scholarly journals Giraffe Translocation Population Viability Analysis

2019 ◽  
Author(s):  
Derek E. Lee ◽  
Elmar Fienieg ◽  
Cock Van Oosterhout ◽  
Zoe Muller ◽  
Megan Strauss ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Growth ◽  
Genetic Load ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Sensitivity Analyses ◽  
Source Population ◽  
Viability Analysis ◽  
Probability Of Extinction ◽  
Founding Populations

ABSTRACTMost populations of giraffes have declined in recent decades, leading to the recent decision to upgrade the species to vulnerable status, and some subspecies to endangered. Translocations have been used as a conservation tool to re-introduce giraffes to previously occupied areas or establish new populations, but guidelines for founding populations are lacking. To provide general guidelines for translocation projects regarding feasibility, we simulated various scenarios of translocated giraffe populations to identify viable age and sex distributions of founding populations using Population Viability Analysis (PVA) implemented in Vortex software. We explored the parameter space for demography (population growth rates: λ = 1.001, 1.010, 1.024), and the genetic load (number of lethal equivalents: LE = 2.5, 6.29, 12.6), examining how variation in founding numbers (N = 5 to 80 females) and sex ratios (M:F = 0.1 to 0.5) affected 100-year probability of extinction and genetic diversity. We found that even very small numbers of founders (N ≤10 females) can appear to be successful in the first decades due to transient positive population growth, but with moderate population growth rate and moderate genetic load, long-term population viability (probability of extinction <0.01) was only achieved with ≥30 females and ≥3 males released. To maintain >95% genetic diversity of the source population in an isolated population, 50 females and 5 males are recommended to comprise the founding population. Sensitivity analyses revealed first-year survival and reproductive rate were the simulation parameters with the greatest proportional influence on probability of extinction and genetic diversity. These simulations highlight important considerations for translocation success, and data gaps including true genetic load in wild giraffe populations.

scholarly journals Giraffe translocation population viability analysis

2020 ◽  
Vol 41 ◽  
pp. 245-252
Author(s):  
DE Lee ◽  
E Fienieg ◽  
C Van Oosterhout ◽  
Z Muller ◽  
M Strauss ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Growth ◽  
Genetic Load ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Sensitivity Analyses ◽  
Source Population ◽  
Viability Analysis ◽  
Probability Of Extinction ◽  
Founding Populations

Most populations of giraffes have declined in recent decades, leading to the recent IUCN decision to upgrade the species to Vulnerable status, and some subspecies to Endangered. Translocations have been used as a conservation tool to re-introduce giraffes to previously occupied areas or establish new populations, but guidelines for founding populations are lacking. To provide general guidelines for translocation projects regarding feasibility, we simulated various scenarios of translocated giraffe populations to identify viable age and sex distributions of founding populations using population viability analysis (PVA) implemented in Vortex software. We explored the parameter space for demography and the genetic load, examining how variation in founding numbers and sex ratios affected 100 yr probability of population extinction and genetic diversity. We found that even very small numbers of founders (N ≤ 10 females) can appear to be successful in the first decades due to transient positive population growth, but with moderate population growth rate and moderate genetic load, long-term population viability (probability of extinction <0.01) was only achieved with ≥30 females and ≥3 males released. To maintain >95% genetic diversity of the source population in an isolated population, 50 females and 5 males are recommended to compose the founding population. Sensitivity analyses revealed first-year survival and reproductive rate were the simulation parameters with the greatest proportional influence on probability of extinction and genetic diversity. These simulations highlight important considerations for translocation success and data gaps including true genetic load in wild giraffe populations.

VORTEX: a computer simulation model for population viability analysis

1993 ◽  
Vol 20 (1) ◽  
pp. 45 ◽  
Author(s):  
RC Lacy
Keyword(s):  
Computer Simulation ◽  
Population Growth ◽  
Simulation Model ◽  
Density Dependence ◽  
Carrying Capacity ◽  
Population Viability Analysis ◽  
Simulation Modelling ◽  
Population Viability ◽  
Reproductive Age ◽  
Viability Analysis

Population Viability Analysis (PVA) is the estimation of extinction probabilities by analyses that incorporate identifiable threats to population survival into models of the extinction process. Extrinsic forces, such as habitat loss, over-harvesting, and competition or predation by introduced species, often lead to population decline. Although the traditional methods of wildlife ecology can reveal such deterministic trends, random fluctuations that increase as populations become smaller can lead to extinction even of populations that have, on average, positive population growth when below carrying capacity. Computer simulation modelling provides a tool for exploring the viability of populations subjected to many complex, interacting deterministic and random processes. One such simulation model, VORTEX, has been used extensively by the Captive Breeding Specialist Group (Species Survival Commission, IUCN), by wildlife agencies, and by university classes. The algorithms, structure, assumptions and applications of VORTEX are described in this paper. VORTEX models population processes as discrete, sequential events, with probabilistic outcomes. VORTEX simulates birth and death processes and the transmission of genes through the generations by generating random numbers to determine whether each animal lives or dies, to determine the number of progeny produced by each female each year, and to determine which of the two alleles at a genetic locus are transmitted from each parent to each offspring. Fecundity is assumed to be independent of age after an animal reaches reproductive age. Mortality rates are specified for each pre-reproductive age-sex class and for reproductive-age animals. Inbreeding depression is modelled as a decrease in viability in inbred animals. The user has the option of modelling density dependence in reproductive rates. As a simple model of density dependence in survival, a carrying capacity is imposed by a probabilistic truncation of each age class if the population size exceeds the specified carrying capacity. VORTEX can model linear trends in the carrying capacity. VORTEX models environmental variation by sampling birth rates, death rates, and the carrying capacity from binomial or normal distributions. Catastrophes are modelled as sporadic random events that reduce survival and reproduction for one year. VORTEX also allows the user to supplement or harvest the population, and multiple subpopulations can be tracked, with user-specified migration among the units. VORTEX outputs summary statistics on population growth rates, the probability of population extinction, the time to extinction, and the mean size and genetic variation in extant populations. VORTEX necessarily makes many assumptions. The model it incorporates is most applicable to species with low fecundity and long lifespans, such as mammals, birds and reptiles. It integrates the interacting effects of many of the deterministic and stochastic processes that have an impact on the viability of small populations, providing opportunity for more complete analysis than is possible by other techniques. PVA by simulation modelling is an important tool for identifying populations at risk of extinction, determining the urgency of action, and evaluating options for management.

scholarly journals Halfway to self-sustainability: Reintroduced migratory European Northern Bald Ibises (Geronticus eremita) still need management interventions for population viability

2021 ◽  
Author(s):  
Sinah Drenske ◽  
Viktoriia Radchuk ◽  
Cédric Scherer ◽  
Corinna Esterer ◽  
Ingo Kowarik ◽  
...  
Keyword(s):  
Population Growth ◽  
Life Stage ◽  
Survival Rates ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Extinction Probability ◽  
Population Growth Rates ◽  
Viability Analysis ◽  
Management Interventions ◽  
Stochastic Events

Northern Bald Ibis (NBI) have disappeared from Europe already in Middle Age. Since 2003 a migratory population is reintroduced in Central Europe. We conducted demographic analyses of survival and reproduction of 384 NBI over a period of 12 years (2008-2019). These data also formed the basis for a population viability analysis (PVA) simulating the possible future development of the NBI population in different scenarios. We tested life-stage specific survival rates for differences between these stages, raising types and colonies as well as the influence of stochastic events and NBI supplements on the population growth. Stage specific survival rates ranged from 0.64 to 0.78. 61% of the mature females reproduce with a mean fecundity of 2.15 fledglings per nest. The complementary PVA indicated that the release population is close to self-sustainability with a given lambda 0.95 and 24% extinction probability within 50 years. Of the 326 future scenarios tested, 94 % reached the criteria of <5% extinction probability and population growth rates >1. In case of positive population growth, stochastic events had a limited effect. Of 820 sub-scenarios with different stochastic event frequencies and severities 87 % show population growth despite the occurrence of stochastic events. Predictions can be made based on the results of the individual-based model as to whether and under what circumstances the reintroduced NBI population can survive. This study shows that a PVA can support reintroduction success that should work closely together with the project in the field for mutual benefit, to optimize future management decisions.

scholarly journals Population Viability Analysis and Genetic Diversity of the Endangered Red DeerCervus elaphusPopulation from Mesola, Italy

2009 ◽  
Vol 15 (2) ◽  
pp. 175-186 ◽  
Author(s):  
Frank E. Zachos ◽  
Ghaiet M. Hajji ◽  
San San Hmwe ◽  
Günther B. Hartl ◽  
Rita Lorenzini ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Viability Analysis

Population viability analysis of common marsupials, Didelphis marsupialis and Didelphis virginiana, in a scenario of constant loss of native vegetation

Mammalia ◽  
2020 ◽  
Vol 84 (5) ◽  
pp. 475-482
Author(s):  
Bárbara Cruz-Salazar ◽  
Lorena Ruiz-Montoya
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Forest Cover ◽  
Environmental Changes ◽  
Mammalian Species ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Didelphis Virginiana ◽  
Metapopulation Dynamics ◽  
Viability Analysis

AbstractWe studied the population viability of two common marsupials, Didelphis marsupialis and Didelphis virginiana, based on field data and published ecological and genetic information. Using the VORTEX v. 10. 2.6 program, a 100-year simulation was performed with 1000 iterations for five populations of D. marsupialis and six of D. virginiana. A low probability of extinction was observed in both species, particularly for D. virginiana (0.000–0.007). Population size is higher considering a metapopulation dynamics approach versus individual populations for the two marsupials: 498.25 individuals for D. marsupialis and 367.41 individuals for D. virginiana. The estimated mean genetic diversity was high for both D. marsupialis (He = 0.77–0.78) and D. virginiana (He = 0.79–0.82). The survival of both species over time could be expected to increase if a metapopulation dynamics is favored over the coming decades, despite a 1.3% loss rate of forest cover. The monitoring of population size and genetic diversity is highly recommended to validate the trends suggested by the model; this is especially true for D. marsupialis, a species associated with conserved areas that are becoming progressively less abundant. This research provides information on the responses of common mammalian species to environmental changes such as deforestation.

scholarly journals A population viability analysis (PVA) for Cabot's Tragopan (Tragopan caboti) in Wuyanling, south-east China

2007 ◽  
Vol 17 (2) ◽  
pp. 151-161 ◽  
Author(s):  
Yanyun Zhang ◽  
Guangmei Zheng
Keyword(s):  
Population Size ◽  
Extinction Risk ◽  
Population Viability Analysis ◽  
Field Studies ◽  
Population Viability ◽  
Sensitivity Analyses ◽  
East China ◽  
Suitable Habitat ◽  
Bird Conservation ◽  
Viability Analysis

AbstractUnderstanding the status of fragmented populations and predicting their fate is an increasingly important part of bird conservation. Population viability analysis (PVA) can help in this process and is widely used for assessing the extinction risk faced by threatened species and for finding the key factors affecting population status and survival prospects. From 1982 to 2004, 14 scientists studied the population of the globally threatened Cabot's Tragopan Tragopan caboti in Wuyanling National Natural Reserve (WNNR), south-east China and collected life-history data on the population. Using VORTEX, we analysed the viability of the population in the reserve and this predicted that the population size will increase for the next 50 years and will then show a very slight decline for the next 50 years. The loss of heterozygosity is predicted to be 14%, suggesting that the population may not be viable in the long term. Sensitivity analyses showed that nest loss is the most important factor affecting population size and the survival probability of the population, which is supported by field studies. Though the new evidence shows that Cabot's Tragopan can build nests in spruce forest successfully, broad-leaf forest is still necessary for them for foraging, especially at some times of the year. The simulation also shows that the probability of survival and the size of the population will decrease markedly if the extent of suitable habitat is reduced even relatively slowly (such as 0.1% per year). Overall, we conclude that the PVA has provided very informative guidance to future management and research on Cabot's Tragopan at Wuyanling National Nature Reserve.

scholarly journals What do population viability analyses tell about the future for Baltic Dunlin Calidris alpina schinzii and Montagu’s Harrier Circus pygargus on Öland?

Ornis Svecica ◽  
2010 ◽  
Vol 20 (2) ◽  
Author(s):  
Per-Eric Betzholtz ◽  
Tobias Berger ◽  
Jan Petersson ◽  
Johan Stedt
Keyword(s):  
Extinction Risk ◽  
Bird Species ◽  
Population Viability Analysis ◽  
Field Work ◽  
Population Viability ◽  
Sensitivity Analyses ◽  
Viability Analysis ◽  
Circus Pygargus ◽  
Montagu’S Harrier ◽  
Montagu's Harrier

Population viability analysis (PVA) has become an important tool in conservation biology. Even though detailed outcomes of PVA:s are constrained by data quality, it is a useful approach when the objective is exploratory, aiming to identify important parameters for viability or to guide future field work on endangered species. In this study we perform PVA:s based on scarce data to explore viability of two endangered bird species, Baltic Dunlin and Montagu’s Harrier, on Öland. Our simulation results underline that both species are under severe threats, with a median time to extinction of 24 years in Baltic Dunlin and 63 years in Montagu’s Harrier. Sensitivity analyses show that population growth rate is the most important factor for the model outcome in both species. Since there are no apparent threats for adult birds on Öland, this suggests that conservation measures should focus on improving conditions for successful breeding on the island. In additional simulations we explore some threats in more detail. In the case of Baltic Dunlin nest predation of eggs and chicks increase the extinction risk. In Montagu’s Harrier viability increases if breeding attempts within agricultural areas are detected and safeguarded. In order to enhance the PVA model, and build a stage-structured model, we suggest that detailed data on fecundity and survival should be collected.

scholarly journals Blanding’s Turtle Demography and Population Viability

2021 ◽  
Author(s):  
Richard B. King ◽  
Callie K. Golba ◽  
Gary A. Glowacki ◽  
Andrew R. Kuhns
Keyword(s):  
Genetic Diversity ◽  
Extinction Risk ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Demographic Parameters ◽  
Initial Population ◽  
Blanding's Turtle ◽  
Viability Analysis ◽  
Initial Population Size ◽  
Blanding’S Turtle

In anticipation of US federal status classification (warranted, warranted but precluded, not warranted), scheduled for 2023, we provide population viability analysis of the Blanding’s turtle Emydoidea blandingii , a long-lived, late-maturing, semi-aquatic species of conservation concern throughout its range. We present demographic data from long-term study of a population in northeastern Illinois and use these data as the basis for viability and sensitivity analyses focused on parameter uncertainty and geographic parameter variation. We use population viability analysis to identify population sizes necessary to provide population resiliency to stochastic disturbance events and catastrophes and demonstrate how alternative definitions of ‘foreseeable future’ might affect status decisions. Demographic parameters within our focal population resulted in optimistic population projections (probability of extinction = 0% over 100 years) but results were less optimistic when catastrophes or uncertainty in parameter estimates were incorporated (probability of extinction = 3% and 16%, respectively). Uncertainty in estimates of age-specific mortality had the biggest impact on population viability analysis outcomes but uncertainty in other parameters (age of first reproduction, environmental variation in age-specific mortality, % females reproducing, clutch size) also contributed. Blanding’s turtle demography varies geographically and incorporating this variation resulted in both mortality- and fecundity-related parameters affecting population viability analysis outcomes. Possibly, compensatory variation among demographic parameters allows for persistence across a wide range of parameter values. We found that extinction risk decreased and retention of genetic diversity increased rapidly with increasing initial population size. In the absence of catastrophes, demographic conservation goals could be met with a smaller initial population size than could genetic conservation goals; ≥20-50 adults were necessary for extinction risk &lt;5% whereas ≥50-110 adults were necessary to retain &gt;95% of existing genetic diversity over 100 yrs. These thresholds shifted upward when catastrophes were included; ≥50-200 adults were necessary for extinction risk &lt;5% and ≥110 to more than 200 adults were necessary to retain &gt;95% of existing genetic diversity over 100 yrs. Impediments to Blanding’s turtle conservation include an incomplete understanding of geographic covariation among demographic parameters, the large amount of effort necessary to estimate and monitor abundance, and uncertainty regarding the impacts of increasingly frequent extreme weather events.

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