scholarly journals Predators and genetic fitness: key threatening factors for the conservation of a bettong species

2017 ◽  
Vol 23 (2) ◽  
pp. 200 ◽  
Author(s):  
Carlo Pacioni ◽  
Matthew R. Williams ◽  
Robert C. Lacy ◽  
Peter B. S. Spencer ◽  
Adrian F. Wayne
Keyword(s):  
Management Strategies ◽  
Population Viability Analysis ◽  
Active Management ◽  
Viability Analysis ◽  
Similar Work ◽  
Bettongia Penicillata ◽  
Viable Population ◽  
Threatening Processes ◽  
Minimum Viable Population Size ◽  
Future Work

Globally, many wildlife species are declining and an increasing number are threatened by extinction or are extinct. Active management is generally required to mitigate these trends and population viability analysis (PVA) enables different scenarios to be evaluated and informs management decisions. Based on population parameters obtained from a threatened bettong, the woylie (Bettongia penicillata ogilbyi), we developed and validated a PVA model. We identified the demographic and genetic responses to different threatening factors and developed a general framework that would facilitate similar work in other bettong species. The two main threatening processes are predation by introduced animals and its interaction with reduced fitness (e.g. due to inbreeding depression or a disease). Although predation alone can drive a decline in certain circumstances (e.g. when predation success is independent from prey population density), synergistically, predation and reduced fitness can be particularly relevant, especially for small populations. The minimum viable population size was estimated at 1000–2000 individuals. In addition, the models identified that research into age-specific mortality rates and predation rates by introduced animals should be the focus of future work. The PVA model created here provides a basis to investigate threatening processes and management strategies in woylie populations and other extant bettong species, given the ecological and physiological similarities among these threatened species.

scholarly journals Use of Bayesian population viability analysis to assess multiple management decisions in the recovery programme for the Endangered takahe Porphyrio hochstetteri

Oryx ◽  
2013 ◽  
Vol 47 (1) ◽  
pp. 144-152 ◽  
Author(s):  
Danilo Hegg ◽  
Darryl I. MacKenzie ◽  
Ian G. Jamieson
Keyword(s):  
Probability Distributions ◽  
Management Strategies ◽  
Population Viability Analysis ◽  
Experimental Manipulation ◽  
Population Modelling ◽  
Deterministic Models ◽  
Logistic Regression Models ◽  
Viability Analysis ◽  
Management Actions ◽  
Captive Rearing

AbstractPopulation modelling is an invaluable tool for identifying effective management strategies for threatened species whose populations are too small for experimental manipulation. Recently developed Bayesian approaches allow us to combine deterministic models with probability distributions to create stochastic models that account for uncertainty. We illustrate this approach in the case of the takahe Porphyrio hochstetteri, an Endangered flightless rail, which is supported by one of New Zealand's costliest recovery programmes. Using mark–recapture and logistic regression models implemented in a Bayesian framework we calculated demographic parameters for a fully stochastic population model based on 25 years of data collected from the last wild population of takahe in the Murchison Mountains, Fiordland. Our model results show that stoat trapping, captive rearing and cross-fostering of eggs/chicks in wild pairs all have a positive effect on takahe demography. If it were not for these management actions the Fiordland population would probably be declining (λ = 0.985; confidence interval, CI = 0.39–1.08), with a non-negligible risk of quasi-extinction (P = 16%) within 20 years. The captive rearing of eggs and chicks has been the main factor responsible for the positive growth observed during the last decade but in the future expanding stoat trapping to cover the entire Murchison Mountains would be the single most beneficial management action for the takahe population (λ = 1.038; CI = 0.86–1.10), followed by captive rearing (λ = 1.027; CI = 0.85–1.09).

Invasive predators represent the greatest extinction threat to the endangered northern bettong (Bettongia tropica)

2018 ◽  
Vol 45 (3) ◽  
pp. 208 ◽  
Author(s):  
Tegan Whitehead ◽  
Karl Vernes ◽  
Miriam Goosem ◽  
Sandra E. Abell
Keyword(s):  
Climate Change ◽  
Synergistic Effects ◽  
Management Strategies ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Active Management ◽  
Feral Cats ◽  
Juvenile Mortality ◽  
Management Actions ◽  
Eastern Australia

Context Identification of key threats to endangered species is vital for devising effective management strategies, but may be hindered when relevant data is limited. A population viability approach may overcome this problem. Aims We aimed to determine the population viability of endangered northern bettongs (Bettongia tropica) in north-eastern Australia. We also assessed the key threats to the population resilience and how the population viability responds to increases in mortality rates and changes in fire and drought frequency. Methods Using population viability analysis (PVA) we modelled survival probability of B. tropica populations under likely scenarios, including: (1) increased predation; (2) changes in drought and fire frequency predicted with anthropogenic climate change; and (3) synergistic effects of predation, fire and drought. Key results Population viability models suggest that populations are highly vulnerable to increases in predation by feral cats (Felis catus), and potentially red fox (Vulpes vulpes) should they colonise the area, as juvenile mortality is the main age class driving population viability. If B. tropica become more vulnerable to predators during post-fire vegetation recovery, more frequent fires could exacerbate effects of low-level cat predation. In contrast, it was predicted that populations would be resilient to the greater frequency of droughts expected as a result of climate change, with high probabilities of extinctions only predicted under the unprecedented and unlikely scenario of four drought years in 10. However, since drought and fire are interlinked, the impacts of predation could be more severe with climate change should predation and fire interact to increase B. tropica mortality risk. Conclusion Like other Potoroids, B. tropica appear highly vulnerable to predation by introduced mammalian predators such as feral cats. Implications Managers need information allowing them to recognise scenarios when populations are most vulnerable to potential threats, such as drought, fire and predation. PVA modelling can assess scenarios and allow pro-active management based on predicted responses rather than requiring collection of extensive field data before management actions. Our analysis suggests that assessing and controlling predator populations and thereby minimising predation, particularly of juveniles, should assist in maintaining stability of populations of the northern bettong.

Viability analyses of an endangered donkey breed: the case of the Asinina de Miranda (Equus asinus)

2015 ◽  
Vol 55 (9) ◽  
pp. 1184 ◽  
Author(s):  
M. Quaresma ◽  
A. M. F. Martins ◽  
J. B. Rodrigues ◽  
J. Colaço ◽  
R. Payan-Carreira
Keyword(s):  
Neonatal Mortality ◽  
Management Strategies ◽  
Population Viability Analysis ◽  
Critical Factor ◽  
Mortality Rates ◽  
Population Viability ◽  
Analysis Program ◽  
Female Mortality ◽  
Viability Analysis ◽  
Equus Asinus

The donkey breed Asinina de Miranda, with fewer than 1000 breeding females, is in danger of extinction. The objectives of this study were to predict the progression of the breed under present management and identify determinants for survival, by means of a population viability analysis program, in order to suggest suitable management strategies. The simulation showed a high risk of extinction. The most critical factor for breed survival was the percentage of females breeding per year, but the actual percentage needed depended on the carrying capacity of the breed. Reducing female mortality and age at production of first offspring, assuring registration in the Studbook, and tracking the foals will significantly foster this donkey breed’s recovery and maintenance. The breed comprised a potentially reproductive population of 589 individuals; however, just 54.1% of the adult females registered in the Studbook ever foaled, and of these 62.7% foaled just once. The overall neonatal mortality for the first month of life was 8.92% and was lower in females (6.51%) than in males (12.0%) (P = 0.028). Neonatal mortality was unevenly distributed throughout the year, with lower mortality rates recorded in February–May and October–November, and higher mortality rates in June–September and again in December–January. The neonatal foal mortality rate was lower with females aged 5–15 years (8.06%) than those younger than 4 years (10.3%) or older than 16 years (14.1%) at foaling.

Modelling the impact of predation on reintroductions of bridled nailtail wallabies.

1995 ◽  
Vol 22 (2) ◽  
pp. 163 ◽  
Author(s):  
H McCallum ◽  
P Timmers ◽  
. Hoyle.S
Keyword(s):  
Population Viability Analysis ◽  
Population Viability ◽  
Predator Prey ◽  
Viability Analysis ◽  
Standard Population ◽  
Viable Population ◽  
Almost All ◽  
The Impact ◽  
Number Of Individuals ◽  
Simple Stochastic Model

Predation by introduced foxes and cats is generally thought to be the main reason for the poor success rate of macropod reintroductions on the Australian mainland. Predator-prey theory suggests that predation may have particularly severe impacts on very small populations, especially if a more common primary prey species is present (such as the rabbit). Thus, a sufficiently large reintroduction may overcome predation and succeed where a smaller one would fail. The minimum viable population would, however, be much larger than that predicted by standard population-viability analysis. We use a simple stochastic model based upon the bridled nailtail wallaby to explore this possibility. Even very small amounts of predation (2-4 individuals per six months) can be sufficient to cause reintroductions of up to 50 animals to fail. No clear threshold population size beyond which reintroductions will succeed is evident and, for a given mean, the probability distribution of predation has a very limited impact on the success of reintroductions. In almost all circumstances, a single reintroduction of a given size is preferable to multiple reintroductions of the same total number of individuals.

Uncertainty in assessing the viability of the Powerful Owl Ninox strenua in Victoria, Australia

1999 ◽  
Vol 5 (2) ◽  
pp. 144 ◽  
Author(s):  
Michael A. McCarthy ◽  
Alan Webster ◽  
Richard H. Loyn ◽  
Kim W. Lowe
Keyword(s):  
Management Strategies ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Large Field ◽  
Adult Survival ◽  
Metapopulation Dynamics ◽  
Viability Analysis ◽  
Term Monitoring ◽  
Predicted Risk

A model of the metapopulation dynamics of Powerful Owls Ninox strenua in Victoria, Australia is described, and its parameters were derived from available data. Sensitivity analysis indicates that the survival rate of adult owls is the most important parameter in the model. Because estimates of this parameter are uncertain, the predictions of the model are uncertain and unreliable. Using the best estimates of the parameters, the predicted risk of decline across Victoria is low, and local populations larger than 100 pairs have a low risk of extinction. If the lower estimates of adult and sub-adult survival are used, the abundance of Powerful Owls across Victoria is predicted to decline exponentially and faces extinction from deterministic forces. A prohibitively large field programme involving monitoring of individuallyrecognizable owls would be required to obtain an improved estimate of adult survival, and so further use of population viability analysis to assess the adequacy of particular management strategies is unlikely to be useful for this species. An alternative is to establish a long-term monitoring programme to document changes in abundance of the species in logged and unlogged landscapes.

scholarly journals A Population Viability Analysis for Sharp-Tailed Grouse to Inform Reintroductions

2018 ◽  
Vol 9 (2) ◽  
pp. 565-581 ◽  
Author(s):  
Megan C. Milligan ◽  
Smith L. Wells ◽  
Lance B. McNew
Keyword(s):  
Habitat Management ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Average Density ◽  
Western Montana ◽  
Management Scenarios ◽  
Winter Habitat ◽  
Viability Analysis ◽  
Continental Divide ◽  
Viable Population

Abstract Sharp-tailed grouse Tympanuchus phasianellus were effectively extirpated from western Montana during the last century as a result of settlement by Euro-Americans. Recent interest in reestablishing the species west of the Continental Divide has identified information gaps related to the potential success of a restoration effort. Elsewhere, sharp-tailed grouse are widespread and exhibit plasticity in habitat use, suggesting a high potential for successful reintroduction. Using life history information from the published literature, we conducted a population viability analysis to assess the potential viability of a reintroduced population of sharp-tailed grouse in western Montana and to evaluate what management scenarios, with regard to both translocation protocols and habitat management, would be necessary to produce a viable population. Results of the population viability analysis indicated that a population parameterized with mean reported demographic rates and related environmental variation would not be viable and suggest a potential downward bias in demographic estimates in the published literature. Based on our simulation results, improvements in both fecundity and annual survival resulting from improvements in nesting and winter habitat would be necessary to produce a viable population of sharp-tailed grouse in western Montana. The minimum amount of habitat required to support a viable population of 280 individuals was 1,867–5,600 ha, assuming habitat is sufficient to support an average density of 5–15 grouse per km2. We provide a review of demographic and reintroduction information for sharp-tailed grouse and recommendations regarding reintroduction approaches based on our population viability analysis results that should increase the relative success of restoration efforts in western Montana and elsewhere. We recommend that nesting and winter habitat improvements be the focus of pre- and postrelease management and that post-translocation population studies be conducted to monitor reintroduced populations and provide site-specific demographic information to update population viability analyses.

Population Viability Analysis for Endangered Roanoke Logperch

2016 ◽  
Vol 7 (1) ◽  
pp. 46-64 ◽  
Author(s):  
James H. Roberts ◽  
Paul L. Angermeier ◽  
Gregory B. Anderson
Keyword(s):  
Population Growth ◽  
Carrying Capacity ◽  
Extinction Risk ◽  
Management Strategies ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Stream Fish ◽  
Fish Kills ◽  
Viability Analysis ◽  
Roanoke Logperch

Abstract A common strategy for recovering endangered species is ensuring that populations exceed the minimum viable population size (MVP), a demographic benchmark that theoretically ensures low long-term extinction risk. One method of establishing MVP is population viability analysis, a modeling technique that simulates population trajectories and forecasts extinction risk based on a series of biological, environmental, and management assumptions. Such models also help identify key uncertainties that have a large influence on extinction risk. We used stochastic count-based simulation models to explore extinction risk, MVP, and the possible benefits of alternative management strategies in populations of Roanoke logperch Percina rex, an endangered stream fish. Estimates of extinction risk were sensitive to the assumed population growth rate and model type, carrying capacity, and catastrophe regime (frequency and severity of anthropogenic fish kills), whereas demographic augmentation did little to reduce extinction risk. Under density-dependent growth, the estimated MVP for Roanoke logperch ranged from 200 to 4200 individuals, depending on the assumed severity of catastrophes. Thus, depending on the MVP threshold, anywhere from two to all five of the logperch populations we assessed were projected to be viable. Despite this uncertainty, these results help identify populations with the greatest relative extinction risk, as well as management strategies that might reduce this risk the most, such as increasing carrying capacity and reducing fish kills. Better estimates of population growth parameters and catastrophe regimes would facilitate the refinement of MVP and extinction-risk estimates, and they should be a high priority for future research on Roanoke logperch and other imperiled stream-fish species.

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

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yashuai Zhang ◽  
Fang Wang ◽  
Zhenxia Cui ◽  
Min Li ◽  
Xia Li ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Carrying Capacity ◽  
Wild Population ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Viability Analysis ◽  
Crested Ibis ◽  
Reintroduced Population

Abstract 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 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. 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.

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