Can we reestablish a self-sustaining population? A case study on reintroduced Crested Ibis with population viability analysis

Yashuai Zhang,Min Li,Zhenxia Cui,Xiaoping Yu,Fang Wang,Xinping Ye,Xia Li

doi:10.1186/s40657-021-00250-z

Abstract

BackgroundOne of the most challenging tasks in wildlife conservation and management is clarifying which and how external and intrinsic factors influence wildlife demography and long-term viability. The wild population of the Crested Ibis (Nipponia nippon) has recovered to approximately 4400, and several reintroduction programs have been carried out in China, Japan and Korea. Population viability analysis on this endangered species has been limited to the wild population, showing that the long-term population growth is restricted by the carrying capacity and inbreeding. However, gaps in knowledge of the viability of the reintroduced population and its drivers in the release environment impede the identification of the most effective population-level priorities for aiding in species recovery.MethodsThe field monitoring data were collected from a reintroduced Crested Ibis population in Ningshan, China from 2007 to 2018. An individual-based VORTEX model (Version 10.3.5.0) was used to predict the future viability of the reintroduced population by incorporating adaptive patterns of ibis movement in relation to catastrophe frequency, mortality and sex ratio.ResultsThe reintroduced population in Ningshan County is unlikely to go extinct in the next 50 years. The population size was estimated to be 367, and the population genetic diversity was estimated to be 0.97. Sensitivity analysis showed that population size and extinction probability were dependent on the carrying capacity and sex ratio. The carrying capacity is the main factor accounting for the population size and genetic diversity, while the sex ratio is the primary factor responsible for the population growth trend.ConclusionsA viable population of the Crested Ibis can be established according to population viability analysis. Based on our results, conservation management should prioritize a balanced sex ratio, high-quality habitat and low mortality.

Highlights

One of the most challenging tasks in wildlife conservation and management is clarifying which and how external and intrinsic factors influence wildlife demography and long-term viability
The sensitivity index (Sx) of the population clearly showed that carrying capacity, sex ratio, frequency of catastrophes, and mortality were the four factors accounting for the population parameters (Table 2)
The carrying capacity affects the genetic diversity of the population

Summary

Introduction

One of the most challenging tasks in wildlife conservation and management is clarifying which and how external and intrinsic factors influence wildlife demography and long-term viability. Population viability analysis on this endangered species has been limited to the wild population, showing that the long-term population growth is restricted by the carrying capacity and inbreeding. Any reintroduction projects may fail to establish populations owing to either external or intrinsic factors that influence wildlife demography and. The PVA results of the Western Lowland Gorillas (Gorilla gorilla gorilla) suggested that the reintroduced gorilla populations have a reasonable chance of persistence over 200 years, but the reinforcement of the populations could significantly improve probabilities of population persistence and retention of genetic diversity (King et al 2014). Simulation results of PVA of the Sharp-tailed Grouse (Tympanuchus phasianellus) showed that, in a fixed scenario, improvement of habitat quality could facilitate the establishment of a minimum viable population by increasing fecundity and wintering survival (Milligan et al 2018)

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Results

Conclusion