DOES POPULATION VIABILITY ANALYSIS SOFTWARE PREDICT THE BEHAVIOR OF REAL POPULATIONS - A RETROSPECTIVE STUDY ON THE LORD-HOWE-ISLAND WOODHEN TRICHOLIMNAS SYLVESTRIS (SCLATER)

Population viability analysis (PVA) is used for quantitatively assessi ng endangerment and comparing management options. Consequently, it is essential that PVA software packages be tested to determine whether th ey can accurately reflect the behaviour of real populations. A retrosp ective PVA was performed on the Lord Howe Island woodhen Tricholimnas sylvestris (1) to compare the predictions of five different PVA packag es (INMAT, GAPPS, RAMAS/age, RAMAS/metapop and VORTEX); and (2) to tes t the predictions of PVA computer simulations against actual field dat a. All packages gave similar but unrealistic results under stochastic, densify-independent conditions. When a ceiling density dependence mod el was applied, projections based on a carrying capacity calculated fr om the habitat area proved too high. A PVA based on the knowledge avai lable at the time of the woodhen recovery program would have produced overly optimistic projections. Only when the carrying capacity was est imated fr om the observed historical population trends did the PVA pac kages give realistic predictions. (C) 1997 Published by Elsevier Scien ce Ltd.