Comparison of the population viability analysis packages GAPPS, INMAT, RAMAS and VORTEX for the whooping crane (Grus americana)

Abstract

Population viability analysis (PVA) is widely used in conservation biology to compare management strategies and predict probabilities of extinction for endangered species. However, it remains unclear whether the available range of generic PVA programs produce similar predictions when applied to common data sets. A comparative analysis was carried out using six commonly applied PVA packages (GAPPS, INMAT, RAMAS Age, RAMAS Metapop, RAMAS Stage and VORTEX), based on the extensive population data available for the endangered whooping crane, Grus americana. Significant differences were found between the projections of the PVA packages. In particular, the introduction of stochastic variation in breeding structure led to large differences between some packages. Surprisingly, two versions of VORTEX produced very different predictions due to a subtle difference in the way monogamous breeding was modelled. The pattern of similarities and differences among the projections of the packages differ depending on the species examined. In contrast to the predictions of comprehensive (realistic) models, simplified (standardized) models were found to be relatively congruent, which probably reflects similarities in the fundamental biological processes being modelled by the PVA packages. The implications for conservation are clear; caution must be exercised when interpreting the projections of a model built using any one PVA package since, due to seemingly subtle differences in what biological assumptions and threatening processes are included in the models, the predictions among PVA packages (or versions of the same program) are not necessarily concordant.

Metapopulation viability of a globally endangered gazelle on the Northeast Qinghai–Tibetan Plateau

“…It has been suggested that although a temporary shortage of males can greatly decrease the breeding rate and increase the extinction risk in monogamous species, this potentially important stochastic element can be ignored in polygamous species (Brook et al, 1999(Brook et al, , 2000a. However in our study, following OFY in importance, the SR also played an important role when predicting extinction risk.…”

“…In comparative studies of PVA programs, Vortex was shown to give an unbiased estimate of extinction risk for well-studied mammals and birds (Brook et al, 1999(Brook et al, , 2000bTian et al, 2011). A detailed description of the package and its features can be found in Miller and Lacy (2005).…”

Population Viability Analysis of the Blue-Throated Macaw (Ara glaucogu-laris) Using Individual-Based and Cohort-Based PVA Programs

“…Uncertainties concerning the predictive reliability of PVA have led to questioning the validity of conclusions drawn from some PVA [20]. However, PVA has proven useful when there is significant information about the species' vital rates [14,21].…”

“…In addition, PVA may be useful to assess levels of threat when species with limited data are analyzed cautiously, taking into consideration model assumptions [22][23][24]. As many conservation actions and management options are currently based on PVA results, PVA predictions should be quantitatively reliable, whether the proposed actions are sufficient or not in order to achieve species recovery [15,20].…”

Do Consumers Prefer Wild, Farmed Bear Bile or Substitutes?

“…To successfully manage and conserve any wildlife species, a basic understanding of the population's structure and group dynamics are required [12][13][14][15]. Demographic parameters (i.e., vital rates) are often used as indices of population's health and stability, and to evaluate a species' status and viability [16,17]. These are commonly assessed using population models (e.g., VORTEX, RAMAS, ALEX) which rely on demographic data, such as sex ratio, fecundity, productivity, age structure, group size, and survival rate, to make temporal predictions [18,19].…”