Comparison of Population Estimators for Medium-Sized Mammals

Hallett, James G.; O’Connell, Margaret A.; Sanders, Gregory D.; Seidensticker, John

doi:10.2307/3809244

Cited by 32 publications

(27 citation statements)

References 19 publications

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“…They concluded that indices were proportional to estimates, i.e., bias was relatively constant. Such high correlations between capture-recapture indices and estimators have been reported for numerous species (Lefebvre et al 1982;Hallett et al 1991;Manning et al 1995;Morris 1996;Nupp and Swihart 1996;Waters and Zabel 1998). Since bias itself is not problematic for relative comparisons, M t+1 can be a valid metric for comparing populations in cases where capture probabilities are relatively constant.…”

Section: Discussionmentioning

confidence: 94%

“…With relatively large sample sizes and high capture probabilities, CAPTURE employs discriminant function analysis to effectively select from 8 potential models addressing the important sources of variability in capture probabilities and produces population estimates with low bias and high precision (Otis et al 1978;White et al 1982). However, when samples are small and capture probabilities low, model selection is poor and population estimates are unreliable (Otis et al 1978;Menkins and Anderson 1988;Hallett et al 1991).…”

Section: Index Conversion In Small-mammal Capture-recapture Studiesmentioning

confidence: 98%

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

McKelvey¹,

Pearson²

2001

Can. J. Zool.

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The use of indices to evaluate small-mammal populations has been heavily criticized, yet a review of smallmammal 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 (M t+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, M t+1 generally exhibited lower variance and less sensitivity to the sources of variation in capture probabilities than the estimators. Résumé: L'utilisation d'indices pour évaluer les populations de petits mammifères est très critiquée et pourtant les études publiées entre 1996 et 2000 sur les petits mammifères démontrent que l'utilisation d'indices est toujours la mé-thode la plus courante d'évaluation des populations. Dans la littérature, 98 % des échantillons recueillis pour les études étaient trop petits pour permettre le choix judicieux d'un modèle d'estimation de population. Les chercheurs se retrouvent donc devant un choix à faire entre une méthode par défaut ou un indice, choix dont les conséquences n'ont pas été évaluées de façon formelle. Nous avons examiné les résultats de l'utilisation d'un indice de dénombrement d'une population fermée, du nombre d'individus particuliers capturés (M t+1 ), et de 3 estimateurs de population pour estimer de petites populations simulées (N = 50) soumises à des effets divers du temps, du comportement relié au piégeage, de l'hétérogénéité dans la probabilité de capture des individus et des probabilités de détection. Les résultats de cette simulation ont démontré que les estimateurs donnent des évaluations qui comportent peu d'erreur et qui sont d'une grande précision lorsque l'estimateur utilisé reflète les sources de variation sous-jacentes des probabilités de capture. Cependant, lorsque les sources de variation sous-jacentes s'éloignent des présuppositions du modèle, les chances d'erreur sont souvent élevées et les résultats sont changeants. Dans nos simulations, M t+1 a généralement une faible variance et manifeste moins de sensibilité aux sources de variation des probabilités de capture que les autres estimateurs. [Traduit par la Rédaction]...

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Section: Discussionmentioning

confidence: 94%

Section: Index Conversion In Small-mammal Capture-recapture Studiesmentioning

confidence: 98%

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

McKelvey¹,

Pearson²

2001

Can. J. Zool.

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“…The frequent selection of the null model has already been reported for Didelphis virginiana Kerr, 1792(HALLET et al 1991 and for rodents and leporids (HAMMOND & ANTHONY 2006) in the United States. In these studies, the results were attributed to the poor performance of model selection tests, which was also a consequence of the small amount of data analyzed.…”

Section: Discussionmentioning

confidence: 99%

“…One of the most commonly used estimators is the minimum number alive (MNA;KREBS 1966), which is an enumeration method that requires closed populations (i.e., no births, deaths, immigration or emigration during the trapping period) and equal capture probabilities among all individuals. Because this estimator disregards individuals that were never captured but are present in the study area, MNA has been considered a negatively biased estimator and is thus the target of criticism by many authors (e.g., HALLET et al 1991, NICHOLS & POLLOCK 1983; however, it is still broadly used, despite the criticism (POCOCK et al 2004, MCKELVEY & PEARSON 2001. The apparent preference for MNA instead of other estimation techniques may be due to its simplicity and ease of use (HALLET et al 1991), the difficulty of selecting the most appropriate estimator (SLADE & BLAIR 2000) and the erroneous idea that MNA is less affected than other methods by variable capture probabilities when probabilities of capture are high (NICHOLS & POLLOCK 1983).…”

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confidence: 99%

A comparison of abundance estimators for small mammal populations

Pacheco¹,

Kajin²,

Gentile³

et al. 2013

Zoologia (Curitiba)

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ABSTRACT. A major difficulty in the application of probabilistic models to estimations of mammal abundance is obtaining a data set that meets all of the assumptions of the model. In this paper, we evaluated the concordance correlation among three population size estimators, the minimum number alive (MNA), jackknife and the model suggested by the selection algorithm in CAPTURE (the best-fit model), using long-term data on three Brazilian small mammal species obtained from three different studies. The concordance correlation coefficients between the abundance estimates indicated that the probabilistic and enumeration estimators were highly correlated, giving concordant population estimates, except for one species in one of the studies. The results indicate the adequacy of using enumeration estimates as indexes for population size when scarce data do not allow for the use of probabilistic methods. Differences observed in the behavior of enumeration and probabilistic methods among species and studies can be related to the exclusive sampling design of each area, species-specific movement characteristics and whether a significant portion of the population could be sampled.

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“…Population estimates were further hindered because foxes did not have equal trappability (Egoscue, 1962(Egoscue, , 1975, and probability of capture declined markedly after the first capture (Egoscue, 1962;O'Farrell and Gilbertson, 1986). Hallett et al (1991) reviewed methods for determining population sizes of small predators. They included mark-recapture methods, enumeration (minimum population size), and estimates based on homerange sizes.…”

Section: Mark and Recapture Analysismentioning

confidence: 99%

Effects of Low-Altitude Aircraft Overflights on the Desert Kit Fox (Vulpes macrotis arsipus) and its Small Mammal Prey on the Barry M. Goldwater Air Force Range, Arizona, 1991-1994

Bowles¹,

Francine²,

Yaeger³

et al. 1995

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Devis Highway, Suite 1204, Arlington, VA 222024302, and to the Office of Management and Budget, Paperwork Reduction Project (07040188), Washington, DC 20503. AGENCY USE ONLY (Leave blank)2. REPORT DATE February 1995 REPORT TYPE AND DATES COVEREDFinal -November 1990 to February 1995 TITLE AND SUBTITLEEffects of Low-Altitude Aircraft Overflights on the Desert Kit Fox (Vulpes macrotis arsipus) and its Small Mammal Prey on the Barry M. Goldwater Air Force Range, Arizona, 1991-1994 Ann E. Bowles,%hn Francine,*Samantha Wisely,*! Scott Yaegef*;*Lee McClenaghan Approved for public release; distribution is unlimited. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Hubbs 12b. DISTRIBUTION CODE ABSTRACT (Maximum 200 words)There has been public concern that wildlife could be affected by military training activities. Of particular interest was the hypothesis that noise from military aircraft would disrupt the ecological balance between predator and prey by giving one or the other an advantage. To gauge these effects, this study was conducted under an Air Force Range in an area receiving levels of exposure higher than normally encountered under a Military Training Route. A nearby control site was exposed to much lower levels of noise. Noise monitors recorded actual exposure, and hearing of one heteromyid species, the kangaroo rat, was measured in situ. A total of 14,455 trap-nights were spent monitoring nocturnal small mammal communities on exposed and control plots. Rodent species diversity, numbers, reproductive activity, recruitment, mean weights, and survival were measured. The kit fox, a predator, was also examined. Although differences were uncovered between kit fox and smal mammal populations between the control and exposed areas, none was large, and none was at odds with the most parsimonious natural explanations. If the effects observed are assumed to be the result of aircraft noise exposure, the consequences to rodents and fox populations were smaller in magnitude than the natural variability observed during the course of the study.14. SUBJECT TERMS acoustics, noise effects, noise impacts, ecological balance, desert kit fox Reproductive activity in male (top) and female (bottom) Chaetodipus penicillatus on exposed and control plots on the Barry M. Goldwater Air Force Range, Arizona. ... 81 igure 5-10 Seasonal rates of recruitment for Dipodomys merriami on exposed and control plots on the Barry M. Goldwater Air Force Range, Arizona 82 igure 5-11 Seasonal rates of recruitment for Perognath...

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Comparison of Population Estimators for Medium-Sized Mammals

Cited by 32 publications

References 19 publications

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

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

A comparison of abundance estimators for small mammal populations

Effects of Low-Altitude Aircraft Overflights on the Desert Kit Fox (Vulpes macrotis arsipus) and its Small Mammal Prey on the Barry M. Goldwater Air Force Range, Arizona, 1991-1994

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