Sampling of Wild Organisms

Question 1

What considerations must be made when sampling?

Answer 1

• Sampling should be carried out in a manner that minimises impact on wild species and habitats.
• Consideration must be given to rare and vulnerable species and habitats, which are protected by legislation.
• The chosen technique must be appropriate to the species being sampled.

Question 2

What is point count sampling?

Answer 2

• A point count involves the observer recording all individuals seen from a fixed point count location.
• This can be compared to other point count locations or with data from the same location gathered at other times.

Question 3

What is transect sampling?

Answer 3

• A transect is a line along which different samples can be taken using a quadrat.
• Quadrats of suitable size and shape can be used for plants and other sessile or slow-moving organisms.
• These are often set up along an area where the terrain or abiotic factors are variable - the impact of these on species abundance can, therefore, be assessed.

Question 4

What is remote detection?

Answer 4

• Capture techniques, e.g. traps or nets, are used for mobile species.
• Elusive species can be sampled directly using camera traps or an indirect method, such as scat sampling.

Question 5

Describe sample sizes.

Answer 5

• Where it is impractical to measure every individual, a representative sample of the population is selected.
• The extent of the natural variation within a population determines the appropriate sample size that should be taken.
• More variable populations require a larger sample size.
• A representative sample should share the same mean and the same degree of variation about the mean as the population as a whole.

Question 6

What is random sampling?

Answer 6

Members of the population have an equal chance of being selected, e.g. randomly placing quadrats in a field.

Question 7

What is systematic sampling?

Answer 7

• Members of a population are selected at regular intervals, e.g. carrying out a line or belt transect.
• In a line transect, a straight line through an area is drawn and any species on the line are recorded.
• In a belt transect, quadrats are placed at intervals along the transect and counted.

Question 8

What is stratified sampling?

Answer 8

• The population is divided into categories that are then sampled proportionally.
• It can be used to sample habitats that are not uniform, e.g. areas of trampled plants in several sections of a larger meadow
• A standard formula can be applied to calculate the number of samples that should be taken from each area.