Mean Population Size Research Articles

Density of a cryptic Australian small mammal: The threatened Julia Creek dunnart (Sminthopsis douglasi).

Globally, hundreds of mammal species face the threat of extinction in the coming decades, and in many cases, their ecology remains poorly understood. Fundamental ecological knowledge is crucial for effective conservation management of these species, but it is particularly lacking for small, cryptic mammals. The Julia Creek dunnart (Sminthopsis douglasi), a threatened, cryptic carnivorous marsupial that occurs in scattered populations in the central west of Queensland, Australia, was once so poorly studied that it was believed extinct. Sporadic research since its rediscovery in the early 1990s has revealed that S. douglasi is distributed across land at risk from many threats. Fundamental knowledge of S. douglasi population density is urgently required to inform conservation management at key sites, yet the species has historically proven hard to detect. Indeed, the status of the largest known population of S. douglasi, in Bladensburg National Park, is unknown. Here, we conducted a population study on S. douglasi at two sites within Bladensburg National Park via live mark-recapture surveys during 2022 and 2023. From likelihood-based spatially explicit capture-recapture (SECR) modelling we provide the first estimates of density and population size for S. douglasi. Live trapping resulted in captures of 49 individual S. douglasi (with 83 captures total, including recaptures). We estimated S. douglasi to occur at a density of 0.38 individuals ha-1 (0.25-0.58) at one site and 0.16 individuals ha-1 (0.09-0.27) at another site, with an estimated mean population size in suitable habitat at Bladensburg National Park of 1211 individuals (776-1646). Our S. douglasi density estimates were similar to that reported for other threatened small mammals in Australia. We also found evidence of extreme S. douglasi population fluctuations over time at Bladensburg National Park, which is of concern for its future conservation. Our study has provided the first estimate of density for S. douglasi, a threatened dasyurid species from the Mitchell Grass Downs of central western Queensland, Australia. Our research provides crucial population data to assist the management of this poorly studied species. We demonstrate a method that can be applied to species with low detection probability to ultimately help address the mammal extinction crisis faced by Australia and the rest of the world.

Fungi and deadwood diversity: A test of the area‐heterogeneity trade‐off hypothesis

Abstract Environmental heterogeneity is one of the most fundamental drivers of species diversity. For decades, ecologists have suggested that heterogeneity–diversity relationships are generally positive. But today, a greater variety of heterogeneity–diversity relationships is discussed. In this study, we contrasted two hypotheses for wood‐inhabiting fungi: The classical heterogeneity–diversity hypothesis, which predicts positive relationships due to an increase in niche dimensionality with increasing heterogeneity. And the more recently stated area‐heterogeneity trade‐off hypothesis, that predicts a unimodal pattern due to an inherent trade‐off between the number of occupied niches and the effective area per species. It allows positive and negative relationships only as special cases. We sampled 3715 deadwood objects on 135 plots along a forest structure gradient in the Black Forest, Germany, and recorded 284 wood‐inhabiting fungal species. To assess heterogeneity of deadwood structures, we calculated two multidimensional structural diversity indices: Structural richness was used as a measure of available niche space, and structural divergence as a measure of multivariate variance within that niche space. Those indices were then related to species richness estimates for rare, common and dominant species using the framework of Hill numbers. We found a linear, positive effect of structural richness and a unimodal effect for structural divergence on estimated species diversity. Structural richness, but not structural divergence, was strongly correlated with the number of sampled deadwood objects. No clear differences between the responses of rare, common and dominant species to the two heterogeneity gradients were found. We also estimated the mean abundance as a proxy for mean population size, which decreased significantly with structural richness but was non‐significantly related to structural divergence. Synthesis. In general, the results of this study suggest a unimodal heterogeneity–diversity relationship for deadwood‐inhabiting fungi and are thereby in line with the area‐heterogeneity trade‐off hypothesis. Thus, the negative effect of heterogeneity should lead to lower species richness and a higher risk of stochastic extinctions at high levels of heterogeneity. However, as deadwood amount and deadwood diversity are often strongly correlated, we argue that the positive effect of resource availability on species richness may mask the negative effect of structural heterogeneity in some cases.

Reorganization of bird communities along a rainforest elevation gradient during a strong El Niño event in Papua New Guinea.

The El Niño 2015 event, most extreme since 1997, led to severe droughts in tropical wet Papua New Guinea (PNG), reducing May to October dry season rainfall by 75% in the lowlands and 25% in the highlands. Such droughts are likely to have significant effects on terrestrial ecosystems, but they have been poorly explored in Papua New Guinea. Here, we report changes in bird community composition prior to, during, and after the 2015 El Niño event along the elevational gradient ranging from 200 m to 2700 m a.s.l. at the Mt. Wilhelm rainforest in PNG. The abundance of birds in the lowlands dropped by 60% but increased by 40% at elevations above 1700 m during El Niño year. In the following year, the individual bird species reached mean population sizes similar to pre-El Niño years but did not fully recover. Species richness roughly followed the pattern of observed abundance and quickly and fully re-established after the event to the pre- El Niño values. Thus, at least some terrestrial birds seem to react quickly to the extreme droughts in lowlands and shift to less affected mountain habitats. We recorded upper elevational range limits to shifts by more than 500 m a.s.l. in 22 bird species (out of 237 recorded in total) during El Niño year, in contrast to their typical ranges. Our study suggests that a strong El Niño event can have strong but reversible effects on bird communities as long as they have an opportunity to move to more favorable sites through undisturbed habitats.

Research on the Application of Improved Apriori Algorithm in Sport-Adaptive Online Teaching System Under Big Data Environment

Each student in an adaptive education system has significant differences in knowledge background, ability level and cognitive style. Therefore, to build an adaptive teaching system, it is necessary to establish an operable, reasonable and individualized student model by clarifying students’ abilities and differences. The improved Apriori algorithm under big data is the most classic association rule algorithm, which is generated by a set of candidates, and it uses the iterative method of hierarchical search to traverse a set of frequency items in the transaction database. After finding the set of frequency items, select the association according to the trust rules. This paper studies how to apply the improved Apriori algorithm to an adaptive online education system in a big data environment. An evolutionary algebra is taken with mean fit of 80, population size of 20, mean fit of 0.28, population size of 60, mean fit of 0.26, population size of 80, mean fit of 0.25, mean population size of 0.25. The population size is 200, and the average fitting is 0.24. The larger the error, the smaller the error between each indicator of the test paper and the corresponding value specified by the user. The improved Apriori algorithm in the big data environment has designed five themes of rule mining, which are mainly used for class management: class linkage, class category linkage, student basic information linkage, lecture and basic information linkage, and lecture mode linkage. They play the role of teaching assistants with a specific role.

Population Status and Threats to Galliform Bird in the Arjo-Didessa River Valley, Southwestern Ethiopia

The study was conducted to assess the species composition, population size, public knowledge, and threats to Galliform birds in the Arjo-Didessa River Valley, Southwestern Ethiopia. Data were collected from January 2018 to December 2020, covering both the dry and wet seasons. The study area was classified into four habitat categories: farmland, forest, grassland, and riverine areas. A line transects survey and point count routes were employed in the open habitats and dense habitats, respectively, to collect data. The species’ composition and relative abundance of Galliformes were estimated by timed species counting and encounter rates. To assess public knowledge and threats, direct inventories, questionnaire surveys, key informant interviews, and informal communications were employed. Three Galliform species, namely, Clapperton’s Francolin (Pternistis clappertoni), Helmeted Guineafowl (Numida meleagris), and Stone Partridge (Ptilopachus petrosus), were recorded in the area. The Helmeted Guineafowl were abundant (66.83%), Clapperton’s Francolin was common (30.14%), and Stone Partridge was a rare (3.03%) species. The population size of Galliformes recorded in the area was 461 during the dry season and 365 during the wet season, with a mean population size of 124.5 ± 11.5, 276 ± 33, and 12.5 ± 3.50 individuals of Clapperton’s Francolin, Helmeted Guineafowl, and Stone Partridge, respectively. The recorded flock size of Galliformes ranged from 1 to 22 individuals per flock. There was a statistically significant difference (F = 90.06, df = 3, and p < 0.05 ) in the population size of Galliformes between habitats, where the highest mean was recorded in the farmland (141.5 ± 7.5) and the lowest in the riverine (61.5 ± 43.5) habitats. The majority of the respondents (86.36%, n = 286) have prior knowledge and awareness about guineafowl and francolin species. They use these species mainly as a source of food (55.06%), eggs and meat consumption, a source of income (28.48%), and other values (16.45%), including foster-rearing and medical practices. In addition, guarding, trapping, scarecrows, and related crop raid protection measures were employed in the area to protect crops from crop damage by these birds. Although there is factual public understanding and a positive attitude towards Galliformes in the study area, habitat destruction and loss, agricultural intensification, overgrazing, fire, fuelwood collection, agrochemicals, and hunting and egg collection were observed as major threats affecting the species and their habitats. Further research and community-based conservation interventions are, therefore, essential to thoroughly monitor the population trends of Galliformes and maintain their habitats in the region.

Population structure and distribution of geladas (Theropithicus gelada, Ruppell 1835) in Kotu forest, Northern Ethiopia.

Endemic gelada populations outside protected areas are less investigated, and population census data are not available. As a result, a study was conducted to investigate the population size, structure, and distribution of geladas in Kotu forest and associated grasslands, in northern Ethiopia. The study area was stratified into five dominant habitat types namely, grassland, wooded grassland, plantation forest, natural forest, and bushland based on dominant vegetation type. Each habitat type was further divided into blocks, and a total counting technique was used to count the individuals of gelada. The total mean population size of gelada in Kotu forest was 229 ± 6.11. The mean ratio of male to female was 1:1.178. The gelada age composition comprised is as follows: 113 (49.34%) adults, 77 (33.62%) sub-adults, and 39 (17.03%) juveniles. The mean number of group one-male unit ranged from 1.5 ± 0.2 in the plantation forest to 4.5 ± 0.7 in the grassland habitat. On the other hand, all-male unit social system group was recorded only from grassland (1.5) and plantation forest (1) habitats. The average band size (number of individuals per band) was 45.0 ± 2.53. The largest number of geladas was recorded from grassland habitat 68 (29.87%), and the lowest was recorded from plantation forest habitat 34 (14.74%). Even though, the sex ratio was female biased, the proportion of juveniles to other age classes was very low compared with geladas in relatively well-protected areas, indicating negative consequences for the future viability of the gelada populations in the area. Geladas were widely distributed over open grassland habitat. Therefore, for sustainable conservation of the geladas in the area, there is a need for integrated management of the area with special attention on the conservation of the grassland habitat.

Zooplankton community size structure across lakes within a semi-arid landscape: the effect of temperature and salinity

AbstractBody size is a master trait controlling biological communities and ecosystem functioning. Mean population size not only depends on the size of individuals, but also on the size distribution of individuals within the population. Mean community size is additionally influenced by the composition of species (larger- or smaller-sized species). Shallow lakes within semi-arid landscapes are prone to experience large changes in temperature and salinity, which affect the zooplankton size structure. Higher temperatures are expected to result in smaller average body size, while the effect of salinity appears to depend on the range under study. Here we analyze zooplankton body size patterns across shallow lakes from the semi-arid central region of Argentina. All community size descriptors point to decreasing size and a narrow size range at higher temperatures. On the other hand, the maximum average community body size occurred at intermediate (~30 gL−1) salinity levels. The combined effect of both variables resulted in a bell-shaped pattern, with maximum community body size toward lower temperatures and intermediate salinities. Based on future temperature scenarios, one may anticipate an overall decrease in community body size. But such prediction is strongly conditioned by regional and local trends in salinity.

Sparing old-growth maximises conservation outcomes within selectively logged Amazonian rainforest

Timber extraction threatens a vast area of tropical ecosystems, making it vital to design productive harvesting operations that limit biodiversity declines. Contrasting management options span a continuum from less-intensive, land-sharing logging applied over a larger area to land-sparing operations that combine intensive harvesting with the preservation of old-growth forest. Combining company-reported extraction rates with dung beetle surveys along an Amazonian logging gradient, we explore how individual species' abundances, geometric mean population sizes, functional diversity, and trait characteristics vary across simulated logging concessions and production targets. We substantially extend previous studies by evaluating 8000 mixed-harvesting scenarios and by assessing the profitability of contrasting practices. Simply maximising old-growth protection delivers the highest species' abundances and population sizes for species negatively affected by logging. Maximising old-growth also supports communities with a functional trait dissimilarity (FDis, RaoQ) and functional structure of nesting guilds, biomass, pronotum volume, front leg area, and front:back leg ratio traits that closely resembles old-growth forest. Functional evenness (FEve), richness (FRic), and divergence (FDiv) did not vary across logging strategies. Some 3 % of mixed approaches outperform extreme sparing (which maximises old-growth retention through intensive logging) but still involve substantial sparing, enabled by intensified logging elsewhere. However more-extensive business-as-usual harvesting is up to 90 % more profitable than extreme sparing, suggesting active policy mechanisms, standards, or regulations would be needed to make spatially-concentrated logging operations (which benefit biodiversity) more commercially attractive. Old-growth sparing appears key to limiting biodiversity declines within tropical timber concessions, but would require payments to compensate for reduced profits.

Population size and diurnal activity patterns of Bohor reedbuck (Redunca redunca Pallas, 1767) in the compound of Alage Agricultural College, Central Rift Valley of Ethiopia

Abstract Bohor reedbuck is a medium-sized, even-toed ungulate species endemic to Africa. Its population is gradually declining, and an estimation of Meta populations is required to determine its current population status and as an input for conservation action. To this end, this study aimed to investigate this species’ population size and diurnal activity patterns in the compound of Alage Agricultural College, Central rift valley of Ethiopia. A total count was conducted to determine the population size of Bohor reedbuck by dividing the study area into different blocks. Continuous focal animal observations were used to collect data on activity patterns by recording group activities with five minutes intervals. The results revealed that the mean population size of Bohor reedbuck counted during the study period was (SE) with a density of 1.74 per km2. Females formed the dominant group in the population. From the mean total population size of Bohor reedbucks, 47.42% were adults. The mean group size of Bohor reedbuck was (SE). Feeding (, 45.81%) was the dominant mean diurnal activity pattern of Bohor reedbuck, followed by Resting (, 31.91%), whereas grooming (, 3.51%) was the least performed activity. There was a significant difference between the diurnal activities performed by Bohor reedbuck (). The studied compound is an important refuge for this species, and minimum management interference can increase the population size of Bohor reedbuck in the area.

Is It Feasible to Preserve a Self-Sustaining Population of Yangtze Finless Porpoise in the Highest Density Section of Yangtze River?

Using the VORTEX v. 10. 5.0.0, population viability analysis (PVA) was performed for Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis) in the highest density section between Hukou and Meilong section (HMS) of the Yangtze River. Baseline model showed that this population was in a relatively vulnerability state; the deterministic growth rate (Det-r) was −0.0230; the stochastic growth rate (Stoch-r) was −0.0385; the probability of extinction (PE) was 0.5690; the mean population size of extant populations (N-extant) was 22; the genetic diversity (GD) was 0.7698. Under the general protection model, the Det-r was 0.0015, and the Stoch-r was −0.0092; Under the medium protection model, the Det-r was 0.0219, and the Stoch-r was 0.0144; Under the optimal protection model, the Det-r was 0.0383, and the Stoch-r was 0.0357. Sensitivity analysis found that adult females breeding rate, sex ratio at birth, and mortality rate of juvenile YFP were sensitive to maintaining population stability. The PVA showed that the conservation of YFP population in HMS depends on: neutralization of all threats affecting YFP population in the HMS; maintenance and, whenever possible, enhancement of the functional connectivity of the waterbody, increasing the food resources of YFP and reducing the risk of injury to YFP caused by human.

Role of maturation and mortality in portfolio effects and climate resilience

The portfolio effect plays a critical role in population productivity and stability. Age structure of spawning salmon represents an example of portfolio effects such that the risks of experiencing unfavorable conditions are spread across time. However, the distribution of maturation ages for Pacific salmon ( Oncorhynchus spp.) is increasingly concentrated into fewer and younger ages, which may impact population resilience to climate change. We explored the population dynamics of Sacramento River fall-run Chinook salmon ( O. tshawytscha) under different age structure scenarios using a life-cycle model and compared two mechanisms that can underlie these changes—mortality and maturation. In addition, we tested whether age structure promotes resilience to drought. We found that high age structure diversity increased the stability of population size and harvest compared with low diversity. However, mean population size responded differently depending on the underlying mechanism. Reduced mortality of adult fish ages 4–5 increased escapement, whereas delayed maturation decreased escapement. Overall, high age structure diversity was able to buffer against the adverse effects of droughts by reducing the variability of population size and harvest compared with low diversity. Our results suggest that age structure promotes stability of salmon in an increasingly variable climate.

Isolated Medial Patellofemoral Ligament Reconstruction for the Treatment of Recurrent Lateral Patellar Dislocations: A Systematic Review and Meta-Analysis

Introduction: Being one of the most common acute knee disorders In children and adolescents, the incidence of patellar dislocations among pediatric patients is estimated to 43 per 100,000 with peak of age at 15 years.1 Briefly, a nonoperative treatment have been considered as the standard of care for patellar dislocations.5 However, recurrent patellar instability, osteochondral fractures with loose bodies, and failed non operative measures of functional rehabilitation benefitted from surgical treatment.6 As for the purpose of return-to-sports after surgery, clinicians have been using the utilization of time, ROM, strength, and subjective measures as guidelines.2,10 Methods: The population size was harvested from each study as well as means/medians and ranges for population age and follow-up time. Recurrent instability were taken to note, preoperative and postoperative Tegner for estimated return to play, positive apprehension test and Kujala scores were extracted. he study calculate means for population size, age, postoperative Tegner scores. Results: The total mean population size of all 6 studies was 217 participants, with a mean age and follow-up of 23.5 years and 30.8 months, respectively. The data extracted from all studies included in the review, as well as all calculated means, are presented in Table 3. The total mean population size of all 6 studies was 217 participants, with a mean age and follow-up of 23.5 years and 30.8 months, respectively. Conclusion: The mean postoperative Tegner score was 5.7, calculated from 4 studies. Preinjury and preoperative Tegner scores were reported in only one study. The pooled proportion of athletes who returned to sports after surgery was 84.1% (95% CI, 71.1%– 97.1%) (Figure 1). The pooled estimated mean from 7 studies that reported means ± SDs for the postoperative Kujala score was 85.8 (95% CI, 81.6–90.0; I2 = 92%) (Figure 2). Also, 4 studies reported the frequency at which patients exhibited a positive apprehension sign during follow-up; the pooled risk from these studies was 3.6% (95% CI, 0%–7.2%) (Figure 3). The pooled total risk of recurrent instability after surgery was 1.2% (95% CI, 0.3%–2.1%; I2 = 0%)

Study of Birth-Death Processes with Immigration

Birth-death processes are applied in the modelling of many biological populations, such as tumour cells and viruses. Various studies have established that birth-death processes, which occurwhen the population size is zero, are not in-line with reality in many situations. Therefore, in this study, the birth-death processes with immigration were investigated. We considered two immigration policies. First, immigration is allowed if and only if the population size is zero. Second, immigration at a constant rate is allowed irrespective of the population size. Birth and death rates were chosen such that the mean population size is a Gompertz function when the immigration rate is zero. The transient population size probability was obtained for both cases. Several tumour growth datasets were fitted using the mean population size of the above models and standard birth-death model without immigration. The two models with immigration provided entirely different probabilities of the population size being zero at an arbitrary epoch when compared with the model without immigration. Moreover, all three models provided a similar fit to the data. For each of the datasets studied, the models that allowed immigration produced less variance than the non-immigration model.

On the equivalence of operator and combinatorial approaches for onestep random Markov processes

Herein, for one-step random Markov processes the comparison of the operator and combinatorial methods based on the use of functional integrals is performed. With the combinatorial approach, the transition from the stochastic differential equation to the functional integral is used. This allows us to obtain the expression for the mean population size in terms of the functional integral. With the operator approach, the transition to the functional integral is performed via the creation and annihilation operators. It is shown that the mean values calculated using the functional integrals arising in the combinatorial and operator approaches coincide.

Population density and abundance of Green Turtles (Chelonia mydas) in one of the largest feeding grounds in the Egyptian Red Sea

Green turtles (Chelonia mydas) are globally endangered and very little is known about their population in Egypt’s Red Sea. Abu Dabbab Bay was believed to contain one of the most dense and important green turtle feeding grounds in the Egyptian Red Sea. The results of our surveys suggest that Abu Dabbab Bay is a high density feeding ground with 612±61.9 turtles/km2 and a mean population size of 104±10 turtles. The density and abundance of green turtles in Abu Dabbab bay has at least doubled, depending upon survey month, in a ten year span This increase could be the result of reduced shark populations in the Red Sea, a temporary reduction of tourist numbers from the Covid 19 pandemic, and/or local initiatives by private stakeholders to reduce disturbance. Regular monitoring the is needed to better understand the reasons for future population trends.

Glass-like transition described by toppling of stability hierarchy* *Dedicated to the memory of Fritz Haake.

Building on the work of Fyodorov (2004) and Fyodorov and Nadal (2012) we examine the critical behaviour of population of saddles with fixed instability index k in high dimensional random energy landscapes. Such landscapes consist of a parabolic confining potential and a random part in N ≫ 1 dimensions. When the relative strength m of the parabolic part is decreasing below a critical value m c, the random energy landscapes exhibit a glass-like transition from a simple phase with very few critical points to a complex phase with the energy surface having exponentially many critical points. We obtain the annealed probability distribution of the instability index k by working out the mean size of the population of saddles with index k relative to the mean size of the entire population of critical points and observe toppling of stability hierarchy which accompanies the underlying glass-like transition. In the transition region m = m c + δN −1/2 the typical instability index scales as k = κN 1/4 and the toppling mechanism affects whole instability index distribution, in particular the most probable value of κ changes from κ = 0 in the simple phase (δ > 0) to a non-zero value κ max ∝ (−δ)3/2 in the complex phase (δ < 0). We also show that a similar phenomenon is observed in random landscapes with an additional fixed energy constraint and in the p-spin spherical model.

No silver bullet? Snow leopard prey selection in Mt. Kangchenjunga, Nepal.

In this study, we investigated the impact of domestic and wild prey availability on snow leopard prey preference in the Kangchenjunga Conservation Area of eastern Nepal—a region where small domestic livestock are absent and small wild ungulate prey are present. We took a comprehensive approach that combined fecal genetic sampling, macro‐ and microscopic analyses of snow leopard diets, and direct observation of blue sheep and livestock in the KCA. Out of the collected 88 putative snow leopard scat samples from 140 transects (290 km) in 27 (4 × 4 km2) sampling grid cells, 73 (83%) were confirmed to be from snow leopard. The genetic analysis accounted for 19 individual snow leopards (10 males and 9 females), with a mean population size estimate of 24 (95% CI: 19–29) and an average density of 3.9 snow leopards/100 km2 within 609 km2. The total available prey biomass of blue sheep and yak was estimated at 355,236 kg (505 kg yak/km2 and 78 kg blue sheep/km2). From the available prey biomass, we estimated snow leopards consumed 7% annually, which comprised wild prey (49%), domestic livestock (45%), and 6% unidentified items. The estimated 47,736 kg blue sheep biomass gives a snow leopard‐to‐blue sheep ratio of 1:59 on a weight basis. The high preference of snow leopard to domestic livestock appears to be influenced by a much smaller available biomass of wild prey than in other regions of Nepal (e.g., 78 kg/km2 in the KCA compared with a range of 200–300 kg/km2 in other regions of Nepal). Along with livestock insurance scheme improvement, there needs to be a focus on improved livestock guarding, predator‐proof corrals as well as engaging and educating local people to be citizen scientists on the importance of snow leopard conservation, involving them in long‐term monitoring programs and promotion of ecotourism.

Using Ecological Niche Models for Population and Range Estimates of a Threatened Snake Species (Crotalus oreganus) in Canada

Modelling the distribution and abundance of species at risk is extremely important for their conservation and management. We used ecological niche models (ENMs) to predict the occurrence of western rattlesnakes (Crotalus oreganus) in British Columbia (BC), Canada. We applied this to existing population estimates to support a threshold of occurrence for management and conservation. We also identified predictors influencing rattlesnake distribution and abundance in this region. Using a Geographic Information Systems platform, we incorporated ENMs, capture–mark–recapture (CMR) and radio-telemetry results, province-wide observations, Landsat imagery and provincial databases for agricultural land use to produce quantitative, spatially explicit, population estimates across BC. Using available western rattlesnake habitat estimated at 183.9 km2 and averaging estimates calculated from densities in three study populations, we generated a mean adult population size of 9722 (±SD 3009; 0.8 relative index of occurrence [RIO] threshold). Only a small area (21.6 km2) of suitable land cover was located within protected areas, potentially protecting an estimated 1144 (±354) adults. Most suitable land cover was within 500 m of roads (170.6 km2), representing potential habitat being used by an estimated 9017 (±2791) adults. At the threshold RIO value chosen (0.8), only a very small area of farmland provided suitable land cover. Our results highlight the possibility of high mortality rates for western rattlesnakes near roads and the fact that protected areas do not provide sufficient coverage to conserve the population. Given that this species has relatively low mobility and high site fidelity to home ranges, our population estimate for BC provides a useful reference for the northern part of the species’ range. It also fulfills a need to estimate population size within political jurisdictions where conservation management decisions are made, as well as presenting a method that can be applied to other parts of the range, including the southern United States. Our study provides an important benchmark for future monitoring of western rattlesnakes in BC using a repeatable and transparent approach. Similar applications can be extrapolated and applied for other threatened species to identify and quantify population distributions and threats, further supporting conservation prioritization tools to be used to maximize the effectiveness of conservation strategies under financial constraints.

Spatial structure and dispersal dynamics in a house sparrow metapopulation.

The effects of spatial structure on metapopulation dynamics depend upon the interaction between local population dynamics and dispersal, and how this relationship is affected by the geographical isolation and spatial heterogeneity in habitat characteristics. Our aim is to examine how emigration and immigration of house sparrows Passer domesticus in a Norwegian archipelagic metapopulation are affected by key factors predicted by classic metapopulation models to affect dispersal-spatial and temporal variation in population size, inter-island distance, local demography and habitat characteristics. This metapopulation can be divided into two major habitat types: (a) islands closer to the mainland where sparrows breed in colonies on farms, and (b) islands without farms, situated farther away from the mainland where sparrows are exposed to harsher environmental conditions. Dispersal was spatially structured within the metapopulation; there was proportionally and numerically less emigration and immigration involving farm islands, as compared to non-farm islands. Furthermore, emigration and immigration occurred mostly between nearby islands. Moreover, emigration in response to spatial differences in mean population size differed between the habitat types, but populations with large mean received more immigrants in both habitat types. The number of emigrants and immigrants was negatively related to long-term recruit production, which was not the case in non-farm islands. The proportion and number of emigrants was positively related to temporal increases in recruit production on farm islands, however not on non-farm islands. Our results demonstrate that spatial heterogeneity in environmental conditions influences how spatial variation in long-term mean population size, and temporal and spatial variation in recruit production, affects dispersal dynamics. The spatial structure of this metapopulation is therefore best described by a spatially explicit model in which the exchange of individuals within each habitat type is strongly affected by the degree of geographical isolation, population size and recruit production. However, these relationships differed between the two habitat types; non-farm islands showing similarities to a mainland-island model type of structure, whereas farm islands showed features more associated with source-sink or balanced dispersal models. Such differential dispersal dynamics between habitat types are expected to have important consequences for the ecological and evolutionary dynamics within this metapopulation.

A hierarchical distance sampling model to estimate spatially explicit sea otter density

AbstractWildlife managers often rely on analyses conducted prior to the widespread adoption of hierarchical models which can lead to questions about the accuracy of previous inferences. Hierarchical models allow observed data to be partitioned into factors that influenced the collection of the data such as detectability of animals (i.e., observation processes) and factors that influence the ecology of a population such as features that affect the distribution of animals (i.e., ecological processes). Population surveys for sea otters in the Aleutian Islands, Alaska, have historically been conducted by conflating the observation and ecological processes potentially leading to inaccurate population estimates. Based on boat and plane‐based sea otter survey data collected in 2017, we sought to overcome many problems of previous sea otter surveys in southwestern Alaska. We developed a spatially explicit hierarchical distance sampling model to estimate the abundance of sea otters in the Eastern Aleutians Management Unit while explicitly accounting for factors that affect the ability to detect sea otters during surveys (i.e., group size, ocean conditions). We also sought to account for the environmental factors leading to the non‐uniform distribution of sea otter groups by identifying relationships between otter group abundance and environmental attributes (i.e., ocean depth, presence of kelp, underwater substrate). Detection of sea otter groups was related to group size, and ocean conditions (e.g., ocean swell size). After accounting for detection, we estimated a mean population size of 8593 individual sea otters (95% CI: 7450–9984) which is considerably higher than previous estimates, although comparisons are difficult given divergent methodologies. Sea otter group density was negatively related to ocean depth and the presence of rock and gravel as underwater substrates. Conversely, sea otter group density was positively related to the presence of kelp and mud as an underwater substrate. Our hierarchical distance sampling model accounted for the observation process which allowed better estimates of the environmental attributes affecting otter abundance. Our research can serve as a template for other study systems requiring spatially explicit density estimates from a distance sampling framework and can help provide a new baseline for managers to gauge future population changes in sea otters.