1. Abundance of Organisms
Biotic Factors
Abundance of Organisms

2. Learning objectives You should be able to:
Identify the different methods for catching moving animals.
Describe and evaluate the Lincoln Index as a way of measuring abundance

3. Pitfall Traps
Organisms?
Advantages / disadvantages?
Bias?

4. Small Mammal Traps Organisms? Advantages / disadvantages? Bias?
The Longworth live trap
Organisms?
Advantages / disadvantages?
Bias?

5. Light Traps
Organisms?
Advantages / disadvantages?
Bias?

6. Tullgren Funnel

7. Lincoln Index Capture, mark, release and recapture.
Estimates the population size of animals that move / don’t appear during the day.
At least 10% needs to be recaptured.
Based on that, what assumptions would have to be made?

8. Lincoln Index Assumptions include: Mixing is complete
Marks do not disappear
Marks are not harmful nor increase predation
It is equally easy to catch every individual
There are no immigration, emigration, births or deaths between sampling

9. Formula n1 = number of animals first marked and released
n2 = number of animals captured in the second sample
m = number of marked animals in the second sample
N = total population

10. Have a go at calculating some populations…

11. Quick Quiz
Name 2 different types of animal trap and the type of animals that they capture.
This is the formula for the Lincoln Index, what do the different letters represent?
What are the advantages and disadvantages of using the Lincoln Index to calculate abundance?