Download 1 Cody Clark Wildlife Ecology Brown Bear

Cody Clark Wildlife Ecology Brown Bear (Ursus arctos) Introduction The brown bear (Ursus arctos) is the most widely distributed ursid in the world, it ranges from North America to Europe. With the decline in population sizes and distribution of these large carnivores, they have been of interest since the early ‘70’s when they were listed as a threatened species on the U.S. Endangered Species Act in 1975 (Hilderbrand et al. 1999). Such a huge decline in numbers brought about great attention considering the population sizes and distributions in places such as Idaho. In the mid 1800’s, brown bears occupied most all of Idaho’s land, until the early ‘90’s when humans decisively eradicated brown bears from most of Idaho. Before brown bears were listed as threated throughout the contiguous 48 states in 1975, by 1970, they were extirpated from over 97% of their previous habitat ranges in Idaho alone (Merrill et al. 1998). These drastic changes resulted in numerous conservation efforts, minimizing of mortality, establishing better quality habitats, and the reintroduction of brown bears in selected ecosystems. With their extremely low reproductive rate due to the direct relation of body fat and reproductive success, brown bears need good habitat and high quality food during the summer and fall to properly survive hibernation, gestation and lactation (Hilderbrand et al. 1999). The ecological importance of brown bears is limited to two main contributions. Being a top predator, gives brown bears the role of influencing population dynamics of other species, keeping their numbers from getting too high. Brown bears also play a major role in seed dispersal and transfer of nutrients from water to riparian ecosystems 1 (Holtgrieve et al, 2009). The economic importance of brown bears is determined by the amount of hunting done in the said location. Brown bears are viewed as a big game trophy, and much of society spends decent amounts of money to obtain such a trophy, as well as its home value to the consumer once the bear is in their possession. In order to fully understand the decline of these magnificent carnivores, we have to look at their population ecology as well as the human interactions they face within their environment. After determining the conservation status and the brown bears threats, we will look at the various methods and research used to help prolong the survival of this species. Population Ecology Since the sudden dramatic decline in brown bear population size and distribution in the 1970’s, wildlife biologists and researchers have been continuously trying to implement new methods and models to halt the decline and begin an increase in their numbers (Merrill et al, 1999). Most methods involve the determination of the favored habitat quality and type. Researchers have determined that brown bears have higher densities in the central portion of their habitat in relation to the overall geographic distribution. This is because the quality of the habitat is greater and less environmental pressures. With this type of distribution brown bears fall under Ideal Free Distribution (IDF), meaning they have higher densities where the habitat quality is higher (Ferguson and McLoughlin 2000). Because brown bear reproductive rates are directly related to the amount of food available and the size of the bear, these bears are generalists. They eat anything from plant parts to meat, in locations where meat is abundant the reproductive rate of brown bears is significantly higher (McDonough and Christ 2012). With brown bears being so diverse in their ability to eat different food groups, they are a perfect species to study geographic 2 variation in relation to population size and size of the bear itself. Thomas McDonough and Aaron Christ modeled the growth in skull size of over 11,000 brown bears across 6 regions throughout Alaska. These 6 study areas had great variation in terms of food availability and habitat types. Since there is such a high demand for energy consumption within the brown bears life stages, using these test areas gave valuable information as to which habitat type and food source is more efficient to the survival of this species (McDonough and Christ 2012). A previous method that was done used cluster analysis, this tool helped delineate brown bears that could be grouped based on their productivity, demography and body size and other variables that were not exactly life-­‐history traits. This model showed that of the 24 brown bear populations, they were divided into 3 main groups that spread from Alaska down to Idaho (Ferguson and McLoughlin 2000). Both these studies show that brown bears are affected physically by their current environment status (habitat type), demography (density) and geographic location. Within each study the results showed that where bears had the opportunity to eat fish as a main diet and had less seasonality, it directly affected their body size and survival rates. (Ferguson and McLoughlin 2000, McDonough and Christ 2012). A study that focused solely on determining the affect of brown bear diets and productivity was constructed in Alaska as well, and used isotope analyses of hair samples to determine the bears diet during the hair growth in the summer and fall time periods (Hilderbrand et al. 1999). This method of study used 13 North American brown bear populations and used their hair samples to indicate the amount of marine meat, terrestrial meal and plant matter consumed in correspondence to their size and demography. The results of this analysis went on to show that coastal brown bears 3 whom consumed meat were the largest of the brown bear species compared to those who were more omnivorous in the interior. Another clarifying result showed a direct correlation of average litter size to a meat-­‐based diet (Hilderbrand et al. 1999). According to a study done in Sweden, female brown bears have less dispersal than males, the females are more philopatric and tend to stay in the center of their home range. The male brown bears have a mean home range of 555km squared, while the females have a much smaller home range consisting of only 147km squared (Beier et al, 2012). This would indicate that dispersal for brown bears is limited to habitat quality in that area (Swenson et al, 1998). Because brown bears are so diverse most of their designated habitat is not spatially explicit, they are able to live in most all climates with various food quality habitats. A resource selection function model was used to determine habitat selection for the brown bears, this study was done in Juneau, AK. Brown bears in the early summer selected for open/closed forests, shrubs, herbaceous landscapes, while in the late summer they selected for areas close to salmon spawning habitat and open forests. Den sites were averaged to be at an elevation of 231 meters (Beier et al, 2012). Although they select for high quality habitats the main precursor for the decline of brown bears throughout was personal human consumption, i.e. hunting. Without proper regulation of human interaction, brown bear populations will continue to decrease, along with other life threatening variables (Merrill et al, 1999). Conservation Status/Threats Considering the hunting of brown bears is the main cause of their dramatic downfall in population size, their conservation status is significantly affected by human interaction. A test study done in Sweden focused on the movement of brown bears before and during 4 the hunting season and witnessed the affect made by human interactions. The goal of this study was to observe movement patterns of the bears without human interaction and then with interaction due to hunting. Behavioral effects of the bears changed significantly when hunting season started up. Before hunting season, bears spend most of the daytime scavenging for food, and rest at night. But with the bears critical time of the year being the same time as hunting season, they cannot efficiently undergo hyperphagia, the over consumption of food sources to store fat for hibernation (Delibes et al, 2012). These researchers observed that bears during hunting season are forced to change their behavioral patterns and search for food at night, therefore lessening the amount of rest they obtain. Hunting alters the bear’s patterns in such a way it decreases the percentage of successful hyperphagia, therefore decreasing the survival during hibernation, regulations on hunting bears should be considered in order to properly conserve their survival. According to the World Wide Fund for Nature (WWF) brown bear populations in the U.S. (not including Alaska) have decreased tremendously, from over 100,000 individuals in early 1900’s to less than 1,000 remain. In Alaska and Canada, where habitat quality is higher and the food abundance is greater, population size is estimated around 30,000 individuals (WWF 2012). These low numbers were first the cause of significant killing off of the bears (Merrill et al, 1999), where now the products that can be attained from hunting them are in less demand, and the real issue is habitat loss. With brown bears being found in less than 2% of their previous range, other industrial trades and advancements are continuing to decrease the available habitat for bear populations to have a chance of increasing. These advancements are mostly logging and road construction with other developments being added to the land (WWF 2012). Brown bears being so diverse in 5 habitat quality, climate change has little to no affect on their lifestyle. When it comes to management of this species, most people turn to persecution because of the violent behaviors brown bears generally present. This creates difficulty in getting the whole community to help establish better habitat and less persecution towards these creatures. With places like Alaska being one of the most prominent habitats for brown bears, there are still some areas within that could use proper management or the populations will decrease over time. Places such as the Kenai Peninsula where the salmon run is huge during the bears hyperphagia time, but also the hunting in the area is huge and residential development and logging are continuing to increase in size (Hilderbrand et al, 1999). Another huge impact is from governmental agencies that design lethal programs, which aim to reduce bear population numbers in hopes of increasing the moose (Alces alces) and caribou (Rangifer tarandus) numbers. This kind of reverse conservational effort favoring the prey over the brown bears is a difficult one to oppose. And in doing so it created smaller numbers in areas that were already on the downfall due to industrial developments (Ballenberghe 2006). With the brown bears continuing to be hunted, and the steady development of residential and industrial landscapes in high quality areas, this species has a hard time of overcoming its obstacles. These factors force the bears to change their movement patterns in such a way that it decreases their ability to obtain high quality foods which in turn decreases their reproductive rate (Hilderbrand et al, 1999). Overall the population viability and the abundance of brown bears depend explicitly on their food source and habitat quality, with the effect of hunting being less than previous years. Each of the studies mentioned all led to a relatively same outcome, the need for conservation of high quality habitat that the bears select for. This tactic will not only benefit other animals 6 and species in the area, but also prolong the survival and population increase of brown bears throughout. Future Research Needs The research that as been done on brown bears is worldwide, and generally incorporates a wide range from the main study point to show dispersal and the need for specific habitat types. The main focus of the studies was to determine the selected habitat and observe which food source is most beneficial to the reproductive rate and survival. Demography of the brown bears was directly correlated to the specific habitat and food sources in that area (McDonough and Christ 2012). One of the main research studies that proved to be beneficial to understand brown bears was done in Alaska and ranged down to Idaho. It used cluster analysis to break down brown bear populations into groups based on certain characteristics. Within these characteristics were demography, body size and climate parameters (Ferguson and McLoughlin 2000). I believe using these variables makes the study more probable of determining an accurate answer. Most of the research papers I used actually end up using information from each other’s studies to help support and influence their own studies. I found this to be quite exceptional and show that each of these methods is on the right track and only needs to be delved into further with more consideration. A complication within some of the studies done on brown bears would be their study area, if it is too localized and doesn’t span out into different states, then it becomes hard to determine where the issue resides. For instance, in Alaska and parts of Canada the population size is 30 times greater than that of the lower 48 states, and in Europe the numbers are even greater (WWF 2012). Yet all around the world studies are continuing to 7 be done to solve the bigger issue at hand, how long will brown bears be around if nothing prominent is established. The most informational study I found based solely in Idaho dated back to early 2000’s, within the Idaho fish and game website, the information provided on brown bear management is completely outdated. This goes to show not much conservation effort is really being applied besides not being able to hunt them in Idaho (IDFG 2011). When reading over all the studies done, and observing their data, it seems like they are all on the right track to proper conservation of brown bear habitat. But for some reason these efforts are not being applied in a timely manner. In order for agencies and programs to remove the brown bear from the Endangered Species Act within their state, they need to take the time to construct a plan that will alleviate this continuing decline of brown bears. In states such as Alaska where the bear population is much higher the mortality of brown bears is controlled, regarding hunting deaths and other types of deaths, conservation efforts regarding habitat aren’t as focused on because most of the habitat type is prominent for brown bears (McDonough and Christ 2012). If we narrow all the studies down to those based in North America we see that most if not all research is done within Alaska and nearby locations. This is because the habitat quality is much higher than anywhere else and researchers can observe how brown bears act in their selected habitat whereas in other locations they are declining due to low quality habitat. By using a proper study location and relating it to another location that has significant decline in numbers, biologists can determine what is necessary to conserve the species in the areas most needed. Since Idaho’s brown bear population has significantly decreased, conservation efforts were attempted to make central Idaho a recovery area, but much controversy arose to whether the security and suitability of the habitat would stay constant (Merrill et al, 1998). 8 Constructing a model that implies restoring a given area within a state where the main cause of bear mortality was human interaction, leads to questionability of how well the model would actually work. If state and conservation agencies plan on restoring populations of brown bears, they need to put forth the time, money and effort into making regulations that keep the bears safe within their recovery areas. After being able to delve into various studies and relate them to one another I am confident that if conservation of habitat solely designated for brown bears is established, and human interaction is kept to a null, population numbers will gradually increase until a stable carry capacity is founded. Once this number is suitable for sustainability, conservation efforts in areas that have previously had sudden declines in populations should be willing to continue with conservation efforts so brown bears can be left in peace. 9 Literature Cited Arthur, S,M., Hanley, T, A., Hilderbrand, G, V., Jacoby, M, E., Robbins, C, T., Servheen, C., Schwartz, C, C. 1999. The importance of meat, particulary salmon, to body size, population productivity, and conservation of North American brown bears. Canadian Journal of Zoology. 77:132-­‐138. Ballenberghe, V, V. 2006. Predator control, politics, and wildlife conservation in Alaska. Alces 42:1-­‐11. Beier, LV, R., Crupi, A, P., Flynn, R, W., Gregovich, D, P., Lewis, S, B., Pendleton, G, W. 2012. Spatial use, habitat selection, and population ecology of brown bears along the proposed Juneau access improvements road corridor, Southeast Alaska. Alaska Department of Fish and Game. Division of Wildlife Conservation. Christ, A, M., and McDonough, T, J. 2012. Geographic variation in size, growth, and sexual dimorphism of Alaska brown bears, Ursus arctos. Journal of Mammology 93(3):686-­‐
697. Delibes, M., Kindberg, J., Ordiz, A., Saebo, S., Stoen, OG., Swenson, J, E. 2012. Do bears know they are being hunted? Biological Conservation. 152:21-­‐28. Ferguson, S, H., and McLoughlin, P, D. 2000. Effect of energy availability, seasonality, and geographic range on brown bear life history. Ecography 23:193-­‐200. Holtgrieve, G, W., Jewett, P, K., Schindler, D, E. 2009. Large predators and biogeochemical hotspots: brown bear (Ursus arctos) predation on salmon alters nitrogen cycling in riparian soils. Ecological Society 24:1125-­‐1135. 10 Idaho Fish and Game [IDFG]. 2011. <http://fishandgame.idaho.gov/public/wildlife/?getPage=248>. Acessed 6 Apr 2013. Mattson, D,J., Merrill, T., Quigley, H,B., Wright, G, R. 1999. Defining landscapes suitable for restoration of grizzly bears (Ursus arctos) in Idaho. Biological Conservation 87:231-­‐
248. Sandegren, F., Soderberg, A., Swenson, J, E. 1998. Geographic expansion of an increasing brown bear population: evidence for presaturaion dispersal. Journal of Animal Ecology 67:819-­‐826. World Wildlife Fund [WWF]. 2012. <http://wwf.panda.org/about_our_earth/species/profiles/mammals/brown_bear2
/>. Accessed 6 Apr 2013. 11