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

sx = survival in age class

lx = survival to age class x

bx = age-specific fecundity

R0 = net reproductive rate

0-1 years, 1-4 years, etc.

proportion in age class that are alive

all the sx up to that age class multiplied

# of female offspring produced by female in that age class

# 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

# observed this timethat 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 owls3. Work on computers4. 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