The Brown Bear: Diet of an Omnivore

The Brown Bear: Diet of an Omnivore and How Humans Play a Role

Background Information on Brown Bears

According to scientists and wildlife managers, distribution, quality and quantity of food resources primarily influence not only the diet but also the life histories of many mammals. Furthermore, supplemental feeding of wild animals affects their behavior and feeding habits. Supplemental feeding of bears has raised a lot of controversy in the recent years not only due to its expensive nature but due to the perils associated with it as well. The various scientific methods applied by two different scientists to determine diet composition of brown bears are discussed in detail in the paper. The results obtained by the scientists, their particular hypothesis and conclusions are also presented in the article. 

The habit of feeding brown bears referred to Ursus arctos by its scientific name has become commonplace in eastern parts of Finland. Although this is mostly done by tourists for recreational purposes, scientists and wildlife managers have raised a lot of concerns arguing that this habit has the potential of creating or leading to the emergence of human-habituated bears. They claim the practice may affect the bear's ability to fend for themselves thus impeding their hunting abilities and potential. Additionally, the practice of feeding brown bears has led to a significant number of bears being killed for self-defense purposes due to their extremely aggressive nature.

Scientific Methods Employed by the Scientists in the Course of the Study

According to available data, 3% of bears killed in Finland was due to purposes of human safety under a license or due to actual emergency where the bears were shot and killed for self-defense reasons. To compare the number of bears shot under police license with those killed during hunting activities, a team of scientists let us say team A, constructed a binary logistic model to aid in the study. In the study, the researcher and his team were interested in finding out whether the unwary behavior of bears in Finland is associated with the feeding of bears at the Finish-Russian border. The examination was based on a comparison of geographical distances between aggressive bears shot at the responsibility of the police and the distance between bears shot in self-defense and those killed in sports hunting. 

During the study, sex of the animals, human concentration, observation density and the distance from their nearest nourishing locations were used as independent variables. Human compactness was crucial in distinguishing bears killed under an authorization issued by the state from those killed during the recreational shooting. The researcher and his team realized that the difference in human density was largest for places far away from the bears feeding sites. The difference in feeding sites was used to distinguish the bears killed for recreational purposes, those killed under a police license and those killed for self-defense. The research did not provide any evidence that recreational feeding of bears, mainly by tourists is connected with the irritation bear problem in the country. However, some perils for human protection are closely linked with bear feeding for leisure reasons. The total number of animals shot and killed in eastern parts of Finland between 1995 and 2008 stands at 1100. Letter N was used to represent the number of bears hence N=1100 bears. 

In the second study, the scientist and his team, let's say team B, were interested in determining the primary components of the brown bear's diet. In the study, 714 bear scats were collected and studied in three locations of Slovenia with different density of additional feeding spots. Despite the fact that a large percentage of bears are provided with supplemental food in Slovenia, human-bear conflicts are still prevalent in the region. Supplemental food was found to be the most dominant in bear diet and represented nearly 30% of yearly estimated dietary energy content. 

The portion of supplemental food in the diet varied with a season of the year and location of study. Furthermore, the part was found to be highest in spring and areas with the highest density of feeding sites. Although many people support the supplemental feeding of bears, they don't realize that supplemental foods have adverse effects on the bears foraging behavior. Moreover, supplemental foods affect several aspects of bear biology, behavior and aggressiveness. The more aggressive the bears, the higher or, the more frequent the incidents of human-bear conflict. Due to these findings, scientist, encourage wildlife managers to desists from providing bears with supplemental foods. 

While the first team of researchers used study area, sexes of the animals in the study, the second team used scats analysis to determine the frequency of two types of supplemental foods such as maize and livestock carrion. The energetic contribution of these foods was later compared to natural food sources. As a result of widespread supplemental feeding, the scientist and his team expected that anthropogenic nutrition would denote a substantial percentage of bear diets in the region. To understand bear preferences for natural food versus supplemental foods, effects of supplemental patterns on bear feeding patterns were studied. The scientist anticipated that the consumption of anthropogenic foods would either lower the seasons with higher natural forage or greater in regions that exhibit high feeding densities.

Materials and Methods

The second study by team B took five years and was conducted in three areas with different intensities of supplemental feeding. The study locations included Sneznik in southwestern Slovenia, Kocevsko in southeastern Slovenia and Menisjia. Central Slovenia. Nearly half of the survey area was inhabited by the brown bear and density of the brown bear in the regions are high. Bear densities in those areas ranged from seven to twenty bears per 100kmsq and locally over 40 brown bears per 100kmsq. Human density was taken into consideration. Human density was established to be 42 inhabitants per ever 100kmsq. In Slovenia, supplemental feeding of bears is used for many reasons such as monitoring of the animals, to prevent the bears for from encroaching into human settlements and for bait hunting purposes. In the course of the study, one feeding carrion site was provided in every 60km of bear habitat (Heikken, 2012) .

The animals also had unlimited access to maize feeding sites. Approximately 60% of the feeding locations were provided with food throughout the year. Supplemental feeding of the brown bear was avoided due to the adoption of European veterinary legislation that bars researchers from feeding livestock to bears during research. Whereas the other research focused on the collection of bear scats for the survey, team A used letter N to represent the number of bears in five regions of Finland. Between 1995-2008. The areas included Kunitivoora, Martin Selkonen, Vartius, Vikiiimo, and Kivikekki. Incidences of the bear shooting were divided into three broad categories. Those shot by police or under police license(N=19), those shot in self-defense(N=14) and those killed in sports hunting (N=1075). The hunting season in Finland lasts three months and the number of animals allowed to be shot at any given time depends on quotas issued by the ministry of agriculture and Forestry.

Between 1995 to 2008, the mean harvest rate stood at 8%. The distance where the animals feed, human density in a given municipality and the density of bear observation was also taken into account (Irena Kavic, 2015) . During statistical analysis, the team log-transformed continuous independent variables and checked for any autocorrelation variable between them. The Pearson correlation coefficient between bear observation density was 0.488 and 0.251 between human density distance to the nearest feeding location. The ratio between bear observation density was found to be 3.40. Just like team B, the team constructed a binary logistic model, one for bears shot under police license and the other for bears killed under self-defense. 

Scat Collection and Analysis

The collected scats were combined and analyzed in the laboratory. The scats were kept at a constant temperature of -20 degrees centigrade. Additionally, only fresh scats were used during analysis. A significant portion of the scats was collected between March and November when most of the bears were active. A small part of scats was collected during winter though they were only analyzed for their respective food content. The collected scats were rinsed with cleaning flowing water through a set of sieves. After approximately a quarter an hour, the nourishment substances were organized and recognized and organized to the least taxonomic level by use of a stereoscope. Each time the researchers found out that more than one food item was present in a given scat, the percentage volume of each volume of each food item was projected visually and consequently rounded to predefined interludes. Two advanced approaches were used to examine the animal remains. The first approach entailed separating the mammals into two groups, livestock carrion which primarily contained cattle and horse carcasses and wild ungulates scavaged by the brown bears. 

Ingested hairs were used to distinguish between domestic and wild ungulates. In the second approach, the team found no need of differentiating between wild and domestic ungulates in the scats. Season-specific ratios were used to analyze the scats. Preliminary analysis revealed that the livestock wild ungulates ratios are the same, but the regions tend to vary between periods of the year.

Data Analysis

The various food items were categorized into seven groups. Livestock carrion, maize, wild ungulates, insects, fruits, plant materials and lastly hard mast. The year was separated into three seasons. Spring which consisted of the period between March and May, summer had three months June, July, and August. The last season was autumn. Since interannual variability in food availability affects diet and food and preferences, of bears, the sample used for the study was collected over an extended period, roughly six years and homogeneously over time and space. The frequency of occurrence of each season and region was also calculated. The acronym FO denoted the frequency of occurrence. Fecal volume, FV for each food category, period and region was also computed. 

Various foods have different digestibility and nutritional composition. Highly digestible and energy-rich are often underestimated in scat based studies. Two groups of correction factors were applied to avoid any errors during analysis. The team used the first group of correction factors, donated by CF1 to approximate initially consumed matter from fecal content. The second group of correction factors, CF2 was applied to translate EDC values into estimated dietary energy content. 

The CF1 used were hard mast 1.8, livestock carrion 2.0, insects 1.1, fruits 0.93 and wild ungulates 1.5. Non-animal consumed was 0.24. CF1 was established by examining the quantity of hair and skin consumed together with meat. To guarantee accuracy and reliability of the findings, the scientist used a correction factor 2.0 for livestock carrion from feeding sites. The CF2 used were found to be, 16.8 Kj g^1 for maize and 19.3Kj g^1 for animal carrion and 17.7Kj g^1 for insects. CF2 for fruits was 11.7Kj ^g 1 and 6.3Kj ^1 for non-animal materials. EDEC was considered to be more important for the interpretation of the results than FV, FO, and EDC. This was because energy contribution of a food item was assumed to signify the importance of the food to the bear. 

Compositional analysis is considered to be more appropriate for analyzing scopes of different classes in a sample. This is because it considers the fact that proportions are not self-regulating variables and can contain fixed values. Zeros represented 58-91 of all values for all individual food group. Logistic regression was later used to identify the impact of period and area on bears food. The team used the presence or the absence of-of the main food items in each scat as the dependent variable and the seven regions and seasons as explanatory variables. 

Since the team emphasized on the occurrence or nonappearance of food items, traces were studied in the same manner as food containing a significant share of the scat. The final model was built by applying backward elimination criteria. Additionally, Bonferroni correction was used to regulate for several evaluations on partly dependent samples. Logistic regression was used to understand the effects of supplemental feeding on the use of supplemental foods by bears. The team combined the findings from two areas, Sneznik and Kocevsko with similar feeding location density. Menisjia and Sneznik were used as binary dependent variables. The percentage of the maze in the bear diet, season and interaction between the proportion of corn season as independent variables. The outcome was weighted to ensure that a balance existed between the seasons. The final model was constructed by backward removal procedure where entry probability was taken to be p^0.05. The scientist did not distinguish between feeding site intended for ungulates and the brown bears since bears consumed maize from both locations. Data carrion consumption was not used because it was never separated into livestock carrion and uninhabited ungulates for samples found from Menisjia. 

Results

Maize and insects were found to be the most valued food for the bears. Other plant materials were frequently ingested although they had little energy content. Animal foods such as insects and ungulates were preferred and considered more valuable than livestock carrion. The EDC value for livestock carrion on a yearly basis was found to be 12.2% when exploratory values were used. The figure, however, increased when samples in which flesh from cattle and wild ungulates was separated in the test center. 

Location affected four out of seven categories with maize being the most affected. Season, on the other hand, affected all food groups except maize with the strongest impact on insects. Furthermore, interaction season region affected corn, insects, and fruits. Corn and carrion were important food items for bear in spring. Insects, on the other hand, represented more than 50% of food consumed in summer. In autumn, the most important food was found to be fruits and hard mast. Although livestock carrion was availed to the bears throughout the year; they preferred consuming it only during spring. In Menisjia, the most important food category was maize, insects in Kocevsko and hard mast in Sneznik. 

The first study found out that sex of the bears had no link to the motives of the shootings. However, a significant number of male bears were shot in self-defense. Logistic regression for bears killed under police license revealed that human density was an important factor since all models that incorporated the parameter provided fit compared to those that did not have human density. Moreover, the sex of the bears and the observation density was not associated with bears shot under police license. The perfect models for bears shot under police license included interactions terms between human density and the distance from feeding sites. Lastly, it was established that the increase in distance from the feeding locations was an important factor for bears killed in self-defense.

Hypothesis of the two Experiments

Team B guessed that it would be difficult to generalize dietary patterns of bears due to high variation in bear diet. The team thought that since the bears took a lot of supplemental foods, it adversely affected their body biology and relation to humans. Team A, on the other hand, guessed that human density and distance from bear sites played a leading role in the increase in some bears killed in self-defense. 

Summary

Although bears in Slovenia feed on bulk natural foods such as insects, fruits, and hard mast, they also feed on anthropogenic foods whenever they come across them. The supplemental foods that the bears feed on provide them with a significant amount of energy. Since additional foods have adverse effects on the bears, they can be regulated by reducing the number of feeding locations.

Personal Opinions

Bears should be continuously monitored using GPS trackers to reduce human-bear conflicts and the number of bears that are usually killed as a result. Although the two experiments involved the use of different materials in the study, the methods employed were largely the same. Both teams applied linear regressions and used various scientific methods to guarantee that their respective experiments were reliable and free from errors. 

References

Heikken, I. K. (2012). Nordic Board for Wildlife Research. Problem brown bears , 44-65.

Irena Kavic, M. A. (2015). Bears: brown bear diet in a human-dominated landscape. Nordic Board for Wildlife Research , 44-66.