This paper was written as part of the 2002 Alaska Ocean Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.
The Critical Status of the Kenai Brown Bear
Tourists visit Alaska with visions of postcard-perfect wildlife and scenery dancing through their heads. They expect to see brown bears plucking salmon out of the beautiful and majestic Kenai River. The problem with this vision is the possible decline of brown bears on the Kenai Peninsula in the not-to-distant future.
Alaska contains 70% of the North American brown bears (Loker, 2000), but the bear population on the Kenai Peninsula bay be in peril. Since bears have a very low reproductive rate, the revival of their population would take a very long time. Bears are killed through hunting and Defense of Life and Property (DLP), resulting from forced human contact due to housing developments and road construction.
During the summer, the majority of the brown bear's diet consists of salmon. When the bears remove the salmon from the river, the deposited carcasses transport Nitrogen-15 (N15) into the forest (Hilderbrand et al., 1999). N15 helps plants grow, and is only of marine origin. Bears are a major transport mechanism and without them, the amount of N15 along the Kenai Peninsula streams and rivers would be dramatically lacking.
In order to stabilize the future population of the Kenai brown bear, we propose further research programs and education for the public. The only way we can help the Kenai brown bears is by finding out as much as possible so we know exactly what we should do. Also be educating the public we can further help prevent DLP kills. We can do this through public meetings and outreach programs. By doing this we can keep the brown bear population up, keep the Kenai Peninsula postcard-perfect, and avoid the economic downturn that will occur if they become placed on the Endangered Species List.
A mother brown bear (Ursus arctos) and her two cubs are standing in a forest area along the Kenai River, Alaska (Figures 1 & 2). Salmon runs had been poor that year and a new housing development had forced the bears out of their normal feeding area, and now they are searching for food. From over a mile away, the smell of cooked ham makes its way along the forest floor. The bears' noses pick up the delicious scent and follow it until they come upon a house where a family is eating their ham dinner in their backyard. The children scream with delight at the sight of the bears, and their mom quickly pulls them into the house as their dad runs for the gun. The mother bear moves toward the picnic table where the ham lays forgotten. The sudden sound of a gunshot rings out through the air. The large bear falls to the ground and dies quickly. The frightened cubs run to the safety of the trees where they will be unable to fend for themselves, and so end the lives of three Kenai Peninsula brown bears.
Variations of this story are being played out year after year on the Kenai Peninsula, in Alaska. As the human population rises, the Kenai Peninsula brown bear "is vulnerable to a significant decline due to low numbers, restricted distribution, dependence on limited habitat resources, or sensitivity to environment disturbance" (Loker, 2000). How and why is the pressure on brown bears important to our environment? After all, brown bears do represent a real threat to humans, and in most parts of the United States brown bears have been eliminated because of human/bear encounters.
Recent work on the complexity of ecosystems provides some answers to this question. For example, Tom Reimchen, ("A Coastal Trinity of Ancient Forests, Big Bears, and Wild Salmon", 1999) studying bears in the Queen Charlotte Islands found that each bear examined consumed about 720 salmon and transferred the remains up to one hundred meters from the small stream he studied. He estimated that the bears ate only one half the salmon and the remaining parts decomposed or were eaten by other animals. Each bear was estimated to haul 1600 kilograms into the forest. In total, he estimated 60 million kilograms of salmon per year are hauled into the forest ecosystems of British Columbia. By measuring the level of nitrogen-15, derived from the sea, researchers estimated that one half the nitrogen in trees within 100 meters from the salmon stream was of marine origin. Thus, bears and salmon provide a bi-directional flow of nutrients from forest to streams and into oceans and then back to the forest via salmon transport. Bears are a primary mechanism for this salmon transport away from the stream to the forest floor ("Pacific Salmon Carcasses", Fishery Management/Habitat, October, 1999). We are going to explore the life history and interactions of the Kenai Peninsula brown bear and salmon populations, to evaluate the importance of bears in the transport of nutrients on the Kenai Peninsula, Alaska, and to make recommendations to keep bear populations healthy.
Life History of Bears
Alaska is home to over 98% of the brown bears in the United States, and 70% of the brown bears in North America (Loker, 2000). The brown bear population on the Kenai Peninsula used to be two or three times its present level, but has dropped around the turn of the century due to trappers, loggers, and hunters. During the 1900's, the numbers stayed around the mid-two hundreds. The population grew to about 300 in the last two decades with managed hunting seasons and higher salmon escapements (Ted Spraker, pers. Comm..).
Brown bears have the lowest reproductive rate of any land mammal in North America, which makes recovery a long process. Litters range from one to four cubs, but the most common litter consists of two. The cubs remain with the mother for two to five years depending on location and food scarcity. Normally, the cubs leave at three and a half years of age, and the female will then mate again within the next two to four years. Bears usually mate between May and July, and usually do not spend more than a week with a single mate. Males may mate with several females during one mating season. Cubs are born the following January and February and will become sexually mature between five and seven years of age, and reproduce until they are approximately 25. The average life span of a bear is between 22 to 26 years old, but has been know to stretch as long as 35 in the wild ("Brown Bear", 2001).
They emerge from their dens in April in search of food and they feed on vegetation, carrion, and young moose or caribou. On average, during this time period, about 72% of their mass-increase is in lean meat. During July, most bears spend their time along the salmon streams feeding on fish until late fall, when salmon runs have decreased. Up to 81% of the bears' mass increase is due to fat intake (Hilderbrand, 1999). These lipid reserves are needed to get ready for hibernation and reproduction.
The males weigh between 500 and 900 pounds. The females can grow to reach about three-quarters of the males' size. Because of dominance and size, larger bears usually have more access to salmon deposits along streams and rivers ("Brown Bear", 2001).
The habitat of the brown bear on the Kenai Peninsula takes up roughly 4500 square miles, or about half of the peninsula, but has been significantly reduced to 30% due to encroachment of human activity ("Brown Bear", 2001). A large portion of the Kenai Peninsula is in both the Kenai Wildlife Refuge and Chugach National Forest. This would be expected to protect the bears to some extent, but encounters between humans and bears still occur at salmon spawning grounds. Most of the bears live in the highest regions of the peninsula during the summer months. They reside above the timberline until July and make their way down to salmon streams prior to hibernation ("Bear Viewing on the Kenai", 1996). Radio tagging studies by the Alaska Department of Fish and Game (ADF&G) indicated that brown bears tend to avoid residential areas unless attracted by smells and have home ranges of approximately 10 square miles (figures 3 & 4).
Because of urban areas encroaching on the brown bear habitat, the bears have been forced into a closer contact with humans and their property, resulting in a higher level of mortalities due to defense of life and property (DLP). Roughly one hundred bears have been killed on the Kenai Peninsula due to DLP's since statehood. In the 1990"s, the average number of bears killed increased from less than two and a half bears per year to over six bears per year (chart 1) (Loker, 2000). Because of the decline, bear hunting has been prohibited in order to stabilize the population.
Life History of Salmon
There are five main species of salmon of the genus Oncorhynchus and they include the sockeye (O. nerka), Chinook (O. tshawytscha), coho (O. kisutch), pink (O. gorbuscher), and chum (O. keta) salmon. Salmon life history patterns follow a basic theme that are typically characterized by accessible cool, clear water with abundant woody debris or other forms of cover, relatively clean spawning gravels, foods, and balanced population of predators (Pacific Salmon and Wildlife, 2002). In fresh water environment of the Pacific Northwest and Alaska – particularly estuaries and coastal upwelling zones – Pacific salmon evolved an ocean-feeding phase in their life cycle. A typical anadromous salmon life cycle has five main stages (Fig. 5): spawning and egg incubation, freshwater rearing seaweed migration, ocean rearing and they then return to freshwater areas to spawn and decompose, returning nutrients into the ecosystem. The stages of development may have much different timing, depending on the species and location. Salmon all die after spawning, a life history strategy known as semelparity. This life history strategy has evolved because of the increased amounts of nutrients and energy in the marine environment, which is then available for production and juvenile survival. Salmon on the Kenai Peninsula all spawn between early summer and February. After approximately two to four months of incubation, salmon fry swim up through the gravel and emerge into the stream. Actual emergence time will depend on the type of salmon. For example, Chinooks emerge in late winter or early spring, while coho emerge in middle to late spring. Emerging fry can vary widely in size, ranging from 20mm to 40mm. Upon emergence, fry actively feed on a variety of aquatic insects, and for those that stay in freshwater for long periods of time, mainly coho, the proportion of terrestrial food items in their diet may increase to over 30%. After completing their freshwater stage, the young become smolt and they head out into the ocean environment. This means they must make osmoregulatory adjustments, which prepare them to inter saltwater. Chum and pink salmon go directly to sea during the first spring or summer of their life. Chinook, coho and sockeye may stay in freshwater for one or two years before smolting. Depending on the species, salmon use the ocean as a feeding ground in different ways. Some stay close to the continent of North America—i.e. Chinook and coho, while other salmon i.e. sockeye, chum, and pink, forage farther out into the Pacific Ocean ("Pacific Salmon and Wildlife").
The populations of salmon on the Kenai Peninsula are healthy, and numbers of salmon entering the streams of the peninsula have increases significantly since statehood. In 1968, 68,000 sockeye salmon entered the Kenai River (Table 1). However, management actions by ADF&G have raised this number by several hundred thousand salmon fish so that at present, the minimum escapement goal for the Kenai River is 500,000 salmon. Similar patterns are evident for all species of salmon utilizing streams on the Kenai Peninsula (Tarbox, pers. Comm..).
The average size of salmon on the Kenai Peninsula varies by species. Average weight by species are listed in Table 2. The most abundant species of salmon on the Kenai Peninsula is the sockeye salmon but every few years, pink salmon can make up a significant part of the return. The availability of salmon to bears and other animals can be just as important as the abundance. For example, in many small tributary streams of the Kenai River, Chinook salmon are more available than sockeye salmon, which tend to spawn mostly in the mainstream of the Kenai River. Slikok Creek, has a few hundred coho and chinook salmon that spawn in the stream, but no sockeye salmon (Tarbox, pers. Comm..).
Ecosystem Complexity and Bears
It is known that salmon are an important component of salmon-spawning streams' ecological processes. For example, (Bilby et al., 1995) summarized the importance of salmon to in stream productivity. He noted that nutrients accumulated in biomass of salmon while in the ocean are transported back to freshwater spawning sites. He further observed in his study area that 30% of nitrogen in juvenile coho was of marine origin. In comparison, marine derived carbon contributed 34% of the carbon in juvenile coho. Piorkowski, (1995) studied the effects of salmon carcasses on south-central Alaskan streams productivity. He observed that macroinvertebrate communities in streams receiving runs of salmon were more taxonomically diverse, and relative abundance was increased for some feeding groups. He concluded that his investigation supported the hypothesis that salmon carcasses are important in structuring aquatic food webs.
Recently, scientific interest in the importance of salmon carcasses to terrestrial/riparian ecosystems adjacent to spawning streams has increased. The mechanisms of transport of carcasses to the forest floor and incorporation of nutrients into plants and animals are of particular interest. Fortunately, nitrogen has a stable isotope (Nitrogen 15) that is rarely found in the atmosphere and is formed predominately in the marine environment (Hilderbrand, 1996). It differs slightly from the more common isotope of N14. The difference between them is that N15 is slightly heavier than N14, carrying an extra neutron and having an atomic mass of 15,000 compared to 14.0031. Therefore, by examining N15 in the terrestrial environment, one can assess the importance of marine derived nutrients in the system and the mechanisms of transport.
As noted earlier, (Reimchen, 1999) was one of the first to recognize the importance of bears in the transport of salmon carcasses to the adjacent forest floor. When brown bears distribute salmon carcasses away from the streams, nutrients like N15 are dispensed from the salmon into the reparian zone, which is normally lacking nitrogen. The nitrogen then help the plants grow more dense and abundant. On the Kenai Peninsula, (Hilderbrand, 1996) while studying coastal brown bears, concluded that the availability of meat during late summer and fall had a major influence on habitat quality for brown bears at both the individual level and the population level. In habitats with abundant food resources, age at first reproduction and intervals between litters are reduced and litter size is increased. Hilderbrand et al. (1999b) also reported that the relative input of salmon-derived nitrogen from brown bear urination, defecation, and transport and decay of salmon carcasses could potentially be 10-25% of the total nitrogen budget of riparian spruce forest. He further noted that bears had distributed roughly 83% of the salmon-derived nitrogen occurring in spruce needles with 500 meters of the streams. Bilby et al. (1996) estimated that 17.5% of total N in vegetation along salmon streams was derived from salmon.
In addition to direct nutrient contributions, bears make salmon biomass available to other animals that reside along salmon streams. As noted, only about half of the salmon captured by bears is actually consumed. The remainder is left for decomposition, and is consumed by other animals. It has been estimated that salmon provide sustenance for about 138 species such as insects or scavenger birds. Mammals such as bobcats, otters, and raccoons benefit from the food supply along the salmon streams (Table 3).
In addition to the important role bears play in the ecosystem, they are a benefit to humans as well. They're one of the most prized animals to see even among the people of Alaska. Stopped among the Seward Highway, you can sometimes be lucky enough to witness one of these majestic creatures living in it's realm. These many brown bears sighting speak to the wilderness of the area. The brown bear is sort of a national monument in the state of Alaska, perhaps like the elephant is to Africa or the kangaroo is the Australia.
However, on the other side of the coin are the problems of bear in our communities. Biologists have blamed problems of foraging brown bears around local homes to careless handling of garbage and food and compost piles. Around these sites, there are too many campsites, bait shops, fishing areas, and exposed garbage piles to keep bears away. It we deliberate on the situation, we realize that the nuisance of bears is inevitable and will probably never end. Plus, there are too many people who think feeding a bear is just a friendly gesture, when in fact it is giving the bear a death penalty because many camps shoot the bears after they hang around a campsite too long waiting for more food. Obviously, this problem is caused by people, but the bears face the consequence.
Bear baiting is also potentially dangerous to anyone encountering a bear at a bait station. For example, recently on the Kenai National Wildlife Refuge, 22 known brown bears were reported visiting bear sites during just one summer. Statewide in 1993, nearly 550 bear cubs, both brown and black, and almost 300 adult brown bears were seen feeding at bear stations and were not shot. These bears then learned to associate human and garbage smells with food, creating potential future danger for human life and property. It is only a matter of time before someone is injured after stumbling on a bait station while a brown bear is present.
There is also a problem with rapid population growth among the brown bears on the Kenai Peninsula. Too many bears in the area can result in a salmon decline, an overflow of tourists, and a shortage of land space for the bears.
Increasing land use infringes on the bear population by using up the bear's natural habitat. Activities such as resource extraction and timber management are not necessarily damaging to bear, as long as measures are taking to avoid impacts on the bears and their habitat. (i.e. protection of fish streams). If the bears have no where to go, then they are likely to invade land used by housing developments, resulting in DLP kills.
The public needs to be continually informed about the problem with bears and their link to our economy and land. They must be educated through public meetings and outreach programs; this will help to prevent negative outcomes in human-bear encounters, and encourage their assistance in the preservation of the brown bear population.
The Conservation Strategy, which was instigated by the ADF&G, is basically a summary of all we are trying to do. They surveyed residents of the Kenai Peninsula and Anchorage and set up meetings to provide the public with information about their strategy.
Perhaps the main reason that the Kenai bear population requires such close observation and major effort is what may occur if their numbers become too low. The ecological requirements of the brown bear may force them to be put on the endangered species lest. The Endangered Species Act will strap major limitations on the local economy and future development. The needs of the Kenai Brown Bear will come first and our economy will come second.
What Is Needed
We propose a three-pronged approach to address the brown bear situation on the Kenai Peninsula.
First is education. The people and businesses must be educated about the importance of the bears to our environment and the dire consequences to the economy if we fail to protect them. Those consequences will most likely be a reduction in tourism and a limit of economic growth if they are placed on the Endangered species list. The only way we can prevent Defense of Life and Property kills is by having an educated population.
The second approach is in data collection. We propose to ask the local utilities and phone companies to include a questionnaire about bear sightings. They will be asked about location (plat and parcel number if at home), approximate age, color, etc. Included with the questionnaire will be information as to bear history, identification, importance, and much more. This will aide in the education of the populace. The Department of Fish and Game will be asked to quantify that data.
The cost of this program will be minimal. We feel that the companies of the major industries of oil and tourism have the most at stake. It seems reasonable that they would be willing to fund the effort.
Thirdly, we also feel the Kenai Borough needs to institute a land use plan. The interaction between bears and humans will only increase as the human population increases. We need to recognize the needs of the Brown Bear and create a land use policy that will allow development that will protect the critical Brown Bear habitat needs.
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