1. Density-Dependence and the Rhino PVA
By the Grad Students

2. Density-Independence with Given Data
Result: 0% probability of extinction
(Everyone did this!)

3. D-I: Changed carrying capacity from 75 to 40
Result: 40% probability of extinction

4. D-I: Increased adult mortality to 10% for females and 15% for males
Result: 80% probability of extinction

5. D-I: Changed female mortality to 8%, male to 10%
Result: 30% probability of extinction

6. Why Use Density-Dependence?
Higher % females may reproduce at lower pop’n sizes
Females may have larger litters at lower pop’n sizes (cannot use this in Vortex w/o fudging)
Pop’ns may be able to recover from catastrophes faster with D-D growth because “r” and/or % of females breeding is greater at low pop’n sizes

7. Density-Dependence vs. Density-Independence in the Rhino PVA
% of females breeding
% fem.
breeding
45%
40%
D-I
33%
K=75
Density

8. Equation for Density-Dependent
Reproduction
% breeding females at pop’n size n =
Po - (Po - Pk) (n/k)b
For given data:
% breeding females at size 64 = 33%
Po= % breeding females at density 0
Pk= % of breeding females at K
n= pop’n size
K= carrying capacity
b = shape parameter (USE 1)

9. Equation for Density-Dependent
Reproduction
% breeding females at pop’n size n =
Po - (Po - Pk) (n/k)b
For given data:
% breeding females at size 64 = 33%
Po= 40% and 45%
Pk= unknown, need to solve for this
n= 64
K= 75
b = 1

10. Density-Dependence with original data
40 % of females breeding (Po)
Result: 10% probability of extinction

11. D-D: Changed female mortality to 8%, male to 10%
Changed % of breeding females (Po) from 33% to 60%
Result: 0% probability of extinction