Density-Dependence and the Rhino PVA By the Grad Students

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

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

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

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

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

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

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)

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

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

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