Lesson Six: Bear Barriers

FWClogoSmallA population is a group of organisms of the same species living in the same area of habitat. The total population of black bears in Florida has changed from an estimated 11,000 individuals at the time of European settlement to approximately 4,000 individuals in 2016. Because Florida black bears prefer densely vegetated habitats and male bears can have home ranges of over 100 square miles in areas such as the Eglin Air Force Base. Exact counts of Florida’s black bear populations have not been possible.

Scientists base their estimates of bear populations on several indices, including genetic analysis of hair samples collected from research stations, periodic road surveys to record evidence of bear activity, such as bite marks on food cans or tracks and scat, as well as data collected from known Florida black bear deaths. Scientists have been collecting data on Florida black bear deaths (mortality) throughout the state for more than 30 years. In addition to keeping track of how many known bear deaths occur each year, scientists collect data on the age, gender, size, overall health, and probable cause of mortality for each dead bear they find. This information is being used by government agencies like the Florida Fish and Wildlife Conservation Commission and conservation organizations like Defenders of Wildlife to pinpoint the types of human activities that threaten black bear populations in Florida and develop ways to minimize the number of bear deaths caused by human activities.

In this Lesson Six: Bear Barriers, students will learn to identify causes of black bear mortality andLesson 6_thumb how it changes during each life stage, how humans influence black bear populations, and how human influence can be reduced.

Lesson 6_Bear Crossing Sign_FWCIn natural systems, the population of organisms in an area is influenced by four factors: birth rate, death rate, immigration (organisms moving into an area), and emigration (organisms moving out of an area). In stable populations, birth rates and death rates tend to balance each other out and immigration rates usually equal emigration rates. In natural systems, a number of factors normally contribute to deaths within a population. The factors that limit the sizes of populations of organisms are called limiting factors. If these natural limiting factors did not exist, birth rates would exceed death rates and the population would grow to exceed the carrying capacity of its habitat. A number of different natural events and factors control the sizes of Florida black bear populations to keep them stable. Natural factors causing death in Florida black bear cubs may including drowning, hypothermia due to den flooding, predation by older bears, starvation, falling from trees, infections from injuries, and predation by other natural predators such as bobcats and coyotes.

Lesson 6_development_Daniel Oines

Photo courtesy of Daniel Oines

At other stages in their lives, natural factors causing death in Florida black bears are primarily injury or death caused by aggressive encounters with other bears, but in rare cases starvation and disease. There is no accurate way to determine exactly how many bears in Florida die of natural causes each year. With the increasing population of people in Florida, the number of human-caused factors resulting in bear mortality has increased. The three main human activities directly resulting in bear mortality in Florida (in order from most to least) are road kills, agency removal for public safety (i.e., humanely killed), and illegal kills (e.g., poisoning, shooting).

Lesson Summary:

Key Question: How do human activities affect Florida black bear populations?

Main Topic: Influence of natural and human-caused factors on Florida black bear survival rates

Format: Role-playing game and math activity

Description: Students participate in a role-playing game to learn about the factors that contribute to Florida black bear mortality.  They also solve simple math problems to compare and contrast the mortality rates of male and female Florida black bears at different stages of their life cycles.

Common Core Standards: Coming Soon

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