Question

.1. A herd of caribou have been closely monitored over the years. In early 2014 the herd contained 146 individuals. Later that year, 8 young were born and 11 caribou were lost to predators or vehicle collisions. In early 2015 the herd was found to contain 163 individuals. .a. Would you consider this to be an open or closed population? Why? [2] .b. Use BIDE dynamics to determine the cause of the net population gain in 2014. What assumptions do you have to make to complete the equation? [2]

Answer 1

Closed population: Individuals are only added or removed from the population by means of birth or death.

Open population: Individuals can join the population from outside(Immigration) or leave the population(emigration) apart from the change in population due to birth and death.

A)

This population is an open population.

As, Initial number of individuals= 146

Number of individuals born = 8

Number of death= 11

Therefore total number of individuals would be (146+8-11) = 143 if it was a closed population.

But as the final number of individuals is 163 which clearly indicates that some individuals have joined the population from outside(immigration). So it is an open population.

B)

Initial Number of individuals in the population= 146

Number of births = 8

Number of deaths= 11

We know, Final Individuals= Initial individuals+ (B-D) + (I-E),

where B is birth rate,

D is death rate,

I is immigration (individuals joining the population)

E is emigration (individuals leaving the population)

or, 163= 146 + (8-11) + I

or, 163 -146 +3= I

or, I = 20

So we can attribute the net gain in population to immigration(Number of individuals joining the population from outside)

Here, we had to assume that no individuals left the population during this course of time, then immigration number will inc release by the number of individuals leaving the population.