An of habitat. The reduction in partridge

An accurate test of PVA predictions must incorporate a large
number of data sets to obtain representative assessments for detailed models
(Brook et al., 2000). However, many field studies regarding wildlife
populations are of too short a duration to detect rare events, quantify the
importance of density dependence, or distinguish long-term trends (Beissinger
& Westphal 1998).

The reliability of the predictions made using VORTEX is
questioned in multiple studies.  The predictions
based on population viability analysis are generally considered overly optimistic
unless all potential threats to an endangered species are included in the model
(Lacy 1993)(Ralls and Taylor 1997). VORTEX software does not consider the
possibility that even without any direct threat to the wildlife, population numbers
can be as affected by habitat fragmentation just as much as they are by overall
loss of habitat. The reduction in partridge spatial density caused by habitat
fragmentation will be likely to be a cause of both the particular pattern of
fragmentation and the demography and behaviour of the partridges (Kendall,
1998)(Lacy et al., 1995). In addition, how threats such as hunting or feeding
competition with other wildlife sharing the habitat, will affect population
numbers and will depend on the pattern of fragmentation and on the demography
and behaviour of the partridges. For instance, the reserve size will affect
poaching intensity because the edges of the reserves will determine how easily
accessible the interior is to poachers and how often animals would roam out of
the relative safety of the reserve (Akcakaya and Burgman, 1995).

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The threats facing endangered species influence population size
through their effects on demographic rates and the spatial structure of habitat
patches (Akçakaya, 2000). Therefore, until population viability analysis model
using VORTEX consider either the demography or spatial structure of wildlife, it
is likely that the results are going to be inaccurate.

In conclusion, the predictive accuracy of a PVA using VORTEX
will only be useful if the distributions of the population rates will not adjust
in the future (Coulson et al., 2001). Due to ecological frameworks being
dynamic, managing procedures can change, however it is typically difficult to
anticipate how or when. Research is required to gauge how changes starting with
one managing factor then another, impact the distribution of vital rates and
population growth rates. Multiple data on the growth rate of populations ought
to be gathered after the induction of a management or conservation strategy, the
results and predictions of PVAs ought to be reassessed, and if it is necessary,
the strategy adjusted after the inclusion of this data. A practical use of PVAs
is to analyse the outcomes of various management or conservation scenarios, and
to investigate the hypothetical implications of model assumptions on extinction
probabilities and population dynamics (Possingham, 1993).


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