scholarly journals Using stationary vital rates in impact assessments may underestimate potential threat

2021 ◽  
Author(s):  
Cat Horswill ◽  
Julie Miller ◽  
Matt J Wood
Keyword(s):  
Predictive Accuracy ◽  
Temporal Trends ◽  
Population Viability Analysis ◽  
Environmental Stochasticity ◽  
Leslie Matrix ◽  
Management Decision ◽  
Vital Rates ◽  
Potential Threat ◽  
Viability Analysis ◽  
Management Decision Making

Population viability analysis (PVA) is commonly used to assess future potential risks to threatened species. These models are typically based on mean vital rates, such as survival and fecundity, with some level of environmental stochasticity. However, the vital rates of wild populations, especially those already exhibiting declining trajectories, may be nonstationary, such that the mean or variance changes over time. In this study, we examined whether including observed temporal trends in vital rates affects the predictive accuracy of PVA, as well as the projected impact associated with a hypothetical threat. To achieve this, we ran a series of simulations using Leslie matrix PVA models that included different combinations of environmental stochasticity, temporal trends in vital rates, and threat. We found that including observed temporal trends in vital rates was (i) crucial for the accurate reconstruction of observed population dynamics and (ii) had a dramatic effect on the projected impact from the hypothetical threat. In an era when many animal and plant populations are declining due to long-term trends in their vital rates, we conclude that this demographic structure is essential for robustly evaluating potential threats using PVA models. Omitting observed temporal trends in vital rates from impact assessments is highly likely to yield unreliable results that could misinform conservation and management decision making.

Age-structured models in a random environment

2019 ◽  
pp. 194-213
Author(s):  
Louis W. Botsford ◽  
J. Wilson White ◽  
Alan Hastings
Keyword(s):  
Time Series ◽  
Environmental Variability ◽  
Extinction Risk ◽  
Population Viability Analysis ◽  
Leslie Matrix ◽  
Vital Rates ◽  
Viability Analysis ◽  
Practical Concern ◽  
Probability Of Extinction ◽  
Age Structured

Most ecological populations exist in a randomly fluctuating environment, and these fluctuations influence vital rates, thus changing population dynamics. These changes are the focus of this chapter. The primary practical concern about environmental variability is the possibility that it could cause a population to go extinct, so the chapter describes several approaches to estimating the probability of extinction. The first is the small fluctuations approximation (SFA) to describe the growth of a population with a randomly varying Leslie matrix. The results reveal that randomly varying populations grow more slowly on average than the equivalent deterministic population. Further applications of the SFA examine how correlated variation in different vital rates affects the probability of extinction, when variability is too large to use the SFA, and how it has been applied to population time series. Finally, several other approaches to estimating extinction risk—also known as population viability analysis—are compared.

scholarly journals The Last-Surviving Moroccan Dorcas Gazelle (Gazella dorcas massaesyla) Viability Analysis [M’Sabih Talaa Reserve, Morocco]

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Ait Baamrane Moulay Abdeljalil ◽  
Znari Mohammed ◽  
El Mercht Said ◽  
Bellout Siham ◽  
Naimi Mohamed
Keyword(s):  
Population Viability Analysis ◽  
Environmental Stochasticity ◽  
General Interest ◽  
Line Transect ◽  
Catastrophic Events ◽  
Viability Analysis ◽  
Line Transect Survey ◽  
Management Measures ◽  
Feral Dogs ◽  
Considerable Impact

The single remnant Moroccan dorcas gazelle (Gazella dorcas massaesyla) has been isolated for more than five decades in the M’Sabih Talaa reserve, an arid area of west-central Morocco. This population has been subject to different disturbances, especially poaching and depredation by feral dogs. A five-season line transect survey revealed that the population size has been halved in less than 15 years with a lower apparent fecundity rate. In the present work, we carried out a population viability analysis simulating different scenarios using VORTEX software based on available demographic and life-history data from captive populations,. A sensitivity analysis revealed that inbreeding depression and possible catastrophic events could have a considerable impact on the population’s prospects. Scenarios of splitting population into two subpopulations with different management measures reducing/deleting mortality sources, is proposed. Such scenarios resulted in reducing the consequences of catastrophic events would significantly mitigate the harmful effects of both inbreeding and environmental stochasticity. These results may be of a general interest to conservationists dealing with this unique and imperiled population.

Out of sight but not out of mind: corvids prey extensively on eggs of burrow-nesting penguins

2015 ◽  
Vol 42 (6) ◽  
pp. 509 ◽  
Author(s):  
Kasun B. Ekanayake ◽  
Duncan R. Sutherland ◽  
Peter Dann ◽  
Michael A. Weston
Keyword(s):  
Population Viability Analysis ◽  
Camera Traps ◽  
Foraging Strategies ◽  
Population Declines ◽  
Egg Predation ◽  
Potential Threat ◽  
Predatory Behaviour ◽  
Population Growth Rates ◽  
Viability Analysis ◽  
Foraging Niche

Context Egg depredation is a major cause of reproductive failure among birds and can drive population declines. In this study we investigate predatory behaviour of a corvid (little raven; Corvus mellori) that has only recently emerged, leading to widespread and intense depredation of eggs of a burrow-nesting seabird (little penguin; Eudyptula minor). Aims The main objective of this study was to measure the rate of penguin egg depredation by ravens to determine potential threat severity. We also examined whether penguin burrow characteristics were associated with the risk of egg depredation. Ravens generally employ two modes of predatory behaviour when attacking penguin nests; thus we examined whether burrow characteristics were associated with these modes of attack. Methods Remote-sensing cameras were deployed on penguin burrows to determine egg predation rates. Burrow measurements, including burrow entrance and tunnel characteristics, were measured at the time of camera deployment. Key results Overall, clutches in 61% of monitored burrows (n = 203) were depredated by ravens, the only predator detected by camera traps. Analysis of burrow characteristics revealed two distinct types of burrows, only one of which was associated with egg depredation by ravens. Clutches depredated by ravens had burrows with wider and higher entrances, thinner soil or vegetation layer above the egg chamber, shorter and curved tunnels and greater areas of bare ground and whitewash near entrances. In addition, 86% were covered by bower spinach (Tetragonia implexicoma), through which ravens could excavate. Ravens used two modes to access the eggs: they attacked through the entrance (25% of burrow attacks, n = 124); or dug a hole through the burrow roof (75% of attacks, n = 124). Burrows that were subject to attack through the entrance had significantly shorter tunnels than burrows accessed through the roof. Conclusions The high rates of clutch loss recorded here highlight the need for population viability analysis of penguins to assess the effect of egg predation on population growth rates. Implications The subterranean foraging niche of a corvid described here may have implications for burrow-nesting species worldwide because many corvid populations are increasing, and they exhibit great capacity to adopt new foraging strategies to exploit novel prey.

Predictive accuracy of population viability analysis in conservation biology

Nature ◽  
2000 ◽  
Vol 404 (6776) ◽  
pp. 385-387 ◽  
Author(s):  
Barry W. Brook ◽  
Julian J. O'Grady ◽  
Andrew P. Chapman ◽  
Mark A. Burgman ◽  
H. Resit Akçakaya ◽  
...  
Keyword(s):  
Conservation Biology ◽  
Predictive Accuracy ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Viability Analysis

Centralization and Effectiveness of Reward Management in Multinational Enterprises

2018 ◽  
Vol 17 (2) ◽  
pp. 55-65 ◽  
Author(s):  
Michael Tekieli ◽  
Marion Festing ◽  
Xavier Baeten
Keyword(s):  
Decision Making ◽  
Social Identity Theory ◽  
Multinational Enterprises ◽  
Role Identity ◽  
Management Decision ◽  
Role Identities ◽  
Management Decision Making ◽  
New Perspective ◽  
Subsidiary Managers ◽  
The Relationship

Abstract. Based on responses from 158 reward managers located at the headquarters or subsidiaries of multinational enterprises, the present study examines the relationship between the centralization of reward management decision making and its perceived effectiveness in multinational enterprises. Our results show that headquarters managers perceive a centralized approach as being more effective, while for subsidiary managers this relationship is moderated by the manager’s role identity. Referring to social identity theory, the present study enriches the standardization versus localization debate through a new perspective focusing on psychological processes, thereby indicating the importance of in-group favoritism in headquarters and the influence of subsidiary managers’ role identities on reward management decision making.

Emergency management decision-making during severe weather

2006 ◽  
Author(s):  
Leigh A. Baumgart ◽  
Ellen J. Bass ◽  
Brenda Philips ◽  
Kevin Kloesel
Keyword(s):  
Decision Making ◽  
Emergency Management ◽  
Severe Weather ◽  
Management Decision ◽  
Management Decision Making
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