scholarly journals Could current fertility control methods be effective for landscape-scale management of populations of wild horses (Equus caballus) in Australia?

2018 ◽  
Vol 45 (3) ◽  
pp. 195 ◽  
Author(s):  
Rebecca J. Hobbs ◽  
Lyn A. Hinds
Keyword(s):  
Population Growth ◽  
Population Size ◽  
National Parks ◽  
Fertility Control ◽  
Management Approach ◽  
Attractive Alternative ◽  
Control Methods ◽  
Animal Populations ◽  
Rate Of Increase

Context Fertility control is seen as an attractive alternative to lethal methods for control of population size and genetic diversity in managed animal populations. Immunocontraceptive vaccines have emerged as the most promising agents for inducing long-term infertility in individual animals. However, after over 20 years of scientific testing of immunocontraceptive vaccines in the horse, the scientific consensus is that their application as a sole management approach for reducing population size is not an effective strategy. Aims The purpose of this review is to evaluate currently available non-lethal fertility-control methods that have been tested for their contraceptive efficacy in Equidae, and to assess their suitability for effective management of wild (feral) horses in an Australian setting. Key results (1) Fertility-control agents, particularly injectable immunocontraceptive vaccines based on porcine zona pellucida (PZP) or gonadotrophin-releasing hormone (GnRH), can induce multi-year infertility (up to 3 years) in the horse. Some formulations require annual or biennial booster treatments. Remote dart delivery (on foot) to horses is possible, although the efficacy of this approach when applied to large numbers of animals is yet to be determined. (2) The proportion of females that must be treated with a fertility-control agent, as well as the frequency of treatment required to achieve defined management outcomes (i.e. halting population growth in the short term and reducing population size in the long term) is likely to be >50% per annum. In national parks, treatment of a large number of wild horses over such a broad area would be challenging and impractical. (3) Fertility control for wild horses could be beneficial, but only if employed in conjunction with other broad-scale population-control practices to achieve population reduction and to minimise environmental impacts. Conclusions In Australia, most populations of wild horses are large, dispersed over varied and difficult-to-access terrain, are timid to approach and open to immigration and introductions. These factors make accessing and effectively managing animals logistically difficult. If application of fertility control could be achieved in more than 50% of the females, it could be used to slow the rate of increase in a population to zero (2–5 years), but it will take more than 10–20 years before population size will begin to decline without further intervention. Thus, use of fertility control as the sole technique for halting population growth is not feasible in Australia.

scholarly journals Elephant population growth in Kruger National Park, South Africa, under a landscape management approach

Koedoe ◽  
2017 ◽  
Vol 59 (1) ◽  
Author(s):  
Sam M. Ferreira ◽  
Cathy Greaver ◽  
Chenay Simms
Keyword(s):  
Population Growth ◽  
National Parks ◽  
National Park ◽  
Landscape Management ◽  
Aerial Survey ◽  
Kruger National Park ◽  
Management Approach ◽  
Intensive Management ◽  
Ecological Processes ◽  
Management Interventions

South African National Parks (SANParks) manage landscapes rather than numbers of elephants (Loxodonta africana) to mitigate the effects that elephants may have on biodiversity, tourism and stakeholder conservation values associated with protected areas. This management philosophy imposes spatial variability of critical resources on elephants. Restoration of such ecological processes through less intensive management predicts a reduction in population growth rates from the eras of intensive management. We collated aerial survey data since 1995 and conducted an aerial total count using a helicopter observation platform during 2015. A minimum of 17 086 elephants were resident in the Kruger National Park (KNP) in 2015, growing at 4.2% per annum over the last generation of elephants (i.e. 12 years), compared to 6.5% annual population growth noted during the intensive management era ending in 1994. This may come from responses of elephants to density and environmental factors manifested through reduced birth rates and increased mortality rates. Authorities should continue to evaluate the demographic responses of elephants to landscape scale interventions directed at restoring the limitation of spatial variance in resource distribution on elephant spatiotemporal dynamics and the consequences that may have for other conservation values.Conservation implications: Conservation managers should continue with surveying elephants in a way that allows the extraction of key variables. Such variables should focus on measures that reflect on how theory predicts elephants should respond to management interventions.

An optimal hunting policy for a stochastic logistic model

1979 ◽  
Vol 16 (2) ◽  
pp. 319-331 ◽  
Author(s):  
Andris Abakuks
Keyword(s):  
Population Growth ◽  
Population Size ◽  
Optimal Policy ◽  
Logistic Model ◽  
Stochastic Version ◽  
Stochastic Logistic Model ◽  
Parameter Values

A stochastic version of the logistic model for population growth is considered, and the general form of an optimal policy is found for hunting the population so as to maximise the long-term average number of captures per unit time. This optimal policy is described by a critical population size x∗such that it is optimal to hunt if and only if the population size is greater than or equal to x∗. Methods of determining x∗for given parameter values are provided, and some properties of the optimal policy as the population size tends to infinity are proved.

An optimal hunting policy for a stochastic logistic model

1979 ◽  
Vol 16 (02) ◽  
pp. 319-331 ◽  
Author(s):  
Andris Abakuks
Keyword(s):  
Population Growth ◽  
Population Size ◽  
Optimal Policy ◽  
Logistic Model ◽  
Stochastic Version ◽  
Stochastic Logistic Model ◽  
Parameter Values

A stochastic version of the logistic model for population growth is considered, and the general form of an optimal policy is found for hunting the population so as to maximise the long-term average number of captures per unit time. This optimal policy is described by a critical population size x∗such that it is optimal to hunt if and only if the population size is greater than or equal to x∗. Methods of determining x∗for given parameter values are provided, and some properties of the optimal policy as the population size tends to infinity are proved.

scholarly journals Breeding Strategies to Optimize Effective Population Size in Low Census Captive Populations: The Case of Gazella cuvieri

Animals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1559
Author(s):  
Candela Ojeda-Marín ◽  
Isabel Cervantes ◽  
Eulalia Moreno ◽  
Félix Goyache ◽  
Juan Pablo Gutiérrez
Keyword(s):  
Genetic Variability ◽  
Population Size ◽  
Effective Population Size ◽  
Significant Loss ◽  
Breeding Systems ◽  
Effective Population ◽  
Evolutionary Pattern ◽  
Animal Populations ◽  
Captive Populations

Small-sized animal populations can undergo significant loss of genetic variability that can lead to their extinction. Therefore, studies on animal breeding have focused on mating systems for minimizing the disappearance of genetic variability. The main objective of this study was to compare, using computer simulations, the performance of different breeding schemes to limit the loss of genetic diversity in small-sized populations. This objective was achieved by monitoring the evolution of the effective population size obtained by 23 strategies throughout 20 generations in two populations of Gazella cuvieri. The scenarios were designed with different assumptions, in both reference subpopulations, regarding: the use of parents coancestry or offspring coancestry, the use of their increases or the coefficients themselves, and the number of males and females involved. Computations were performed using an experimental module of Endog v4.9 developed for this purpose. The results of the study showed that strategies for minimizing the coancestry of the parents were better in the short term; however, these strategies were worse in the long term. Minimizing the average coancestry of the offspring was a better approach in the long term. Nevertheless, in both populations, the best results were obtained when both the coancestry of the parents and the coancestry of the offspring were weighted at 5% each and neither males nor females were assumed to contribute to the next generation. In any case, not all strategies had the same evolutionary pattern throughout generations in both populations. The current results show that neither traditional nor new strategies have any general use. Therefore, it is important to carefully test these strategies before applying them to different populations with different breeding needs under different conditions, such as different generation intervals, and different natural breeding systems such as monogamy or polygyny.

Malthus's Vision of the Population Problem in the Essay on Population

1990 ◽  
Vol 12 (1) ◽  
pp. 1-26 ◽  
Author(s):  
Samuel Hollander
Keyword(s):  
Population Growth ◽  
Population Size ◽  
Presidential Address ◽  
Long Run ◽  
Preventive Check ◽  
Economic Association ◽  
Gary Becker ◽  
The Face ◽  
The Stability

In his Presidential address to the American Economic Association, Gary Becker alludes to Thomas Malthus's “great contribution” (1988, p. 1) in a prologue to a wider exploratory discussion of some of the implications for macroeconomics flowing from recent programs in family economics. The content of the contribution as represented here (p. 2) includes diminishing returns to increases in employment “when land and other capital are fixed;” population growth positively related to the wage, the lower population growth at low wages turning on reduced birth rates (the preventive check) and increased death rates (the positive check); and a long-run equilibrium wage at which population is constant at a level determined by the production function. Becker emphasizes the stability of the equilibrium wage in the face of disturbances. A catastrophic reduction in population size (eg. the Black Death) and consequently a wage increase will be followed by positive population growth which restores both the wage and population size to their respective equilibrium levels. In the event of increases in the amount of usuable land, population size will become permanently higher with the wage ultimately reduced to its original long-run level. Becker represents Malthus as reaching “much more pessimistic conclusions about the long-term economic prospects of the average family” than, for example, Godwin and Condorcet who had maintained that the economic position of mankind will continue to improve over time.

Update on the Boundaries of the Curly Birch Range

2020 ◽  
pp. 9-21
Author(s):  
L.V. Vetchinnikova ◽  
◽  
A.F. Titov ◽  
◽  
Keyword(s):  
Population Size ◽  
Natural Populations ◽  
Forest Tree ◽  
Published Data ◽  
Population Approach ◽  
Key Factors ◽  
History Of ◽  
Individual Trees ◽  
Karelian Birch

The article reports on the application of the best known principles for mapping natural populations of curly (Karelian) birch Betula pendula Roth var. carelica (Mercklin) Hämet-Ahti – one of the most appealing representatives of the forest tree flora. Relying on the synthesis and analysis of the published data amassed over nearly 100 years and the data from own full-scale studies done in the past few decades almost throughout the area where curly birch has grown naturally, it is concluded that its range outlined in the middle of the 20th century and since then hardly revised is outdated. The key factors and reasons necessitating its revision are specified. Herewith it is suggested that the range is delineated using the population approach, and the key element will be the critical population size below which the population is no longer viable in the long term. This approach implies that the boundaries of the taxon range depend on the boundaries of local populations (rather than the locations of individual trees or small clumps of trees), the size of which should not be lower than the critical value, which is supposed to be around 100–500 trees for curly birch. A schematic map of the curly birch range delineated using this approach is provided. We specially address the problem of determining the minimum population size to secure genetic diversity maintenance. The advantages of the population approach to delineating the distribution range of curly birch with regard to its biological features are highlighted. The authors argue that it enables a more accurate delineation of the range; shows the natural evolutionary history of the taxon (although it is not yet officially recognized as a species) and its range; can be relatively easily updated (e.g. depending on the scope of reintroduction); should be taken into account when working on the strategy of conservation and other actions designed to maintain and regenerate this unique representative of the forest tree flora.

scholarly journals Inflammatory Neuropsychiatric Disorders and COVID-19 Neuroinflammation

2021 ◽  
pp. 1-55
Author(s):  
Siu Wa Tang ◽  
Daiga Helmeste ◽  
Brian Leonard
Keyword(s):  
Immune Responses ◽  
Clinical Management ◽  
Neuronal Damage ◽  
Treatment Resistance ◽  
Neuropsychiatric Disorders ◽  
Acute Stage ◽  
Management Approach ◽  
Neuropsychiatric Diseases ◽  
Anti Inflammatory

Abstract Neuropsychiatric sequalae to COVID-19 infection are beginning to emerge, like previous Spanish influenza and SARS episodes. Streptococcal infection in pediatric patients causing OCD (PANDAS) is another recent example of an infection-based psychiatric disorder. Inflammation associated with neuropsychiatric disorders has been previously reported but there is no standard clinical management approach established. Part of the reason is that it is unclear what factors determine the specific neuronal vulnerability and the efficacy of anti-inflammatory treatment in neuroinflammation. The emerging COVID-19 data suggested that in the acute stage, wide-spread neuronal damage appears to be the result of abnormal and overactive immune responses and cytokine storm is associated with poor prognosis. It is still too early to know if there are long term specific neuronal or brain regional damages associated with COVID-19, resulting in distinct neuropsychiatric disorders. In several major psychiatric disorders where neuroinflammation is present, patients with abnormal inflammatory markers may also experience less than favorable response or treatment resistance when standard treatment is used alone. Evidence regarding the benefits of co-administered anti-inflammatory agents such as COX-2 inhibitor is encouraging in selected patients though may not benefit others. Disease modifying therapies are increasingly being applied to neuropsychiatric diseases characterized by abnormal or hyperreactive immune responses. Adjunct anti-inflammatory treatment may benefit selected patients and is definitely an important component of clinical management in the presence of neuroinflammation.

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.

scholarly journals Long-term changes in the plant ecology of an African savanna landscape and the implications for ecosystem theory and conservation management

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
David Western ◽  
Victor N. Mose ◽  
David Maitumo ◽  
Caroline Mburu
Keyword(s):  
Human Impact ◽  
National Parks ◽  
Conservation Management ◽  
Plant Ecology ◽  
Ecological Resilience ◽  
Pasture Production ◽  
Ecosystem Theory ◽  
The Impact

Abstract Background Studies of the African savannas have used national parks to test ecological theories of natural ecosystems, including equilibrium, non-equilibrium, complex adaptive systems, and the role of top-down and bottom-up physical and biotic forces. Most such studies have excluded the impact of pastoralists in shaping grassland ecosystems and, over the last half century, the growing human impact on the world’s rangelands. The mounting human impact calls for selecting indicators and integrated monitoring methods able to track ecosystem changes and the role of natural and human agencies. Our study draws on five decades of monitoring the Amboseli landscape in southern Kenya to document the declining role of natural agencies in shaping plant ecology with rising human impact. Results We show that plant diversity and productivity have declined, biomass turnover has increased in response to a downsizing of mean plant size, and that ecological resilience has declined with the rising probability of extreme shortfalls in pasture production. The signature of rainfall and physical agencies in driving ecosystem properties has decreased sharply with growing human impact. We compare the Amboseli findings to the long-term studies of Kruger and Serengeti national parks to show that the human influence, whether by design or default, is increasingly shaping the ecology of savanna ecosystems. We look at the findings in the larger perspective of human impact on African grasslands and the world rangelands, in general, and discuss the implications for ecosystem theory and conservation policy and management. Conclusions The Amboseli study shows the value of using long-term integrated ecological monitoring to track the spatial and temporal changes in the species composition, structure, and function of rangeland ecosystems and the role of natural and human agencies in the process of change. The study echoes the widespread changes underway across African savannas and world’s rangelands, concluding that some level of ecosystem management is needed to prevent land degradation and the erosion of ecological function, services, and resilience. Despite the weak application of ecological theory to conservation management, a plant trait-based approach is shown to be useful in explaining the macroecological changes underway.

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