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Ken M
Bears, like most animals, exist in a complex ecosystem, and they require predation of some sort to keep their numbers in check, so as to maintain a healthy population.
This is true for ungulates with a much different social makeup. Overabundance of prey species can certainly damage habitat and limit biodiversity. Still, I prefer pointy teeth be allowed to do the bulk of that job where possible, as predatory species don't tend to weed out the larger and healthier individuals from a population as human predators do. I've not seen evidence that California black bears are negatively impacting their environment? Modern "wildlife management" needs an overhaul, it's too focused on numbers, little on social dynamics.
Gray wolves, for instance, are a self-regulating apex predator (http://www.aphis.usda.gov/wildlife_damage/nwrc/publications/11pubs/breck113.pdf). Rarely a competitor may manage to kill a wolf, whether an individual is ambushed by a puma, or an inexperienced pup-of-the-year is rushed down by a grizzly claiming a moose kill as his own. Rarely.
When human-caused mortality is mostly taken out of the equation we find that intraspecific mortality takes the lead. Wolves are a highly territorial, family oriented species. They breed once a year in the winter, and generally the alphas (mom and pop) are the only ones to do so. It's enforced. The family-unit or pack fiercely defends its territory (refrigerator\nursery) from other wolves; the size of which is inversely proportional to prey abundance. Even before human thrill killers began taking a toll on the Yellowstone National Park population, the average wolf lifespan was 4 years old. Often enough, territorial breaches lead to grave injury or death. This occurs even when wolf densities are low and prey densities are high. However, declining access to food is a primary reason for increases in intraspecific strife. Gray wolves are not particularly efficient predators as is... only 1 out of 10 hunts are successful. They must claim a wide area to be able to track down enough young, old, or otherwise infirm ungulates to feed their families and survive.
“Wolves are not perfect predators. They lack physical characteristics to kill prey swiftly, so they rely on athletic ability and endurance, which diminishes with age. They’re like 100-meter sprinters. They need to be in top condition to perform.” - Dan MacNulty, a postdoctoral researcher in the College of Biological Sciences’ Department of Ecology, Evolution and Behavior.
Ungulates fight back as all life that means to continue living does. From bison to even deer, these are all powerful animals. Examination of numerous wolf remains have revealed many a traumatic injury from hoofed blows. From cracked ribs to skull fractures. In a 1984 study, Phillips found a frequency of 22% cranial injuries from such kicks. When wolves survive these and are in the process of healing, they are completely dependent on family.
Meanwhile, ungulates are also doing their best to avoid wolves. They are even in tune to wolf territories and will spend time in buffers between them for added protection. Desperation would be the needed motivator for wolves to cross into these zones.
The Yellowstone population post-reintroduction has never grown beyond 175 wolves. The population swiftly grew, decelerated and declined. This, due to disease such as mange (which was actually once introduced into the wilds of North America to specifically eradicate wolves), intraspecific mortality, and in response to a declining prey base ("At Yellowstone, elk numbers have declined on the northern range, but those declines have been driven predominantly by hunter harvest and severe weather events." -
http://www.jstor.org/discover/10.2307/3548695 -
http://www.jstor.org/discover/10.2307/3785031). Then federal protections were lifted outside of the park and the chance of studying another natural equilibrium being reached has been muddled, at the very least. There are few unmanaged wolf populations to observe. Isle Royale is another one, but here in the 55th year of that predator-prey study the wolves are about to blink out of existence, not their prey the moose. Isolation and inbreeding has taken its toll.
Black bears are not wolves. Although, they are also not deer. Their home ranges do broadly overlap between the sexes, sometimes amongst mature individuals of the same sex. In these cases, dominance hierarchies are maintained rather than territories. Black bears are solitary and practice avoidance outside of breeding season or a site offering an abundance of food. In regions of low habitat productivity territory is mutually exclusive amongst mature individuals of the same sex, with females tending to be the most territorial. However, in the fall, boundaries may dissolve as bears seek out a higher caloric intake. Similar to wolves and puma, subadults will disperse and experience higher rates of mortality during the dangerous process of finding and establishing one's own territory. Females may breed every other year and keep their cubs close for 1 1/2 years. How much might these and other intrinsic behaviors limit their density? We do know that habitat quality and quantity plays a large role. Black bears are listed by the CDFW as an indicator species for oak woodlands.
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Ken M
Unfortunately, the bear population is exploding, having doubled in Ca in the last 20 years or so. The major natural predator of the California Black Bear, was the Grizzly Bear, no longer found here.
Up until 1948 there were no restrictions on when people could kill black bears, nor restrictions on the amount of black bears one could kill, nor even the method of killing them. They were historically viewed as unwanted pests by Euro-American settlers, a theme. It wasn't until 1957 that CDFW started issuing tags and attempting to determine how many of these bears were being killed. Still, in some years non-reporting was as high as 65%, and poaching in some regions was exceeding recruitment. A couple counties continued to allow year round killing until 1961. In 1972 they decided to prohibit the slaughter of mothers and cubs. How kind. ...So in 1982 they finally determined a population estimate of 10,000-15,000 black bears. What might their natural historic levels have been before this all but certain low point? It is no wonder that in the past 25 years we have seen an increase with or without the presence of grizzly bears, whose return I would welcome. An increase and another decline:
"In the new “2011 California Bear Take Report” issued Oct. 1 (2012) by the California Department of Fish and Game, the population of black bears was 5,000 fewer than the department estimated for 2010 and nearly 10,000 fewer since 2009—a combined reduction of approximately 25 percent of the population in just the past two years. ... The report estimates that California’s black bear population is now approximately 26,390 (plus or minus 6,889), down from an estimated 31,432 (plus or minus 7,991) last year and approximately 36,000 (confidence unknown) the previous year. " -
http://www.humanesociety.org/news/press_releases/2012/10/california-black-bear-population-decline-100212.htmlWhilst their numbers have increased as range has expanded (including via transplant from Yosemite NP to the San Gabriel and San Bernardino mountains), what about black bear density? Here is the most recent data the CDFW offers for the region:
"The Sierra Nevada subpopulation encompasses the Sierra Floristic province (Jepson 1993) and extends from Plumas County south to Kern County. Black bears inhabit the entire region. Forty percent of the statewide black bear population inhabits the Sierra Nevada Mountains. Bear Populations are less dense in the Sierra with between 0.5 and 1.0 bears per square mile (Grenfell and Brody 1983, Koch 1983, Sitton 1982). Over two-thirds of the bear habitat is administered by the U.S. Forest Service and two large National Parks are located within this region." -
http://www.dfg.ca.gov/wildlife/hunting/bear/population.htmlGrizzly bears don't seem to be major predators of black bears, regardless:
"Both grizzly and black bears live in Yellowstone National Park. In this and other areas where grizzly bears and black bears are sympatric (share habitat), temporal isolation and behavioral differences tend to reduce direct competition between the two species." -
http://www.greateryellowstonescience.org/files/pdf/ys5-gunther.pdfIn the lower 48 states, Glacier National Park is home to the largest population of grizzlies. It also has a rather healthy population of black bears:
"Preliminary results suggest that the density of GNP’s black bear population was equal to or greater than other interior populations sympatric with grizzlies, despite the high density of grizzlies. This project represents the first estimate of black bear density for this area, and demonstrates the efficiency of multi–species projects to inform management." -
http://scholarworks.montana.edu/xmlui/handle/1/461Quote
Ken M
Extending hunting protections would probably be a bad thing, inasmuch as it would increase population pressures, and result in a less healthy general population.
I don't think CDFW issues tags to "control" the population at all. Note this question and answer:
"
Effects of hunting bears and bobcats without dogsGovernor Brown signed SB 1221 on Sept. 26, 2012 to repeal authorization for the use of dogs to pursue bears and bobcats. The DFG has received a large number of questions from the public regarding what effects it may cause. Below are some of those frequently asked Q&As:
What will be the effect on the bear population?The DFG does not believe this law will negatively affect the State’s black bear population. Any increase or decrease in the overall bear population will likely be reflective of bear habitat, since habitat quantity and quality have more impact on the bear population than current hunting effort." -
http://californiaoutdoorsqas.com/page/4/And what of the ecological niche of grizzlies? Ursus arctos californicus is tragically gone, never to be again. What if their next closest kin are never allowed to return, either? Might black bears fulfill a similar enough niche to be better than a bear-shaped hole in the tapestry?
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Ken M
It is easy in complex systems to create unintended consequences. For example, the protections for mountain lions has led to the near-extinction of the Big Horn Sheep, that the increased lion population targets ever higher.
What led to the near extinction of Sierra Nevada bighorn sheep was unregulated commercial hunting and disease spread by domestic sheep.
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http://www.nps.gov/yose/naturescience/sheep.htmOnly because of this, these dwindling herds are having trouble with *natural levels* of predation. Indiscriminate killing of puma elsewhere in the state, or even regionally, would not aid the bighorn.
Loss of Predators in Northern Hemisphere Affecting Ecosystem Health -
http://www.sciencedaily.com/releases/2012/04/120409133924.htmSadly and hypocritically, there is much anti-predator sentiment in the world. California only has two large predators left, and one of them eats mostly vegetation. May wolf recover soon.
If we go back far enough, we would find Naegele's giant jaguar, sabertooth cat, scimitar cat, American cheetah (possibly), Jaguar, California grizzly bear, giant short-faced bear, gray wolf, and dire wolf all living within the same period alongside puma and black bear. I'm certain the competition was fiercer then. It's interesting to consider that some living apex predator species actually co-evolved as mesopredators for most of their existence, and that some of their behaviors may be refined reflections of this era. They survived through all of that until a certain population of Homo sapiens came along.
Edited 1 time(s). Last edit at 05/14/2013 03:20PM by Kayucian.