Lab 12: Population Ecology
What is Population Ecology?
• Ecology:
•
study of interactions
between organisms and
their environment
• Population:
•
group of conspecifics
living in the same area
• Population ecology:
•
how the environment
influences a population
and vice versa
What is Population Ecology?
• Population Ecology
Topics:
•
population growth
•
endangered species
(conservation)
•
effects of habitat
fragmentation on the
population
Population Growth & Demography
• Demography:
•
Study of populations
•
How many?
•
What’s the age structure?
• Growth rate determined
by:
•
Birth rate
•
Death rate
•
Immigration and
emigration
Population Growth & Demography
• Demography:
•
Study of populations
•
How many?
•
What’s the age structure?
• Growth rate determined
by:
•
Birth rate
•
Death rate
•
Immigration and
emigration
What can affect Population Size?
• Stochasticity
•
random events such as
drought, severe winter,
fire, etc.
• Demographics – age
distribution of population
•
How many are of
reproductive age?
•
Pre-reproductive age?
•
Post reproductive age?
How can we tell if a population is growing or shrinking?
Life Tables
• Used to estimate age-specific fecundity and survival
rates
•
Fecundity = reproduction
• Look at Table 12.5 on page 202
•
You’ll be filling this out in lab today
• Made for females – too difficult for males
• Cohort life table
•
Follow individuals born at the same time for their whole lives
• Static life table
•
Random sample of individuals, marked at the same time
Life Tables – what’s in them?
x = age class 0-1 years, 1-4 years, etc.
proportion in age class that
sx = survival in age class
are alive
lx = survival to age class x all the sx up to that age class
multiplied
bx = age-specific fecundity # of female offspring produced
by female in that age class
R0 = net reproductive rate # of female offspring produced
by a female during its
lifetime
You’ll have to do these calculations – look at pg 187!
How do we estimate population
size?
Mark-Recapture Method
(you’ll be doing this today)
1. Animals are trapped, marked for ID, and then
released
•
In birds, we mark them by putting colored bands on
their leg
2. Later, a second set of animals is trapped (or
observed) from the same population
•
Some of these animals will be from the first,
marked group
3. The total number of animals within the
population can then be estimated (pg. 188)
Total in population
Total that were banded
in the 1st round
Total observed this time
BandedTotal *ObservedTotal
N=
BandedObserved
# observed this time
that were banded
Radio Telemetry
• Place transmitter on
animal – use receiver to
pick up signal
• Uses
•
Find animals to observe
•
Track activities
•
•
Determine home range size
•
Look at dispersal
•
Look at migration
•
Etc.
Mortality
Triangulation
(you’ll be doing this today)
• Used to find animal from
far away
• Use receiver to get
directional readings at 2
locations
• Use map and compass
to draw lines
• Where lines cross is
location of transmitter
Plan for today
1. Take a look at lab report BEFORE starting lab
•
There are some things you will need to do before
leaving
2. Go out and find owls
3. Work on computers
4. Lab report
Hints and tips
• For table 12.7 – only change one parameter per
age class – don’t change it too much
• Find 40-50 living owls (won’t take too long)
• For the discussion in the lab report – read page
195 carefully
• Will need to discuss biology and conservation
concerns
• Think about which age class is having trouble – is
there something we can do to help that age class?
• Think about old growth vs new growth forests