POPULATION VIABILITY ANALYSIS OF THE FLORIDA GRASSHOPPER SPARROW (AMMODRAMUS SAVANNARUM FLORIDANUS): TESTING RECOVERY GOALS AND MANAGEMENT OPTIONS

The Auk ◽  
2008 ◽  
Vol 125 (1) ◽  
pp. 167-177 ◽  
Author(s):  
DUSTIN W. PERKINS ◽  
PETER D. VICKERY ◽  
W. GREGORY SHRIVER
1999 ◽  
Vol 5 (1) ◽  
pp. 56 ◽  
Author(s):  
Stephen M. Jackson

The population viability analysis (PVA) program VORTEX was used to examine the viability of different sized populations of the Mahogany Glider Petaurus gracilis, and to examine the impact of a one in a hundred year catastrophe (each requiring a different reserve size) of different severities on different sized populations. The PVA showed that populations up to 300 individuals (1 500 ha) have a negative population growth rate, high losses of genetic diversity and a greater than 5% chance of extinction within 100 years. Populations of 400?700 individuals (2 000?3 500 ha) showed a decreasing trend in population size suggesting they are likely to become extinct after 100 years. A population of 800 individuals (4 000 ha) was needed for the population size to stabilize. Sensitivity analysis showed adult mortality of greater than 25% to be important in decreasing the viability of populations. Populations of 400 were resistant to a one in 100 year catastrophe which had a 20% mortality and 20% decrease in reproduction. When the mortality was 70%, with 70% decrease in reproduction, a population of 1 000 still had a 12% chance of extinction. As only approximately 50% of the available habitat appears to be occupied, an area up to 8 000 ha (800 individuals) is suggested to be required to maintain viable populations of Mahogany Gliders. A number of management options are recommended including the retention of habitat, establishing corridors between key populations, and using fire to minimize rainforest expansion.


2002 ◽  
Vol 24 (2) ◽  
pp. 251
Author(s):  
Reviewed by BW Brook

PREDICTING the persistence of small populations is a key issue in population ecology and conservation biology. A large and increasing number of species are threatened with extinction from factors associated with humans (such as habitat loss, over-exploitation, pollution and introduced species) and stochastic hazards (demographic and environmental fluctuations, natural catastrophes, inbreeding and loss of genetic variation). In order to address such problems in a systematic way, the process of ?population viability analysis? (PVA) has been developed over the past few decades, and has now become one of the major unifying disciplines in conservation biology. PVA is a technique, usually employing complex computer simulations, for predicting the future fate of wildlife populations and comparing competing management options, based on the integrated modelling of demographic, environmental, genetic and habitat-related information. Using PVA allows time, money and onground action to be rationally and efficiently allocated.


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