Estimating animal populations

Question 1

Why are animal populations difficult to sample and measure?

Answer 1

Because most species are highly mobile and not easily visible because they are hiding from predators.

Question 2

Name one method used to estimate animal populations.

Answer 2

The capture/recapture method, also known as the Lincoln Index

Question 3

How does this method work?

Answer 3

1) Animals are caught humanely. Their numbers are counted and recorded.
2) The animals are marked in some way so they are identifiable.
3) the marked animals are then released back into the population for a suitable amount of time.
4) A second sample is obtained, some of the animals caught will be marked and some unmarked. Both unmarked and marked animals will be counted.
5) The following formula is then used to estimate the total population size in the habitat:

Population size = no.in 1st sample (all marked) x no. in 2nd sample (marked and unmarked) all divided by no. in 2nd sample sguch were previously marked

Question 4

What assumptions are made when using capture/recapture data?

Answer 4

• No death, immigration or emigration.
• Each sample is collected in exactly the same way without bias.
• The marks given to the animals do not affect their survival rate,