Imagine that you have been studying the population biology of ground squirrels o
ID: 42070 • Letter: I
Question
Imagine that you have been studying the population biology of ground squirrels on the UCSC campus for a number of years and have obtained the following information. A sample of 75 females in 2014 had the age structure shown in column 2 below. Additional longer-term studies of cohort survival and reproduction produced the information on age-specific survival probability [l(x)] and reproduction [b(x)] shown in columns 3 and 4 below.
Age Number of females l(x) Number of births per female [b(x)]
0 25 1.0 0
1 20 0.5 0
2 15 0.4 2
3 10 0.3 2
4 5 0.1 1
5 0
Using the data above, project the age structure and size of the population from 2014 to 2015.
Was the population at a stable age distribution in 2014? Why or why not?
Explanation / Answer
AGE
NO OF FEMALES
Lx
bx
lxbx
0
25
1
0
0
1
20
0.5
0
0
2
15
0.4
2
0.8
3
10
0.3
2
0.6
4
5
0.1
1
0.1
Ro=?lxbx
Ro=1.5
Ro>1 hence the population is growing
When age specific survival and fecundity are constant, the population grows at a fixed rate. The age structure does not change from one year to the next. It has a stable age distribution
AGE
NO OF FEMALES
Lx
bx
lxbx
0
25
1
0
0
1
20
0.5
0
0
2
15
0.4
2
0.8
3
10
0.3
2
0.6
4
5
0.1
1
0.1