Russell Alpizar-Jara- PhD
- Professor (Associate) at Universidade de Évora
Russell Alpizar-Jara
- PhD
- Professor (Associate) at Universidade de Évora
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73
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Current institution
Publications
Publications (73)
While multiple studies have focused on the motivations surrounding antibiotic prescription among veterinarians, little is known about companion animal owners’ knowledge, attitude and perception (KAP) regarding the topic. A nationwide survey directed toward Portuguese dog and cat owners was conducted online and at veterinary practices to characteriz...
Game species with home ranges exceeding the area of the management units may entail conflicts over hunting rights and cause damage to crops and forest stands in surrounding areas. This is currently the case in the Mendro Mountain Range (Portugal), inhabited by free-ranging red (Cervus elaphus) and fallow deer (Dama dama) populations. This study’s p...
Red and fallow deer have become overabundant species in some areas of the Iberian Peninsula, namely in enclosures located in agro-silvo-pastoral systems called “montado” in Portugal and “dehesa” in Spain. Reliable methods to estimate deer density in such conditions are required for proper population management. Inconsistent conclusions regarding th...
Roads can block animal movement and reduce persistence of species living in road surroundings. Movement restrictions on local populations may even increase extinction risk of abundant small mammals. However, road verges (road managed area between
the edge of the road and the beginning of private land) may provide refuge and corridors for small mamm...
Recent studies have highlighted the positive effects of road verges on the
abundance of small mammals. However, most of these studies occurred in intensively grazed or cultivated areas, where verges were the last remnants of suitable
habitats, which could mask the true effects of roads on population traits. We analysed the effects of roads on small...
Roads disrupt landscape connectivity for many species. These infrastructures can be barriers to movement and, in the long-term, threaten the persistence of several mammal populations living on roadsides. It is widely recognized that small mammals use road verges as habitat and corridor when roads cross intensively managed landscapes. Nevertheless,...
Various animal species have been evaluated in depth for their potential as Tick-borne encephalitis virus (TBEV) sentinel species, although evidence for equine capacity is incomplete. Therefore, a comprehensive cross-sectional stratified serosurvey and PCR analysis of selected horses (n = 301) were performed in TBEV endemic localities in Lithuania....
Research Highlights: Daily airborne Cupressaceae pollen disruption ranged from 20 to 90%; relative humidity (RH), rainfall and atmospheric pressure (AtP) were the major meteorological determinants of this phenomenon. Background and Objectives: Cupressaceae family includes several species that are widely used as ornamental plants pollinating in late...
Genetic non-invasive sampling (gNIS) may provide valuable information for population monitoring, as it allows inferences of population density and key behavioural traits such as dispersal, kinship and reproduction. Despite its enormous potential, gNIS has
rarely been applied to small mammals, for which live-trapping is still the most commonly used...
Estimating the size of animal populations is essential for understanding the demography and conservation status of species. Genetic Non-Invasive Sampling (gNIS) combined with Spatially Explicit Capture-Recapture (SECR) modelling may provide a practical tool to obtain such estimates. Here we evaluate for the first time the potential and limitations...
Individual heterogeneity in capture probabilities and time dependence are fundamentally important for estimating the closed animal population parameters in capture-recapture studies. A generalized estimating equations (GEE) approach accounts for linear correlation among capture-recapture occasions, and individual heterogeneity in capture probabilit...
Recent studies have highlighted the positive effects of road verges on the abundance of small mammals. However, most of these studies occurred in intensively grazed or cultivated areas, where verges were the last remnants of suitable habitats, which could mask the true effects of roads on population traits. We analysed the effects of roads on small...
Distance sampling is being extensively used to estimate the abundance of animal populations. Nevertheless, the great variety of ways in which data can be analyzed may limit comparisons due to the lack of standardization of such protocols. In this study, the influence of analytical procedures for distance sampling data on density estimates and their...
The estimation of animal population parameters, such as capture probability, population size, or population density, is an important issue in many ecological applications. Capture–recapture data may be considered as repeated observations that are often correlated over time. If these correlations are not taken into account then parameter estimates m...
Population density is a key parameter to assess the status of threatened species. However, accurate density estimates are often difficult to obtain, particularly in the case of rare and patchily distributed species, for which sampling is constrained by time, finance, and manpower. Knowledge of the most cost-effective sampling and modeling technique...
Evidence that roads have mainly positive or neutral effects on small mammals has been gathered recently despite the fact that these species are one of the most road killed mammal groups. Most of the previously positive documented effects of roads were mainly due to abundance evaluations in habitats under high grazing or agricultural pressure what m...
Modeling individual heterogeneity in capture probabilities has been one of the most challenging tasks in capture–recapture studies. Heterogeneity in capture probabilities can be modeled as a function of individual covariates, but correlation structure among capture occasions should be taking into account. A proposed generalized estimating equations...
The deep-sea lantern shark Etmopterus spinax occurs in the northeast Atlantic on or near the bottoms of the outer continental shelves and slopes, and is regularly captured as bycatch in deep-water commercial fisheries. Given the lack of knowledge on the impacts of fisheries on this species, a demographic analysis using age-based Leslie matrices was...
Heterogeneity in capture probabilities represents a serious problem when estimating population size in capture-recapture studies. A generalized estimating equations (GEE) approach is applied to data from a capture-recapture experiment to model capture probabilities through a logit-link function of the covariates. The model accounts for heterogeneit...
Estimation of animal population parameters is an important issue in ecological statistics. Many estimation methods have been developed for the capture-recapture closed population models (Otis et al., 1978; Amstrup et al., 2005). Development of capture-recapture models dealing with individual heterogeneity in capture probabilities has been one of th...
A amostragem por distâncias foi inicialmente desenvolvida para regiões de estudo planas ou pouco acidentadas. Nesta técnica a probabilidade de deteção é estimada a partir de uma função ajustada às distâncias observadas (perpendiculares ou radiais) entre os animais e o observador, sendo esta função designada por função de deteção (Buckland et al., 2...
Studies of wild vertebrates have provided evidence of substantial differences in lifetime reproduction among individuals and the sequences of life history ‘states’ during life (breeding, nonbreeding, etc.). Such differences may reflect ‘fixed’ differences in fitness components among individuals determined before, or at the onset of reproductive lif...
Modeling heterogeneity in capture probabilities is a critical issue when estimating animal abundance from capture-recapture data. Capture-recapture data are collected on the same individuals across successive points in time; i.e., the outcome variable is measured on the same individual at several occasions. Thus, in a capture-recapture study, obser...
Na literatura sobre a estimação de parâmetros populacionais é possível encontrar vários métodos para estimar a abundância e as taxas de incidência e prevalência. A escolha do método depende não só do tipo e características da população em estudo como também do conjunto de pressupostos em que os métodos de amostragem assentam. Neste trabalho efectua...
The estimation of the size of a closed wildlife population is a vital issue in many ecolog-ical applications. Capture-recapture data are collected on the individuals across successive points in times; these repeated observations are often correlated over time. If these correlations are not taken into account when estimating capture probabilities, t...
The estimation of the size of a closed wildlife population is a crucial problem in many ecological applications. A common method for this purpose is the capture-recapture experiment, where animals are repeatedly captured or observed. Capture probabilities often depend on individual covariates such as age, sex or weight. Typically, this dependence i...
Distance Sampling theory is based on measurements of perpendicular distances from a line (or radial distances from a point transect) to detected animals, in order to estimate their probability of detection. In plain terrains, these distances are often measured directly, with readily available instruments. In mountainous terrains, several types of d...
Algumas populações são raras ou tendem a distribuir-se apenas em certas zonas. A amostragem
adaptativa garante que uma maior parte do esforço seja gasto nas zonas com maior densidade
de animais, aumentando assim a dimensão da amostra. Recentemente foram propostos desenhos
em duas fases adaptativos para estimar a abundância de populações raras [2]....
Recentemente, foram propostos estimadores para a taxa de encontro da amostragem
por transectos linearess com a disposição aleatória dos transectos que mostraram ter um melhor
desempenho do que o estimador empírico, habitualmente utilizado, em cenários homogéneos ou
com gradiente de densidade [4]. Neste trabalho pretende-se avaliar o desempenho dest...
Habitualmente, na amostragem por distâncias a estimação da abundância e da densidade é realizada assumindo que os indivíduos são detectados até uma distância máxima de observação, w, que é conhecida e constante. Sob este pressuposto, vários modelos de detectabilidade são ajustados às distâncias observadas e é usado o critério de informação de Akaik...
From a literature review of five wildlife ecology journals since 1937, we document how using indices to monitor ungulate body
condition is common practice, with the kidney fat index (KFI = weight of fat around the kidneys/weight of kidneys without
fat × 100) as the favoured tool (82% of studies). In this context, we highlight the problems of using...
Nas últimas décadas, os modelos de captura-recaptura em populações fechadas têm sido muito utilizados para estimar o número de falhas num sistema. Modelos que tomam em conta a heterogeneidade das probabilidades de detecção de falhas, diferenças nas probabilidades de detecção por parte dos avaliadores, e simpli- cações destes modelos têm sido propos...
O método mais conhecido com tamanhos de amostras adaptativos foi proposto por Prabhu et al. (1993) e Costa (1994) e é conhecido por VSS (Variable Sample Sizes). Neste, uma amostra maior é utilizada quando a estatística amostral cai numa região próxima dos limites de controlo e uma amostra menor é utilizada quando a estatística amostral cai na regiã...
Several mountain ungulates species present an important degree of aggregation in animals spatial distribution. Mountain topography often makes it difficult to traverse transects, and visibility problems frequently arise due to rocks and trees. We argue that distance sampling could be a useful method to sample this species; however, assumptions can...
Wileyto et al. [E.P. Wileyto, W.J. Ewens, M.A. Mullen, Markov-recapture population estimates: a tool for improving interpretation of trapping experiments, Ecology 75 (1994) 1109] propose a four-state discrete time Markov process, which describes the structure of a marking-capture experiment as a method of population estimation. They propose this me...
In this paper we assess, through a simulation study, the performance of conventional distance sampling estimators when the spatial distribution of individuals in the study area follows a non-homogeneous Poisson process: 1) when individuals in the study area are fixed, but belong to a non-homogenous population (in each simulation different transects...
RESUMEN Cuando se estima la densidad o abundancia de grupos o individuos con la técnica de muestreo por distancias, tenemos de decidir qué método debemos utilizar para estimar la varianza de la tasa de encuentro: varianza empírica o varianza teórica Poisson donde Var(n) = E(n). Normalmente, los ungulados como las cabras monteses muestran un cierto...
Many management actions involving mountain ungulates require unbiased and precise estimations of their numbers. Topography, among other factors, makes difficult the use of direct methods and to assess the effective area sampled. On the other hand, social behaviour of animals increases the risk to violate the assumption that observations must be ind...
Abstract: Capture-recapture models have been widely used to estimate animal population size. This work considers models for closed populations, which assume that the number of individuals in the population remains constant during the study period. An estimator for population size will be biased under presence of heterogeneity in capture probability...
We conduct a simulation study to assess the performance of conventional distance sampling estimators
when the spatial distribution of individuals in the study area follows a non-homogeneous Poisson process.
The following two approaches are considered: 1) objects in the study area are fixed, but different transects
are randomly allocated in every si...
Resumo: Em captura-recaptura, o estudo da dependência entre amostras é muito importante uma vez que o pressuposto de independência pode ser facilmente violado, o que geralmente se traduz em estimativas enviesadas. Uma forma de abordar o pro-blema da dependência entre várias amostras é mediante o uso dos modelos log-lineares. Domingo-Salvany et al....
Direct counts (DC) and line distance sampling (LDS) were applied to estímate the abundance of a recently reintroduced populatíon of Iberian ibex (Capra pyrenaica) in Peneda-Gerés National Park, a mountain region of northern Portugal. Annual counts of this ibex population are being conducted since 2001. Evidence of rapid population growth coupled wi...
Advanced Distance Sampling: Estimating Abundance of Biological Populations (S. T. Buckland, D. R. Anderson, K. P. Burnham, J. L. Laake, D. L. Borchers, and L. Thomas, eds) Russell Alpizar-Jara Flowgraph Models for Multistate Time-to-Event Data (A. V. Huzurbazar) Per Kragh Andersen Spatial Analysis: A Guide for Ecologists (M.-J. Fortin and M. R. T....
As Actas da SPE, publicadas desde a realização do 1o Congresso, constituem um importante veículo de divulgação da estatística e da investigação cientí ca e são um claro incentivo à publicação de artigos, em particular, por parte dos mais jovens. Em ano jubilar e de debate da política editorial da SPE, pensamos que será de grande utilidade analisar...
Ao longo do tempo tem-se verificado uma grande utilização da amostragem por distâncias para estimar a densidade e/ou a abundância de populações biológicas devido, essencialmente, à sua simplicidade de aplicação. Mas, quando estamos perante uma população rara cujos indivíduos tendem a agrupar-se, o número de indivíduos detectados é geralmente muito...
Abstract: This work is intended to estimate population size using the combined line transect and capture-recapture model (Alpizar-Jara e Pollock, 1999) through Bayesian Inference. The probability of sighting an animal (or an object) on the transect line, g 0 , is estimated assuming that is less or equal to 1. The posterior distributions of the key...
Book of invited conferences and accepted refereed papers submitted to the Procedings of the XII Congresso Anual da Sociedade Portuguesa de Estatística (Évora, Portugal, 2005)
The combined mark-recapture and line transect sampling methodology proposed by Alpizar-Jara and Pollock [Journal of Environmental and Ecological Statistics, 3(4), 311–327, 1996; In Marine Mammal Survey and Assessment Methods Symposium. G.W. Garner, S.C. Amstrup, J.L. Laake, B.F.J. Manly, L.L. McDonald, and D.C. Robertson (Eds.), A.A. Balkema, Rotte...
In community-level ecological studies, generally not all species present in sampled areas are detected. Many authors have proposed the use of estimation methods that allow detection probabilities that are <1 and that are heterogeneous among species. These methods can also be used to estimate community-dynamic parameters such as species local extinc...
Accurate assessment of the populations of mountain ungulates is difficult. Topography and behaviour of animals are important factors influencing detectability, on which direct methods are based. Sympathry with other wild and domestic ungulates increases error of dung identification. Other factors, such as the size of the area to be surveyed, or unm...
We used a probabilistic approach to address the influence of sampling artifacts on the form of species-area relationships(SAR's). We developed a model in which the increase in observed species richness is a function of sampling effort exclusively. We assumed that effort depends on area sampled, and we generated species--area curves under that model...
Distributing and supporting wildlife modeling software is difficult and expensive, and can be burdensome to the user who tries to install and run it. We developed a population dynamics model for the eastern wild turkey (Meleagris galapavo) that requires only access to the Internet. Users can select either a deterministic or a stochastic version of...
Hunting can have potentially significant impacts on wild turkey (Meleagris gallopavo) populations. We developed a 2-sex Leslie-type matrix model that predicts wild turkey population size for spring-summer and fall-winter periods to understand the effects of hunting on the dynamics of wild turkey populations in Virginia and West Virginia. A base mod...
The effect of fall either-sex hunting on eastern wild turkey (Meleagris gallopavo silvestris) populations is a common concern of wildlife agencies. We examined the effect of fall either-sex hunting on survival of radiotagged female wild turkeys from 1989 to 1994 in Virginia and West Virginia. We tested the hypothesis that survival of female wild tu...
We present a robust sampling methodology to estimate population size using line transect and capture-recapture procedures for aerial surveys. Aerial surveys usually underestimate population density due to animals being missed. A combination of capture-recapture and line transect sampling methods with multiple observers allows violation of the assum...
The combined mark-recapture and line transect sampling methodology proposed by Alpizar-Jara and Pollock (1997) is used to illustrate estimation of populations with prominent nesting structures (e.g. bald eagles). In the context ofa bald eagle population, the number of nests in a list frame corresponds to a pre-marked sample of nests, and an area fr...
We evaluate the effects of measurement error in population parameter estimation from a line transect sampling model,. characterize the error. distribution, and illustrate . using data from a controlled field experiment (Stakes data set, Laake 1978). We de-scribe a methodology to estimate the measurement error variance from a replicated experiment a...
