Age class	N1	b	s	Recruit N1	N2	Recruit N2	N3
0 to 1	50	1	1	50	179	179	433
1 to 2	25	3	1	75	50	150	179
2 to 3	10	3	1	30	25	75	50
3 to 4	9	2	1	18	10	20	25
4 to 5	6	1	0	6	9	9	10
Total	100			179	273	433	697

From the literature, you will be required to determine 4 demographic parameters for your population:

1) Longevity – How long your species lives will dictate the number of rows in your model. There should be 1 row/year such that an animal that lives to 10 will have rows 0-1, 1-2, 2-3…9-10.

2) Initial age distribution – How many individuals are in each age class in the N1 population? For game species or endangered species, there may be good information on this variable, however, for many species you will have to make an educated guess. There will always be more individuals in the younger age class than in the older age classes.

3) Birth rate – or the “b” column. This is the number of offspring that a female or a pair produces. Keep in mind that you might want to incorporate a number that is slightly smaller than the number of eggs or litter size, as many of these will not survive to maturity. If your species has a delayed reproductive maturity, you will enter 0’s for b until the species reaches breeding age.

4) Survival rate – or the “s” column. This is the probability that an animal will live until the next year. Generally this number will be lower in younger age classes and increase with age. For your first model, s = 1 for all age classes until the last age class, at which time all individuals die.

For recruitment, you will multiply the number of individuals in each age class by their birth rate. Thus, for recruitment, you are only using the proper N column (here N1) and the b column. In this example, 50 0-1’s with a birth rate of 1.0 lead to 50 new individuals recruited into the population. Likewise, 25 1-2’s with a birth rate of 3.0 produce 75 new individuals. The total recruits for N1 will be the total number of 0-1 year olds in N2. In the model, you can see that the total 179 are now the first cell in N2.

For the rest of the N2 column, you will be using the N1 column and the s column. Here it is important to remember that since N1, all members of the population are 1 year older, so the 0-1 year olds are now 1-2 years old, the 1-2 year olds are now 2-3 years old, etc. Thus, you will multiply the number in the population by the survival rate, but the product will be placed one cell lower on the table. So here, 50 0-1 year olds * 1.0 (survival rate) leads to 50 1-2 year olds; 25 2-3 year olds * 1.0 survival rate leads to 25 2-3 year olds, etc.

Now, you will continue to the population until you complete the N10 generation.