Mark-recapture Research Articles

Using population register data and capture-recapture models to estimate over-coverage in Sweden

Over-coverage occurs when individuals who reside in a country leave or pass away, and this demographic event is not recorded in population registers, leading to population size overestimation. This problem can have important policy and decision-making consequences. With the increased reliance on incomplete but overlapping official registers for documenting whole populations or subgroups of populations, there is a need for more sophisticated modelling techniques that reliably estimate population size, and hence over-coverage, from such registers. Previous approaches have considered multiple systems estimation (MSE) for monitoring over-coverage, but MSE does not naturally extend to cases where individuals are followed over time. In this paper, motivated by the case study of Sweden, we develop a capture-recapture (CR) modelling framework for population registers that allows us to estimate the population size each year, the probability of presence for each individual in the population, conditional on their records, each year and to quantify the effect of demographic characteristics on the probability of emigration and re-immigration, amongst other parameters. Our results suggest that the CR approach, which accounts for the whole time series for each individual, gives a more realistic estimate of the population size compared to existing, deterministic approaches, especially when considering the subgroup of newly arrived individuals, and that it provides new insights on individual behaviour in terms of migration patterns than existing MSE approaches.

Capture–recapture estimates of Antarctic blue whale abundance and population growth rate

AbstractPhoto‐identifications of Antarctic blue whales (Balaenoptera musculus intermedia) collected from 2003/2004 to 2018/2019 were used in a capture–recapture analysis to estimate abundance and population growth rate for the circumpolar Antarctic. Two capture–recapture models, POPAN and Pradel, were applied to these data. Estimates of annual abundance and their variances from the left and right side photo data were inferred using multimodel averaging, weighted by corrected Akaike information criterion (AICc), of 26 model configurations with prespecified survival rates from .75 to 1.0. These estimates based on the left and right side databases were then combined using inverse‐variance averaging into single estimates for each year. The POPAN superpopulation estimate (total number of individuals present during the sampling period) was 3,506 whales, 95% confidence interval (CI) [2,107, 5,832]. The estimated abundance from the final year of the study in 2018/2019 was 1,817 whales, 95% CI [714, 4,624]. The abundance estimates in this study may be biased downwards due to capture heterogeneity as a result of unequal spatial sampling. Population growth rate estimates were 11% from Pradel and 10% from POPAN. These rates were within the confidence interval estimated by a previous study for Antarctic blue whale population growth rate.

Quantifying uncertainty in anthropogenic causes of injury and mortality for an endangered baleen whale

AbstractUnderstanding the causes of mortality for a declining species is essential for developing effective conservation and management strategies, particularly when anthropogenic activities are the primary threat. Using a competing hazards framework allows for robust estimation of the cause‐specific variation in risk that may exist across multiple dimensions, such as time and individual. Here, we estimated cause‐specific rates of severe injury and mortality for North Atlantic right whales (Eubalaena glacialis), a critically endangered species that is currently in peril due to human‐caused interactions. We developed a multistate capture–recapture model that leveraged 30 years of intensive survey effort yielding sightings of individuals with injury assessments and necropsies of carcass recoveries. We examined variation in the hazard rates of severe injury and mortality due to entanglements in fishing gear and vessel strikes as explained by temporal patterns and the age and reproductive status of the individual. We found strong evidence for increased rates of severe entanglement injuries after 2013 and for females with calves, with consequently higher marginal mortality. The model results also suggested that despite vessel strikes causing a lower average rate of severe injuries, the higher mortality rate conditional on injury results in significant total mortality risk, particularly for females resting from a recent calving event. Large uncertainty in the estimation of carcass recovery rate for vessel strike deaths permeated into the apportionment of mortality causes. The increased rates of North Atlantic right whale mortality in the last decade, particularly for reproducing females, has been responsible for the severe decline in the species. By apportioning the human‐caused threats using a quantitative approach with estimation of relevant uncertainty, this work can guide development of conservation and management strategies to facilitate species recovery. Our approach is relevant to other monitored populations where cause‐specific injuries from multiple threats can be observed in live and dead individuals.

Utilizing a capture–recapture strategy to accelerate infectious disease surveillance

Utilizing a capture–recapture strategy to accelerate infectious disease surveillance

Drug use patterns and health problems among people who use drugs in Guinea-Bissau (2022): A cross-sectional survey using respondent-driven sampling

BackgroundLittle data exists on the use of cocaine, methamphetamine, tramadol and heroin or related health conditions in Guinea Bissau. We aimed to estimate drug use practices and the prevalence of selected blood-borne infections, depression and population size estimates of people who use injectable drugs in Guinea-Bissau. MethodsWe used respondent-driven sampling to recruit adults who use injectable drugs in this cross sectional survey in three cities (Bissau, Bafatá and Gabú) between July and September 2022. Participants completed an interviewer administered survey enquiring about sociodemographic characteristics, drug use practices and mental health. Rapid diagnostic testing was done for HIV, hepatitis B surface antigen (HBsAg) and hepatitis C antibody (anti-HCV). Data was weighted in RDS-Analyst using self-reported network size and Gile's Sequential Sampling Estimator. Population size estimates were generated using the two point capture-recapture method. ResultsOverall, 750 participants were recruited. People who use drugs were estimated to be mostly unemployed males aged between 25 and 49 years. Methamphetamine and crack cocaine were most commonly used. Prevalence of ever injecting ranged from 6 % to 44 %. Between 44 % and 52 % of people experience symptoms of depression. Prevalence ranges from 1.9 % to 5.2 % for HIV, and 5.7–8.3 % for HBsAg and 0.42–0.66 % for anti-HCV. The population estimates of people who use injectable drugs were 1637 in Bissau, 1314 in Bafatá and 424 in Gabú. ConclusionMethamphetamine and crack cocaine are the most commonly used injectable drugs in Guinea-Bissau. Symptoms of depression are common among people who use drugs in the country. Access to evidence-based drug use treatment and harm reduction interventions that integrate mental health care services are needed to improve the health and wellbeing of people who use drugs in Guinea-Bissau.

Raccoon density estimation from camera traps for raccoon rabies management

AbstractDensity estimation for unmarked animals is particularly challenging, yet density estimates are often necessary for effective wildlife management. Raccoons (Procyon lotor) are the primary terrestrial wildlife reservoir for Lyssavirus rabies within the United States. The raccoon rabies variant (RRVV) is actively managed at landscape scales using oral rabies vaccination (ORV) within the eastern United States. To effectively manage RRVV, it is important to know the density of raccoons to appropriately scale the density of ORV baits distributed on the landscape. We compared methods to estimate raccoon densities from camera‐trap data versus more intensive capture‐mark‐recapture (CMR) estimates across 2 land cover types (upland pine and bottomland hardwood) in the southeastern United States during 2019 and 2020. We evaluated the effect of alternative camera configurations and durations of camera trapping on density estimates and used an N‐mixture model to estimate raccoon densities, including covariates on abundance and detection. We further compared different methods of scaling camera‐based counts, with the maximum number of raccoons seen on any given image within a day best explaining density. Camera‐trap density estimates were moderately correlated with CMR estimates (r = 0.56). However, densities from camera‐trap data were more reliable when classifying category of density as an index used to inform management (83% correct when compared to CMR estimates), although the densities in our study fell into the 2 lowest density classes only. Using more cameras reduced bias and uncertainty around density estimates; however, if ≤6 camera traps were used at a site, a line transect approach proved less biased than a grid design. Camera trapping should be conducted for at least 3 weeks for more accurate estimates of raccoon population density in our study area (<5% bias). We show that camera‐trap data can be used to assign raccoon densities to management‐relevant density index bins, but more studies are needed to ensure reliability across a greater range of environmental conditions and raccoon densities.

The 2009 FDA PRO guidance, Potential Type I error, Descriptive Statistics and Pragmatic estimation of the number of interviews for item elicitation.

A statistical methodology named "capture recapture", a Kaplan-Meier Summary Statistic, and an urn model framework are presented to describe the elicitation, then estimate both the number of interviews and the total number of items ("codes") that will be elicited during patient interviews, and present a summary graphical statistic that "saturation" has occurred. This methodology is developed to address a gap in the FDA 2009 PRO and 2012 PFDD guidance for determining the number of interviews (sample size). This estimate of the number of interviews (sample size) uses a two-step procedure. The estimate of the total number of items is then used to estimate the number of interviews to elicit all items. A framework called an urn model is a framework for describing the elicitation and demonstrate the algorithm for declaring saturation "first interview with zero new codes". A caveat emptor is that due to independence assumptions, the urn model is not used as a method for estimating probabilities. The URN model provides a framework to demonstrate that an algorithm such as "first interview with zero new codes" may establish that all codes have been elicited. The limitations of the Urn model, capture recapture, and Kaplan-Meier are summarized. The statistical methods and the estimates supplement but do not replace expert judgement and declaration of "saturation." A graphical summary statistic is presented to summarize "saturation," after expert declaration for two algorithms. An example of a capture-recapture estimate, using simulated data is provided. The example suggests that the estimate of total number of codes may be accurate when prepared as early as the second interview. A second simulation is presented with an URN model, under a strong assumption of independence that an algorithm such as 'first interview with zero new codes" may fail to identify all codes. Potential errors in declaration of saturation are presented. Recommendations are presented for additional research and the use of the algorithm "first interview with zero new codes."

Platypus fyke-netting methods: a review of recommended field protocols and options for assessing population abundance

Fyke nets are the preferred type of equipment used for platypus (Ornithorhynchus anatinus) live-trapping surveys in shallow watercourses. However, numerous factors other than abundance may affect the frequency of platypus captures, including when, where and how nets are set, stream discharge and entry into nets by rakali (Hydromys chrysogaster), which create exit holes that are then also available to a platypus. A threefold difference in the mean monthly frequency of platypus captures in fyke nets is also evident across the year. To limit net evasion, it makes sense to reduce net visibility and minimise opportunities for animals to squeeze under, climb over or walk around nets. Time-lapse cameras can also be deployed at fyke-netting sites to estimate how many individuals evade capture. To protect platypus welfare and the welfare of non-target species held in fyke nets, it is important to ensure that captured animals have access to air, to check nets frequently throughout the time they are set and to release bycatch when first encountered. Fyke-netting studies typically generate sparse platypus population data, so care is needed when selecting and interpreting platypus abundance metrics generated through mark–recapture modelling or use of indices.

Estimating the rates of dementia using administrative data linked to cohort studies.

Current estimates of dementia and Alzheimer's disease incidence and prevalence are required to understand the health needs of the elderly. We used two Australia cohort studies, administrative datasets, and data linkage techniques to estimate dementia rates in Australia. The study used Australian Longitudinal Study on Women's Health and the Health in Men Cohort Study. Records of dementia were obtained from linked sources and incidence and prevalence estimates were produced. Capture-recapture methods were used to estimate numbers of dementia cases not identified through data linkage. There were 3399 (28.5%) men with dementia identified from any source and 3767 (34.8%) women. Rates of dementia incidence and prevalence were similar between sexes but were raised in men once estimates of unidentified cases were included. Cohort studies and linked administrative data can be used together to produce current estimates of dementia prevalence and incidence comparable to other population estimates.

Unraveling demographic patterns in tropical birds across an elevational gradient

Abstract An increasing body of evidence has displayed upslope shifts in the high-diversity avian communities of tropical mountains. Such shifts have largely been attributed to warming climates, although their actual mechanisms remain poorly understood. One likely possibility is that changes in species-specific demographic rates underlie elevational range shifts. Fine-scale population monitoring and capture–mark–recapture (CMR) analysis could shed light on these mechanisms but, until recently, analytical constraints have limited our ability to model multiple demographic rates across bird communities while accounting for transient individuals. Here, we used Bayesian hierarchical multi-species CMR models to estimate the apparent survival, recruitment, and realized population growth rates of 17 bird species along an elevational gradient in the cloud forests of Honduras. For 6 species, we also modeled demographic rates across elevation and time. Although demographic rates varied among species, population growth rates tended to be higher in lower elevation species. Moreover, some species showed higher population growth rates at higher elevations, and elevational differences in growth rates were positively associated with previous estimates of upslope shifts at the study site. We also found that demographic rates showed contrasting trends across the duration of the study, with recruitment decreasing and apparent survival increasing, and stronger effects at lower elevations. Collectively, we provide the methodological tools to encourage more multi-species demographic analyses in other systems, while highlighting the potential for the demographic impacts of global change. We provide a Spanish translation in the Supplementary Materials.

Interplay of abiotic conditions, density, and body size in shaping demography in a high‐elevation toad population

AbstractIn natural populations, vital rates such as survival and reproduction are influenced by a complex interplay of abiotic conditions (e.g., environment), density dependence, and individual factors (e.g., phenotypic traits). Studies at the extremes of species distributions, particularly high elevations, offer unique insights due to the intensified effects of abiotic stressors, which can amplify both direct and indirect effects on vital rates. In this study, we focus on a high‐elevation population of the common toad (Bufo bufo) located near the upper limit of its elevational range in the Swiss Alps. This setting provides a critical context for examining how extreme abiotic conditions interact with density dependence and individual factors to influence life history traits. Utilizing 28 years of capture–mark–recapture data and individual body size measurements from nearly 2500 toads, we applied in a Bayesian statistical framework a Cormack–Jolly–Seber model for estimating male survival probabilities, and a multistate model for assessing female survival and breeding probabilities, alongside sex‐specific growth curves. Our analysis indicates that survival probabilities are significantly impacted by interactions between abiotic conditions such as the active season length and temperature at emergence from hibernation, density dependence, and individual phenotypic traits such as body size. The breeding patterns of females showed a biennial cycle, with temperature at hibernation emergence influencing the likelihood of skipping breeding events and density affecting the resumption of breeding. These results highlight the role of abiotic conditions and density in shaping physiological and reproductive strategies in a high‐stress ecological niche. Moreover, we uncovered indications of indirect effects, where both abiotic conditions and density potentially affect asymptotic growth and thus survival, mediated through changes in body size. Our findings illustrate the complex dynamics at play in high‐elevation populations and the importance of long‐term, individual‐based data in studying these processes. This study underscores the value of integrating multiple sources of variation to understand population dynamics comprehensively, particularly in understudied, extreme environments where traditional ecological models may not fully capture the nuanced interdependencies of natural systems.

A comparison of thermal drones and camera trap population estimates for Sitka black‐tailed deer in Alaska

One of the most difficult challenges for wildlife managers is reliably estimating wildlife populations. Camera traps combined with spatial capture–recapture (SCR) models are a popular tool for population estimation. They have limitations, however, including long data processing times. Drones with thermal imagery are an emerging tool for estimating wildlife populations, but how they compare to other methods remain poorly studied. We compared the use of camera traps and SCR models to drone surveys for estimating population densities of Sitka black‐tailed deer Odocoileus hemionus sitkensis on Afognak Island, Alaska. We deployed 26 camera traps from 1 September until 6 October 2022 and individually identified males using antler characteristics, for the SCR model. At the same site we conducted three drone surveys between October and December 2022, identified sex composition and obtained deer counts. The estimated density from the SCR model was 3.7 males ± 0.8 (SE) km‐2, and 14.1 ± 3.1 adults km‐2 of clear‐cut forest. Results from the drone survey produced similar estimates with 2.1 ± 0.9 males km‐2 and 13.4 ± 1.6 adults km‐2. The similarity in estimates suggests that both methods converged on an accurate representation of the population in this habitat, but these methods diverge in levels of sampling effort, duration, and financial cost. Camera traps offer further insights on behavior and home‐range size but require longer data processing times, can be subject to malfunctions, and are difficult to deploy and maintain in remote areas. Drones are subject to legal restrictions, have difficulty in closed canopy habitat and can be initially costly, but they provide results faster and require less data analysis. Camera traps and drones are useful for determining population dynamics but are subject to their limitations. Wildlife managers should make survey decisions based on their specific goals, habitat type, focal species ecology and financial limitations.

Prevalence of problematic drug use in Martinique in 2006: The NEMO study

ObjectivesSubstance use disorders are of worldwide public health interest. Local estimates of problematic drug use provide useful indicators to regional public health agencies in developing prevention and treatment programs. The purpose of the current study was to estimate the prevalence of problematic drug use in Martinique. MethodsThe capture-recapture method was applied to a multisource data collection (eight specialized drug and two law enforcement sources) to provide an estimate of drug use (opiates, cocaine hydrochloride, crack (cocaine base), stimulants and/or hallucinogens). Data collection was organized over a period of six consecutive months (September 2005 to March 2006) and concerned all persons residing in Martinique longer than three months and who had consumed at least one of the studied drugs in the month prior to the study. ResultsWe identified 287 cases (86% male; mean age 36.1±9.6 years), 98% of whom had used crack. Comorbid use of illicit drugs other than alcohol and cannabis was 4%. Our study showed that patients with problematic drug use in Martinique is estimated to be 1.936 [95% CI: 964,2907] in a total population of 380.863 (INSEE, 1999). Prevalence rates were 5.0 per thousand among the global population and 7.7 per thousand in the adult population aged 15–64 years. ConclusionsOur study is the first to provide relevant data on the extent of problematic drug use in Martinique for health policies and decision-makers.

Testing of UV fluorescence marking with daily recaptures of a low-mobile bush-cricket species

The primary goal of developing new mark–release–recapture (MRR) methods is to make MMR more cost-effective and able to provide more information. To test the effectiveness of UV fluorescence marking, a case study was carried out on an Isophya costata population occurring in a mown grassland with a heterogeneous vegetation pattern. The marked individuals were examined daily, from the emergence of imagos until the mowing of the habitat. The 40 marked insects (20 males and 20 females) were recaptured in 206 cases over 16 days (32.2% of the potential maximal recaptures). The finding of males was 26.2% successful, and the finding of females was 38.1% successful. Females released in shorter and sparse vegetation were recaptured more than those released in dense vegetation or than males. Recaptures showed a significant decrease during the study period in almost all groups based on Mann–Kendall trend tests. Detections were made on the upper third of the vertical structure of the vegetation in 88% of cases. In most of the detections (males: 70%, females: 62%), the axis of the insect’s body was more likely to be located vertically. The results showed that the chance of detection is significantly reduced when the position of the insect’s body is facing the axis of UV illumination. Thus, the visibility of individuals can be greatly increased by marking all sides of the body.

Leishmaniasis in Tuscany: investigation of hidden human cases and comparison with canine incidence

Abstract The Mediterranean basin hosts endemic areas for leishmaniasis, mainly attributable to the presence of sand flies. Leishmaniasis has gained importance in Europe due to climate change, globalisation and migration. For at least the last 10 years in Tuscany, Italy, there has been an important discrepancy between official notifications of visceral and cutaneous leishmaniasis cases in humans and the number of hospital admissions, highlighting an important underestimation, despite mandatory notification. Moreover, official reports have increased alarmingly in the last three years. Human leishmaniasis does not always require hospitalisation: it often presents cutaneous manifestations, whereas in the immunocompetent individual it may not occur at all. For this reason, it is reasonable to assume that the number of cases is higher than the number of hospitalisations. The project aims to investigate the underreporting of human leishmaniasis cases from 2014 to 2023 by analysing laboratory diagnoses (considering any laboratory test that, according to the Italian Ministry of Health guidelines, is useful to identify a ‘confirmed case’, thus serological tests; parasitological tests; culture tests; PCR). To estimate the extent of underreporting, the capture-recapture method will be used, taking into account laboratory data, official reports and hospital data. Subsequently, a comparison will be made with the incidence, in the same territory, of veterinary cases, particularly in dogs, using data obtained from the Lazio-Tuscany Zooprophylactic Institute, to compare the trend of human and canine cases over time. Analyses are in progress and the results will be presented at the conference. Poor surveillance leads to ineffective prevention policies. The impact of the project is to strengthen the leishmaniasis surveillance system in Tuscany in order to reinforce prevention systems and face emergencies. Key messages • Due to climate change, globalization, and migration, there has been an increase in diagnoses of vector-borne diseases, including Leishmaniasis. • Leishmaniasis surveillance need to be strengthened in order to enhance prevention systems and address emergencies.

Epidemiology of Dementia in the Campania Region (Italy): A 2015-2020 population-based study

Abstract As the global population ages, dementia poses a significant health challenge, ranking seventh among leading causes of death worldwide. Considering the high societal and financial burden of dementia, our study aims to provide estimates of prevalence and incidence for any dementia and Alzheimer’s dementia (AD) in the Campania Region (South Italy). It is Population-based study, using routinely collected healthcare data of individuals living in the Campania Region (South Italy) from 2015 to 2020. We included individuals aged ≥65 years who had at least one administrative record for dementia and/or AD. Prevalence rates adjusted for age and sex used 2020 European population as reference. To estimate incidence, we tested three possible algorithms, which differed for the duration of the time interval between study baseline (Jan 1, 2015) and index date (first record for dementia and/or AD in administrative databases). We employed a clinical database for the validation of our algorithms towards neuropsychological test results. Among individuals, 80,392 had dementia, of which 35,748 had AD. The age- and sex-standardized prevalence rates per 1,000 individuals for any dementia and AD were 77.64 (95%CI=77.57; 77.68) and 34.05 (95%CI=34.01; 34.09), respectively. There were 82.10 incident cases of any dementia per 100,000 per year (0.79 sensitivity and 0.62 specificity), and 59.89 incident cases of AD per 100,000 per year (0.80 sensitivity and 0.59 specificity). The capture-recapture method showed low number of undetected cases (1.7% for any dementia and 3.0% for AD). Our algorithms showed acceptable performance with AUC ranging from 0.59 to 0.72, and double likelihood ratio of correctly identifying individuals above and below MMSE standard cut-offs (24 and 26). Our algorithm, integrating administrative and clinical data, holds potential for assessing dementia’s epidemiological burden, identifying risk factors, planning healthcare access, and developing prevention strategies. Key messages • Providing comprehensive estimates of dementia burden aids public health planning and resource allocation. • Integrated administrative and clinical data provide robust tools for epidemiological analysis and preventive strategies.

SINAVE’s quality: completeness for Meningococcal Disease – Northern Portugal, 2020-2022

Abstract Due to Meningococcal’s Disease (MD) severity and impact in public health, in Portugal it is mandatory to notify the suspicious cases to implement effective control measures. MD cases are notified in the National Surveillance System (SINAVE), which triggers epidemiological investigation, risk assessment and community intervention. The quality of SINAVE is defined by various attributes, being their evaluation crucial to improve and guarantee quality standards. Our goal is to evaluate the external and internal completeness of SINAVE for MD in northern Portugal from 2020 to 2022. We have conducted a cross-sectional study, using MD cases from 2020 to 2022. External Completeness was estimated using a two-source capture-recapture method, with data from SINAVE and Diagnostic-Related Group (DRG) cases. Hospital readmissions’, duplicates and cases from other regions were excluded. Internal completeness of SINAVE was accessed for each case and for each non-mandatory variable. For external completeness (EC) analysis, 21 of the 23 DRG cases were eligible for matching. Out of 31 SINAVE confirmed cases, 20 were eligible for matching. EC of SINAVE was 66,7%. For internal completeness (IC) analysis, we excluded 7 cases that did not meet the criteria for inclusion. The mean IC was 73,5% (min 38,5%, max 85,7%) when analysing by case. When assessing each of the 30 non-mandatory variables of the reports, 7 (23,3%) had an IC of 100% and 13 (43,3%) had an IC of 0%, the mean value was 49,7%. SINAVE assessment, as a routine, is crucial to identify the need for improvement. Completeness is fundamental to ensure an effective public health response. Our results confirm under-reporting and incomplete report of MD. There is a need to strengthen the improvement of data quality of SINAVE. Future studies may be important to estimate true incidence of MD and compare the results for other diseases in order to improve public health actions. Key messages • Meningococcal disease requires timely public health intervention. • valuation of the surveillance system is crucial, with completeness playing an important role for data quality and prompt response.

Using the Capture–Recapture Technique to Supplement a Point-in-Time Count of Homeless Adults in Kittitas County, Washington

Abstract Capture–recapture (CRC) is a method of population estimation pioneered in biology that allows the surveyor to approximate the proportion of individuals who evaded sampling efforts (i.e., captures) based on repeated samples from the same population. The current national standard for estimating homelessness is a single-day enumeration called the point-in-time (PIT) count. By using a local community action agency’s homeless outreach program and a cold weather shelter as two distinct sampling sources to capture data using CRC methodology, the current study sought to estimate the homeless population in Kittitas County, Washington, and compare CRC with PIT count estimates. Four months of data collection for the two sampling sources yielded an estimate of 115 (95% CI [93, 137]) homeless individuals in the county using CRC methodology. The PIT count conducted in the same year sampled 61 individuals, supporting the idea that cross-sectional enumeration (i.e., PIT counts) underestimate the homeless population and could be supplemented by CRC methods, particularly in rural areas where resources to conduct PIT counts may be limited. Greater accuracy in homelessness enumeration may aid in advocacy efforts, provide baseline data for researching interventions designed to reduce homelessness, and yield statistics to better guide legislative and policy initiatives.

Using Improved Two-Source Capture-Recapture Methods In Settling Disputed Election Results

Introduction of new technology to check rigging and manipulation of election results by the Independent National Electoral Commission (INEC) raised hopes and dreams of many Nigerians, especially the new electorates, that the 2023 general election in Nigeria would be free and fair. Cross-checking INEC declared election results using this recapture model is supposed go beyond questionnaires. Sampling technique to select polling units where re-run election is to take place is necessary. They have been issues of vote suppression, rigging, manipulation or intimation in those areas would have largely been reduced. The new estimator has shown that there were no serious cases of vote suppression, manipulation or intimation by any political party, as far as this Local Government Area is concerned. If there were vote suppression, it is only about 1.78% which is negligible. Using simulated data, we found that efficient recapture model (Me) provides better and more reliable estimate than the conventional models.

On the nose: validating a novel, non-invasive method to identify individual koalas using unique nose patterns

Context Non-invasive identification of individual animals in wild populations can occur in species with unique coat patterns (e.g. zebras, giraffes, jaguars). However, identification in other species often relies on capture-mark–recapture techniques, involving physical handling of animals. Identification of individual koalas (Phascolarctos cinereus) is difficult and has so far relied mostly on invasive methods such as ear tagging, microchipping and/or collaring, which require capture. The validation of a non-invasive method to identify koalas could improve monitoring of individuals in the wild, allowing targeting of specific koalas in disease and survival studies, reducing the need to capture individuals. Aims This study describes a novel effective method to identify koalas from their nose markings, specifically using the unpigmented pattern of the nose to determine unique features of individuals. Methods Photographs of koalas from different populations in Victoria and New South Wales (NSW), Australia, were examined in the study. Nose patterns were traced from photographs and matched through visual assessment if they were thought to belong to the same individual. Differences in identification success between datasets from different populations and the effect of sex on match success were evaluated statistically. For the NSW koalas, the effect of lighting conditions and photographic angle were also assessed. Key results Overall identification success was 89.7% (range 87.1–91.8%) and was not affected by any of the variables tested, demonstrating that nose patterns can be used reliably to identify individual koalas. Conclusions The proposed non-invasive method is simple, yet accurate and stable over time, hence it offers a vital tool for monitoring endangered koalas whilst minimising human interference. Implications Pattern-based recognition of koalas is cost-effective, reduces stress on the animals, has the potential to improve data collection and allows involvement of citizen scientists in monitoring of populations or individuals.