Mark, release, recapture Method.
- Some animals are trapped, e.g. using pitfall traps.
- They are marked in some harmless way then released.
- Traps are used a few days later.
- The number of marked and unmarked animals are recorded.
- The population size is estimated usinf this formula:
Population size: Number in 1st sample X Number in 2nd sample
Number in 2nd sample previously marked
- E.g. 10 animals were trapped, marked and released. 2 days later, 20 animals were trapped, where 5 were found to be marked:
Population size: 10 X 20 = 200 = 40 5 5
- Marked animals will mix with origninal population.
- The marking doesn't affect their survival.
- No deaths and no births - population size stays the same ( stable )
- No movement of animals in and out of the area.
Animals that move are tricky to sample
- Move around - could be counted twice.
- A risk of not counting all the animals if they are moving about.
- Some animals may be active at different times of the day.
- Animals ma run away or hide from you as you approach them to sample them.
- You cannot be certain if an animal actually belongs to the habitat you re sampling.
- Large animals can be observed.
- Smaller animals and microbes trapped using appropriate equipment.
- Mark, release ,recapture method can be used to estimate the population.