@Shawn, interesting comments if indeed they were factual. I'll leave wolves out of this for now, since most of your comments were about grizzly bears. You state that you "see...grizzly in this area quite frequently" and I'm assuming you mean the Washington state area since that's where you're from. You must be a lucky guy indeed, as grizzly bears are listed as endangered in Washington and there is a resident population of just 20 individuals in the Cascades with the potential for a few more in the Selkirks in the northeast part of the state (a population estimated to be 40-50 bears in an area that is primarily in BC and Idaho). Don't believe me? Check this out: http://www.fws.gov/mountain-prairie/species/mammals/grizzly/index.htm I'd say that qualifies as not only "endangered," but "rare," too.

Contrary to your statements, grizzly bears do not respond to low population levels by having multiple young, their number of young is directly tied to their food supply. And that reproduction rate is based on the abundance of berries and salmon in August and September (so in Washington state where grizzlies exist, that means it's solely reliant on the abundance of berries -- after a poor berry year, female grizzlies will often not have any cubs). Grizzly bears do almost no hunting of mammals at this critical time of year in terms of reproduction (for the vast majority of mountain grizzlies, meat makes up less than 15% of their diet, with the majority of that meat being scavenged from wolf and cougar kills), and in fact, many mountain grizzlies rarely hunt mammals at all (that's not to say there aren't exceptions, but the vast majority of Selkirk and Cascade grizzlies don't hunt mammals beyond getting the odd calf or fawn in spring).

Your second-to-last statement is almost comical in how incorrect it is (it would be funny if the truth wasn't so sad). If grizzly bears did indeed bounce back "fairly quickly", then they wouldn't be an endangered species in the lower 48, they wouldn't be extirpated from the Canadian prairies, and they wouldn't be a threatened species in Alberta. They have one of the lowest reproductive rates of any mammal on earth: an average of two cubs every four years, with a survival rate of less than 50% for each of those two cubs.

As for the rest of your comments, yes, mountain/woodland caribou are indeed about as threatened as can be right now. There are five key factors that have been identified in this population collapse, one of which involves predator levels. Any guesses as to what the other four factors are? I'll give you a hint, it sounds kind of like 'humans' and 'roads' and 'development' and 'logging of old-growth habitat'.

Yes, I, too, was taken aback at the inaccuracy of your comments concering grizzlies, Shawn. John Marriott is correct, that they do not demonstrate compensatory reproduction as some species do when their populations reach low levels. Grizzlies are, in fact, the second slowest reproducing land mammal in North America, after musk ox. Grizzlies breed in spring but undergo delayed implantation. That means the embryos do not implant in the uterus until fall, and they only actually do implant if the female grizzly has been able to obtain enough food and put on enough fat reserves to support her through hibernation along with a pregnancy and then nursing cubs (born in the den in Jan/Feb). So reproductive rate is tied to food supply, especially fall food supply, as John has noted, rather than grizzly population levels.

You are lucky to be seeing grizzlies frequently - but are you sure you are seeing several different bears, or perhaps it is the same few bears repeatedly. Frequent sightings of bears does not necessarily mean they are present in high numbers unless you are able to determine that you are, indeed, seeing different individual bears. This is very doable as bears can be readily recognized as individuals in most cases.

Roberta Olenick, M.Sc.
zoologist
Vancouver, BC
www.neverspook.com

There still could be density dependent response to food availability, even if fluctuating food levels ultimately drive reproduction. Imagine 2 successive years with 2 and 4 tons available of berries. Clearly, there is twice as much available food the second year so the probability of reproducing successfully may be approximately double. Now imagine we have a population of 10 versus 20 bears. For the 10 bear population, there are roughly 0.2 and 0.4 tons of berries available per bear in year 1 and 2, respectively. For the 20 bear population, however, that number drops to 0.1 and 0.2 tons per bear in each year. So, by doubling the population we've effectively removed the benefit associated with the second "good" year, relative to the 10 bear population. The implications here are that, yes, reproduction will ultimately be driven by variation in food abundance (e.g. berry crops), but the actual rate of reproduction in any given year will still be partially a function of density.

If you believe food is a limiting factor, than density plays into the availability of food at the individual level, because per capita food resources are a function of food supply and the number of bears that are competing for that food supply. If you don't believe population density contributes to reproductive output, then you are explicitly assuming that food is unlimited, or there is no competition among individuals (i.e. if animals are strictly territorial, although even in that case territory size is usually negatively related to density). I could imagine a situation with, say, healthy salmon runs, where food would be super abundant and density a non-issue.



RI

I don't see grizzly in WA state. We don't really have an established population like you guys have up there. I travel to the Jasper/Banff areas yearly as do many of my photography friends (I even use your ebook on the parkway). I have some images from the last year of grizzlies on my website with many more on the hard drive. Most are different bears and I have photographed quite a few. Just 2 weeks ago on Saturday/Sunday I saw 7 grizzly in two days. Some days none, some days more. I know you live in this area and frequent it more often then I do. I never see caribou and rarely see moose anymore. Finding elk around Banff is much more tough than it use to be. Finding elk outside of a townsite is much more difficult. But you know all that already.

Which gets us to the definition of devils advocate. The definition: "a person who advocates an opposing or unpopular cause for the sake of argument or to expose it to a thorough examination." That's simply what I was doing. I know grizzly bear are endangered and there are human related issues and mortality issues. I felt the need to respond to give you an additional point of view. I have heard for years the grizzly are critically endangered in the area yet I see them regularly. It makes me wonder though as I am always surprised at how little I see other species such as deer, moose, caribou, etc., however.

So I'll continue to give you a different point of view (if it doesn't get personal and if you want?) and we can discuss the issues in the last 3 posts. Survival of cubs is density dependent. In fact, cub litter size is directly related to the density of the population in an area. I couldn't find any studies that stated initial litter size was related to population density but I did find some that stated that cub/litter survival is density dependent. Studies have shown that cubs survive well in relatively poor habitat that has a low density of dominant male bear. Nature reacts to changes in circumstances and population levels in their own species and the prey species. Food competition was brought up as well. That is yet another factor related to population density as another poster stated. If the density is low, more food is available for the bear so they have a higher chance of survival. Additionally, if the density is low, then more cubs survive predation from males in their own species. Grizzly are sexually mature in 3-6 years. They also have the ability to conceive when they still possess yearling cubs. Given this, it seems a grizzly bear population has the chance to bounce back from a low density given the right conditions. Yellowstone is a great example of this. The population has tripled there in the last 20 years. They stopped hunting them and gave them a good food supply. Human conflict has been high and has stayed constant over this time period and numerous bear are killed every year.
(http://www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_9/Aune_Mace_Carney_Vol_9.pdf)

So what are we talking about here? Stop human influenced mortality in grizzly bear. That seems like a good issue to spearhead. I just wish we focused as much on other species as we do the big sexy grizzly bear and wolf. We just allocated millions more on bear research down here...