Abundance of Organisms Biotic Factors Abundance of Organisms
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
Pitfall Traps Organisms? Advantages / disadvantages? Bias?
Small Mammal Traps Organisms? Advantages / disadvantages? Bias? The Longworth live trap Organisms? Advantages / disadvantages? Bias?
Light Traps Organisms? Advantages / disadvantages? Bias?
Tullgren Funnel
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?
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
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
Have a go at calculating some populations…
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?