scholarly journals Multi-surveyor detection-mark-redetection as a powerful tool for butterfly population monitoring in the pre-imaginal stage

2022 ◽  
Author(s):  
Heiko Hinneberg ◽  
Jörg Döring ◽  
Gabriel Hermann ◽  
Gregor Markl ◽  
Jennifer Theobald ◽  
...  
Keyword(s):  
Population Monitoring ◽  
Population Estimates ◽  
Life Stages ◽  
Monitoring Methods ◽  
Model Assumption ◽  
Clear Cut ◽  
Detection Probabilities ◽  
Nymphalid Butterfly ◽  
Butterfly Population ◽  
Sessile Organisms

1. For many elusive insect species, which are difficult to cover by standard monitoring schemes, innovative monitoring methods are needed to gain robust data on population trends. We suggest a monitoring of overwintering larvae for the endangered nymphalid butterfly Limenitis reducta. 2. We tested one removal and three detection-mark-redetection (DMR) approaches in a field study in the “Alb-Donau” region, Germany. We replaced movement of the study organisms by random movement of multiple different surveyors, and we examined the model assumption of equal detectability using simulations. 3. Our results indicate that multi-surveyor removal/DMR techniques are suitable for estimating abundance of overwintering L. reducta larvae. Detection probabilities varied with surveyor experience and the uncertainty of population estimates increased with a decrease in personnel expenditure. Estimated larval densities on a spruce clear-cut ranged between one and three individuals per 100 m². 4. We suggest a detection-mark-redetection (DMR) approach with three trained surveyors for the monitoring of L. reducta populations in the pre-imaginal stage. Besides L. reducta, the proposed method is likely to be suitable for other insect taxa with specific immobile life-stages and some sessile organisms, e.g. corals, elusive plants, or fungi.

scholarly journals Learning to count: adapting population monitoring for Endangered huemul deer Hippocamelus bisulcus to meet conservation objectives

2020 ◽  
Author(s):  
Heiko Wittmer ◽  
P Corti ◽  
C Saucedo ◽  
J Galaz
Keyword(s):  
Survey Data ◽  
Survey Methods ◽  
Cost Effective ◽  
Population Monitoring ◽  
Population Trends ◽  
Monitoring Methods ◽  
Monitoring Method ◽  
Hippocamelus Bisulcus ◽  
Detection Probabilities ◽  
Current Survey

Considerable efforts have been invested in recent years to improve methods for both data collection and analyses required for population monitoring. Where historical or current estimates of population size are not adjusted for detection probabilities they may be too inaccurate to provide meaningful estimates of trends and thus monitoring methods need to be adapted. Here, we use data from the Endangered huemul deer Hippocamelus bisulcus to outline a framework to develop accurate robust estimates of detection probabilities that can be incorporated into new surveys in a cost-effective way and applied to existing survey data sets. In particular, by retroactively estimating detection probabilities for surveys of huemul, we show that current survey methods for huemul are inadequate to determine population trends reliably. Based on these results we propose a new monitoring method for the huemul and discuss the importance of estimating accuracies of historical survey data to ensure that changes in the abundance of the species reflect real population trends and are not an artefact of variation over time in the accuracy of survey data. © 2010 Fauna & Flora International.

scholarly journals Learning to count: adapting population monitoring for Endangered huemul deer Hippocamelus bisulcus to meet conservation objectives

2020 ◽  
Author(s):  
Heiko Wittmer ◽  
P Corti ◽  
C Saucedo ◽  
J Galaz
Keyword(s):  
Survey Data ◽  
Survey Methods ◽  
Cost Effective ◽  
Population Monitoring ◽  
Population Trends ◽  
Monitoring Methods ◽  
Monitoring Method ◽  
Hippocamelus Bisulcus ◽  
Detection Probabilities ◽  
Current Survey

Considerable efforts have been invested in recent years to improve methods for both data collection and analyses required for population monitoring. Where historical or current estimates of population size are not adjusted for detection probabilities they may be too inaccurate to provide meaningful estimates of trends and thus monitoring methods need to be adapted. Here, we use data from the Endangered huemul deer Hippocamelus bisulcus to outline a framework to develop accurate robust estimates of detection probabilities that can be incorporated into new surveys in a cost-effective way and applied to existing survey data sets. In particular, by retroactively estimating detection probabilities for surveys of huemul, we show that current survey methods for huemul are inadequate to determine population trends reliably. Based on these results we propose a new monitoring method for the huemul and discuss the importance of estimating accuracies of historical survey data to ensure that changes in the abundance of the species reflect real population trends and are not an artefact of variation over time in the accuracy of survey data. © 2010 Fauna & Flora International.

scholarly journals Learning to count: adapting population monitoring for Endangered huemul deer Hippocamelus bisulcus to meet conservation objectives

Oryx ◽  
2010 ◽  
Vol 44 (4) ◽  
pp. 516-522 ◽  
Author(s):  
Heiko U. Wittmer ◽  
Paulo Corti ◽  
Cristián Saucedo ◽  
José Luis Galaz
Keyword(s):  
Survey Data ◽  
Survey Methods ◽  
Cost Effective ◽  
Population Monitoring ◽  
Population Trends ◽  
Monitoring Methods ◽  
Monitoring Method ◽  
Hippocamelus Bisulcus ◽  
Detection Probabilities ◽  
Current Survey

AbstractConsiderable efforts have been invested in recent years to improve methods for both data collection and analyses required for population monitoring. Where historical or current estimates of population size are not adjusted for detection probabilities they may be too inaccurate to provide meaningful estimates of trends and thus monitoring methods need to be adapted. Here, we use data from the Endangered huemul deer Hippocamelus bisulcus to outline a framework to develop accurate robust estimates of detection probabilities that can be incorporated into new surveys in a cost-effective way and applied to existing survey data sets. In particular, by retroactively estimating detection probabilities for surveys of huemul, we show that current survey methods for huemul are inadequate to determine population trends reliably. Based on these results we propose a new monitoring method for the huemul and discuss the importance of estimating accuracies of historical survey data to ensure that changes in the abundance of the species reflect real population trends and are not an artefact of variation over time in the accuracy of survey data.

Detecting, counting and following the giants of the sea: a review of monitoring methods for aquatic megavertebrates in the Caribbean

2019 ◽  
Vol 46 (7) ◽  
pp. 545
Author(s):  
D. N. Castelblanco-Martínez ◽  
M. P. Blanco-Parra ◽  
P. Charruau ◽  
B. Prezas ◽  
I. Zamora-Vilchis ◽  
...  
Keyword(s):  
Critical Role ◽  
Critical Evaluation ◽  
Population Monitoring ◽  
Tourism Industry ◽  
Caribbean Region ◽  
Monitoring Methods ◽  
Photo Identification ◽  
Important Region ◽  
The Caribbean ◽  
Marine Megafauna

Abstract The Caribbean is a mega-diverse and bio-geographically important region that consists of the Caribbean Sea, its islands, and surrounding coastlines. Among the billions of aquatic species inhabiting this region, the mega-vertebrates stand out for their social, economic and ecologic relevance. However, the Caribbean has been threatened by climate change, poverty, pollution, environmental degradation and intense growth of the tourism industry, affecting megafauna species directly and indirectly. Population monitoring plays a critical role in an informed conservation process and helps guide management decisions at several scales. The aim of the present review was to critically examine the methods employed for monitoring marine megafauna in the Caribbean, so as to create a framework for future monitoring efforts. In total, 235 documents describing protocols for the monitoring of sirenians, cetaceans, elasmobranchs, sea turtles and crocodilians in the Caribbean region, were reviewed. The methods included community-based monitoring (interviews, citizen science and fisheries monitoring), aerial surveys (by manned and unmanned aerial vehicles), boat-based surveys (including manta tow, and side-scan sonars), land-based surveys, acoustic monitoring, underwater surveys, baited remote underwater video, mark–recapture, photo-identification and telemetry. Monitoring efforts invested on aquatic megafauna in the Caribbean have been highly different, with some species and/or groups being prioritised over others. The present critical review provides a country-based overview of the current and emerging methods for monitoring marine megafauna and a critical evaluation of their known advantages, disadvantages and biases.

Population estimation with sparse data: the role of estimators versus indices revisited

2001 ◽  
Vol 79 (10) ◽  
pp. 1754-1765 ◽  
Author(s):  
Kevin S McKelvey ◽  
Dean E Pearson
Keyword(s):  
Small Mammal ◽  
Population Estimation ◽  
Population Estimates ◽  
Small Populations ◽  
Primary Methods ◽  
Closed Population ◽  
Detection Probabilities ◽  
Sources Of Variation ◽  
Estimation Models

The use of indices to evaluate small-mammal populations has been heavily criticized, yet a review of small-mammal studies published from 1996 through 2000 indicated that indices are still the primary methods employed for measuring populations. The literature review also found that 98% of the samples collected in these studies were too small for reliable selection among population-estimation models. Researchers therefore generally have a choice between using a default estimator or an index, a choice for which the consequences have not been critically evaluated. We examined the use of a closed-population enumeration index, the number of unique individuals captured (Mt+1), and 3 population estimators for estimating simulated small populations (N = 50) under variable effects of time, trap-induced behavior, individual heterogeneity in trapping probabilities, and detection probabilities. Simulation results indicated that the estimators produced population estimates with low bias and high precision when the estimator reflected the underlying sources of variation in capture probability. However, when the underlying sources of variation deviated from model assumptions, bias was often high and results were inconsistent. In our simulations, Mt+1 generally exhibited lower variance and less sensitivity to the sources of variation in capture probabilities than the estimators.

scholarly journals Environmental DNA facilitates accurate, indigenous-led, inexpensive, and multi-year population estimates of millions of Eulachon fish

2019 ◽  
Author(s):  
Meredith Pochardt ◽  
Jennifer M. Allen ◽  
Ted Hart ◽  
Sophie D. L. Miller ◽  
Douglas W. Yu ◽  
...  
Keyword(s):  
Area Under The Curve ◽  
Cost Savings ◽  
Environmental Dna ◽  
Population Monitoring ◽  
Population Estimates ◽  
Water Sampling ◽  
Mark Recapture ◽  
Temporal Sampling ◽  
The Relationship

AbstractAlthough environmental DNA shed from an organism is now widely used for species detection in a wide variety of contexts, mobilizing environmental DNA for management requires estimation of population size and trends rather than simply assessing presence or absence. However, the efficacy of environmental-DNA-based indices of abundance for long-term population monitoring have not yet been assessed. Here we report on the relationship between six years of mark-recapture population estimates for eulachon (Thaleichthys pacificus) and ‘eDNA rates,’ which are calculated from the product of stream flow and DNA concentration. Eulachon are a culturally and biologically important anadromous fish that have significantly declined in the southern part of their range but were historically rendered into oil and traded. Both the peak eDNA rate and the area under the curve of the daily eDNA rate were highly predictive of the mark-recapture population estimate, explaining 84.96% and 92.53% of the deviance respectively. Even in the absence of flow correction, the peak of the daily eDNA concentration explained an astonishing 89.53% while the area under the curve explained 90.74% of the deviance. These results support the use of eDNA to monitor eulachon population trends and represent a >80% cost savings over mark-recapture, which could be further increased with automated water sampling, reduced replication, and focused temporal sampling. Due to its logistical ease and affordability, eDNA sampling can facilitate monitoring a larger number of rivers and in remote locations where mark-recapture is infeasible.

scholarly journals Variation in herpetofauna detection probabilities: implications for study design

2021 ◽  
Vol 193 (10) ◽  
Author(s):  
Jeremy A. Baumgardt ◽  
Michael L. Morrison ◽  
Leonard A. Brennan ◽  
Madeleine Thornley ◽  
Tyler A. Campbell
Keyword(s):  
Detection Probability ◽  
Relative Effectiveness ◽  
Population Monitoring ◽  
Occupancy Modeling ◽  
Pitfall Traps ◽  
Modeling Framework ◽  
Detection Probabilities ◽  
Study Sites ◽  
Sampling Duration ◽  
Biodiversity Decline

AbstractPopulation monitoring is fundamental for informing management decisions aimed at reducing the rapid rate of global biodiversity decline. Herpetofauna are experiencing declines worldwide and include species that are challenging to monitor. Raw counts and associated metrics such as richness indices are common for monitoring populations of herpetofauna; however, these methods are susceptible to bias as they fail to account for varying detection probabilities. Our goal was to develop a program for efficiently monitoring herpetofauna in southern Texas. Our objectives were to (1) estimate detection probabilities in an occupancy modeling framework using trap arrays for a diverse group of herpetofauna and (2) to evaluate the relative effectiveness of funnel traps, pitfall traps, and cover boards. We collected data with 36 arrays at 2 study sites in 2015 and 2016, for 2105 array-days resulting in 4839 detections of 51 species. We modeled occupancy for 21 species and found support for the hypothesis that detection probability varied over our sampling duration for 10 species and with rainfall for 10 species. For herpetofauna in our study, we found 14 and 12 species were most efficiently captured with funnel traps and pitfall traps, respectively, and no species were most efficiently captured with cover boards. Our results show that using methods that do not account for variations in detection probability are highly subject to bias unless the likelihood of false absences is minimized with exceptionally long capture durations. For monitoring herpetofauna in southern Texas, we recommend using arrays with funnel and pitfall traps and an analytical method such as occupancy modeling that accounts for variation in detection.

scholarly journals Population monitoring for kangaroo management.

2004 ◽  
Vol 26 (1) ◽  
pp. 37 ◽  
Author(s):  
AR Pople
Keyword(s):  
Population Size ◽  
Large Scale ◽  
Research Effort ◽  
Population Monitoring ◽  
Estimation Methods ◽  
Accurate Estimation ◽  
Population Estimates ◽  
Monitoring Tools ◽  
Harvest Strategy ◽  
The Relationship

In wildlife management, the program of monitoring will depend on the management objective. If the objective is damage mitigation, then ideally it is damage that should be monitored. Alternatively, population size (N) can be used as a surrogate for damage, but the relationship between N and damage obviously needs to be known. If the management objective is a sustainable harvest, then the system of monitoring will depend on the harvesting strategy. In general, the harvest strategy in all states has been to offer a quota that is a constant proportion of population size. This strategy has a number of advantages over alternative strategies, including a low risk of over- or underharvest in a stochastic environment, simplicity, robustness to bias in population estimates and allowing harvest policy to be proactive rather than reactive. However, the strategy requires an estimate of absolute population size that needs to be made regularly for a fluctuating population. Trends in population size and in various harvest statistics, while of interest, are secondary. This explains the large research effort in further developing accurate estimation methods for kangaroo populations. Direct monitoring on a large scale is costly. Aerial surveys are conducted annually at best, and precision of population estimates declines with the area over which estimates are made. Management at a fine scale (temporal or spatial) therefore requires other monitoring tools. Indirect monitoring through harvest statistics and habitat models, that include rainfall or a greenness index from satellite imagery, may prove useful.

scholarly journals Horizontal or vertical? Camera trap orientations and recording modes for detecting potoroos, bandicoots and pademelons

2014 ◽  
Vol 36 (1) ◽  
pp. 60 ◽  
Author(s):  
Brendan D. Taylor ◽  
Ross L. Goldingay ◽  
John M. Lindsay
Keyword(s):  
Detection Probability ◽  
New South ◽  
Population Monitoring ◽  
Camera Trap ◽  
Probability Of Detection ◽  
Camera Traps ◽  
North East ◽  
South Wales ◽  
Detection Probabilities ◽  
The Stability

Camera traps can detect rare and cryptic species, and may enable description of the stability of populations of threatened species. We investigated the relative performance of cameras oriented horizontally or vertically, and recording mode (still and video) to detect the vulnerable long-nosed potoroo (Potorous tridactylus) as a precursor to population monitoring. We established camera traps for periods of 13–21 days across 21 sites in Richmond Range National Park in north-east New South Wales. Each camera trap set consisted of three KeepGuard KG680V cameras directed at a bait container – one horizontal and one vertical camera in still mode and one horizontal camera in video mode. Potoroos and bandicoots (Perameles nasuta and Isoodon macrourus) were detected at 14 sites and pademelons (Thylogale stigmatica and T. thetis) were detected at 19 sites. We used program Presence to compare detection probabilities for each camera category. The detection probability for all three taxa groups was lowest for the vertical still and similar for the horizontal cameras. The detection probability (horizontal still) was highest for the potoroos (0.43) compared with the bandicoots (0.16) and pademelons (0.25). We estimate that the horizontal stills camera could achieve a 95% probability of detection of a potoroo within 6 days compared with 8 days using a vertical stills camera. This suggests that horizontal cameras in still mode have great potential for monitoring the dynamics of this potoroo population.

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