Species’ ranges arise from the interplay between environmental preferences, biotic and abiotic environmental conditions, and accessibility. Understanding of – and predictive models on – species distributions often build from the assumption that these factors apply homogenously within each species, but there is growing evidence for individual variation. Here, I use movement data to investigate individual-level decisions and compromises regarding the different costs and benefits influencing individuals’ geographic locations, and the species-level spatial patterns that emerge from these. I first developed a new method that uses tracking data to quantify individual specialisation in geographic space (site fidelity) or in environmental space (environmental specialisation). Applying it to two species of albatrosses, I found evidence of site fidelity but weak environmental specialisation. My results have implications for how limited research efforts are best-targeted: if animals are generalists, effort are best spent by understanding in depth individual patterns, i.e., better to track fewer individuals for long periods of time; whereas if animals tend to be specialists, efforts should be dedicated to tracking as many individuals as possible, even if for shorter periods. I then investigated individual migratory strategies and their drivers in nine North American bird species, using ringing/recovery data. I found latitudinal redistribution of individuals within the breeding and non-breeding ranges that generally did not follow textbook patterns (‘chain migration’ or ‘leapfrog migration’). Migratory individuals tend to trade off the benefits of migration (better tracking of climatic niche; better access to resources) and its costs (increasing with migratory distance). I found that birds are more likely to remain as residents in areas with warmer winter temperatures, higher summer resource surpluses and higher human population densities (presumably because of a buffering effect of urban areas). Overall, my results highlight the importance of considering individual variation to understanding the ecological processes underpinning species’ spatial patterns.

Piaget, Inhelder et Szeminska (1948) ont analysé l’évolution avec l’âge de la copie d’un dessin géométrique angulaire composé de deux traits formant deux angles. Les résultats obtenus sont interprétés dans le modèle stadiste piagétien. En accord avec le modèle de choix de stratégies de Siegler (1996 ; 2007) et l’importance de la variabilité intra-individuelle (Lautrey, 2003), notre thèse reprend cette analyse en faisant l’hypothèse que chaque participant dispose de plusieurs procédures. Nous explorons le répertoire de procédures des enfants âgés de 6 à 12 ans et des adultes en proposant la copie dans plusieurs conditions expérimentales : copie spontanée, plusieurs copies successives en demandant au participant de copier autrement, copie avec l’utilisation d’un instrument spécifique. Nous tentons ensuite d’enrichir ce répertoire en montrant au participant une procédure qu’il n’a pas pu produite seul. Les résultats obtenus sont cohérents avec les modèles pluralistes du développement : dès 10 ans, les enfants disposent de plusieurs procédures pour copier le dessin. Cependant, la mise en évidence de la variabilité intra-individuelle dans cette tâche est contrainte par les conditions expérimentales et les connaissances instrumentales et conceptuelles du participant, notamment l’acquisition du concept d’angle. / Piaget, Inhelder and Szeminska (1948) analysed the age evolution of a geometric drawing two-lines composed and forming an angle. The results obtained are interpreted in the stadist piagetian model. In accordance with the strategy choice model (Siegler, 1996; 2007) and with the intra-individual variability importance (Lautrey, 2003), our thesis takes up this analysis with hypothesis that each participant have at his disposal several procedures. We explore the 6 to 12 aged children and adult procedural repertory by suggesting the copy in different experimental conditions: spontaneous copy, several copies in proceeding (in other way), copy with specific instrument use,. We also attempt to complete this repertory by showing the participant a procedure he could not have produced by himself. The obtained results are suitable with plural models of development: from the age of ten, the children have several strategies for copying the drawing. However, the intra-individual variability observed in this task is forced by experimental conditions and instrumental and conceptual knowledge of the participant, in particular the acquisition of angle concept .

L'objectif général de cette thèse est d'explorer comment les enfantes perçoivent des traits de surface du langage à différents niveaux. Plus spécifiquement, on a examiné dans une population typique et atypique 1) la perception des traits acoustiques de bas-niveau et sa relation avec le développement du vocabulaire, et 2) la sensibilité à la fréquence des mots pour générer la représentation linguistique abstraite des catégories lexicales et de leur ordre relatif. Selon les modèles de bootstrapping, il est possible d'extraire des informations structurelles et abstraites de la langue à partir de traits acoustiques disponibles dans l'input et corrélés avec la structure linguistique sous-jacente (p. ex. grammaire et syntaxe). Pour examiner le lien entre la perception de bas niveau, les traits de surfaces et les connaissances grammaticales plus abstraites, cette thèse s'articule en deux parties principales. Dans la première partie, deux études longitudinales sont présentées. Chaque enfant était testé sur son seuil de discrimination auditive (avec un paradigme de traitement rapide) et sur une tâche de reconnaissance visuelle pour contrôler les compétences cognitives. Le seuil acoustique était évalué en utilisant des sons non-linguistiques (tons) dans un groupe d'enfants et linguistiques (syllabes) dans un autre groupe d'enfants à 9 mois pour déterminer si l'impact du traitement auditif est spécifique au langage. Enfin, le niveau de vocabulaire a été mesuré à 12, 14, 18 et 24 mois et un test cognitif (Mullen Scale) a été réalisé entre 18 et 20 mois comme supplémentaire contrôle cognitif. Les résultats montrent que les capacités mesurées sont prédictives du développement du vocabulaire chez les enfantes typiques. De plus, les enfants atypiques ont montré des capacités de traitement moins efficaces dans les modalités visuelle et acoustique. Dans la deuxième partie, le rôle de la fréquence des mots dans l'amorçage des catégories lexicales des mots de fonction et de contenu et leur ordre relatif est explorée. Les deux catégories lexicales sont différentes dans leur fonction linguistique, leurs caractéristiques phonologiques et leur fréquence dans la parole. Ainsi, leur catégorisation basée sur la fréquence pourrait constituer un mécanisme initial robuste pour acquérir les constructions de base de la langue. Comme les mots de fonction constituent une classe fermée, alors que les mots de contenu constituent de classes ouvertes, nous avons examiné si les nourrissons français âgés de 8 mois étaient sensibles à la fréquence des mots pour catégoriser les mots de fonction et pour les traiter comme des éléments non-remplaçables dans des classes fermées, et les mots de contenu comme des éléments librement remplaçables dans des classes ouvertes. Les cinq expériences de grammaire artificielle menées ont confirmé cette hypothèse. De plus, les nourrissons associent l'ordre relatif de ces catégories avec l'ordre des mots de base de leur langue maternelle, le français. Les participants atypiques ont montré des capacités de discrimination, de codage et de mémoire inférieures à leurs pairs typiques. En conclusion, ce travail a permis une meilleure compréhension des capacités de perception contribuant au développement du langage. De plus, cette thèse a identifié de potentiels marqueurs comportementaux pouvant servir à l'identification précoce des apprenants atypiques. / The purpose of this work is to explore how infants perceive surface features of language at different levels of processing. Specifically, in both typical and atypical populations, we examined 1) the processing of low-level auditory cues and its relationship with later language outcomes and 2) the sensitivity to word frequency to create abstract linguistic representations of lexical categories and their relative word order. Accordingly to bootstrapping models learners are able to extract abstract, structural and hence directly unobservable properties of the target language from perceptually available surface cues in the input that correlate with the underlying structure. Indeed, infants are sensitive to certain acoustic and phonological properties of the speech input, which in turn correlate with specific grammatical/syntactic structures. In order to map the link between the perception of these low-level, surface cues and more abstract grammatical knowledge, this work is organized in two main parts. In the first part, two longitudinal studies are reported. Each infant received an auditory discrimination threshold task (using the rapid auditory processing paradigm) followed by a habituation/visual novelty detection task used as a control for general cognitive skills. The auditory discrimination threshold was evaluated using non-linguistic (tones) sounds in one cohort of infants and linguistic sounds (syllables) in another cohort of infants at 9 months in order to investigate the language-specificity of the process within the auditory modality. Subsequently, infants' vocabulary was assessed at 12-14-18 and 24 months and a cognitive test (Mullen scale) was performed at 18-20 months as another control measure for early processing competence. Results show that early processing abilities are predictive of later vocabulary size in typical infants. Importantly, atypical participants exhibited slower and less efficient processing abilities in both visual and acoustic modality. In the second part, the role of word frequency in bootstrapping the basic lexical categories of function and content words and their relative order is explored. The two lexical categories differ in their linguistic functions, phonological makeup and frequency of occurrence. Thus, their frequency-based discrimination could constitute a powerful initial mechanism for infants to acquire the basic building blocks of language. As functors constitute closed classes, while content words come in open classes, we examined whether 8 month-old French monolinguals relied on word frequency to categorize and track functors as non-replaceable items in a closed class, and content words as freely replaceable items in open classes. In five artificial grammar-learning experiments we have found that infants treat frequent words as belonging to closed classes, and infrequent words as belonging to open classes and they map the relative order of these categories onto the basic word order of their native language, French, a functor-initial language. Importantly, atypical participants showed lower ability of discrimination, encoding and memory when compared to typically developing peers. Overall this work contributes to a better understanding of the perceptual abilities that directly contribute to language development. Moreover, it proposes possible behavioural markers that can be potentially useful in the early identification of atypical learners.

No description available.

Introduction: The current development strategy of population pharmacokinetic models is a complex and iterative process that is manually performed by modellers. Such a strategy is time-demanding, subjective, and dependent on the modellers’ experience. This thesis presents a novel model building tool that automates the development process of pharmacokinetic (PK) structural models. Methods: Modelsearch is a tool in Pharmpy library, an open-source package for pharmacometrics modelling, that searches for the best structural model using an exhaustive stepwise search algorithm. Given a dataset, a starting model and a pre-specified model search space of structural model features, the tool creates and fits a series of candidate models that are then ranked based on a selection criterion, leading to the selection of the best model. The Modelsearch tool was used to develop structural models for 10 clinical PK datasets (5 orally and 5 i.v. administered drugs). A starting model for each dataset was generated using the assemblerr package in R, which included a first-order (FO) absorption without any absorption delay for oral drugs, one-compartment disposition, FO elimination, a proportional residual error model, and inter-individual variability on the starting model parameters with a correlation between clearance (CL) and central volume of distribution (VC). The model search space included aspects of absorption and absorption delay (for oral drugs), distribution and elimination. In order to understand the effects of different IIV structures on structural model selection, five model search approaches were investigated that differ in the IIV structure of candidate models: 1. naïve pooling, 2. IIV on starting model parameters only, 3. additional IIV on mean delay time parameter, 4. additional diagonal IIVs on newly added parameters, and 5. full block IIVs. Additionally, the implementation of structural model selection in the workflow of the fully automatic model development was investigated. Three strategies were evaluated: SIR, SRI, and RSI depending on the development order of structural model (S), IIV model (I) and residual error model (R). Moreover, the NONMEM errors encountered when using the tool were investigated and categorized in order to be handled in the automatic model building workflow. Results: Differences in the final selected structural models for each drug were observed between the five different model search approaches. The same distribution components were selected through Approaches 1 and 2 for 6/10 drugs. Approach 2 has also identified an absorption delay component in 4/5 oral drugs, whilst the naïve pooling approach only identified an absorption delay model in 2 drugs. Compared to Approaches 1 and 2, Approaches 3, 4 and 5 tended to select more complex models and more often resulted in minimization errors during the search. For the SIR, SRI and RSI investigations, the same structural model was selected in 9/10 drugs with a significant higher run time in RSI strategy compared to the other strategies. The NONMEM errors were categorized into four categories based on the handling suggestions which is valuable to further improve the tool in its automatic error handling. Conclusions: The Modelsearch tool was able to automatically select a structural model with different strategies of setting the IIV model structure. This novel tool enables the evaluation of numerous combinations of model components, which would not be possible using a traditional manual model building strategy. Furthermore, the tool is flexible and can support multiple research investigations for how to best implement structural model selection in a fully automatic model development workflow.

<p>  </p> <p>Appetitive sensations are widely viewed as important signals for eating decisions. Intra- and inter-individual variability have been reported in short-term studies, but it is still unknown whether individual differences are consistent over time and, whether individuals at the appetite extremes vary in energy intake. Therefore, a seventeen-week observational study was conducted to examine the stability of appetitive sensations (hunger, fullness, and thirst), implications of individual differences in appetite on energy intake and eating patterns, as well as associations between appetitive sensations and selected individual characteristics (age, gender, BMI). </p> <p>Ninety-seven (90 completers) healthy adults recorded the intensity of their hunger, fullness, and thirst hourly during all waking hours and reported their energy intake  for three days at weeks 1, 9 and 17. There were marked and stable inter-individual differences for each sensation over the 17 weeks: hunger (ANOVA, p<0.001, correlation coefficients of ratings between weeks: week 1 vs week 9, r=0.72 (p<0.001), week 1 vs week 17, r=0.67 (p<0.001), week 9 vs week 17, r=0.77 (p<0.001)), fullness (ANOVA, p<0.001, correlation coefficients of ratings between weeks: week 1 vs week 9 r=0.74 (p<0.001), week 1 vs week 17, r=0.71 (p<0.001), week 9 vs week 17, r=0.81 (p<0.001)), and thirst (ANOVA, p<0.001, correlation coefficients of ratings between weeks: week 1 vs week 9 r=0.82 (p<0.001), week 1 vs week 17, r=0.81 (p<0.001), week 9 vs week 17, r=0.88 (p<0.001)). Cross-correlation functions revealed energy intake and eating pattern exerted stronger effects on appetitive sensations than the reverse. However, the absolute effect sizes of the directional effects were small. No robust effects of the studied individual characteristics (gender, age, BMI) were observed. The primary finding is that acute and chronic sensations of hunger, fullness and thirst are stable across individuals, but are poor predictors of energy intake. </p> <p>This dissertation focuses on the study above, but as part of the training experience, two additional studies were conducted. One entailed appetite concept training to improve the validity of appetite measurements. A potential barrier to accurate appetite measurement is low conceptual understanding by study participants and resulting poor sensitivity and accuracy of responses. While each appetitive sensation is independent and has a unique definition, reported similar patterns between appetitive sensations in multiple studies raise questions about whether participants fully comprehend appetite concepts and provide accurate responses. To overcome this potential limitation, appetite concept materials were developed, and two groups of individuals were provided training either with these materials or unrelated sensory information followed by measurement of appetite responses to five different pre-loads. This study terminated early due to the COVID-19 pandemic and thus we cannot draw a conclusion for now due to the limited number of participants.  </p> <p>A second study sought to gain insights on the sensory qualities of fatty acids as part of an effort to determine if oral fat detection is based, in part, on gustatory cues. It has been argued that if fat taste is a primary, the sensations imparted by fats should yield unique percepts and these may be determined by fatty acid chain length. In particular, because acids impart a sour taste, free fatty acids may simply be detected as sour. The fat taste study entailed measurement of intensity ratings with or without sour adaptation (to assess sour notes), tongue locations of taste detection, and subjective descriptors of fatty acids. This study examined intensity and quality ratings of NEFA's ranging from C2 to C18. Oral sites and the time course of sensations were also monitored. Given all NEFA contain carboxylic acid moieties capable of donating hydrogen ions, the primary stimulus for sour taste, testing was conducted with and without sour adaptation to explore the contribution of sour taste across the range of NEFA. Short chain NEFA (C2-C6) were rated as predominantly sour, and this was diminished in C2 and C4 by sour adaptation. Medium chain NEFA (C8-C12) were rated as mainly irritating with long chain NEFA (C18) described mostly as bitter. The latter may reflect the lack of “fatty” lexicon to describe the sensation. Short chain NEFA were mostly localized to the anterior tongue and were of rapid onset. The sensation from medium chain NEFA was attributed to the lateral tongue while medium and long chain NEFA sensations were predominantly localized to the back of the tongue and throat and had a longer lag time. The findings indicate there is a systematic transition of NEFA taste quality and irritation with increments in chain length and this is consistent with multiple modes of transduction.</p>

Située dans le Nord-Est de la Colombie-Britannique, la formation de Montney est une zone d’exploitation gazière par fracturation hydraulique capable de rejeter des contaminants comme les éléments-traces, dont certains peuvent affecter la santé des femmes enceintes et leur enfant. Notre étude visait 1) l’évaluation de l’exposition de femmes enceintes de cette région à plusieurs éléments-traces à partir d’échantillons urinaires répétés, 2) la comparaison des concentrations à celles de populations de référence et 3) l’évaluation de la variabilité intra- et inter-individuelle dans les concentrations urinaires. 85 femmes enceintes participant à notre étude Exposures in the Peace River Valley (EXPERIVA) ont fourni 1 échantillon urinaire quotidien pendant 7 jours consécutifs. 20 éléments-traces y ont été analysés. Des statistiques descriptives ont été effectuées et la variabilité a été évaluée à l’aide du coefficient de corrélation intraclasse (CCI). Les concentrations urinaires médianes étaient supérieures à celles des populations de référence pour le baryum (2 fois), le cobalt (3 fois) et le strontium (2 fois). Durant la semaine, le 95e centile de référence était dépassé au moins 1 fois par de nombreuses participantes pour le baryum (58%), le cobalt (73%), le cuivre (29%), le manganèse (28%), le sélénium (38%), le strontium (60%) et le vanadium (100%). Les CCI variaient de 0.288 à 0.722 selon l’élément-trace. Nos résultats laissent supposer que les femmes enceintes de cette région peuvent être particulièrement exposées à certains éléments-traces (baryum, cobalt, cuivre, manganèse, sélénium, strontium et vanadium) et qu’un seul échantillon urinaire peut être insuffisant pour estimer adéquatement l’exposition à certains éléments-traces. / Located in Northeastern British-Columbia, the Montney formation is an important area of gas exploitation by hydraulic fracturing which can release contaminants like trace elements. Gestational exposure to these contaminants may lead to deleterious developmental effects. Our study aimed to assess gestational exposure to trace-elements in women living in this region through repeated urinary measurements, to compare these values to those from reference populations, and to evaluate inter- and intra-individual variability. 85 pregnant women participating in the Exposures in the Peace River Valley (EXPERIVA)study provided daily spot urine samples over 7 consecutive days. Samples were analyzed for 20 trace elements. Descriptive statistics were performed, and variability was evaluated through intraclass correlation coefficient (ICC) calculation for each trace element. When compared with those from North American populations, median urinary levels were higher in our population for barium (2 times), cobalt (3 times) and strontium (2 times). The 95th percentile of reference populations was exceeded at least 1 time by many participants during the week for barium (58%), cobalt (73%), copper (29%), manganese (28%), selenium (38%), strontium (60%) and vanadium (100%). ICCs varied from 0.288 to 0.722 depending on the trace element. Our results suggest that pregnant women living in this region may be more exposed to certain trace elements (barium, cobalt, copper, manganese, selenium, strontium, and vanadium), and that one urine spot sample could be insufficient to adequately estimate exposure to certain trace elements.

Although the research literature supports the notion of language growth trajectories, primarily in monolingual English children, the shape and direction of English-language learners' (ELLs) language growth trajectories are largely unknown. The present study examined the shape of ELLs' language growth trajectories by estimating the initial status and the growth rates of specific oral language skills (mean length of utterance in words (MLUw), number of different words (NDW), and words per minute (WPM)) in each language during the first 3 years of formal schooling. This study was framed from the perspective of language as a dynamic system, composed of linguistic subsystems that change over time. This study utilized secondary data from a larger project, the Bilingual Language Literacy Project (BLLP), which collected narrative retell language samples produced in Spanish and English from ELL children. The final longitudinal dataset used in this study consisted of 12,248 oral narrative language samples (6,516 Spanish; 5,732 English) that were produced by 1,723 ELLs. This study examined the effect of three predictors on language growth: academic semester (metric of time), gender, and schooling. Growth curve model (GCM) testing was used to profile the longitudinal growth of the ELLs' oral language skills in Spanish and English over time. This study had a number of important findings regarding change over time, intra- and inter-individual variability, and the impact of initial status on growth. With regard to change over time: MLUw, NDW, and WPM demonstrated growth over time in Spanish and English; the shapes of Spanish (curvilinear, non-monotonic, and continuous) and English growth (linear, non-monotonic, and discontinuous) were similar within-language; language growth in Spanish was predicted by academic semester and gender; and language growth in English was predicted by academic semester, gender, and schooling. With regard to intra- and inter-individual variability: significant intra-individual differences in the growth of all the oral language measures, across each wave of measurement, were found for both languages; significant intra-individual differences in the initial status of participants for all the oral language measures were found for both languages; significant inter-individual differences in the growth rates were found for WPM-Spanish; and significant inter-individual differences in the growth rates were found for all the oral language measures in English. With regard to the impact of initial status on growth: the growth of MLUw-Spanish was systematically related to initial status (lower performers at initial status may not catch up to higher performers); the growth of NDW- and WPM-Spanish were unrelated to its initial status (lower performers at initial status may, or may not catch up to higher performers); and the growth of MLUw-, NDW-, and WPM-English was systematically related to initial status (lower performers at initial status may catch up to higher performers). With regard to the co-development of interconnected subsystems, qualitative observations (non-empirically tested) based on visual inspection and GCM estimates provided initial insight into the possible co-development occurring within- and across-languages. The present study broke new ground by specifying the shape of growth for MLUw, NDW, and WPM in the Spanish and English of ELLs during their first 3 years of formal schooling. The study had a number of methodological limitations that will guide and motivate future work on the language growth of ELLs. / Communication Sciences

The biological characteristics of fisheries stocks that are assessed for management considerations are rarely homogeneous over time or space. However, stock assessment scientists largely ignore this heterogeneity in their models. This thesis addresses the effects of spatial and temporal heterogeneity on stock assessment models using Atlantic Weakfish (Cynoscion regalis) as a case study. First, spatial and temporal variation was incorporated into length-, weight-, and maturity-at-age estimates using mixed-effects models (Chapter Two). The resulting heterogeneous weight and maturity parameters then were applied to per-recruit analyses to examine the sensitivity of biological reference points to spatial and temporal variation in life history attributes (Chapter Three). Mixed-effects life history models incorporating spatial and temporal variation revealed distinct regional and annual trends that were not visible from standard homogeneous models. In several instances, the homogeneous modelling approach produced life history estimates that varied significantly from the spatial and temporal means produced by the heterogeneous models. In some cases, this difference was so great that the homogeneous means were much higher or lower than the heterogeneous means for all regions or years. Minimized AIC statistics revealed that spatially and temporally integrated mixed-effects models were more robust and descriptive of Atlantic Weakfish life history than the standard homogeneous models. Per-recruit and biological reference points derived from these life history estimates in Chapter Three were found to be highly sensitive to spatial and temporal variations in weight parameters. In several cases, reference points used as management targets were so significantly different that ignoring spatial and temporal heterogeneity in Atlantic Weakfish life history would likely cause overfishing and decline of Weakfish in certain regions and years. / Master of Science

A percepção e interpretação da interação de indivíduos e populações com o ambiente e a forma como tal relação condiciona sua distribuição espacial é questão-chave e recorrente em estudos ecológicos. Padrões de uso de área observados para populações emergem em ultima análise da variabilidade entre seus indivíduos em selecionar habitats e interagir com os mesmos. Este estudo teve como foco o uso de área pela população do boto-cinza, Sotalia guianensis, e sua variabilidade individual no estuário de Cananeia, localizado na costa sudeste do Brasil (25°03\' S; 47°55\' W), durante o verão e o inverno de 2015 e o verão de 2016. Parâmetros ambientais e geográficos (distâncias da desembocadura de rios, da entrada do estuário e de áreas urbanas, profundidade, maré e autocorrelação espacial) foram testados para explicar a distribuição da população e de seus indivíduos a partir de funções de probabilidade de seleção de recursos (RSPF) em modelos aditivos generalizados (GAM). Onze indivíduos fotoidentificados com 18 ou mais recapturas foram avaliados com o uso de modelos individuais de ocupação e sua interpretação foi subsidiada por estimativas de áreas domiciliares obtidas a partir de kerneis fixos de densidade. Nas três temporadas a população apresentou densidades de grupos desiguais ao longo do estuário e todas as variáveis, com exceção da distância de áreas urbanas, explicaram as probabilidades de presença observadas. Análises individuais revelaram discrepâncias nos tamanhos e disposição geográfica de áreas domiciliares e diferenças na composição e estimativa dos parâmetros selecionados para cada indivíduo. A variabilidade individual na população deve ter papel fundamental em termos de utilização do espaço e seleção de habitat pelo boto-cinza no estuário local. / Understanding and interpreting the interaction of individuals and populations with the environment and how this relationship outlines their spatial distribution is a key question common in ecological studies. Area use patterns observed for populations are ultimately an outcome from individual variability in habitat selection and their interaction with such environments. Are use and habitat selection by the population of Guiana dolphins, Sotalia guianensis, and its individual variability were accessed in the Cananeia estuary (25°03\' S; 47°55\' W), southeastern Brazil, during the summer and winter of 2015 and the summer of 2016. Environmental and geographic parameters were estimated aiming to explain population distribution and differences within individuals. For this purpose, resource selection probability functions (RSPF) were applied in generalized additive models (GAM). Covariates tested included: distance to river mouths, distance to the estuary entrance, distance to urban areas, depth and tide. Geographic coordinates were used to model spatial autocorrelation. Eleven photo-identified individuals had their occupancy modelled and accessed in relation to their home range obtained from fixed kernel densities estimates. The population exhibited patchy group densities throughout the estuary in all seasons. Except from distance to urban areas all variables were selected in our final model for the population\'s RSPF. Individual analysis revealed discrepancies in size and location of home ranges which lead to remarkable differences in the composition and estimates of parameters selected in the models for each individual.