Ecological Methods

Question 1

Write a bullet pointed method that would allow you to investigate whether there is a difference between the mean density of dandelions in a field A and B

Answer 1

-use measuring tapes layer at a right angle to create an X and Y axis
-use a random number generator online to pick out the coordinates (to avoid experimenter bias)
-use 30 or more quadrats
-count the total dandelions in each, find the mean and divide by the area of the quadrat

Question 2

Write a bullet pointed method that would allow you to determine the change in percentage cover in yellow rattle along a light gradient

Answer 2

-place the transect belt along a straight measuring tapes from a dark to light area
-measure the light intensity and number of yellow rattle at regular intervals
-repeat again at the same intervals
-use the results to determine the % change

Question 3

Write a bullet point method of how you would estimate the number of butterflies in an area

Answer 3

-use a capture-recapture method:
-use a net to capture a first sample of butterflies
-count the total number of butterflies
-release them back and allow some time for them to evenly redistribute back into the population
-use a net to take a second sample
-count the total butterflies recaptured (marked) and the total butterflies caught in the second sample
-use the Lincoln index to calculate the number of butterflies:

Total caught in first sample x total caught in second sample / number of marked/recaptured organisms

Question 5

What is the purpose of mark-release capture?

Answer 5

To estimate the population size (number of individuals of a species in a particular place at a particular time) of a motile species

Question 6

What is the purpose of the mark in capture-recapture

Answer 6

To be able to identify an individual as having been caught already

Question 7

What is the purpose of release in capture-recapture? An what is the purpose of the recapture?

Answer 7

-calculation relies on the ratio of marked to unmarked remaining constant between the sampling points.to scale up to the whole population, marked organisms must evenly redistribute with unmarked organisms before the second sample is taken

-the recapture is to take the second sample

Question 8

Describe the estimations of mark release capture

Answer 8

-breeding season: populations is potentially increasing between samples 1 &2, young animals are leaving the nest and joining adult populations
-territories: no mixing of marked and unmarked, animals are moving into/away from an area to leave or join a population
-animals not released after first sample: population decreases between samples, fewer marked over time, change in ratio of marked:unmarked = an over/underestimation of the population size
-the mark itself: its not toxic, increase population, or rub off so it doesn’t kill animals, get the animal killed or so we dont think the animal was unmarked.