Low Capture Probabilities Research Articles

The largest known population of Eden's whale aggregates in the Beibu Gulf, southern China

AbstractBasic information on the distribution, survival, and abundance of Eden's whale (Balaenoptera edeni edeni) is lacking. During April 2018 to April 2024, we monitored Eden's whales in the Beibu Gulf, southern China. Using characteristics of the dorsal fin left and right side, 83 and 88 whales were identified, respectively (mean 3.5 times). The POPAN and Cormack–Jolly–Seber (CJS) open models in MARK resulted in low apparent survival of .824 and .817 for left dorsal fin data set, .816 and .822 for right dorsal fin data set and lower capture probability of .522 and .427 for left, .468 and .461 for right. The POPAN model estimated 82–123 identifiable whales and 100–160 whales adjusted by mark ratio, indicating the largest reported population worldwide. The mean annual population size ranged from 26 to 58, with a yearly increasing–decreasing fluctuation. The low survival, capture probability, and annual population size, and increasing discovery curve indicate that the population dynamics are complex, possibly reflecting wider movement beyond the study area. We speculate that some individuals were residents in the Beibu Gulf, while most whales were transients that migrate yearly between the Beibu Gulf and the East China Sea, South China Sea, or/and Southeast Asia.

Model for random internalization of nanoparticles by cells.

We propose a stochastic model for the internalization of nanoparticles by cells formulating cellular uptake as a compound Poisson process with a random probability of success. This is an alternative approach to the one presented by Rees etal. [Nat. Commun. 10, 2341 (2019)2041-172310.1038/s41467-018-07882-8] who explained overdispersion in nanoparticle uptake and associated negative binomial distribution by considering a Poisson distribution for particle arrival and a gamma-distributed cell area. In our stochastic model, the formation of new pits is represented by the Poisson process, whereas the capturing process and the population heterogeneity are described by a random Bernoulli process with a beta-distributed probability of success. The random probability of success generates ensemble-averaged conditional transition probabilities that increase with the number of newly formed pits (self-reinforcement). As a result, an ensemble-averaged nanoparticle uptake can be represented as a Polya process. We derive an explicit formula for the distribution of the random number of pits containing nanoparticles. In the limit of the fast nucleation and low probability of nanoparticle capture, we find the negative binomial distribution.

Avoiding bias in estimates of population size for translocation management.

Mark-recapture surveys are commonly used to monitor translocated populations globally. Data gathered are then used to estimate demographic parameters, such as abundance and survival, using Jolly-Seber (JS) models. However, in translocated populations initial population size is known and failure to account for this may bias parameter estimates, which are important for informing conservation decisions during population establishment. Here, we provide methods to account for known initial population size in JS models by incorporating a separate component likelihood for translocated individuals, using a maximum-likelihood estimation, with models that can be fitted using either R or MATLAB. We use simulated data and a case study of a threatened lizard species with low capture probability to demonstrate that unconstrained JS models may overestimate the size of translocated populations, especially in the early stages of post-release monitoring. Our approach corrects this bias; we use our simulations to demonstrate that overestimates of population size between 78% and 130% can occur in the unconstrained JS models when the detection probability is below 0.3 compared to 1%-8.9% for our constrained model. Our case study did not show an overestimate; however accounting for the initial population size greatly reduced error in all parameter estimates and prevented boundary estimates. Adopting the corrected JS model for translocations will help managers to obtain more robust estimates of the population sizes of translocated animals, better informing future management including reinforcement decisions, and ultimately improving translocation success.

A new technique for estimating the probability of attentional capture.

Latency-based metrics of attentional capture are limited: They indicate whether or not capture occurred, but they do not indicate how often capture occurred. The present study introduces a new technique for estimating the probability of capture. In a spatial cueing paradigm, participants searched for a target letter defined by color while attempting to ignore salient cues that were drawn in either a relevant or irrelevant color. The results demonstrated the typical contingent capture effect: larger cue validity effects from relevant cues than irrelevant cues. Importantly, using a novel analytical approach, we were able to estimate the probability that the salient cue captured attention. This approach revealed a surprisingly low probability of attentional capture in the spatial cuing paradigm. Relevant cues are thought to be one of the strongest attractors of attention, yet they were estimated to capture attention on only about 30% of trials. This new metric provides an index of capture strength that can be meaningfully compared across different experimental contexts, which was not possible until now.

A Simulation Study on Increasing Capture Periods in Bayesian Closed Population Capture-Recapture Models with Heterogeneity

Capture-Recapture models are useful in estimating unknown population sizes. A common modeling challenge for closed population models involves modeling unequal animal catchability in each capture period, referred to as animal heterogeneity. Inference about population size N is dependent on the assumed distribution of animal capture probabilities in the population, and that different models can fit a data set equally well but provide contradictory inferences about N. Three common Bayesian Capture-Recapture heterogeneity models are studied with simulated data to study the prevalence of contradictory inferences is in different population sizes with relatively low capture probabilities, specifically at different numbers of capture periods in the study.

A 3-YEAR POPULATION STUDY OF Guerlinguetus brasiliensis ingrami (RODENTIA, SCIURIDAE) AT THE SERRA DA BOCAINA NATIONAL PARK, RIO DE JANEIRO STATE, BRAZIL

The Brazilian Squirrel Guerlinguetus brasiliensis ingrami (Rodentia, Sciuridae) is commonly observed in the wild, yet its population parameters are poorly known because this species is rarely captured with traditional live-traps. Here we evaluated the population parameters of G. b. ingrami in a 3-year capture-mark-recapture study at the Serra da Bocaina National Park, Rio de Janeiro state, Brazil. Population parameters were evaluated using the Jolly-Seber model POPAN and the Minimum Number Known to be Alive (MNKA). Population size estimates ranged between 3.2 ± 2.4 (mean ± SE) and 51.3 ± 15.0 individuals based on POPAN, and 2 and 10 individuals based on MNKA. Our population density estimates (1.3 to 74.3 individuals/km 2 )were similar to those documented in previous studies carried out in the Atlantic Forest. Monthly survival was high (0.94 ± 0.02) and capture probability was low (0.16 ± 0.05), probably reflecting the species trap-shyness. The low capture probability of G. b. ingrami evidences the importance of the unique population data presented in this study for increasing basic knowledge on this species.

Shrimp trap selectivity in a Mediterranean small-scale-fishery

Small-scale shrimp trap fisheries, which have received very little attention in areas with limited potential for economic diversification, could offer a sustainable and socially beneficial option for profitable businesses in these regions. This study explores the effect of mesh size on selectivity of the commercially important narwal shrimp, Plesionika narval, in the Mediterranean Sea. Three different mesh sizes (8 × 8, 12 × 12 and 12 × 25 mm) were tested in fishing trials, with a theoretical Minimum Landing Size (MLS) using a defined maturity size of 12 mm to support interpretation of the results. Using the retention rates and the estimations on population fractions above and below MLS, we show that the use of the smallest- and largest-sized meshes would not support sustainable or efficient fishery. The results demonstrate a significant decrease in capture probability of undersized narwal shrimps with increased mesh size. The medium-sized mesh traps prove to be the best compromise for the fishery with high catch efficiency of commercial size shrimp and a low capture probability of undersized individuals. The results outlined in this article could be used to develop management plans for small-scale trap fisheries as a basis for developing viable enterprises in remote coastal communities.

Piracy and Privateers in the Golden Age: Lessons for Today

ABSTRACTCustomary international law has governed high seas piracy for many centuries and is now codified in the United Nations Convention on the Law of the Sea (LOSC). In this article, we discuss the reasons why enforcement against piracy today is less effective than three hundred years ago. We contend that crime, including the crime of piracy, can be modeled as a rational choice that is responsive to expected rewards and punishments. Based on this view, we argue that three hundred years ago, the free rider problem resulting from enforcement on the high seas was less prevalent than it is today because seaborne trade was more concentrated in the vessels of a few countries, making enforcement more like internal than international policing. The persistence of piracy today also stems from a continuing low probability of capture coupled with lenient punishments. In addition to enforcement differences, we contrast the sources of piracy in the two eras—in the earlier period, the end of privateering led many privateers to engage in piracy, whereas today, the main source of pirates in the Western Indian Ocean is the existence of a “failed state,” and off West Africa and South East Asia pirates are common criminals.

Inferring species interactions through joint mark-recapture analysis.

Introduced species are frequently implicated in declines of native species. In many cases, however, evidence linking introduced species to native declines is weak. Failure to make strong inferences regarding the role of introduced species can hamper attempts to predict population viability and delay effective management responses. For many species, mark-recapture analysis is the more rigorous form of demographic analysis. However, to our knowledge, there are no mark-recapture models that allow for joint modeling of interacting species. Here, we introduce a two-species mark-recapture population model in which the vital rates (and capture probabilities) of one species are allowed to vary in response to the abundance of the other species. We use a simulation study to explore bias and choose an approach to model selection. We then use the model to investigate species interactions between endangered humpback chub (Gila cypha) and introduced rainbow trout (Oncorhynchus mykiss) in the Colorado River between 2009 and 2016. In particular, we test hypotheses about how two environmental factors (turbidity and temperature), intraspecific density dependence, and rainbow trout abundance are related to survival, growth, and capture of juvenile humpback chub. We also project the long-term effects of different rainbow trout abundances on adult humpback chub abundances. Our simulation study suggests this approach has minimal bias under potentially challenging circumstances (i.e., low capture probabilities) that characterized our application and that model selection using indicator variables could reliably identify the true generating model even when process error was high. When the model was applied to rainbow trout and humpback chub, we identified negative relationships between rainbow trout abundance and the survival, growth, and capture probability of juvenile humpback chub. Effects on interspecific interactions on survival and capture probability were strongly supported, whereas support for the growth effect was weaker. Environmental factors were also identified to be important and in many cases stronger than interspecific interactions, and there was still substantial unexplained variation in growth and survival rates. The general approach presented here for combining mark-recapture data for two species is applicable in many other systems and could be modified to model abundance of the invader via other modeling approaches.

Estimating population parameters of longsnout seahorses, Hippocampus reidi (Teleostei: Syngnathidae) through mark-recapture

ABSTRACT Estimating population parameters is essential for understanding the ecology of species, which ultimately helps to assess their conservation status. The seahorse Hippocampus reidi is directly exposed to anthropogenic threats along the Brazilian coast, but the species still figures as Data Deficient (DD) at IUCN’s Red List. To provide better information on the ecology of this species, we studied how population parameters vary over time in a natural subtropical environment. By combing mark-recapture models for open and closed populations, we estimated abundance, survival rate, emigration probability, and capture probability. We marked 111 individuals, which showed a 1:1 sex ratio, and an average size of 10.5 cm. The population showed high survival rate, low temporary emigration probability and variable capture probability and abundance. Our models considering relevant biological criteria illuminate the relatively poorly known population ecology and life history of seahorses. It is our hope that this study inspires the use of mark-recapture methods in other populations of H. reidi in a collective effort to properly assess their conservation status.

Challenges in confirming eradication success of invasive red-eared sliders

Confirming eradication success can be notoriously difficult and costly, especially when the species is still present but remains undetected, due to very low population densities and imperfect detection methods. There has been a lack of research on appropriate guidelines and estimation procedures for declaring eradication success for programs aimed at eradicating alien reptiles. Here we develop quantitative rules for confirmation monitoring in eradication campaigns of the red-eared slider turtle (Trachemys scripta elegans). We used a database of slider trapping data from control and eradication campaigns conducted in localities across the Iberian Peninsula and southern France to construct models for inferring appropriate trapping efforts for confirming slider turtle eradication. Basking traps were slightly more efficient than net traps in capturing sliders, although trapping was an inefficient monitoring method given the low capture probabilities estimated. The results of our spatially-explicit eradication scenarios revealed the importance of habitat configuration in declaring eradication success. Declaration of eradication success is contingent on the thresholds set to minimise false positives (i.e., falsely declaring eradication successful), but in any scenario large trapping efforts were required to confirm eradication. Given the low estimated capture probabilities, alternative methods such as eDNA and visual surveys should be considered for monitoring sliders. We suggest that if the costs associated with the impact of alien sliders can be adequately estimated, then eradication can be confirmed by rules minimising both false positive and negative error rates. Otherwise, rules minimising false positive errors would be more appropriate.

Characteristics and behaviour of brushtail possums initially moving into a depopulated area

ABSTRACTBrushtail possums are controlled extensively in New Zealand because they are a livestock disease vector and have an impact on native biodiversity. Reinvasion of controlled areas and subsequent population recovery is a significant management problem but little attention has been paid to what influences the settlement of possums in depopulated areas. To address this gap we trapped possums out of an area of about 24 ha in native podocarp–hardwood forest and studied reinvasion and settlement in the central c. 14 ha over 22 months. Most new possums were young males, but adults were also trapped. Many of the new possums caught on the study site post-depopulation did not settle there, most likely because they continued to disperse, but some may have returned to their ranges nearby or were residents with a very low probability of capture. This finding highlights the need for better information about the origins and settlement of possums in depopulated areas to improve management of population recovery and long-term sustained control of possums.

Capture success of Fijian bats (Pteropodidae) and their evaluation as umbrella species for conservation

Easily captured species provide powerful opportunities to motivate research and conservation action. Conversely, rare and cryptic species with low capture probability can be difficult to study. We examined the capture success of Fiji’s Pteropodidae (Pteropus tonganus, P. samoensis, Notopteris macdonaldi, and Mirimiri acrodonta) and incorporated capture success and associated observations into an assessment of their suitability as umbrella species for conservation. We caught 252 bats from 2493 mist-net-hours in lowland rainforest near Waisali on Vanua Levu, and 38 bats from 1915 mist-net-hours in cloud forest on Taveuni. Of these captures, 67% were N. macdonaldi, 16% P. tonganus, 18% P. samoensis, and <1% M. acrodonta. All species were difficult to net in cloud forest, where we recorded a female sex bias. Capture success was affected by site, season, and net height; peak capture times varied among species and between sites. N. macdonaldi was recaptured most frequently (8.8%), revealing habitual nightly movements. It has strong potential as an umbrella species for rainforest and cave-dwelling organisms of Fiji, and was readily netted. P. tonganus is an unsuitable umbrella species, P. samoensis has potential as an umbrella species, and M. acrodonta has many attributes of a flagship species. Capture efficiency of N. macdonaldi provides opportunities for monitoring and conservation management activities in Fiji. However, variability in capture success among species means that different approaches should be explored for conserving bats effectively with limited resources.

Reliability of different mark-recapture methods for population size estimation tested against reference population sizes constructed from field data.

Reliable estimates of population size are fundamental in many ecological studies and biodiversity conservation. Selecting appropriate methods to estimate abundance is often very difficult, especially if data are scarce. Most studies concerning the reliability of different estimators used simulation data based on assumptions about capture variability that do not necessarily reflect conditions in natural populations. Here, we used data from an intensively studied closed population of the arboreal gecko Gehyra variegata to construct reference population sizes for assessing twelve different population size estimators in terms of bias, precision, accuracy, and their 95%-confidence intervals. Two of the reference populations reflect natural biological entities, whereas the other reference populations reflect artificial subsets of the population. Since individual heterogeneity was assumed, we tested modifications of the Lincoln-Petersen estimator, a set of models in programs MARK and CARE-2, and a truncated geometric distribution. Ranking of methods was similar across criteria. Models accounting for individual heterogeneity performed best in all assessment criteria. For populations from heterogeneous habitats without obvious covariates explaining individual heterogeneity, we recommend using the moment estimator or the interpolated jackknife estimator (both implemented in CAPTURE/MARK). If data for capture frequencies are substantial, we recommend the sample coverage or the estimating equation (both models implemented in CARE-2). Depending on the distribution of catchabilities, our proposed multiple Lincoln-Petersen and a truncated geometric distribution obtained comparably good results. The former usually resulted in a minimum population size and the latter can be recommended when there is a long tail of low capture probabilities. Models with covariates and mixture models performed poorly. Our approach identified suitable methods and extended options to evaluate the performance of mark-recapture population size estimators under field conditions, which is essential for selecting an appropriate method and obtaining reliable results in ecology and conservation biology, and thus for sound management.

Distribution and reproduction of Procambarus clarkii in relation to water management, salinity and habitat type in the Camargue

ABSTRACTProcambarus clarkii, one of the most invasive aquatic species worldwide, is present in Mediterranean estuarine regions. Water management of these deltas involves massive freshwater inputs, reducing wetland salinity and altering natural flooding periods, two important factors for P. clarkii. The paper examines whether water management affects the distribution and reproduction success of P. clarkii in Mediterranean estuarine regions.Procambarus clarkii was sampled in the Camargue every 6 weeks throughout a whole year. Forty‐eight stations were sampled to represent the available habitats and water management types in the study region: temporary ponds, semi‐permanent marshes, permanent marshes, canals and ricefields. Salinity and habitat effects on capture probability, abundance and proportion of juveniles were explored within each season to study species distribution, to identify suitable habitats for reproduction and its timing, and to assess how salinity affects these traits.Only a few crayfish were found above 10 g L–1 salinity and a few juveniles were found above 5 g L–1. Procambarus clarkii was found in the five habitat types sampled but with lower capture probability and abundance in ricefields and canals. The proportion of juveniles was highest in temporary ponds during their seasonal peak.These results suggest that low salinity increases the occurrence, the abundance and the reproduction success of P. clarkii but that hydroperiod length per se does not affect P. clarkii. Furthermore, the results suggest that temporary water bodies within the salinity range of the species are used as safe sites for reproduction.A significant reduction of freshwater inputs into estuarine ecosystems is needed to restore a higher salinity level and to reduce the reproductive success and expansion of P. clarkii. Copyright © 2013 John Wiley & Sons, Ltd.

Coffee Agroforests Remain Beneficial for Neotropical Bird Community Conservation across Seasons

Coffee agroforestry systems and secondary forests have been shown to support similar bird communities but comparing these habitat types are challenged by potential biases due to differences in detectability between habitats. Furthermore, seasonal dynamics may influence bird communities differently in different habitat types and therefore seasonal effects should be considered in comparisons. To address these issues, we incorporated seasonal effects and factors potentially affecting bird detectability into models to compare avian community composition and dynamics between coffee agroforests and secondary forest fragments. In particular, we modeled community composition and community dynamics of bird functional groups based on habitat type (coffee agroforest vs. secondary forest) and season while accounting for variation in capture probability (i.e. detectability). The models we used estimated capture probability to be similar between habitat types for each dietary guild, but omnivores had a lower capture probability than frugivores and insectivores. Although apparent species richness was higher in coffee agroforest than secondary forest, model results indicated that omnivores and insectivores were more common in secondary forest when accounting for heterogeneity in capture probability. Our results largely support the notion that shade-coffee can serve as a surrogate habitat for secondary forest with respect to avian communities. Small coffee agroforests embedded within the typical tropical countryside matrix of secondary forest patches and small-scale agriculture, therefore, may host avian communities that resemble those of surrounding secondary forest, and may serve as viable corridors linking patches of forest within these landscapes. This information is an important step toward effective landscape-scale conservation in Neotropical agricultural landscapes.

Using simulation to compare methods for estimating density from capture–recapture data

Estimation of animal density is fundamental to wildlife research and management, but estimation via mark–recapture is often complicated by lack of geographic closure of study sites. Contemporary methods for estimating density using mark–recapture data include (1) approximating the effective area sampled by an array of detectors based on the mean maximum distance moved (MMDM) by animals during the sampling session, (2) spatially explicit capture–recapture (SECR) methods that formulate the problem hierarchically with a process model for animal density and an observation model in which detection probability declines with distance from a detector, and (3) a telemetry estimator (TELEM) that uses auxiliary telemetry information to estimate the proportion of animals on the study site. We used simulation to compare relative performance (percent error) of these methods under all combinations of three levels of detection probability (0.2, 0.4, 0.6), three levels of occasions (5, 7, 10), and three levels of abundance (10, 20, 40 animals). We also tested each estimator using five different models for animal home ranges. TELEM performed best across most combinations of capture probabilities, sampling occasions, true densities, and home range configurations, and performance was unaffected by home range shape. SECR outperformed MMDM estimators in nearly all comparisons and may be preferable to TELEM at low capture probabilities, but performance varied with home range configuration. MMDM estimators exhibited substantial positive bias for most simulations, but performance improved for elongated or infinite home ranges.

Modeling the effects of life-history traits on estimation of population parameters for a cryptic stream species

Estimating demographic values and rates for populations of cryptic stream species frequently is difficult because of prohibitively low capture probabilities. When assessing cryptic populations, researchers often are forced to make simplifying assumptions that could alter their conclusions about a population. We constructed models based on different assumptions about cohort structure, behavioral responses to capture, temporary emigration, and survival in a cryptic, larval population of red salamanders (Pseudotriton ruber) and fitted models to capture-mark-recapture data. Overall, models based on 2 cohorts were favored over models based on 1 cohort. Models based on assumptions of constant survival, behavioral responses to capture, and random temporary emigration were ranked higher than models lacking these assumptions. Consistent behavioral responses to capture demonstrated that using uncorrected counts to assess trends for this, and perhaps other larval amphibian populations, yields misleading results. Counts that are not corrected for trap-shy behavior may inherently show negative temporal trends. Temporary emigration was a critical assumption when describing larval salamander demography because only 27% of the larvae were active on the surface (the rest were in substratum habitats). Our study demonstrates the importance of making appropriate assumptions about demographic parameters and shows how population models can quantify aspects of the natural history of cryptic species.

Seasonal abundance and adult survival of bottlenose dolphins (Tursiops truncatus) in a community that cooperatively forages with fishermen in southern Brazil

AbstractA subgroup of a population of Tursiops truncatus in southern Brazil is known for a cooperative behavior with artisanal fishermen whereby the dolphins shoal fish towards net‐casting fishermen. Combining photo‐identification data collected between September 2007 and 2009 with mark‐recapture and Pollock's robust design models, we assessed abundance within seasons and survival and temporary emigration rates of dolphins between seasons. We also reanalyzed a previous data set collected during 1989–1991, and Cormack‐Jolly‐Seber models were applied to estimate survival rates for each of the study periods. The abundance of marked “cooperative” dolphins varied between seasons from 18 (CI: 17–24) to 21 (CI: 20–24). The total abundance varied from 59 in the winter of 2008 (CI: 49–72) to 50 in the autumn of 2009 (CI: 40–62). The annual adult survival was estimated to be 0.917 (CI: 0.876–0.961), close to that estimated from data collected in the 1990s (0.941; CI: 0.888–0.998). The emigration probability was low (0.031; CI: 0.011–0.084) and different capture probabilities between the “cooperative” and “noncooperative” dolphins indicated a degree of behavioral segregation. The precision of our estimates is likely to provide sufficient power to detect population change, but we recommend a precautionary management approach to protect this vulnerable dolphin community and its unique cooperative feeding tradition.

A multiple data source approach to improve abundance estimates of small populations: The brown bear in the Apennines, Italy

When dealing with small populations of elusive species, capture–recapture methods suffer from sampling and analytical limitations, making abundance assessment particularly challenging. We present an empirical and theoretical evaluation of multiple data source sampling as a flexible and effective way to improve the performance of capture–recapture models for abundance estimation of small populations. We integrated three data sources to estimate the size of the relict Apennine brown bear (Ursus arctos marsicanus) population in central Italy, and supported our results with simulations to assess the robustness of multiple data source capture–recapture models to violations of main assumptions. During May–August 2008, we non-invasively sampled bears using systematic hair traps on a grid of 41 5×5km cells, moving trap locations between five sampling sessions. We also live-trapped, ear-tagged, and genotyped 17 bears (2004–2008), and integrated resights of marked bears and family units (July–September 2008) into a multiple data source capture–recapture dataset. Population size was estimated at 40 (95% CI=37–52) bears, with a corresponding closure-corrected density of 32 bears/1000km2 (95% CI=28–36). Given the average capture probability we obtained with all data sources combined (pˆ=0.311), simulations suggested that the expected degree of correlation among data sources did not seriously affect model performance, with expected level of bias <5%. Our results refine previous simulation work on larger populations, cautioning on the combined effect of lack of independence and low capture probability in application of multiple data source sampling to very small populations (N<100).