Reliability of Different Mark-Recapture Methods for Population Size Estimation Tested against Reference Population Sizes Constructed from Field Data

Grimm, Annegret; Gruber, Bernd; Henle, Klaus

doi:10.1371/journal.pone.0098840

Cited by 47 publications

(39 citation statements)

References 51 publications

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“…This estimator was already proven to fit our data set particularly well (Grimm et al. ). We further determined the coefficient of variation (CV) describing the individual heterogeneity present per year (Chao et al.…”

Section: Methodssupporting

confidence: 55%

“…We estimated annual population sizes using the first sample coverage estimator accounting for individual heterogeneity (Lee and Chao 1994) as implemented in CARE-2 (Chao and Yang 2003). This estimator was already proven to fit our data set particularly well (Grimm et al 2014). We further determined the coefficient of variation (CV) describing the individual heterogeneity present per year (Chao et al 1992, Lee andChao 1994).…”

Section: Population Sizementioning

confidence: 99%

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Some like it hot: from individual to population responses of an arboreal arid‐zone gecko to local and distant climate

Grimm‐Seyfarth

Mihoub

Gruber

et al. 2018

Ecological Monographs

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Accumulating evidence has demonstrated considerable impact of climate change on biodiversity, with terrestrial ectotherms being particularly vulnerable. While climate‐induced range shifts are often addressed in the literature, little is known about the underlying ecological responses at individual and population levels. Using a 30‐yr monitoring study of the long‐living nocturnal gecko Gehyra variegata in arid Australia, we determined the relative contribution of climatic factors acting locally (temperature, rainfall) or distantly (La Niña induced flooding) on ecological processes ranging from traits at the individual level (body condition, body growth) to the demography at population level (survival, sexual maturity, population sizes). We also investigated whether thermoregulatory activity during both active (night) and resting (daytime) periods of the day can explain these responses. Gehyra variegata responded to local and distant climatic effects. Both high temperatures and high water availability enhanced individual and demographic parameters. Moreover, the impact of water availability was scale independent as local rainfall and La Niña induced flooding compensated each other. When water availability was low, however, extremely high temperatures delayed body growth and sexual maturity while survival of individuals and population sizes remained stable. This suggests a trade‐off with traits at the individual level that may potentially buffer the consequences of adverse climatic conditions at the population level. Moreover, hot temperatures did not impact nocturnal nor diurnal behavior. Instead, only cool temperatures induced diurnal thermoregulatory behavior with individuals moving to exposed hollow branches and even outside tree hollows for sun‐basking during the day. Since diurnal behavioral thermoregulation likely induced costs on fitness, this could decrease performance at both individual and population level under cool temperatures. Our findings show that water availability rather than high temperature is the limiting factor in our focal population of G. variegata. In contrast to previous studies, we stress that drier rather than warmer conditions are expected to be detrimental for nocturnal desert reptiles. Identifying the actual limiting climatic factors at different scales and their functional interactions at different ecological levels is critical to be able to predict reliably future population dynamics and support conservation planning in arid ecosystems.

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Section: Methodssupporting

confidence: 55%

Section: Population Sizementioning

confidence: 99%

Some like it hot: from individual to population responses of an arboreal arid‐zone gecko to local and distant climate

Grimm‐Seyfarth

Mihoub

Gruber

et al. 2018

Ecological Monographs

Self Cite

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show abstract

“…This was evident from the internationally coordinated survey in spring 2015, where subsequent surveys showed that the population count must have been too low (see http://pinkfootedgoose.aewa.info/node/195). Nonetheless, throughout the African-Eurasian region, such counts are the standard way of monitoring waterbird populations according to AEWA guidelines (AEWA 2005), and alternative measures of population size obtained from capture-mark-recapture methods or bag indices are often characterised by large annual fluctuations and associated with a number of assumptions that are rarely met (Ganter & Madsen 2001;Imperio et al 2010;Grimm, Gruber & Henle 2014). The pink-footed goose count is coordinated both locally and internationally and carried out by experienced observers with many years of training in counting geese.…”

Section: Discussionmentioning

confidence: 99%

Impact of hunting along the migration corridor of pink‐footed geeseAnser brachyrhynchus– implications for sustainable harvest management

Clausen

Christensen

Gundersen

et al. 2017

Journal of Applied Ecology

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Summary1. Hunting can potentially affect population size, age composition, sex-ratio, behaviour and distribution of natural populations, and understanding its impacts is a prerequisite to manage quarry species sustainably. Harvest management relies strongly on the existence of both strictly regulated hunting efforts and efficient monitoring of populations, their demography and harvest. These conditions are rarely met in practice. 2. For the Svalbard-breeding population of the pink-footed goose Anser brachyrhynchus, an internationally coordinated adaptive harvest management framework enables a flyway-based assessment of harvest impact. Based on 25 years of population assessment and harvest data, we evaluate the differential impact of harvest along the migration corridor of the population. 3. The analysis reveals that (i) total harvest and harvest rate (proportion of the population killed by hunting) have increased substantially in recent years, (ii) compared to adult geese, juveniles were overrepresented in the hunting bag by a factor of 3Á7, (iii) the proportion of juveniles in the hunting bag differed between the two countries (Norway and Denmark) with an open season, and was more than twice as high in the former compared to the latter, and (iv) the increase in harvest rate seemed to be driven by increased hunting mortality of juvenile birds, with no clear impact on the growth rate of the population. However, this may partly relate to the transient dynamics and population inertia commonly seen in long-lived species such as geese, and a 3-year consecutive decline towards the end of our study period might be the first signs of an impending decline. 4. Synthesis and applications. Our findings highlight that the impact of harvest varies along the migration corridor and between age classes of a single species and suggest that allocation of hunting effort in time and space is important to optimise harvest. Our example demonstrates the need for internationally coordinated, detailed population and harvest data which are essential for sustainable harvest management.

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“…One critical assumption is whether capture probability is constant or changes with time or among individuals. Whenever capture probability is expected to vary, models accounting for individual heterogeneity perform best, while Peterson–Lincoln's formula tends to underestimate population size (Grimm, Gruber & Henle, ).…”

Section: Discussionmentioning

confidence: 55%

An indirect method for assessing the abundance of introduced pest Myocastor coypus (Rodentia) in agricultural landscapes

et al. 2015

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Pest management requires the development of robust monitoring tools. In Italy, coypu Myocastor coypus (nutria) have been controlled since the early 1990s, but the effectiveness of these measures has never been tested. With the aim of developing a reliable and volunteer‐based method for the long‐term monitoring of coypu abundance in agricultural landscapes, we calibrated an index based on surveys for coypu paths against density estimates obtained through a standardized mark–recapture technique. Two trapping sessions were performed in winter for each of 12 1‐km long stretches of irrigation canals and watercourses using 15 baited cage traps. Trapping sessions lasted 7 days each, with a 10‐day break between sessions. Population size was assessed using three methods: Peterson–Lincoln's formula, capwire estimators and accumulation curves. Active coypu paths and five habitat variables were recorded by walking on the edge of both banks. The variables were then related to population size (y) by means of multi‐regressive models, testing for the predictive power of the selected models by leave‐one‐out cross‐validation. Multi‐regressive models included only the number of coypu paths with the best performances achieved by the model based on Peterson–Lincoln formula, supporting path count as an effective method to assess the abundance of the coypu in agricultural landscapes. Concurrently, to assess the field suitability of the indirect method, surveys for coypu paths were carried out on 122 randomly chosen 3‐km long stretches of irrigation canals and watercourses in the central part of the River Po valley (c. 15 000 km2; N Italy). The highest (>8/100 m) mean number of paths was recorded in the central part of the study area. According to the regression models, the overall number of coypu is predicted to range between 350 000 and 1 100 000, raising doubts about the effectiveness of current control measures.

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Reliability of Different Mark-Recapture Methods for Population Size Estimation Tested against Reference Population Sizes Constructed from Field Data

Cited by 47 publications

References 51 publications

Some like it hot: from individual to population responses of an arboreal arid‐zone gecko to local and distant climate

Some like it hot: from individual to population responses of an arboreal arid‐zone gecko to local and distant climate

Impact of hunting along the migration corridor of pink‐footed geeseAnser brachyrhynchus– implications for sustainable harvest management

An indirect method for assessing the abundance of introduced pest Myocastor coypus (Rodentia) in agricultural landscapes

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