Announcements Corrected mistakes on slides from last lectures VORTEX Help –READ VORTEX survival guide! Leads you step by step through VORTEX. –Get started this weekend so you can identify any problems before its too late!

General Predictors of Extinction Population Growth + - Population Size Current population size

Deterministic Variation in B&D: Density Calculation of r from life table assumes density-independent model

Density-Dependence in Vortex Population Size Time 0 X DD DI: growth w/ ceiling K, maximum size

Where Are We Measuring “r” Growth Rate Density “Intrinsic” r or r-max K 0 “Realized” r

Are we measuring “r” at K? Growth Rate Density r-max K 0 DI Model DD Model

DD in Vortex

Implication of DD vs. DI Assuming DI may bias the probability of persistence, depending on where r-realized is measured Unfortunately, these essential data are rarely available!

Rhino PVA % Breeding Density Additional assignment for grad. students: Report to class next Wednesday.

DD in Vortex Only possible for % females breeding. “Work around” possible for DD in survivorship. If DD growth is expected for your population, specify that reproduction is DD, and follow instructions (see Tashi or myself for help).

The Allee Effect in Vortex Decide if an Allee effect is appropriate for your population. If so, specify that reproduction is DD, and follow instructions (see Tashi or myself for help).

Critiques of PVA Models require too much data –Models typically result in wide confidence intervals. Models can not be “validated” –Focus instead on parameter estimation. Models are error prone

Model Output = Model Input Parameter Estimates Vortex Model Predictions

Creativity and VORTEX Vortex assumes one reproductive season/year. If your species has 2 clutches/yr., then:

A Defense of PVA Brook, B. W., J. J. O'Grady, A. P. Chapman, M. A. Burgman, H. R. Akçakaya, and R. Frankham Predictive accuracy of population viability analysis in conservation biology. Nature 404:

Conceptual Utility of PVA It identifies the population, not land, as the critical unit for conservation purposes. The term “viability” stresses long term population persistence and emphasizes self- sustainability. The idea of “minimum” emphasizes that there may be a threshold below which a population is doomed to extinction.