GRASPING MY CONCEPTS
ON CHAPTER 3.4&3.5
by Josh C
Hi, so where here to learn about Leslie Models today and I'm going to teach. In a Leslie model there are three different columns which are: Age, Birthrate, and Survival rate of your topic. In order to make this formula work you have to follow these proceeding steps:
For this example I'm going to make up random numbers for age,
birthrate, and survival rate of an Owl.
Age
(years)
Birthrate
Survival rate
| 0-1 | 0 | .5 |
| 2-3 | .4 | .8 |
| 4-5 | .7 | .4 |
| 6-0 | 0 | 0 |
Age (years)
0-1
2-3
4-5 6-0
Number
12
10
6 0
Using the table above I'll show you how to solve a Leslie matrix. You might be wondering how many owls will be born after 1 month (1 cycle). You can determine the exact number of owl births by multiplying the birthrate by the corresponding number of owls in that age group.
Ex. 12(0) + 10(.4) + 6(.7) + 0(0)
= 0 + 4 + 4.2 + 0 = 8.2
The number of owls after about 1 year is just a little over 8. And the number of owls who survive become the survival rate (SR).
Age (years) # SR # moving up
|
0 -1 |
12 | .5 | (12)(.5) move up to 2-3 |
|
2-3 |
10 | .8 | (10)(.8) move up to 4-5 |
| 4-5 | 6 | .4 | (6)(.4) move up to 6-0 |
| 6-0 | 0 | 0 | No owl lives beyond 6 years. |
3.5
This section just lets you see into the future, a lot further, a lot quicker. I'm going to show you how to work this shorter method using the same numbers in the previous example. A person by the name of Mark L, in my math class, came up with the simplest way to do this formula. It's called BS. What you do is take the B (birthrate) and list it down the left side of the matrix. Then you take the S (survival rate) and take the 1st number and place it next to the 1st number of the birthrate. And as your going down the matrix you have to add 0(zero) in between the 2nd number of the birthrate and the survival rate. As you go down the rest of the matrix you keep adding another zero.
| 0 | .5 | 0 | 0 | 0 |
| .4 | 0 | .8 | 0 | 0 |
| .7 | 0 | 0 | .4 | 0 |
| 0 | 0 | 0 | 0 | 0 |