekstra 1998, Herrero and Fleck 1990, Herrero and Higgins 1999 for discussions).

Of the dangerous animals discussed in the series, bears are the ones that most people need to be aware of, and to think about when entering the woods. Do not do stupid things in bear country, like walk around imitating the sounds of animals to attract bears (yes, it has happened), improperly store your food, try to feed the bears, get too close while taking pictures, or tease or taunt the bears. Common sense and awareness that these majestic creatures are sharing our woods will ensure that your adventures will have only the typical amount of excitement.

Associate Press. 2010. Bear who mauled caretaker is put to death in Ohio. NPR. http://www.npr.org/templates/story/story.php?storyId=129321688.

Clark, D. 2003. Polar Bear – human interactions in Canadian National Parks, 1986-2000. Ursus 14(1):65-71.

Gunther, K. A., and H. E. Hoekstra. 1998. Bear-inflicted human injuries in Yellowstone National Park, 1970-1994. Ursus 10:377-384.

Herrero, S., and S. Fleck. 1990. Injury to people inflicted by Black, Grizzly or Polar Bears: recent trends and new insights. Bears: Their Biology and Management 8:25-32.

Herrero, S., and A. Higgins. 1999. Human injuries inflicted by bears in British Columbia: 1960 – 97. Ursus 11:209-218.

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Effects of climate change on polar bears

Polar bears (Ursus maritimus) are in the news again because of dire predictions for the coming decades on their population numbers. The effects of climate change have been predicted to impact the polar regions first and most dramatically according to most models, and indeed, it is at the poles where we are recording some of the most dramatic examples of climate change. Polar bears, being the largest of the living bear species, are charismatic and popular, and because of the likely impact that climate change will have on them they have become a poster species for the climate issue.

polar bear

Polar bear, Ursus maritimus.

In a recent interview bear expert Andrew Derocher predicted that one population of polar bears (western Hudson Bay) could see its numbers drop too low to be viable within three decades (Yale Environment 360 2010). We have explored polar bears and their populations in other posts. Here I want to examine why changes in sea ice and warmer periods are such a concern for polar bears.

Polar bears evolved relatively recently, diverging from an ancestral brown bear population about 150,000 years ago (Lindqvist et al. 2010). There is a unique population of brown bears that live on Admiralty, Baranof, and Chichagof (ABC) islands of southeastern Alaska’s Alexander Archipelago. This population, called the ABC bears, is the closest brown bear relatives of the polar bears—early members of this population split off to live full time on the sea ice, evolving into the modern polar bear species. Thus, polar bears are an example of rapid mammalian evolution, undergoing morphologic changes such as elongated snouts, overall size changes, furry padded feet, and color changes, as well as social and metabolic changes to adapt to the rhythms of the arctic seasons.

It is their complex adaptations to living on the rugged ice that makes them most susceptible to changes in that habitat. They use the ice as a platform for hunting seals, as a habitat for finding mates and mating, and for traveling long distances. As the ice breaks up earlier in the spring, and re-freezes later in the winter, several weeks of prime hunting time are taken away from the polar bears. Today, they are able to spend almost three weeks less on the ice hunting than they were able to several decades ago. This is critical because after the ice breaks up for the year, the bears must fast until the next season, and longer times of open water means long fasting periods.

This can be critical for a female bear that must gestate her young, birth them, and begin to nurse them to a size large enough that they can accompany her onto the ice for hunting the next season. So, she is expending a great deal of energy in contributing to the growth of her young while fasting. If she did not build enough fat reserves the year before to withstand this metabolic marathon, she and her offspring will not survive into the following year. A few additional weeks of having to fast can be the difference between life and death.

The intimate connection that polar bears have evolved with their arctic habitat means that they are finely tuned to changes in that world. And with the effects of climate change appearing in the arctic regions first, they are in fact akin to the “canary in the coal mine,” a harbinger of things to come.

References:

Lindqvist, C., S. C. Schuster, Y. Sun, S. L. Talbot, J. Qi, A. Ratan, L. P. Tomsho, L. Kasson, E. Zeyl, J. Aars, W. Miller, Ó. Ingólfsson, L. Bachmann, and Ø. Wiig. 2010. Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear. Proceeding of the National Academy of Sciences.

Yale Environment 360. 2010. For Hudson Bay polar bears, the end is already in sight. http://e360.yale.edu/content/feature.msp?id=2293.

Additional related posts:
Polar Bear Populations
Public Opinion and a Geologic Perspective on the Effects of Global Warming
IPCC

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Polar Bear populations

In an earlier post about the effects of climate change I made the point that there is a lack of intellectual honesty in the political climate change debate and a comment on that article provides a perfect example.

The commenter quoted an opinion piece by Gerald Warner. Mr. Warner cites population estimates by the International Union for Conservation of Nature (IUCN) Polar Bear Specialist Group that summarizes 19 sub-populations of bears. The summary of the population status is that 8 are declining, 3 are stable, 1 is increasing, and the other 7 are unknown. They currently estimate a world population of approximately 25,000 individuals. (See the footnote)

The most flagrant claim made by Mr. Warner is “the actual statistics” that since 1970 polar bear population has quintupled from 5,000 to an estimated 25,000 individuals.

A quick search revealed an article by Terence Jeffrey that gives at least partial references for “the actual statistics.” In his article, Jeffrey relates a history of scientific polar bear population estimates over the last five decades. An honest reading of his article shows that less was known early on and with increased efforts made to study polar bear numbers, we have better estimates now. Who would have guessed?

Quoting from Jeffrey, in 1965 world population of polar bears was estimated to be “5,000 to 8,000 animals,” “over 10,000” or “17,000 to 19,000 animals.” So, the apparent basis of “the actual statistics” of Mr. Warner comes from the extreme lowest estimate of bear populations in the 1960s to the estimate of the modern populations to get a quintupling. I am not sure in which universe this counts as “actual statistics.”

All of this clearly demonstrates one of the main points I made in the earlier story—the dishonest manipulation of scientific information for the express purpose of confounding the public is all too common in the political debate of climate. I am afraid it is only going to get worse, and my stated hope for intellectual honesty in politics is looking less likely all the time.

International Union for Conservation of Nature (IUCN) Polar Bear Specialist Group. http://pbsg.npolar.no/en/index.html

Jeffrey, T. 2008. The great polar bear population puzzle. http://www.humanevents.com/article.php?id=26627

Warner, G. 2010. Climategate: two more bricks fall out of the wall of deceit—rainforests and polar bears. http://blogs.telegraph.co.uk/news/geraldwarner/100030204/climategate-two-more-bricks-fall-out-of-the-ipcc-wall-of-deceit-rainforests-and-polar-bears/

Footnote: I wanted to examine the trends in the known population numbers a bit more as given by the IUCN, so here are some observations. Of the 19 sub-populations, they currently estimate the population of 14 and declare a status for 12 of them. By taking an average of the high and low population estimate for each of the given areas, the sum is 18,461.5 bears. This is the sum of the averages for all the estimated areas. There are 5 areas with un-estimated populations, so there are more bears in the world. Plus, the average may not be the best estimate for each area and is no doubt low for some areas and high for others. So, a total global estimate of 25,000 is reasonable enough.

If we sum the estimated populations by status (declining, increasing, stable, and unknown) we see that 52% of the known population is classed as declining; 2% are classed as increasing; 19% are classed as stable; and 28% have an unknown status.

So, over half the known population of polar bears are in declining populations. More than a quarter are unknown as to their population status. Almost 20% appear at this time to be stable in population numbers, and 2% seem to be increasing. I fail to see how anyone could construe these data to say that “polar bears appear to thrive on warming” (quote from Warner).

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