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

Background: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 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.Methods:The 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.Results:The reintroduced population in Ningshan County is unlikely to go extinct in the next 50 years.The popula-tion 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.Conclusions:A 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.

Population viability analysis of small population:a case study for Asian elephant in China

Small populations are at risk of extinction from deterministic and stochastic factors.Less than 250 Asian elephants(Elephas maximus)remain in China,and are distributed in a few isolated areas;yet,population viability analyses of this endangered population have not been conducted.Here,the current genetic status of the Pu’Er-Mengyang Asian elephant populations in China was analyzed,and the risk of extinction was predicted over the next 500 years.Factors affecting the viability of this population were determined through simulations.The genetic diversity of the population was very low(mean allele number:3.1;expected heterozygosity:0.463),even though a recent population bottleneck was not detected.The effective population size was approximately 24.1 adult elephants.Enough adult breeding individuals exist to maintain population viability.VORTEX simulation model showed that this population would not go extinct in the next 500 years.However,illegal poaching and harvesting could negatively affect population size.A sensitivity analysis showed that the mean stochastic growth rate of the study population is sensitive to sex ratio,number of breeding females,mortality of females of different age classes,carrying capacity,and lethal equivalents.Based on our results,we suggest that action should be taken to alleviate inbreeding and any further loss of genetic diversity,by connecting fragmented elephant habitat or by translocating individual elephants.In addition,human–elephant conflict should be mitigated using various modern approaches,including crop guarding techniques,and by encouraging farmers to switch to crops and income sources not vulnerable to elephant raids.

Population viability analysis: using a modeling tool to assess the viability of tapir populations in fragmented landscapes

A population viability analysis(PVA)was conducted of the lowland tapir populations in the Atlantic Forest of the Pontal do Paranapanema region,Brazil,including Morro do Diabo State Park(MDSP)and surrounding forest fragments.Results from the model projected that the population of 126 tapirs in MDSP is likely to per-sist over the next 100 years;however,200 tapirs would be required to maintain a viable population.Sensitiv-ity analysis showed that sub-adult mortality and adult mortality have the strongest influence on the dynamics of lowland tapir populations.High road-kill has a major impact on the MDSP tapir population and can lead to population extinction.Metapopulation modeling showed that dispersal of tapirs from MDSP to the surrounding fragments can be detrimental to the overall metapopulation,as fragments act as sinks.Nevertheless,the model showed that under certain conditions the maintenance of the metapopulation dynamics might be determinant for the persistence of tapirs in the region,particularly in the smaller fragments.The establishment of corridors con-necting MDSP to the forest fragments models resulted in an increase in the stochastic growth rate,making ta-pirs more resilient to threats and catastrophes,but only if rates of mortality were not increased when using cor-ridors.The PVA showed that the conservation of tapirs in the Pontal region depends on:the effective protection of MDSP;maintenance and,whenever possible,enhancement of the functional connectivity of the landscape,reducing mortality during dispersal and threats in the unprotected forest fragments;and neutralization of all threats affecting tapirs in the smaller forest fragments.

Addressing the impact of canine distemper spreading on an isolated tiger population in northeast Asia

The continuation of the isolated Amur tiger(Panthera tigris altaica)population living along the China-Russia border is facing serious challenges due to factors such as its small size(including 38 individuals)and canine distemper virus(CDV).We use a population viability analysis metamodel,which consists of a traditional individual-based demographic model linked to an epidemiological model,to assess options for controlling the impact of negative factors through domestic dog management in protected areas,increasing connectivity to the neighboring large population(including more than 400 individuals),and habitat expansion.Without intervention,under inbreeding depression of 3.14,6.29,and 12.26 lethal equivalents,our metamodel predicted the extinction within 100 years is 64.4%,90.6%,and 99.8%,respectively.In addition,the simulation results showed that dog management or habitat expansion independently will not ensure tiger population viability for the next 100 years,and connectivity to the neighboring population would only keep the population size from rapidly declining.However,when the above three conservation scenarios are combined,even at the highest level of 12.26 lethal equivalents inbreeding depression,population size will not decline and the probability of extinction will be<5.8%.Our findings highlight that protecting the Amur tiger necessitates a multifaceted synergistic effort.Our key management recommendations for this population underline the importance of reducing CDV threats and expanding tiger occupancy to its former range in China,but re-establishing habitat connectivity to the neighboring population is an important long-term objective.

Rapid ongoing decline of Baird’s tapir in Cusuco National Park, Honduras

During the International Tapir Symposium 16-21 Oct 2011,the conservation of Baird's tapir(Tapirus baindi)in Honduras received a boost with the signing of a memorandum of understanding between the Minister Direc-tor of the Honduran Instute of Conservation and Forestry(CF)and the Tapir Specialist Group(TSG)Despite this agreement,accelerating levels of hunting and habitat loss contimue to pose a threat to Baird's tapir in Hon-duras.An ongoing study in Cusuco National Park in northwestern Honduras has been monitoring changes in population dynamics of Baird's tapir since 2006 through the collection of occupancy data.The study has iden-tified an increase in hunting pressure,coinciding with a drastic decline in the encounter rate with Baird's tapir spoor.Here,we examine the significance of a range of demographic variables on Baird's tapir occupancy in Cu-suco National Park using the software PRESENCE,and simulate the effects of different management strategies on the fiuture dynamics of the population using the stochastic simulation software VORTEX The predictions of the theoretical population models are compared to observed changes in occupancy levels.We found that non-intervention resulted in the local extinction of Baird's tapir within a very short time fiame,but that various in-tervention models enabled the population to recover to near carrying capacity.Occupancy and extinction prob-ability were shown to respond marlkedly to the increase in hunting pressure;and occupancy models supported the fiuture population predictions generated by VORTEX.Our study suggests that immediate intervention is re-quired to reduce hunting pressure to near historical levels to prevent the imminent 1ocal extinction of the species.