Using N-mixture models to estimate abundance and temporal trends of black rhinoceros (Diceros bicornis L.) populations from aerial counts

Kidwai, Zaara; Jímenez, José; Louw, Cornelius J.; Nel, H.P.; Marshal, Jason P.

doi:10.1016/j.gecco.2019.e00687

Cited by 22 publications

(17 citation statements)

References 48 publications

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“…The DM model relaxes the closure assumption of Royle [ 39 ] and includes explicit parameters (γ = “recruitment”, ω = “survival”) that collectively describe changes in a population over time [ 38 ]. Open N-mixture models are often used to estimate local abundances and rates of population change of unmarked animals (e.g., [ 40 , 41 ]), but have not been previously used to estimate nest density. We review the assumptions and suitability of open N-mixture models relative to the estimation of nest density in S1 Appendix in the supplemental materials.…”

Section: Methodsmentioning

confidence: 99%

Nest density drives productivity in chestnut-collared longspurs: Implications for grassland bird conservation

et al. 2021

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Grassland birds are declining faster than any other avian guild in North America and are increasingly a focus of conservation concern. Adaptive, outcome-based management of rangelands could do much to mitigate declines. However, this approach relies on quantitative, generalizable habitat targets that have been difficult to extrapolate from the literature. Past work relies heavily on individual versus population response, and direct response to management (e.g. grazing) versus response to outcomes. We compared individual and population-level responses to vegetation conditions across scales to identify quantitative targets of habitat quality for an imperiled grassland songbird, the chestnut-collared longspur (Calcarius ornatus) in northern Montana, USA during 2017–2018. We estimated nest density and nest survival within 9-ha survey plots using open N-mixture and nest survival models, respectively, and evaluated relationships with plot- and nest-site vegetation conditions. Plot-scale conditions influenced nest density, whereas nest survival was unaffected by any measured condition. Nest-site and plot-scale vegetation measurements were only weakly correlated, suggesting that management targets based on nest sites only would be incomplete. While nest survival is often assumed to be the key driver of bird productivity, our results suggest that nest density and plot-scale conditions are more important for productivity of longspurs at the core of the breeding distribution. Habitat outcomes for grassland birds should incorporate nest density and average conditions at scale(s) relevant to management (e.g. paddock or pasture).

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Section: Methodsmentioning

confidence: 99%

Nest density drives productivity in chestnut-collared longspurs: Implications for grassland bird conservation

et al. 2021

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“…This essentially means that, in circumstances where pupfish cannot be captured or marked, N ‐mixture models fitted to VC data represent an alternative for developing abundance indices that could benefit conservation actions. From this perspective, this research provides insight into the trade‐offs between traditional handling and marking of individuals and less invasive census protocols (Ficetola et al, 2018; Griffiths, Fister, Wilkinson, & Sewell, 2015; Kidwai, Jimenez, Louw, Nel, & Marshal, 2019) aimed at addressing the challenge of establishing quantitative measures of response to habitat improvement (Hermoso et al, 2016; Nel et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Greater differences emerged when N-mixture models were applied to these same sampling methods, although a consistent pattern of greater CSP abundance in restored ciénegas was apparent.This essentially means that, in circumstances where pupfish cannot be captured or marked, N-mixture models fitted to VC data represent an alternative for developing abundance indices that could benefit conservation actions. From this perspective, this research provides insight into the trade-offs between traditional handling and marking of individuals and less invasive census protocols(Ficetola et al, 2018;Griffiths, Fister, Wilkinson, & Sewell, 2015;Kidwai, Jimenez, Louw, Nel, & Marshal, 2019) aimed at addressing the challenge of establishing quantitative measures of response to habitat improvement (Hermoso et al, 2016; Nel et al, 2009).F I G U R E 3 Density estimates and 95% confidence intervals for Comanche Springs pupfish for principal habitats in the San Solomon Spring System based on (a) mark-recapture methods and (b) Nmixture modelling. VC: visual count; MT: minnow trap.…”

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Multiple survey methods reveal greater abundance of endangered pupfish in restored habitats

Acre

Perkin

Bean

2020

Aquatic Conservation

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Freshwater organisms inhabiting arid ecosystems are imperilled by human alterations to water‐limited landscapes. This is especially true among desert‐dwelling cyprinodontid fishes, 90% of which are imperilled by habitat destruction within limited or shrinking ranges. Constructing habitats that mimic natural habitat form and function may provide a tool for species conservation, especially within freshwater protected areas. However, pupfish population assessments within degraded compared with restored habitats are infrequent, and few comparisons among survey methods exist. Density estimates were developed for Endangered Comanche Springs pupfish Cyprinodon elegans throughout altered and restored habitats in a freshwater protected area by using mark–recapture and N‐mixture models fitted to data collected using minnow trap and visual count survey methods. This allowed comparison of habitats, survey methods, and statistical methods commonly used to generate population size estimates for imperilled pupfish. Population estimates varied across major habitat types and were largest among habitats constructed to mimic naturally occurring ciénegas. Estimates using visual counts were higher than estimates from minnow traps where water was deeper and where macroalgae cover was highest. N‐mixture models generally estimated higher abundances than mark–recapture and were not limited by recapture ability. The results provide strong evidence that restored habitats house greater abundances of pupfish, but survey and statistical methods commonly used to detect these differences have trade‐offs in performance according to the habitats surveyed. This work benefits the field of conservation biology by providing guidance for existing and emerging monitoring programmes assessing abundance‐based fish responses to habitat improvements.

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“…We organized the model selection procedure in five steps, each encompassing a multi-model comparison based on the AIC criterion (e.g. Kidwai et al 2019). In each step, the parameters' value corresponding to the model with the lowest AIC was selected and it was fixed for the following comparisons.…”

Section: Model Selection and Estimation Of Population Sizementioning

confidence: 99%

Microhabitat Selection and Population Density of Nehalennia Speciosa Charpentier, 1840 (Odonata: Coenagrionidae) in a Peripheral Microrefugium

et al. 2021

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Peripheral populations of boreal tyrphophilic animals and plants often occupy relict Alpine peatlands, which act as microrefugia. Ecological conditions within local peatlands can lead to uncommon adaptations, highly valuable for the long-term conservation of species and habitats. The pigmy damselfly (Nehalennia speciosa) is an endangered Odonata distributed in Central and Eastern Europe with peripheral populations in the Alps. We investigated the microscale species-habitat association and the conservation status of one of these populations in a relict raised bog. We applied dynamic N-mixture models to assess population ecology and density, while disentangling predictors’ effect on ecological and observation process. We counted N. speciosa individuals in spring 2018 along with vegetation, water, soil and weather conditions during surveys. Final model resulted reliable according to performance measures. Spatial variation in N. speciosa abundance was driven by vegetation type, with a strong selection for flooded hollows where C. rostrata, R. alba and S. palustris vegetation occupy acidic and oligotrophic shallow pools. Population density showed a peak in the first decade of June and increased with accumulation of superficial water. Detection probability was generally low and decreased further when wind blew. The reduced ecological plasticity of the species imperil the species to habitat and climate changes, which will be particularly threatening for its peripheral Alpine populations in the near future, causing water imbalance and rapid vegetation turnover within the peatlands’ fragile microhabitat. The studied peat bog could thus be retained a key future microrefugium for the long-term conservation of tyrphopilous wildlife and habitats.

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Using N-mixture models to estimate abundance and temporal trends of black rhinoceros (Diceros bicornis L.) populations from aerial counts

Cited by 22 publications

References 48 publications

Nest density drives productivity in chestnut-collared longspurs: Implications for grassland bird conservation

Nest density drives productivity in chestnut-collared longspurs: Implications for grassland bird conservation

Multiple survey methods reveal greater abundance of endangered pupfish in restored habitats

Microhabitat Selection and Population Density of Nehalennia Speciosa Charpentier, 1840 (Odonata: Coenagrionidae) in a Peripheral Microrefugium

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