What are the steps involved in the mark-release-recapture technique and which factors does it rely upon?

Mark-release-recapture is a technique used to estimate the size of a population of a particular species. The steps involved are:

1. Capture and count animals.

2. Mark them in a way which is not toxic/harmful to them.

3. Release them back into the community.

4. Capture a second sample and count them.

5. Record the number of marked individuals recaptured.

The estimated population size is:

(total no. in 1st sample x total no. in 2nd sample) / no.of marked individuals recaptured

However, this technique only works if the following factors are in place:

1. There are few births and deaths in the population.

2. The population has a definite boundary; there is no emigration or immigration.

3. The proportion of marked:unmarked individuals in the second sample is the same as the proportion in the population as a whole.

4. Marked individuals from the first sample distribute themselves evenly amongst the rest of the population and have sufficient time to do so.

5. The method of marking is non toxic / does not make them more conspicuous to predation.

6. The method of marking is not lost / rubbed off during the investigation.

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