scholarly journals Comparison of Two Sampling Methods to Estimate the Abundance of Lucanus cervus with Application of n-Mixture Models

Forests ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1085 ◽  
Author(s):  
Francesca Della Rocca ◽  
Pietro Milanesi ◽  
Francesca Magna ◽  
Livio Mola ◽  
Tea Bezzicheri ◽  
...  
Keyword(s):  
Population Size ◽  
Mixture Models ◽  
Type I Error ◽  
Conservation Status ◽  
Type I ◽  
Mark Recapture ◽  
Non Invasive ◽  
Abundance Estimates ◽  
Species Population ◽  
Population Density Estimate

Monitoring programs should be based on the measurement of two main pillars for evaluating the conservation status of a species: population size and geographical distribution. To date, the only way reported in the literature to obtain detailed information on L. cervus population size is to use the capture-mark-recapture method. This is an expensive and time-consuming technique that implies physical capture and handling of individuals, which could affect their survival. Therefore, in this study we tested and compared two non-invasive sampling approaches, namely evening walk transects and diurnal tree trunk surveys, to derive accurate abundance estimates by means of N-mixture models in a Bayesian framework. In our study, both methods showed relatively high detection probability (≥56%). However, tree surveys performed better than walk transects (≈80%), especially with the progression of the sampling season. Tree surveys proved to be more effective than walk transects in providing data for an accurate population density estimate (much smaller 95% Bayesian Confidence Intervals). In light of a cost and benefit assessment, the tree survey is undoubtedly more convenient, as well as more effective, as it is more time consuming but less expensive than a walk transect (one operator for 2–3 h vs. two operators for 30 min each). Moreover, it needs fewer expert operators because of the greater proximity to the species, increasing the probability of correctly identifying it, i.e., reducing type I error (false positive or overestimation of counts). For the first time, we applied N-mixture models for estimating population abundance of L. cervus. Overcoming all the limits imposed by the use of the capture-mark-recapture method, in this study we performed a further step forward in the planning of monitoring aimed at the conservation of L. cervus and the evaluation of its demographic trend.

scholarly journals Challenges and opportunities for monitoring wild Nile crocodiles with scute mark-recapture photography

Koedoe ◽  
2018 ◽  
Vol 60 (1) ◽  
Author(s):  
Bernard W.T. Coetzee ◽  
Sam M. Ferreira ◽  
Kristine Maciejewski
Keyword(s):  
Conservation Status ◽  
Field Conditions ◽  
High Turnover ◽  
Mark Recapture ◽  
Non Invasive ◽  
Open Population ◽  
Challenges And Opportunities ◽  
In Captivity ◽  
In The Wild

The global conservation status of Nile crocodiles (Crocodylus niloticus) was last assessed in 1996. The species presents particular difficulty in monitoring because it can be cryptic, require expertise to handle, and caudal tail tags and transmitters are often lost. Some studies advocate mark-recapture techniques based on photograph identification of the unique scute markings of crocodile tails as a non-invasive means of monitoring their populations. Researchers developed this method with crocodiles in captivity. In this study, we test the technique under field conditions by monitoring crocodiles from 2015 to 2017 in the Sunset Dam in the Kruger National Park. Using a Cormack-Jolly-Seber open population model, we found that the dam may host 15–30 individuals, but that there is a high turnover of individuals and much uncertainty in model outputs. The dam’s population thus has high rates of immigration and emigration. The method proved challenging under field conditions, as there was bias in identifying scute markings consistently. The efficient use of the method requires an exceptional quality of photographic equipment. Animal crypsis, however, remains an issue. In this study, we discuss how to improve the mark-recapture photography methodology, especially to adapt the technique for citizen science initiatives.Conservation implications: Using scute mark-recapture photography presents challenges under field conditions. These challenges require innovative, practical and analytical solutions to successfully use the technique before monitoring programmes, aimed at ensuring the persistence of crocodiles in the wild, can be implemented.

Pitfalls in using counts of roaring stags to index red deer (Cervus elaphus) population size

2009 ◽  
Vol 36 (2) ◽  
pp. 126 ◽  
Author(s):  
Paolo Ciucci ◽  
Gianluca Catullo ◽  
Luigi Boitani
Keyword(s):  
Population Size ◽  
Cervus Elaphus ◽  
Red Deer ◽  
Population Monitoring ◽  
Weather Conditions ◽  
Error Rates ◽  
Type I ◽  
High Type ◽  
Abundance Estimates ◽  
Absolute Density

Counting roaring stags during the rut has been proposed as a means to assess deer population size and trends but few, if any, attempts have been made to evaluate the reliability of this technique. By means of a commonly used field protocol, we assessed to what extent relative abundance estimates of red deer (Cervus elaphus) based on roaring-stag counts in the northern Apennines (Italy) were susceptible to exogenous and unpredictable sources of variability. By using up to 26 simultaneous observers in an area of 5218 ha, we estimated densities from 0.45 to 0.61 roaring stags per 100 ha in 3 consecutive years (1992–94), corresponding to annual changes in the number of counted roaring stags ranging from –21% to +35.7%. However, only in two of the three years were seasonal trends and peaks in roaring activity apparent, and timing of the survey was not always synchronous with the roaring peak. In addition, annual and nocturnal variation in roaring activity, and weather conditions during the survey, might have influenced the counts to some extent, probably determining high Type I and Type II error rates. We contend that additional sources of error, associated with unknown demographic and ecological settings, may further increase unreliability of the technique when it is used to estimate absolute density of red deer populations. We conclude by emphasising that managers should not use this method for population monitoring unless they can prove it can yield reliable results.

scholarly journals An estimate of the area of occupancy and population size of Brachycephalus tridactylus (Anura: Brachycephalidae) to reassess its conservation status, with a proposal for conservation measures

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12687
Author(s):  
Marcos R. Bornschein ◽  
Júnior Nadaline ◽  
Luiz Fernando Ribeiro ◽  
Giovanna Sandretti-Silva ◽  
Maria Fernanda Ferreira Rivas ◽  
...  
Keyword(s):  
New Species ◽  
Population Size ◽  
Conservation Status ◽  
Species Conservation ◽  
Type Locality ◽  
Area Of Occupancy ◽  
Conservation Measures ◽  
New Localities ◽  
Species Population ◽  
Surrounding Areas

Background We are experiencing a global crisis in conservation, which has led to the prioritization of targets, such as nations, regions, and animal groups, which are necessary while resources are disputed. Brazil is a priority not only because of its megadiversity, high rates of endemism, and frequent descriptions of new species but also because of its high levels of deforestation. Among the species groups prioritized for conservation is the anurans (Amphibia: Anura), the population of which is severely declining. One group of anurans is the genus Brachycephalus, which includes 37 endemic species in the Brazilian Atlantic Rainforest. Some of these species have highly restricted distributions (<100 ha). Thirty new species have been described since 2000, and 55.3% of all species are threatened with extinction. Brachycephalus tridactylus was only recently described and remains restricted to its type locality. Because of its reduced geographical distribution (0.41 km2), it has been proposed to be considered as Vulnerable. The objective of this study is to reevaluate the conservation status of Brachycephalus tridactylus and propose conservation measures. Methods We searched for new populations during 2016–2020, evaluated in loco impacts and potential impacts on the species’ population, and performed an analysis of the density of this population and estimated its size. International Union for Conservation of Nature (IUCN) criteria were used to assess the conservation status of the species. Results We recorded the species in seven new localities (from 715–1,140 m above sea level) in the state of São Paulo up to 33 km from the type locality of the species (in state of Paraná). We estimated the area of occupancy as 148.44 km2, densities as one calling male per 4.05 m2 and 130.00 m2, and a total population size of 4,429,722 adult individuals. Based on our finding, we proposed three lines of management: (1) formation of fire brigades, (2) management of residents’ mules in the conservation unit and surrounding areas, and (3) management of degraded areas. We recommend changing the species’ conservation status from Vulnerable to Endangered because of its fragmented distribution and decline in the area of occupancy and in the quality of its habitat. Our results have expanded the species previous geographic distribution and delimited areas without previous records. Our estimates of population density and size are in accordance with those verified for congeners. The conservation of this species benefits the environments and other species that inhabit them, being, therefore, strategic for receiving conservation actions that will spread throughout the ecosystem.

Population size estimation of an Asian elephant population in eastern Cambodia through non-invasive mark-recapture sampling

2014 ◽  
Vol 15 (4) ◽  
pp. 803-810 ◽  
Author(s):  
Thomas N. E. Gray ◽  
T. N. C. Vidya ◽  
Sheetal Potdar ◽  
D. K. Bharti ◽  
Prum Sovanna
Keyword(s):  
Population Size ◽  
Population Size Estimation ◽  
Asian Elephant ◽  
Size Estimation ◽  
Mark Recapture ◽  
Non Invasive ◽  
Elephant Population

scholarly journals Population size estimates of pink river dolphins (Inia geoffrensis) using mark-recapture methods on photo-identification

2014 ◽  
Vol 9 (2) ◽  
pp. 132-139 ◽  
Author(s):  
Catalina Gómez-Salazar ◽  
Hal Whitehead ◽  
Fernando Trujillo
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Freshwater Ecosystems ◽  
Mark Recapture ◽  
Photo Identification ◽  
Population Size Estimate ◽  
Population Size Estimates ◽  
Inia Geoffrensis ◽  
Colombian Amazon ◽  
Size Estimates

Population size estimates of pink river dolphins (Inia geoffrensis) are critical to assess the conservation status of this species and the impacts of increasing human stressors in freshwater ecosystems. Photo-identifications of Inia dolphins were collected between February 2007 and August 2009 in two locations of the Colombian Amazon and Orinoco river basins. Population sizes of Inia were obtained by using the closed (Petersen) mark-recapture model on photo-identifications. The total population size estimate for right/left side individuals was 129/71 Inia dolphins (CV=0.36/0.35) in the Amazon location and 125/58 Inia dolphins (CV=0.77/0.69) in the Orinoco location. The survey and analysis protocols were designed to try to meet mark-recapture assumptions. However, photo-identification was incomplete in both study areas, and there could be recruitment and unequal probabilities of capture due to preferences of individuals for certain areas. Further effort should be focused towards expanding the photo-identification catalogues and creating long-term monitoring programs.

scholarly journals Estimating effective population size from temporal allele frequency changes in experimental evolution

2016 ◽  
Author(s):  
Ágnes Jónás ◽  
Thomas Taus ◽  
Carolin Kosiol ◽  
Christian Schlötterer ◽  
Andreas Futschik
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Allele Frequency ◽  
Experimental Evolution ◽  
Type I Error ◽  
Recursive Partitioning ◽  
Cost Effective ◽  
Type I ◽  
Effective Population ◽  
Frequency Changes

AbstractThe effective population size (Ne) is a major factor determining allele frequency changes in natural and experimental populations. Temporal methods provide a powerful and simple approach to estimate short-term Ne. They use allele frequency shifts between temporal samples to calculate the standardized variance, which is directly related to Ne. Here we focus on experimental evolution studies that often rely on repeated sequencing of samples in pools (Pool-Seq). Pool-Seq is cost-effective and outperforms individual-based sequencing in estimating allele frequencies, but it is associated with atypical sampling properties: additional to sampling individuals, sequencing DNA in pools leads to a second round of sampling increasing the estimated allele frequency variance. We propose a new estimator of Ne, which relies on allele frequency changes in temporal data and corrects for the variance in both sampling steps. In simulations, we obtain accurate Ne estimates, as long as the drift variance is not too small compared to the sampling and sequencing variance. In addition to genome-wide Ne estimates, we extend our method using a recursive partitioning approach to estimate Ne locally along the chromosome. Since type I error is accounted for, our method permits the identification of genomic regions that differ significantly in Ne. We present an application to Pool-Seq data from experimental evolution with Drosophila, and provide recommendations for whole-genome data. The estimator is computationally efficient and available as an R-package at https://github.com/ThomasTaus/Nest.

Smoothing Facilitates the Detection of Coupled Responses in Psychophysiological Time Series

2000 ◽  
Vol 14 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Joni Kettunen ◽  
Niklas Ravaja ◽  
Liisa Keltikangas-Järvinen
Keyword(s):  
Time Series ◽  
Type I Error ◽  
Electrodermal Activity ◽  
Moving Average ◽  
Type I ◽  
Facial Electromyography ◽  
Response Characteristics ◽  
Smoothing Methods ◽  
Response Systems ◽  
Different Response

Abstract We examined the use of smoothing to enhance the detection of response coupling from the activity of different response systems. Three different types of moving average smoothers were applied to both simulated interbeat interval (IBI) and electrodermal activity (EDA) time series and to empirical IBI, EDA, and facial electromyography time series. The results indicated that progressive smoothing increased the efficiency of the detection of response coupling but did not increase the probability of Type I error. The power of the smoothing methods depended on the response characteristics. The benefits and use of the smoothing methods to extract information from psychophysiological time series are discussed.

Sign in / Sign up

Export Citation Format

Share Document