Question

A scientist is conducting surveys in the tropics of rare lizards. They used the mark-and-recapture method to determine their population size. Over a period of 4 months they initially collected and marked 553 lizards. A year later, they returned and collected 345 lizards, of which 123 were marked.

a) Calculate the estimated population size.

b)Describe the assumptions of the method used to calculate the population size.

c)If these species have a type 2 survival curve and a life expectancy of 5 years, would you over or under estimate their population?

d)What would be your revised population estimate?

Answer 1

Answer:

Based on the given information:

• Number of lizards marked initially (M) = 553
• Number of lizards collected a year later (n) = 345
• Number of lizards collected a year later which were marked (m) = 123

a) Calculate the estimated population size (N).

• Estimated Population Size (N) = (M*n) / m = (553 * 345) / 123 = 1551

b) Describe the assumptions of the method used to calculate the population size.

• The population of organism must be closed.
• There should be no immigration or emigration of organisms.
• There must be complete mixing of the marked organism with the rest of the population.
• All organisms must have an equal chance or probability of being recaptured.

c) If these species have a type 2 survival curve and a life expectancy of 5 years, would you over or under estimate their population?

• Individuals or organisms that have a type 2 survival curve die at equal rates irrespective of age. That means death rate or mortality remains constant throughout the entire lifespan.
• Population estimate is neither overestimate nor underestimated.

d)What would be your revised population estimate?

• It will remain same