Ecology, Spring 1999

More example problems, Test 2

I have asked these questions on past tests:

1. An ecologist wishes to estimate the size of the population of purple gallinules (a really pretty bird) at Anhinga Trail in the Everglades. She captures 26 individuals, marks them all with bird bands, and releases them. Three weeks later, she traps 30 gallinules in the same location, 2 of which were marked. If the SE of the estimate =

between what two numbers can we be 95% sure the real population lies between? (Where M=# marked on first visit, n=total number captured on 2^nd visit, R = number of marked individuals recaptured on 2^nd visit) Is the Lincoln Index an appropriate estimation method in this case? What assumptions must be met?

2. A population of mice grows from 100 to 200 in 4 months. If the population were allowed to grow unchecked, how many mice would there be in 1 year? 5 years?

3. Gilligan and the 6 other castaways gave up on being rescued from the desert isle, and formed a new country. The professor determined that the water supply on the island could support a population of 5000. Given that lambda= 1.05, how many years will it take to reach a population size of 4000? Use the logistic equation to find your answer. State the major assumptions that you must make to answer this question!