Pellet group count methods to estimate red deer densities: Precision, potential accuracy and efficiency

Alves, Joana; Silva, António Alves da; Soares, Amadeu M.V.M.; Fonseca, Carlos

doi:10.1016/j.mambio.2012.08.003

Cited by 47 publications

(50 citation statements)

References 29 publications

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“…The overall density estimated for the study area (92,053 ha) was lower than in previous studies, but if we consider the density estimated for the distribution area (59,914 ha) it is quite similar (5.20 ind./100 ha in 15,000 ha, Fonseca et al (2009); 5.37 ind./100 ha in 2500 ha, Alves et al (2013)). However, as the methodologies used was different, caution is needed.…”

Section: Discussionmentioning

confidence: 47%

“…The pellet group disappearance rate was specific for the species and for the study area (Alves et al 2013), so lower bias is expected however, since disappearance days can vary among habitats, the use of a site-specific value for each dominant habitat in each place, over the mean value, should be assessed in Table 2. Red deer abundance, density and 95% CI estimated for both areas referenced in this study.…”

Section: Discussionmentioning

confidence: 99%

“…The scrublands are present in almost 50% of the area and are dominated by heathers Erica spp., Calluna vulgaris, and Ulex spp. (Alves et al 2013). …”

Section: Study Areamentioning

confidence: 99%

“…This methodology requires two conversion factors -the pellet group disappearance rate and the production rate -to convert the density of pellet groups into the density of animals (see Valente et al 2014 for details). The pellet group disappearance rate used was of 581 ± 55 days, obtained for red deer in the same region (Alves et al 2013), while the production rate used, of 25 pellets a day, was based on literature (Mayle 1996). Both Conventional Distance Sampling and Multiple Covariate Distance Sampling were tested in Distance 6.0 (Thomas et al 2010).…”

Section: Study Areamentioning

confidence: 99%

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The success of species reintroductions: a case study of red deer in Portugal two decades after reintroduction

Valente

Fonseca

et al. 2017

International Journal of Biodiversity Science, Ecosystem Servic

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Reintroduction programs are important tools in the recovery or establishment of animal populations, but post-release monitoring, essential to evaluate their success, generally lacks in most projects. During the 1990s, a red deer (Cervus elaphus) reintroduction program took place in central Portugal. Almost two decades after the reintroduction, this study aimed to establish the current state of red deer populations. Density estimates were obtained through pellet group counts coupled with distance sampling using 61 linear transects. The results showed that red deer densities are of 3.10 ind./100 ha (95% confidence interval: 1.6-5.9) and this species is widely distributed throughout the area. Due to increase in numbers and range since the beginning of the reintroduction, this program can be considered a case of success; however, future monitoring programs should continue to be developed. ARTICLE HISTORY

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Section: Discussionmentioning

confidence: 47%

Section: Discussionmentioning

confidence: 99%

“…The scrublands are present in almost 50% of the area and are dominated by heathers Erica spp., Calluna vulgaris, and Ulex spp. (Alves et al 2013). …”

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

See 2 more Smart Citations

The success of species reintroductions: a case study of red deer in Portugal two decades after reintroduction

Valente

Fonseca

et al. 2017

International Journal of Biodiversity Science, Ecosystem Servic

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“…We chose the standing crop (SC) approach over the accumulation rate (AR) approach for counting dung piles in sampling plots. Using the SC approach has been shown to increase precision of density estimates (Alves et al., 2013). The difference between the two approaches is that AR is measured by clearing sample plots of dung piles and then revisiting the plots to determine the rate of dung pile accumulation between two points in time, while SC is measured by counting dung piles in a plot without prior clearing or revisits (Acevedo et al., 2010; Putman, 1984).…”

Section: Methodsmentioning

confidence: 99%

Estimating densities of large herbivores in tropical forests: Rigorous evaluation of a dung‐based method

Ahrestani¹,

Kumar

Vaidyanathan³

et al. 2018

Ecology and Evolution

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When sighting‐based surveys to estimate population densities of large herbivores in tropical dense forests are not practical or affordable, surveys that rely on animal dung are sometimes used. This study tested one such dung‐based method by deriving population densities from observed dung densities of six large herbivores (chital, elephant, gaur, muntjac, sambar, and wild pig) in two habitats, dry deciduous forests (DDF) and moist deciduous forests (MDF), within Nagarahole National Park, southern India. Using the program DUNGSURV, dung pile counts, decay rates estimated from field experiments, and defecation rates derived from literature were analyzed together by a model that allows for random events affecting dung decay. Densities of chital were the highest, followed by sambar. Wild pig densities were similar in the two habitats, sambar densities were higher in DDF, and densities of the other species were higher in MDF than in DDF. We compared DUNGSURV estimates with densities estimated using distance sampling in the same season. DUNGSURV estimates were substantially higher for all species in both habitats. These differences highlight the challenges that researchers face in computing unbiased estimates of dung decay rates and in relying on defecation rates from literature. Besides the elephant, this study is the first to rigorously test the efficacy of using a dung‐based approach to estimate densities of large herbivore species in Asia, and based on this evaluation, we provide specific recommendations to address issues that require careful consideration before observed dung densities are used to derive animal densities. Our results underline the need for an experimental study of a known population in a fenced reserve to validate the true potential of using dung‐based approaches to estimate population densities.

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Biological traits, rather than environment, shape detection curves of large vertebrates in neotropical rainforests

Denis

Richard‐Hansen

Brunaux

et al. 2017

Ecological Applications

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Line transect surveys are widely used in Neotropical rainforests to estimate the population abundance of medium- and large-sized vertebrates. The use of indices such as encounter rate has been criticized because the probability of animal detection may fluctuate due to the heterogeneity of environmental conditions among sites. In addition, the morphological and behavioral characteristics (biological traits) of species affect their detectability. In this study, we compared the extent to which environmental conditions and species' biological traits bias abundance estimates in terra firme rainforests in French Guiana. The selected environmental conditions included both physical conditions and forest structure covariates, while the selected biological traits included the morphological and behavioral characteristics of species. We used the distance sampling method to model the detection probability as an explicit function of environmental conditions and biological traits and implemented a model selection process to determine the relative importance of each group of covariates. Biological traits contributed to the variability of animal detectability more than environmental conditions, which had only a marginal effect. Detectability was best for large animals with uniform or disruptive markings that live in groups in the canopy top. Detectability was worst for small, solitary, terrestrial animals with mottled markings. In the terra firme rainforests that represent ~80% of the Amazonia and Guianas regions, our findings support the use of relative indices such as the encounter rate to compare population abundance between sites in species-specific studies. Even though terra firme rainforests may appear similar between regions of Amazonia and the Guianas, comparability must be ensured, especially in forests disturbed by human activity. The detection probability can be used as an indicator of species' vulnerability to hunting and, thus, to the risk of local extinction. Only a few biological trait covariates are required to correctly estimate the detectability of the majority of medium- and large-sized vertebrates. Thus, a biological trait model could be useful in predicting the detection probabilities of rare, uncommon, or localized species for which few data are available to fit the detection function.

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Pellet group count methods to estimate red deer densities: Precision, potential accuracy and efficiency

Cited by 47 publications

References 29 publications

The success of species reintroductions: a case study of red deer in Portugal two decades after reintroduction

The success of species reintroductions: a case study of red deer in Portugal two decades after reintroduction

Estimating densities of large herbivores in tropical forests: Rigorous evaluation of a dung‐based method

Biological traits, rather than environment, shape detection curves of large vertebrates in neotropical rainforests

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