Estimating Sustainable Harvest in Wolverine Populations Using Logistic Regression

Abstract: Population viability analysis (PVA) is a common tool to evaluate population vulnerability. However, most techniques require reliable estimates of underlying population parameters, which are often difficult to obtain and PVA are, therefore, best used in a qualitative context. Logistic regression is a powerful alternative to traditional PVA methods but has received surprisingly limited attention. Logistic regression fits regression equations to binary output from PVA models at a specific point in time to predict probability of a binary response over a range of parameter values. We used logistic regression on output from stochastic population models to evaluate the relative importance of demographic parameters for wolverine (Gulo gulo) populations and to estimate sustainable harvest in a wolverine population in Alaska. Our analysis indicated that adult survival is the most important demographic parameter to reliably estimate in wolverine populations because it had a greater effect on population persistence than did both fecundity and subadult survival. In accordance with this, harvest rate had a greater effect on population persistence than did any of the other harvest- and migration-related variables we tested. Furthermore, a high proportion of harvested females strengthened the effect of harvest. Hypothetical wolverine populations suffered high probabilities of both extinction and population decline over a range of realistic population sizes and harvest regimes. We suggest that harvested wolverine populations must be regarded as sink populations and that source populations in combination with sufficient dispersal corridors must be secured for any wolverine harvest to be sustainable.     

Learning to live with black bears: A psychological model of acceptance

The reappearance and recovery of large carnivores in human-dominated landscapes creates a need to understand how people will respond to the presence of these animals. We tested a psychological model of acceptance to determine what variables most influence people's acceptance for black bears (Ursus americanus) in an area with an emerging black bear population (Ohio, USA). We hypothesized that people's perceptions of risk and benefit related to bears would mediate the effect of trust (in wildlife management agencies) and personal control (over interactions with and management of wildlife) on acceptance for black bears. We used a mail-back survey of Ohio residents (n = 9,400; adjusted response rate = 35%) to assess the variables of interest and test the hypothesized model. Based on multiple criteria of model fit, the hypothesized model fit the data acceptably well. The model explained approximately 62% of the variance in acceptance, and perception of risk associated with black bears had the largest impact on the level of acceptance. As large carnivore populations expand and interactions with humans increase, our results will aid managers in designing outreach materials and communications aimed at promoting acceptance for large carnivores. Our model suggests that interventions raising an individual's social trust in the managing agency, or personal control can indirectly raise stakeholders' acceptance by reducing risk perception and increasing perception of benefit from carnivores. © 2012 The Wildlife Society.     

Bet-hedging applications for conservation

One of the early tenets of conservation biology is that population viability is enhanced by maintaining multiple populations of a species. The strength of this tenet is justified by principles of bet-hedging. Management strategies that reduce variance in population size will also reduce risk of extinction. Asynchrony in population fluctuations in independent populations reduces variance in the aggregate of populations whereas environmental correlation among areas increases the risk that all populations will go extinct. We review the theoretical rationale of bet-hedging and suggest applications for conservation management of least terns in Nebraska and grizzly bears in the northern Rocky Mountains of the United States. The risk of extinction for least terns will be reduced if we can sustain the small central Platte River population in addition to the larger population on the lower Platte. Similarly, by restoring grizzly bears to the Bitterroot wilderness of Idaho and Montana can reduce the probability of extinction for grizzly bears in the Rocky Mountains of the United States by as much as 69–93%.     

Assessing Population Viability of Black Bears using Spatial Capture-Recapture Models

The Central Georgia Bear Population (CGP) is the least abundant and most isolated of Georgia's 3 American black bear (Ursus americanus) populations. Beginning in 2011, changes to regulations governing harvest of the CGP resulted in an increase in female bear harvest, creating concern that future harvest could be an important influence on population viability. Hence, our objective was to assess viability of the CGP under various levels of female mortality. During 2012–2016, we used barbed-wire hair snares to collect bear hair samples from within the range of the CGP in Georgia, USA. We used microsatellite genotyping to identify individual bears and created robust-design, spatial detection histories for all female bears detected. We fit open population spatial capture-recapture (SCR) models to the detection histories in a Bayesian framework. We used the Widely Applicable Information Criterion (WAIC) to rank models that varied with respect to sources of variation in detection probability, survival, and per capita recruitment, and used the model with the lowest WAIC to forecast dynamics of the CGP 50 years into the future under various levels of female mortality. We assessed the 50-year extinction probability under a continuation of mortality levels documented during 2012–2016, and under incremental increases in female mortality above this baseline. The top model included density-dependent per capita recruitment, annual variation in detection probability, and a trap-level behavioral response. Abundance increased from 106 (95% CI = 86–132) females in 2012 to 136 (95% CI = 113–161) females in 2013 and remained relatively stable thereafter. Annual female survival was 0.75 (95% CI = 0.69–0.82) and did not vary among years. The per capita recruitment rate decreased over time as density increased, and was 0.49 (95% CI = 0.33–0.66) during the first time interval and 0.29 (95% CI = 0.20–0.38) during the final time interval. Annual growth rate () was 1.28 (95% CI = 1.07–1.52) between 2012 and 2013 but decreased throughout the study, ending at 1.04 (95% CI = 0.93–1.17). Forecasts indicated continuation of the female mortality levels experienced from 2012–2016 were sustainable over 50 years, with the estimated extinction risk being <0.001%. Increasing annual harvest by 5 females introduced a negligible increase in the 50-year probability of extinction, but harvesting an additional 10 females/year caused extinction risk to rise to 1.15%. We recommend that harvest regulations are structured such that mortality rates remain at current levels or do not increase by more than an annual average of 5 females above levels observed during our study. Furthermore, we recommend that managers continue to monitor the population so that harvest regulations and population models can be refined over time. © 2020 The Wildlife Society.     

Evaluation of Connectivity Among American Black Bear Populations in Georgia

Habitat fragmentation and loss contribute to isolation of wildlife populations and increased extinction risks for various species, including many large carnivores. We studied a small and isolated population of American black bears (Ursus americanus) that is of conservation concern in central Georgia, USA (i.e., central Georgia bear population [CGBP]). Our goal was to evaluate the potential for demographic and genetic interchange from neighboring bear populations to the CGBP. To evaluate resource selection and movement potential, we used 35,487 global positioning system locations collected every 20 minutes from 2012 to 2014 from 33 male bears in the CGBP. We then developed a step selection function model based on conditional logistic regression. Male bears chose steps that avoided crops, roads, and human developments and were closer to forests and woody wetlands than expected based on availability. We used a geographic information system to simulate 300 bear movement paths from nearby bear populations in northern Florida, northern Georgia, and southern Georgia to estimate the potential for immigration to the CGBP. Only 4 simulated movement paths from the nearby populations intersected the CGBP. The creation of a hypothetical 1-km-wide corridor between the southern Georgia population and the CGBP produced only minor improvements in interchange. Our findings suggest that demographic connectivity between the CGBP and surrounding bear populations may be limited, and coupled with previous works showing genetic isolation in the CGBP, that creation of corridors may have only marginal effects on restoring gene flow, at least in the near term. Management actions such as translocation and the establishment of stepping stone populations may be needed to increase the genetic diversity and demographic stability of bears in the CGBP. © 2021 The Wildlife Society.     

Population parameters and harvest risks for polar bears (<Emphasis Type="Italic">Ursus maritimus</Emphasis>) of Kane Basin,Canada and Greenland

We estimated demographic parameters and current harvest risks for a population of polar bears (Ursus maritimus Phipps) inhabiting northern Smith Sound and Kane Basin, Canada and Greenland. Our demographic analysis included a detailed assessment of age- and sex-specific survival and recruitment from 141 marked polar bears, using information contained within the standing age distribution of captures and mark-recapture analysis. Total survival rates for females were: 0.374 ± 0.180 (cubs), 0.686 ± 0.157 (ages 1–4), and 0.967 ± 0.043 (ages 5+). Mean litter size was 1.67 ± 0.08 cubs. Females did not reproduce until at least age 6, which is late compared to other populations of polar bears. The model-averaged, mark–recapture estimate of mean abundance (±1 SE) for years 1994–1997 was 164 ± 35 bears. We incorporated demographic parameters and their variances into a harvest risk analysis (i.e., a stochastic, harvested population viability analysis, PVA). Results suggest that polar bears in the region were severely over-harvested during the mark–recapture interval (1992–1997). The current status of the population is unknown.     

The importance of inverse density dependence in population viability analysis: an example using threatened woodland caribou in Canada

[First paragraph]Population viability analysis (PVA) refers to a group of analytical and modelling approaches for assessing the risk of population extinction. PVA is commonly used to estimate absolute time to extinction or probability of persistence under either current or novel conditions. However, the amount of information of species specific biology as well as the dynamics of small populations needed to confidently estimate population persistence is high, a fact often overlooked in the light of increasing availability of easy-to-use software packages.     

Evaluation of Accuracy and Precision of Downing Population Reconstruction

ABSTRACT Downing population reconstruction uses harvest-by-age data and backward addition of cohorts to estimate minimum population size over time. Although this technique is currently being used for management of black bear (Ursus americanus) and white-tailed deer (Odocoileus virginianus) populations, it had not undergone a rigorous evaluation of accuracy. We used computer simulations to evaluate the impacts of collapsing age classes and violating the assumptions of this technique on population reconstruction estimates and trends. Changes in harvest rate or survival over time affected accuracy of reconstructed population estimates and trends. The technique was quite robust to collapsing age classes as far as 3+ for bears and deer. This method would be suitable for estimating population growth rate (λ) for populations experiencing no trend in harvest rate or natural mortality rate over time. Our evaluation showed Downing population reconstruction to be a potentially valuable tool for managing harvested species with high harvest rates and low natural mortality, with possible application to black bear and white-tailed deer populations.     

Important population viability analysis parameters for giant pandas (Aliuropoda melanoleuca)

Population viability analysis(PVA) is a tool to evaluate the risk of extinction for endangered species and aid conservation decision-making.The quality of PVA output is dependent on parameters related to population dynamics and life-history;however,it has been difficult to collect this information for the giant panda(Aliuropoda melanoleuca),a rare and endangered mammal native to China,confined to some 30 fragmented habitat patches.Since giant pandas are long-lived,mature late,have lower reproductive rates,and show little sexual dimorphism,obtaining data to perform adequate PVA has been difficult.Here,we develop a parameter sensitivity index by modeling the dynamics of six giant panda populations in the Minshan Mountains,in order to determine the parameters most influential to giant panda populations.Our data shows that the giant panda populations are most sensitive to changes in four female parameters:initial breeding age,reproductive rate,mortality rate between age 0 and 1,and mortality rate of adults.The parameter sensitivity index strongly correlated with initial population size,as smaller populations were more sensitive to changes in these four variables.This model suggests that demographic parameters of females have more influence on the results of PVA,indicating that females may play a more important role in giant panda population dynamics than males.Consequently,reintroduction of female individuals to a small giant panda population should be a high priority for conservation efforts.Our findings form a technical basis for the coming program of giant panda reintroduction,and inform which parameters are crucial to successfully and feasibly monitoring wild giant panda populations.     

Demography and population viability of polar bears in the Gulf of Boothia, Nunavut

We estimated demographic parameters and harvest risks for polar bears ( Ursus maritimus ) inhabiting the Gulf of Boothia, Nunavut, from 1976 to 2000. We computed survival and abundance from capture–recapture and recovery data (630 marks) using a Burnham joint live–dead model implemented in program MARK. Annual mean total survival (including harvest) was 0.889 ± 0.179 (± 1 SE) for cubs, 0.883 ± 0.087 for subadults (ages 1–4), 0.919 ± 0.044 for adult females, and 0.917 ± 0.041 for adult males. Abundance in the last 3 yr of study was 1,592 ± 361 bears. Mean size of newborn litters was 1.648 ± 0.098 cubs. By age 7, 0.97 ± 0.30 of available females were producing litters. Harvest averaged 38.4 ± 4.2 bears/year in the last 5 yr of study; however, the 2002–2007 kill averaged 56.4 bears/yr. We used a harvested Population Viability Analysis (PVA) to examine impacts of increasing rates of harvest. We estimated the current population growth rate, λ _H , to be 1.025 ± 0.032. Although this suggests the population is growing, progressive environmental changes may require more frequent population inventory studies to maintain the same levels of harvest risk.     

Use of population viability analysis models for Atlantic and Pacific salmon recovery planning

Uncertainty and risk abound in making natural resource management decisions. Population viability analysis (PVA) includes a variety of qualitative or quantitative analyses to predict the future status of a population or collection of populations and to predict the risk of extinction (or quasi-extinction) over time given some assumptions of the factors driving population dynamics. In this paper, we review the various PVA models applied to Atlantic and Pacific salmon for determination of listing under the Endangered Species Act and in planning recovery actions. We also review the numerous cautions involved in developing PVA models and in interpreting their results. There have been a larger number of PVA models applied to Pacific salmon compared to Atlantic salmon due to the greater geographic range and number of species of Pacific salmon. Models for both Atlantic and Pacific salmon have ranged from simple models that view populations as simply a number of organisms to complex age- or stage-structured models depending on the purpose of the model and available data for model parameterization. The real value of PVA models to salmon conservation is not in making absolute predictions of the risk of extinction, but rather in evaluating relative effects of management alternatives on extinction risk and informing decision making within an adaptive management framework. As computing power, quantitative techniques, and knowledge of mechanistic linkages between terrestrial, freshwater, and marine environments advance, PVA models will become an even more powerful tool in conservation planning for salmon species.     

Population viability analysis for Guarianthe aurantiaca, an ornamental epiphytic orchid harvested in Southeast México

The trade of wild epiphytic orchids has put many populations at risk of extinction; however, little is known about the impact of repeated harvesting of individuals on population dynamics. A population viability analysis (PVA) was developed to simulate the impact of harvesting on the risk of extinction of a population of an epiphytic orchid that is sold in Mexican markets. In January 2004, 388 individuals of Guarianthe aurantiaca were labeled and measured. The same individuals were measured again in December 2005 and December 2006. Capsule production and mortality were also recorded. Deterministic (d) and stochastic (s) matrix models were developed to estimate the population growth rate (λ). A PVA was developed to evaluate the probability of extinction over a 100-year period, given a threshold of 5% of the initial population and different harvest intensities of G. aurantiaca . The λ_d values were statistically indistinguishable from unity (0.989 ± 0.103 for 2004–2005; 0.990 ± 0.087 for 2005–2006); the λ_s values were below unity (0.988 ± 0.001). The reproductive stages had the highest elasticity values, whereas the persistence of individuals in their category was the demographic process with the highest elasticity. A life table response experiment showed that the difference in the λ_d values was accounted for by the positive contribution of the stasis of individuals in category j and the retrogression of individuals in category r₁ to category j. The extinction risk was 100% when more than 5% of the reproductive individuals were harvested. The results suggest that this G. aurantiaca population is in a precarious equilibrium and harvesting should be controlled and restricted to immature individuals.     

East Greenland and Barents Sea polar bears (Ursus maritimus): adaptive variation between two populations using skull morphometrics as an indicator of environmental and genetic differences

A morphometric study was conducted on four skull traits of 37 male and 18 female adult East Greenland polar bears (Ursus maritimus) collected 1892-1968, and on 54 male and 44 female adult Barents Sea polar bears collected 1950-1969. The aim was to compare differences in size and shape of the bear skulls using a multivariate approach, characterizing the variation between the two populations using morphometric traits as an indicator of environmental and genetic differences. Mixture analysis testing for geographic differentiation within each population revealed three clusters for Barents Sea males and three clusters for Barents Sea females. East Greenland consisted of one female and one male cluster. A principal component analysis (PCA) conducted on the clusters defined by the mixture analysis, showed that East Greenland and Barents Sea polar bear populations overlapped to a large degree, especially with regards to females. Multivariate analyses of variance (MANOVA) showed no significant differences in morphometric means between the two populations, but differences were detected between clusters from each respective geographic locality. To estimate the importance of genetics and environment in the morphometric differences between the bears, a PCA was performed on the covariance matrix derived from the skull measurements. Skull trait size (PC1) explained approx. 80% of the morphometric variation, whereas shape (PC2) defined approx. 15%, indicating some genetic differentiation. Hence, both environmental and genetic factors seem to have contributed to the observed skull differences between the two populations. Overall, results indicate that many Barents Sea polar bears are morphometrically similar to the East Greenland ones, suggesting an exchange of individuals between the two populations. Furthermore, a subpopulation structure in the Barents Sea population was also indicated from the present analyses, which should be considered with regards to future management decisions.     

With Allee effects,life for the social carnivore is complicated

Anthropogenic modification of the landscape, resultant habitat loss, and decades of persecution have resulted in severe decline and fragmentation of large carnivore populations worldwide. Infectious disease is also identified as a primary threat to many carnivores. In wildlife species, population demography and group persistence are strongly influenced by group or population size. This is referred to as the Allee effect, in which a population or group is at an increased risk of extinction when the number or density of individuals falls below some threshold due to ecological and/or genetic factors. However, in social mammalian species, the relationship between the number of individuals and the risk of extinction is complicated because aggregation may enhance pathogen exposure and transmission. Although theoretical studies of the interaction between infectious disease transmission and Allee effects reveal important implications for carnivore management and population extinction risk, information about the interaction has yet to be synthesized. In this paper, we assess life history strategies of medium to large carnivore species (≥2.4 kg) and their influence on population dynamics, with a special focus on infectious disease. While declining population trends are observed in 73 % of all carnivores (both social and solitary species), infectious disease is identified as a significant cause of population decline in 45 % of social carnivores and 3 % of solitary carnivores. Furthermore, where carnivores suffer a combination of rapid population decline and infectious disease, Allee effects may be more likely to impact social as compared to solitary carnivore populations. These potentially additive interactions may strongly influence disease transmission dynamics and population persistence potential. Understanding the mechanisms that can result in Allee effects in endangered carnivore populations and the manner in which infectious disease interfaces at this nexus may define the outcome of developed conservation strategies.     

Andean Condor (Vultur gryphus) in Ecuador: Geographic Distribution,Population Size and Extinction Risk

The Andean Condor (Vultur gryphus) in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA) for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km². During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation.     

A stochastic population model for Lepidium papilliferum (Brassicaceae), a rare desert ephemeral with a persistent seed bank

Population viability analysis (PVA) is a valuable tool for rare plant conservation, but PVA for plants with persistent seed banks is difficult without reliable information on seed bank processes. We modeled the population dynamics of the Snake River Plains ephemeral Lepidium papilliferum using data from an 11-yr artificial seed bank experiment to estimate age-specific vital rates for viability loss and germination. We related variation in postgermination demographic parameters to annual variation in precipitation patterns and used these relationships to construct a stochastic population model using precipitation driver variables. This enabled us to incorporate realistic levels of environmental variability into the model. A model incorporating best estimates for parameter values resulted in a mean trajectory for seed bank size that remained essentially stable through time, although there was a measurable risk of extinction over a 100-yr period for the study population under this scenario. Doubling the annual seed viability loss rate resulted in near-certain extinction, as did increasing first-year germination to 100%, showing the importance of the persistent seed bank. Interestingly, increasing environmental variance substantially decreased the risk of extinction, presumably because this plant relies on extremely good years to restock the persistent seed bank, while extremely bad years have little impact. If every year were average in this desert environment, the species could not persist. Simulated effects of livestock trampling resulted in greatly increased extinction risk, even over time frames as short as 15 years.     

Genetic consequences of habitat fragmentation and loss: the case of the Florida black bear (<Emphasis Type="Italic">Ursus americanus floridanus</Emphasis>)

Habitat loss and fragmentation can influence the genetic structure of biological populations. We studied the genetic consequences of habitat fragmentation in Florida black bear (Ursus americanus floridanus) populations. Genetic samples were collected from 339 bears, representing nine populations. Bears were genotyped for 12 microsatellite loci to estimate genetic variation and to characterize genetic structure. None of the nine study populations deviated from Hardy–Weinberg equilibrium. Genetic variation, quantified by mean expected heterozygosity (H _E), ranged from 0.27 to 0.71 and was substantially lower in smaller and less connected populations. High levels of genetic differentiation among populations (global F _ST = 0.224; global R _ST = 0.245) suggest that fragmentation of once contiguous habitat has resulted in genetically distinct populations. There was no isolation-by-distance relationship among Florida black bear populations, likely because of barriers to gene flow created by habitat fragmentation and other anthropogenic disturbances. These factors resulted in genetic differentiation among populations, even those that were geographically close. Population assignment tests indicated that most individuals were genetically assigned to the population where they were sampled. Habitat fragmentation and anthropogenic barriers to movement appear to have limited the dispersal capabilities of the Florida black bear, thereby reducing gene flow among populations. Regional corridors or translocation of bears may be needed to restore historical levels of genetic variation. Our results suggest that management actions to mitigate genetic consequences of habitat fragmentation are needed to ensure long-term persistence of the Florida black bear.     

Demographic and traditional knowledge perspectives on the current status of Canadian polar bear subpopulations

Subpopulation growth rates and the probability of decline at current harvest levels were determined for 13 subpopulations of polar bears (Ursus maritimus) that are within or shared with Canada based on mark–recapture estimates of population numbers and vital rates, and harvest statistics using population viability analyses (PVA). Aboriginal traditional ecological knowledge (TEK) on subpopulation trend agreed with the seven stable/increasing results and one of the declining results, but disagreed with PVA status of five other declining subpopulations. The decline in the Baffin Bay subpopulation appeared to be due to over‐reporting of harvested numbers from outside Canada. The remaining four disputed subpopulations (Southern Beaufort Sea, Northern Beaufort Sea, Southern Hudson Bay, and Western Hudson Bay) were all incompletely mark–recapture (M‐R) sampled, which may have biased their survival and subpopulation estimates. Three of the four incompletely sampled subpopulations were PVA identified as nonviable (i.e., declining even with zero harvest mortality). TEK disagreement was nonrandom with respect to M‐R sampling protocols. Cluster analysis also grouped subpopulations with ambiguous demographic and harvest rate estimates separately from those with apparently reliable demographic estimates based on PVA probability of decline and unharvested subpopulation growth rate criteria. We suggest that the correspondence between TEK and scientific results can be used to improve the reliability of information on natural systems and thus improve resource management. Considering both TEK and scientific information, we suggest that the current status of Canadian polar bear subpopulations in 2013 was 12 stable/increasing and one declining (Kane Basin). We do not find support for the perspective that polar bears within or shared with Canada are currently in any sort of climate crisis. We suggest that monitoring the impacts of climate change (including sea ice decline) on polar bear subpopulations should be continued and enhanced and that adaptive management practices are warranted.     

Estimates of Abundance and Harvest Rates of Female Black Bears Across a Large Spatial Extent

American black bears (Ursus americanus) are an iconic wildlife species in the southern Appalachian highlands of the eastern United States and have increased in number and range since the early 1980s. Given an increasing number of human-bear conflicts in the region, many management agencies have liberalized harvest regulations to reduce bear populations to socially acceptable levels. Wildlife managers need reliable population data for assessing the effects of management actions for this high-profile species. Our goal was to use DNA extracted from hair collected at barbed-wire enclosures (i.e., hair traps) to identify individual bears and then use spatially explicit capture-recapture methods to estimate female black bear density, abundance, and harvest rate. We established 888 hair traps across 66,678 km² of the southern Appalachian highlands in Georgia, North Carolina, South Carolina, and Tennessee, USA, in 2017 and 2018, arranged in 174 clusters of 2–9 traps/cluster. We collected 9,113 hair samples from those sites over 6 weeks of sampling, of which 1,954 were successfully genotyped to 462 individual female bears. Our spatially explicit estimator included a percent forest covariate to explain inhomogeneous bear density across the region. Densities ranged up to 0.410 female bears/km² and regional abundance was 5,950 (95% CI = 4,988–7,098) female bears. Based on hunter kill data from 2016 to 2018, mean annual harvest rates for females were 12.7% in Georgia, 17.6% in North Carolina, 17.6% in South Carolina, and 22.8% in Tennessee. Our estimated harvest rates for most states approached or exceeded theoretical maximum sustainable levels, and population trend data (i.e., bait-station indices) indicated decreasing growth rates since about 2009. These data suggest that the increased harvest goals and poor hard mast production over a series of prior years reduced bear population abundance in many states. We were able to obtain reasonable population abundance and density estimates because of spatially explicit capture-recapture methods, cluster sampling, and a large spatial extent. Continued monitoring of bear populations (e.g., annual bait-station surveys and periodic population estimation using spatially explicit methods) by state jurisdictions would help to ensure that population trajectories are consistent with management goals. © 2021 The Wildlife Society.     

Population viability analysis of Walia ibex (Capra walie) at Simien Mountains National Park (SMNP), Ethiopia

Population viability analysis (PVA) has been applied to the management of many threatened populations. The objective of this study was, therefore, to estimate the PVA of Walia ibex at the Simen Mountains National Park, in the north‐central highlands of Ethiopia, with respect to population growth parameters, the probability of the population reaching a lower extinction threshold and the mean time to extinction. Direct census of the population was carried out in 2009. Secondary census data were also collected from park authorities and the literature reviews. The result revealed that the estimates of the infinitesimal mean, μ (0.04117) was greater than the infinitesimal variance, σ² (0.0219). The probability that the population reaches the extinction threshold was very low (0.15%). The mean time required for the counts to decline from the existing population size to one individual animal was 160 years. But threatened species are adversely affected by changes in landscape. These changes can be brought by short‐ and long‐term human and climate change impacts, respectively. Therefore, with the absence of environmental and demographic stochasticity and, with the application of appropriate reproductions and habitat management, the population of Walia ibex will be viable and reaches its mean time of extinctions after 160 years.