scholarly journals Conservation of Northwestern and Southwestern Pond Turtles: Threats, Population Size Estimates, and Population Viability Analysis

2021 ◽  
Author(s):  
Stephanie Manzo ◽  
E. Griffin Nicholson ◽  
Zachary Devereux ◽  
Robert N. Fisher ◽  
Chris W. Brown ◽  
...  
Keyword(s):  
Natural Disasters ◽  
Population Size ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Population Declines ◽  
Viability Analysis ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Size Estimates

Accurate status assessments of long-lived, widely distributed taxa depend on the availability of long-term monitoring data from multiple populations. However, monitoring populations across large temporal and spatial scales is often beyond the scope of any one researcher or research group. Consequently, wildlife managers may be tasked with utilizing limited information from different sources to detect range-wide evidence of population declines and their causes. When assessments need to be made under such constraints, the research and management communities must determine how to extrapolate from variable population data to species-level inferences. Here, using three different approaches, we integrate and analyze data from the peer-reviewed literature and government agency reports to inform conservation for northwestern pond turtles (NPT) Actinemys marmorata and southwestern pond turtles (SPT) Actinemys pallida. Both NPT and SPT are long-lived freshwater turtles distributed along the west coast of the United States and Mexico. Conservation concerns exist for both species; however, SPT may face more severe threats and are thought to exist at lower densities throughout their range than NPT. For each species, we ranked the impacts of 13 potential threats, estimated population sizes, and modeled population viability with and without long-term droughts. Our results suggest that predation of hatchlings by invasive predators, such as American bullfrogs Lithobates catesbeianus and Largemouth Bass Micropterus salmoides, is a high-ranking threat for NPT and SPT. Southwestern pond turtles may also face more severe impacts associated with natural disasters (droughts, wildfires, and floods) than NPT. Population size estimates from trapping surveys indicate that SPT have smaller population sizes on average than NPT (p = 0.0003), suggesting they may be at greater risk of local extirpation. Population viability analysis models revealed that long-term droughts are a key environmental parameter; as the frequency of severe droughts increases with climate change, the likelihood of population recovery decreases, especially when census sizes are low. Given current population trends and vulnerability to natural disasters throughout their range, we suggest that conservation and recovery actions first focus on SPT to prevent further population declines.

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.

Predictions of the impacts of changes in population size and environmental variablitity on Leadbeater's possum, Gymnobelideus leadbeateri McCoy (Marsupialia: Petauridae) using population viability analysis: an application of the computer program VORTEX.

1993 ◽  
Vol 20 (1) ◽  
pp. 67 ◽  
Author(s):  
DB Lindenmayer ◽  
RC Lacy ◽  
VC Thomas ◽  
TW Clark
Keyword(s):  
Computer Program ◽  
Population Size ◽  
Carrying Capacity ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Suitable Habitat ◽  
Viability Analysis ◽  
Nest Sites ◽  
Leadbeater's Possum

Population Viability Analysis (PVA) uses computer modelling to simulate interacting deterministic and stochastic factors (e.g. demographic, genetic, spatial, environmental and catastrophic processes) that act on small populations and assess their long-term vulnerability to extinction. The computer program VORTEX was used in a PVA of Leadbeater's possum, Gymnobelideus leadbeateri McCoy, an endangered arboreal marsupial that is restricted to the montane ash forests of the central highlands of Victoria. PVA was used to examine the impacts of changes in the size of subpopulations and the effects of environmental variation. Our analyses demonstrated that an annual linear decline in the carrying capacity in all or parts of the habitat will lead to the extinction of G. leadbeateri in those areas. Mean time to extinction was related to the rate of annual decrease. This conclusion is of practical and management importance as there is presently a decline in suitable habitat because of an annual loss of more than 3.5% of trees with hollows, which provide nest sites for G. leadbeateri. Because nest sites are a factor that limits populations of G. leadbeateri, the species could be lost from large areas within the next 50 years. PVA was also used to determine the viability of populations in areas, such as oldgrowth forest, where there is not likely to be a steady decline in habitat carrying capacity resulting from the loss of trees with hollows. This allowed an analysis of the cumulative impacts of small population size, environmental variation and genetic factors, which showed that, for a 100-year projection, simulated populations of 200 animals or more remained demographically stable and experienced a less than 10% decline in predicted genetic variability. However, the relatively simplified nature of population modelling and the suite of assumptions that underpin VORTEX mean that the probability of extinction of populations of this size may be greater than determined in this study. As a result, it is possible that only populations of more than 200 animals may persist in the long term where suitable habitat can be conserved or established and subsequently maintained without a reduction in carrying capacity.

Estimation of Catchabilities and Population Sizes of Lobsters

1963 ◽  
Vol 20 (1) ◽  
pp. 59-88 ◽  
Author(s):  
J. E. Paloheimo
Keyword(s):  
Environmental Factors ◽  
Population Size ◽  
Atlantic Coast ◽  
Temperature Data ◽  
New Method ◽  
Bottom Temperature ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Estimate Population Size ◽  
Size Estimates

Techniques of estimating population size, level of fishing, and the degree of dependence of fishing success on environmental factors are examined on the basis of tagging, catch and effort data. A new method is developed to estimate population size from catch, effort, and temperature data when the catchability varies with temperature.The methods of estimation discussed are applied to data collected from a number of lobster fisheries on Canada's Atlantic coast. Analysis confirms a relationship between the catchability of lobsters and bottom temperature. Differences in this relationship are found between areas and between tagged and untagged lobsters within areas. It is suggested that these differences are attributable to the differences in densities as well as to aggregations of lobsters and fishing. The effect of these aggregations on population size estimates is considered.Calculated average catchabilities at comparable temperatures are different for different areas. These differences are correlated with the numbers of trap hauls per day per square miles fished. It is suggested that the differences in the catchabilities might be due to interactions between units of gear not predicted by the customary relationship between catch and effort.

Population viability analysis on a native Danish cattle breed

2016 ◽  
Vol 59 ◽  
pp. 105-112 ◽  
Author(s):  
Morten Hertz ◽  
Iben Ravnborg Jensen ◽  
Laura Østergaard Jensen ◽  
Iben Vejrum Nielsen ◽  
Jacob Winde ◽  
...  
Keyword(s):  
Bos Taurus ◽  
Extinction Risk ◽  
Population Viability Analysis ◽  
Cattle Breed ◽  
Population Viability ◽  
Small Population ◽  
Viability Analysis ◽  
Probability Of Survival ◽  
Population Sizes ◽  
Breeding Pool

SummaryMany domestic breeds face challenges concerning genetic variability, because of their small population sizes along with a high risk of inbreeding. Therefore, it is important to obtain knowledge on their extinction risk, along with the possible benefits of certain breeding strategies. Since many domestic breeds face the same problems, results from such studies can be applied across breeds and species. Here a Population Viability Analysis (PVA) was implemented to simulate the future probability of extinction for a population of the endangered Danish Jutland cattle (Bos taurus), based on the software Vortex. A PVA evaluates the extinction risk of a population by including threats and demographic values. According to the results from the PVA the population will go extinct after 122 years with the current management. Four scenarios were created to investigate which changes in the breeding scheme would have the largest effect on the survival probabilities, including Scenario 1: More females in the breeding pool, scenario 2: More males in the breeding pool, scenario 3: Increased carrying capacity, and scenario 4: Supplementing males to the population through artificial insemination using semen from bulls used in the populations in past generations. All scenarios showed a positive effect on the population's probability of survival, and with a combination of the different scenarios, the population size seems to be stabilized.

Reproductive biology, post-fire succession dynamics and population viability analysis of the critically endangered Western Australian shrub Calytrix breviseta subsp. breviseta (Myrtaceae)

2009 ◽  
Vol 57 (6) ◽  
pp. 451 ◽  
Author(s):  
Andrew P. Nield ◽  
Philip G. Ladd ◽  
Colin J. Yates
Keyword(s):  
Reproductive Biology ◽  
Carrying Capacity ◽  
Seedling Recruitment ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Fire Return Interval ◽  
Viability Analysis ◽  
Return Interval ◽  
Western Australian

Calytrix breviseta Lindl. subsp. breviseta is a critically endangered, obligate-seeder shrub within fire-prone kwongan of south-west Western Australia. Little is known about the species’ reproductive biology and how threatening processes, particularly altered fire regimes and exotic species invasion, will impact the long-term viability of the species. This study aims to elucidate the species’ reproductive biology and patterns of seedling recruitment during succession after fire. The effects of changes to the fire return interval and exotic species invasion on the long-term viability of the species is also described. The species exhibits abundant recruitment following fire and the application of a smoke treatment significantly improves germination, similar to many other Western Australian shrubs. However, significant inter-fire recruitment was observed up to 10 years following fire, leading to the presence of multi-aged subpopulations, although seedling recruitment was negligible >20 years after fire. The juvenile period is short at 3–4 years to first flowering. Population viability analysis (PVA) predicted that the optimal fire return interval to maintain C. breviseta subsp. breviseta was dependent on the carrying capacity (K) of the community and the number of individuals present. Carrying capacity will be related to site quality and competition from invasive species. PVA showed that if K remains high, then the optimal fire return interval is ~15–20 years, but under lower carrying capacity, (i.e. weed competition) fires decrease the likelihood of population survival.

Mark-release-recapture studies on three anthropophilic populations of Aedes (Stegomyia) simpsoni comple(Diptera: Culicidae) in Uganda

1994 ◽  
Vol 84 (4) ◽  
pp. 521-527 ◽  
Author(s):  
J.J. Lutwama ◽  
L.G. Mukwaya
Keyword(s):  
Population Size ◽  
Human Population ◽  
Yellow Fever Virus ◽  
Survival Rates ◽  
Estimated Parameters ◽  
Mark Release Recapture ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Size Estimates ◽  
Aedes Simpsoni

AbstractMultiple mark-release-recapture experiments were carried out on females of three anthropophilic populations of Aedes simpsoni (Theobald) complex at Nkokonjeru and Bwamba in Uganda to determine and compare the population size, survival rates and longevity of the adult stages. There were high recapture rates (26.23%, 2 7.42% and 28.28%) at the different sites. The population sizes, estimated by Jolly's stochastic method for the three sites (465, 561 and 675 female mosquitoes) were not significantly different, neither were the survival rates of the females (0.6026, 0.7145 and 0.8152). Other parameters estimated for the three populations were also similar. Population size estimates by Jolly's stochastic model and the simple Lincoln Index methods were not in agreement. The other method over-estimated population size. Since the estimated parameters for the Nkokonjeru population are similar to those of the Bwamba populations, there is a potential for the transmission of yellow fever virus to the human population at Nkokonjeru, as at Bwamba.

scholarly journals Updated population viability analysis, population trends and PBRs for Hector’s and Maui dolphin

2020 ◽  
Author(s):  
Elisabeth Slooten ◽  
Stephen Michael Dawson
Keyword(s):  
Statistical Power ◽  
East Coast ◽  
Population Decline ◽  
Population Viability Analysis ◽  
Population Viability ◽  
List Type ◽  
Population Declines ◽  
The South ◽  
Executive Summary ◽  
Viability Analysis

EXECUTIVE SUMMARYUpdated population viability analyses, incorporating the latest abundance and bycatch data indicate that: The estimated population decline for Maui dolphin is 2% per yearThere is a 68% probability that the population is continuing to declineAfter 30 years (6 more surveys) statistical power of detecting this rate of decline would be < 15%Only very large declines (37%) and recovery (45%) would be detectable with 80% statistical power after 30 years (6 more surveys)The level of conservation threat for Hector’s dolphin remains high despite a recent, larger population estimate off the east coast of the South IslandIncreased overlap between dolphins and fisheries, due to more extensive offshore distribution of dolphins off the South Island east coast, more than offsets the apparently higher population sizeThe Hector’s dolphin population has declined 70% over the last 3 generations, exceeding the 50% threshold for EndangeredPopulation declines are predicted to continue under current protection levelsThe results of this research are consistent with:◯ NOAA proposal to list Hector’s and Maui dolphins under the US Endangered Species Act◯ IWC recommendation to ban gillnets and trawling throughout Maui dolphin habitat◯ IUCN recommendation to ban gillnets and trawling throughout Hector’s and Maui dolphin habitat

Preliminary predictions of the impacts of habitat area and catastrophes on the viability of Mahogany Glider Petaurus gracilis populations

1999 ◽  
Vol 5 (1) ◽  
pp. 56 ◽  
Author(s):  
Stephen M. Jackson
Keyword(s):  
Population Size ◽  
Population Viability Analysis ◽  
Adult Mortality ◽  
Population Viability ◽  
Key Populations ◽  
Management Options ◽  
Viability Analysis ◽  
Reserve Size ◽  
The Impact ◽  
Negative Population

The population viability analysis (PVA) program VORTEX was used to examine the viability of different sized populations of the Mahogany Glider Petaurus gracilis, and to examine the impact of a one in a hundred year catastrophe (each requiring a different reserve size) of different severities on different sized populations. The PVA showed that populations up to 300 individuals (1 500 ha) have a negative population growth rate, high losses of genetic diversity and a greater than 5% chance of extinction within 100 years. Populations of 400?700 individuals (2 000?3 500 ha) showed a decreasing trend in population size suggesting they are likely to become extinct after 100 years. A population of 800 individuals (4 000 ha) was needed for the population size to stabilize. Sensitivity analysis showed adult mortality of greater than 25% to be important in decreasing the viability of populations. Populations of 400 were resistant to a one in 100 year catastrophe which had a 20% mortality and 20% decrease in reproduction. When the mortality was 70%, with 70% decrease in reproduction, a population of 1 000 still had a 12% chance of extinction. As only approximately 50% of the available habitat appears to be occupied, an area up to 8 000 ha (800 individuals) is suggested to be required to maintain viable populations of Mahogany Gliders. A number of management options are recommended including the retention of habitat, establishing corridors between key populations, and using fire to minimize rainforest expansion.

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 Two species, one island: Retrospective analysis of threatened fauna translocations with divergent outcomes

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0253962
Author(s):  
Kelly Rayner ◽  
Cheryl A. Lohr ◽  
Sean Garretson ◽  
Peter Speldewinde
Keyword(s):  
Natural Disasters ◽  
Expert Knowledge ◽  
Species Conservation ◽  
Population Viability Analysis ◽  
Storm Surges ◽  
Predictive Modelling ◽  
Population Viability ◽  
Cyclonic Storm ◽  
Viability Analysis ◽  
Shark Bay

Translocations are globally a popular tool used with the intention of improving threatened species conservation and re-establishing ecosystem function. While practitioners strive for successful outcomes the failure rate of translocations continues to be high. We demonstrate how predictive modelling can contribute to more informed decision making and hence potentially improve the success rate of translocation programs. Two species, the Djoongari (Shark Bay mouse) Pseudomys fieldi and the golden bandicoot Isoodon auratus barrowensis, were introduced independently to Doole Island in the Exmouth Gulf of Western Australia. We used population viability analysis to critique the outcomes of these translocations and provide an example of how this tool can be incorporated with expert knowledge to predict likely outcomes of translocations. Djoongari did not establish on the island after seven translocations over nine years, while golden bandicoots established a population after just one release event. Retrospective population viability analysis (of data that was unavailable prior to the translocations) predicted and clarified the reasons behind the outcomes of both translocations. Golden bandicoots have considerably higher demographic plasticity than Djoongari, which were never likely to establish on the island. We conclude that the failure of the Djoongari translocation was due to interactions between sparse habitat, native predators and cyclonic storm surges, whereas golden bandicoots have demonstrated habitat flexibility and an ability to recover from multiple natural disasters. As a result we (1) remind conservation planners of the importance of quantifying likely refuges and habitat availability at release sites, (2) suggest practitioners consider how different threats (including natural disasters) may interact at potential release sites and (3) advocate for the incorporation of predictive modelling during the planning stages of translocations, particularly for conservation introductions where no precedent exists for the species’ survival at a particular location.

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