Population Ecology
Branch of ecology that studies the structure and dynamics of populations
What is a population?
Collection of the same species living in the same area
Methods for Determining a Population
Count
What is the female population in the room?
What is the white-tailed deer population in Blair County?
Not necessarily the best or easiest method
Census:
Including all members of a population
Random Sampling
Estimating a population by counting the individuals in a small portion of a specific area
(density)
Makes a lot of assumptions
Yearly counts can be used to track population growth or decline
Example:
Turkeys in a field
Count the number of turkeys in half the field and double it
If there are 24 turkeys in the field, how many can be in the entire field
Random Sampling Example
Sample vs. Census
Lower cost relative to census.
If the budget is small, take a sample, if large take a census.
Time needed.
If short, sample. If large, census.
Population size
Capture - Recapture
1st – Capturing, marking/tagging and releasing
Keep a count of the number captured and tagged
2nd – Capture a number and count the number with tags
Equation
Equation
m=M
n N
What Can Change a Population?
Increase
Births (B)
Immigration (I)
Decrease
Deaths (D)
Emmigration (E)
Limiting Factors
Disease/parasites
Starvation
Predators
Pollution
Accidents
Old Age
Hunting
Loss of Habitat
Population Equation
N = starting population
100 Elk
N +1 = population during the next year
N + 1= B – D + 1 – E
Answer?
Population & Habitat
A habitat is where an organism lives.
What does it provide?
Are those things in endless supply?
Carrying Capacity (K)
The number of individuals that the resources of a habitat can support.
Often decreases in winter when less food and cover is available.
If there are more individuals in an area than the habitat can support, some will have to
die or leave.
Carrying Capacity (K)
Carrying Capacity (K)
Population Graphs
Linear – constant increase
Exponential – population increases without limit on resources or is adversely affected
Population Management Strategies
What techniques can be used to control populations?
Increase?
Decrease?
Keep it the same?
What can be done if the population exceeds the carrying capacity of the habitat?
Population Management Studies
Hunting
Removal (plants)
Trap and Transfer
Reproduction Studies
Species Introduction
Habitat Restoration
Wildlife Management Agencies
PA Game Commission
http://www.pgc.state.pa.us/
PA Fish and Boat Commission
http://sites.state.pa.us/PA_Exec/Fish_Boat/mpag1.htm