Assessing the impact of removal scenarios on population viability of a threatened, long-lived avian scavenger.

Antoni Margalida,Daniel Oro,José A Donázar,Raphaël Arlettaz,Mª Àngels Colomer,Ma Àngels Colomer

doi:10.1038/srep16962

Abstract

The removal of eggs or chicks from wild populations to create captive populations, reinforce free-ranging populations or reintroduce species into the wild is a restoration tool that requires an assessment of potential detrimental effects upon the donor population. This is an absolute prerequisite when wild donor populations are scarce and small. Here, we forecast the population trend of the largest European population of the bearded vulture (Gypaetus barbatus) over the next 30 years under different demographic and management scenarios (removal of eggs, chicks or fledglings). Projections derived from the combination of a PDP model (Population Dynamic P-system) and a Box-Behnken design would lead to a decline in 77% of all 57 scenarios analysed. Among the 13 scenarios predicting a population increase, only 4 seem realistic in terms of growth rate (0.04%–1.01%), at least if current age at first breeding and productivity would remain constant over time. Our simulations thus suggest that most extraction scenarios would have detrimental effects on the demography of the donor population. Release of captive-born young or removal of only the second hatched chick for subsequent captive rearing and translocation into the wild appear to represent much better supplementation and reintroduction options in this threatened species.

Highlights

Tool among managers and policy makers who often need to make quick decisions based on sensible demographic predictions[1,4,6,11,12,13,14,15,16]
We assessed the viability of the Pyrenean population by combining a PDP model (Population Dynamic P-system) with a Box-Benkhen design that models using the full value range of known demographic parameters
Let us provide an example of how these interactions between vital rates can dramatically affect demographic trajectories

Summary

Introduction

Tool among managers and policy makers who often need to make quick decisions based on sensible demographic predictions[1,4,6,11,12,13,14,15,16]. We assessed the viability of the Pyrenean population by combining a PDP model (Population Dynamic P-system) with a Box-Benkhen design that models using the full value range (minimum and maximum) of known demographic parameters. This latter tool enables both predicting population trends and identifying the most sensitive parameters influencing population dynamics. We 1) built a model assessing the Pyrenean population trend under different extraction scenarios while determining the relative sensitivity of key vital rates (fecundity, survival of different age classes, age at first reproduction) and accounting for density-dependent regulatory mechanisms; and 2) simulated the effects of different extraction scenarios (removal of eggs, chicks or fledglings)–foreseen for reintroducing the species in currently abandoned Spanish mountain ranges–upon the dynamics of the population serving as a donor

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