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Rotas migratórias, áreas de uso intenso e padrões de mergulho de tartarugas-de couro (Dermochelys coriacea) no Atlântico Sul Ocidental / Migratory routes, high use areas and dive patterns of leatherback turtles (Dermochelys coriacea) in the Southwest AtlanticMaria de los Milagros López Mendilaharsu 09 February 2011 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As tartarugas marinhas são espécies ameaçadas, altamente migratórias que
apresentam um ciclo de vida longo e uma ampla distribuição geográfica. Assim,
melhorar a nossa compreensão sobre a ecologia espacial das tartarugas marinhas é
essencial para a elucidação de aspectos da sua história de vida e para o
desenvolvimento de medidas eficazes de conservação. Esta tese compreende um
conjunto de artigos ou capítulos que visam contribuir ao conhecimento da ecologia
espacial da tartaruga-de-couro, Dermochelys coriacea. Este estudo utilizou novas
tecnologias como à telemetria por satélite (que proporciona um método útil para
monitorar os movimentos de espécies migratórias) e um conjunto de ferramentas de
geoprocessamento como abordagem metodológica que visou: examinar os
movimentos e migrações da tartaruga-de-couro, identificar áreas de uso intenso e
padrões espaço-temporais no uso do habitat, e integrar dados biológicos e
oceanográficos para descrever as estratégias comportamentais desta espécie. Cinco
tartarugas-de-couro (um subaduto, dois machos adultos e duas fêmeas adultas)
foram equipadas com transmissores por satélite no Atlântico Sul Ocidental entre
2005 e 2008. Além de fornecer dados de localização geográfica os tansmissores
permitiram registrar informações de mergulho tais como profundidade e duração
máxima e media dos mergulhos, perfis completos de mergulhos individuais e dados
de temperatura do mar. Movimentos e migrações de tartarugas-de-couro marcadas
no Atlântico Sul foram documentados pela primeira vez. Alem disso, foi posível
identificar áreas de uso intenso (ou alimentação) previamente desconhecidas para a
espécie, assim como uma residência sazonal nestas áreas localizadas em águas
tropicais e temperadas fora da costa sul-americana (19-45S). A sazonalidade dos
movimentos esteve intimamente associada a processos físicos sazonais de pequena
e mesoescala. Dependendo do ambiente marinho explorado, durante os períodos de
residência, as tartarugas apresentaram diferentes estratégias alimentares
identificadas através da análise dos padrões de mergulho. / Sea turtles are long-lived, highly migratory endangered species with a wide
distribution. Thus improving our knowledge of the spatial ecology of sea turtles is
essential for elucidating aspects of their life history and for the development of
effective conservation measures. This thesis comprises a collection of articles or
chapters that aim to contribute to the knowledge of the spatial ecology of the
leatherback turtle, Dermochelys coriacea. This study used new technologies such as
satellite telemetry (which provides a useful approach for tracking the movements of
migratory species) and a set of geoprocessing tools as a methodological approach
that aimed to: examine the movements and migrations of leatherback turtles, identify
high use areas and spatio-temporal patterns of habitat use, and integrate biological
and environmental data to describe foraging strategies of this species.
Five leatherback turtles (a subadut, two adult males and two adult females) were
fitted with satellite transmitters in the Southwest Atlantic between 2005 and 2008.
Besides providing geographical location data the transmitters also recorded dive
information such as mean and maximum dive depth and duration, individual dive
profiles and water temperature data. For the first time the movements and migrations
of leatherback turtles tagged in the South Atlantic were documented. Previously
unidentified high use areas (or foraging areas) were recognized for this species, also
a seasonal residence along those areas located in tropical and temperate areas off
the coast of South America (19-45 S). The seasonal movements were closely
associated with small and mesoscale physical seasonal processes. Depending on
the marine environment exploited during periods of residence, the turtles showed
different foraging strategies identified through the analysis of the diving patterns.
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Habitats adequados e aspectos ecológicos do tubarão-baleia (Rhincodon, typus Smith 1828) no Oceano Atlântico Sudoeste e EquatorialROCHA, Bruno César Luz 01 December 2016 (has links)
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Previous issue date: 2016-12-01 / CNPQ / Compreender detalhadamente a história de vida do tubarão-baleia é fundamental para
assegurar a sua conservação. No entanto, apesar da espécie possuir distribuição circumglobal
e ser relativamente bem estudada entre os elasmobrânquios, ainda existe uma grande escassez
de informações relacionadas a muitos dos seus aspectos ecológicos e biológicos em todo o
mundo, principalmente no que diz respeito aos seus movimentos migratórios e ciclo
reprodutivo. No Oceano Atlântico, particularmente, a espécie vem sendo investigada
majoritariamente no Golfo do México/ Mar do Caribe, permanecendo uma grande lacuna para
o restante dessa bacia oceânica. O presente estudo representa a primeira iniciativa de
investigação da distribuição espacial do tubarão-baleia em escala oceânica no sudoeste do
Atlântico baseada em registros de ocorrências na costa do Brasil, além de ter sido o primeiro
trabalho também sobre o rastreamento de tubarões-baleia na região equatorial. Com o objetivo
de complementar o conhecimento acerca da distribuição geográfica e movimentação do
tubarão-baleia nas regiões sudoeste e equatorial do oceano Atlântico, foram empregadas
técnicas modernas de modelagem ecológica e rastreamento via satélite, além da utilização do
método tradicional de censo visual para identificação de aspectos populacionais no
Arquipélago de São Pedro e São Paulo (ASPSP). Primeiramente, foram realizadas predições
referentes à distribuição espacial de habitats adequados para alimentação e inferências sobre a
influência de variáveis ambientais específicas para ocorrência do tubarão-baleia na costa do
Brasil/ sudoeste do oceano Atlântico. Em seguida, a sazonalidade, a abundância relativa e a
estrutura populacional dos tubarões-baleia que visitam o ASPSP foram investigadas,
incluindo inferências acerca da importância de ecossistemas insulares oceânicos para a
parcela madura da espécie. Por fim, na terceira parte da Tese, os deslocamentos horizontais e
verticais de tubarões-baleia marcados com transmissores via satélite no ASPSP foram
descritos e o comportamento de mergulho avaliado com relação a fatores biofísicos e
ambientais específicos. Os resultados obtidos no presente estudo são relevantes não somente
para a conservação do tubarão-baleia, mas para o ecossistema marinho na costa do Brasil, de
uma forma geral, posto que o mapeamento de habitats ideais para alimentação da espécie
também serve para identificar áreas ecologicamente importantes para outras espécies.
Ademais, a identificação do ASPSP como uma área importante para a parcela adulta dos
tubarões-baleia ressalta sua importância ecológica no ciclo de vida da espécie, destacando a
necessidade de se envidar maiores esforços para a conservação do local. / Understanding the life history of the whale shark is fundamental to assure its conservation.
However, in spite of the circumglobal distribution of the species and the fact that it is
relatively well studied among elasmobranchs, there is still a serious lack of information
concerning its biology in the entire world, mainly regarding its migratory movements and
reproductive cycle. In the Atlantic Ocean, particularly, the whale sharks have been
predominantly studied in the Gulf of Mexico/Caribbean Sea, with a big gap still remaining for
the rest of this ocean basin. Aiming to help to fill this gap on geographical distribution and
movement patterns of whale sharks in the Equatorial and Southwest Atlantic regions, modern
techniques of ecological modelling and satellite tracking were used, in addition to the use of
scientific traditional method of visual census to describe the population aspects of the species
in the archipelago of São Pedro and São Paulo (ASPSP). Firstly, geographical predictions of
suitable habitats for whale shark feeding and inferences of the influence of specific
environmental variables on the occurrence distribution in the Brazilian coast/southwestern
Atlantic Ocean were conducted to describe the potential spatial distribution of the species.
Then, the seasonality of occurrence, relative abundance and population structure of the whale
sharks visiting the ASPSP were investigated, including a discussion regarding the importance
of the insular oceanic ecosystems to the mature portion of the species. Finally, in the third part
of the thesis, the horizontal and vertical displacements of whale sharks satellite tagged off
ASPSP were described and the diving behavior assessed in relation to specific biophysical
and environmental factors. The present study represents the first oceanic-scale spatial
distribution investigation effort in the southwest Atlantic on whale shark presence records
from the Brazilian coast, besides of being the first study using satellite tracking on the species
in the equatorial Atlantic as well. The results presented here are of great relevance not only
for the whale shark conservation but also for the Brazilian marine ecosystem, as the mapping
of suitable feeding habitats could contribute to the identification of areas of ecological
importance to other marine species. Moreover, the identification of the ASPSP as an
important area for the mature part of whale shark populations highlights its ecological
relevance on the species life cycle, emphasizing the need of increasing the conservation
efforts in this habitat.
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FORAGING ECOLOGY OF NESTING GREEN, OLIVE RIDLEY, AND LEATHERBACK TURTLES FROM NORTHWEST COSTA RICAAlison Jenele Meeth (10716291) 28 April 2021 (has links)
<div>Understanding what sea turtles are feeding on and where they are feeding is key to understand their overall biology and will aid in understanding what type of management actions are necessary in order to conserve and protect these endangered species. Here I set out to (1) examine the population-level isotopic profiles of three sea turtle species in the Eastern Tropical Pacific; (2) determine differences in their foraging strategies; (3) attempt to gain insights about their pre-nesting origins; and (4) determine whether body size would influence the isotopic values of an individual turtle.</div><div>Stable isotope analysis (δ<sup>13</sup>C and δ<sup>15</sup>N values) was conducted on tissue samples from 52 sea turtles nesting on Playa Cabuyal, Costa Rica; 28 Pacific green (<i>Chelonia mydas</i>), 20 olive ridley (<i>Lepidochelys olivacea</i>), and 4 leatherback (<i>Dermochelys coriacea</i>). Nine satellite transmitters were also deployed on a separate population of post-nesting Pacific green turtles from Playa Cabuyal.</div><div>Based on isotopic profiles, green turtles in the Eastern Tropical Pacific were found to be feeding at a higher trophic level when compared to green turtles in other regions and this was supported by their increased δ<sup>15</sup>N values (16 ± 0.8 ‰). Rather than shifting to herbivory as adults, green turtles foraging in the eastern Pacific are potentially remaining omnivorous. Tracking data further confirmed that green turtles are coastal migrators and are probably inhabiting areas with high δ<sup>15</sup>N values within this region. Olive ridley turtles are exhibiting similar behavior to olive ridley turtles elsewhere due to minimal variance in their isotopic profiles (δ<sup>13</sup>C = -15.1 ± 0.7 ‰, δ<sup>15</sup>N =14.2 ± 0.8 ‰) and their known nomadic behavior. Although a small sample size, leatherback turtles showed a shift in their foraging habitats suggesting they are also feeding inshore in addition to their pelagic behavior due to their increased δ<sup>13</sup>C values (-15.5 ± 0.4 ‰). Further, as body size increased in olive ridley’s, the δ<sup>15</sup>N values significantly decreased suggesting that larger turtles prefer deeper pelagic waters with less enriched N isotope concentrations. However, in order to rule out possible external factors influencing this relationship, knowing where the turtle is originating from is crucial. This project provides data for developing isoscapes in the Eastern Tropical Pacific to aid in understanding the spatial distribution of sea turtles and their foraging grounds and the impact that foraging area may have on overall biology of these species. This information can be used to prioritize high use foraging habitats and determine the most effective management practices for protecting these species and the prey and habitat on which they rely.</div>
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Movement ecology of long-distance migrants: insights from the Eleonora's falcon and other raptors / Ecología del movimiento de migradores de larga distancia: ejemplos con el halcón de Eleonora y otras rapacesMellone, Ugo 28 June 2013 (has links)
No description available.
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Niche partitioning among fur sealsPage, Brad, page.bradley@saugov.sa.gov.au January 2005 (has links)
At Cape Gantheaume, Kangaroo Island (South Australia), adult male, lactating female
and juvenile New Zealand (NZ) and Australian fur seals regularly return to the same
colony, creating the potential for intra- and inter-specific foraging competition in nearby
waters. I hypothesised that these demographic groups would exhibit distinct foraging
strategies, which reduce competition and facilitate their coexistence. I analysed the diet
of adult male, adult female and juvenile NZ fur seals and adult male Australian fur seals
and studied the diving behaviour of adult male and lactating female NZ fur seals and the
at-sea movements of juvenile, adult male and lactating female NZ fur seals. Female diet
reflected that of a generalist predator, influenced by prey availability and their
dependant pups� fasting abilities. In contrast, adult male NZ and Australian fur seals
used larger and more energy-rich prey, most likely because they could more efficiently
access and handle such prey. Juvenile fur seals primarily utilised small lantern fish,
which occur south of the shelf break, in pelagic waters. Juveniles undertook the longest
foraging trips and adult males conducted more lengthy trips than lactating females,
which perform relatively brief trips in order to regularly nurse their pups. Unlike lactating
females, some adult males appeared to rest underwater by performing dives that were
characterised by a period of passive drifting through the water column. The large body
sizes of adult males and lactating females facilitated the use of both benthic and pelagic
habitats, but adult males dived deeper and for longer than lactating females, facilitating
vertical separation of their foraging habitats. Spatial overlap in foraging habitats among
the age/sex groups was minimal, because lactating females typically utilised continental
shelf waters and males used deeper water over the shelf break, beyond female foraging
grounds. Furthermore, juveniles used pelagic waters, up to 1000 km south of the
regions used by lactating females and adult males. The age and sex groups in this
study employed dramatically different strategies to maximise their survival and
reproductive success. Their prey and foraging habitats are likely to be shaped by body
size differences, which determine their different physiological constraints and metabolic
requirements. I suggest that these physiological constraints and the lactation
constraints on females are the primary factors that reduce competition, thereby
facilitating niche partitioning.
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Niche partitioning among fur sealsPage, Brad, page.bradley@saugov.sa.gov.au January 2005 (has links)
At Cape Gantheaume, Kangaroo Island (South Australia), adult male, lactating female
and juvenile New Zealand (NZ) and Australian fur seals regularly return to the same
colony, creating the potential for intra- and inter-specific foraging competition in nearby
waters. I hypothesised that these demographic groups would exhibit distinct foraging
strategies, which reduce competition and facilitate their coexistence. I analysed the diet
of adult male, adult female and juvenile NZ fur seals and adult male Australian fur seals
and studied the diving behaviour of adult male and lactating female NZ fur seals and the
at-sea movements of juvenile, adult male and lactating female NZ fur seals. Female diet
reflected that of a generalist predator, influenced by prey availability and their
dependant pups� fasting abilities. In contrast, adult male NZ and Australian fur seals
used larger and more energy-rich prey, most likely because they could more efficiently
access and handle such prey. Juvenile fur seals primarily utilised small lantern fish,
which occur south of the shelf break, in pelagic waters. Juveniles undertook the longest
foraging trips and adult males conducted more lengthy trips than lactating females,
which perform relatively brief trips in order to regularly nurse their pups. Unlike lactating
females, some adult males appeared to rest underwater by performing dives that were
characterised by a period of passive drifting through the water column. The large body
sizes of adult males and lactating females facilitated the use of both benthic and pelagic
habitats, but adult males dived deeper and for longer than lactating females, facilitating
vertical separation of their foraging habitats. Spatial overlap in foraging habitats among
the age/sex groups was minimal, because lactating females typically utilised continental
shelf waters and males used deeper water over the shelf break, beyond female foraging
grounds. Furthermore, juveniles used pelagic waters, up to 1000 km south of the
regions used by lactating females and adult males. The age and sex groups in this
study employed dramatically different strategies to maximise their survival and
reproductive success. Their prey and foraging habitats are likely to be shaped by body
size differences, which determine their different physiological constraints and metabolic
requirements. I suggest that these physiological constraints and the lactation
constraints on females are the primary factors that reduce competition, thereby
facilitating niche partitioning.
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Representatividade das áreas prioritárias e protegidas nas zonas costeira e marinha brasileiras considerando os movimentos das baleias-jubarte, Megaptera novaeangliae (Borowski, 1781)Castro, Franciele Rezende de 09 February 2012 (has links)
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Previous issue date: 2012-02-09 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O estabelecimento de um sistema representativo de Áreas Protegidas é parte das estratégias de conservação das baleias-jubarte (Megaptera novaeangliae Borowski, 1781). Este estudo teve como objetivo avaliar a representatividade das Áreas Prioritárias para a Conservação (APCs) e das Unidades de Conservação (UCs) considerando os movimentos desta espécie na costa brasileira. O uso destas Àreas por baleias-jubarte foi medido pela freqüência da ocorrência de posições registradas no interior das APCs e UCs. Dados de localização por telemetria satelital foram filtrados e modelados pelo Modelo de Estado e Espaço (State-Space Model) e sobrepostos aos polígonos representantes de cada APC e UC (banco de dados Ministério do Meio Ambiente - MMA e Instituto Brasileiro do Meio Ambiente e Recursos Renováveis – IBAMA). As análises foram realizadas com o software R 2.11.1 e ArcGIS 9.3. De um total de 131 APCs registradas na, atualmente, conhecida área de distribuição da espécie na costa brasileira 53 Áreas Prioritárias para a Conservação foram usadas por baleias-jubarte. As frequências foram maiores dentro do que fora de APCs (p<0,001). E de 73 UCs registradas dentro da mesma área, 13 Unidades de Conservação foram usadas pela espécie e as freqüências foram menores dentro do que fora de UCs
(p <0,001). Concluímos que as novas APCs identificadas, Áreas ainda não protegidas, são representativas considerando o movimento das baleias-jubarte. Já as Unidades de Conservação considerando a reduzida freqüência de ocorrência de baleias nestas Áreas já manejadas apresentam baixa representatividade. Estudos de telemetria por satélite mostram-se úteis para avaliar a representatividade das Áreas Prioritárias e Protegidas na conservação indireta de baleias-jubarte, contribuindo para estratégias de gestão da espécie em águas brasileiras. / The establishment of representative systems of Protected Area is part of conservation strategies of humpback whales (Megaptera novaeangliae Borowski, 1781) conservation. This study aimed to evaluate the use of the Priority Areas for Conservation (PACs) and Conservation Units (CUs) by humpback whale along the Brazilian coast. The use was measured by the frequency of positions registered inside the PACs and CUs. Locations data from satellite telemetry were filtered and modeled by State Space Model and overlapped on the PACs and CUs shapes (Ministério do Meio Ambiente - MMA and Instituto Brasileiro do Meio Ambiente e Recursos Renováveis – IBAMA databases). The analyses were performed using the software R 2.11.1 and ArcGIS 9.3. From a total of 131 PACs, recorded in the currently known limit of distribution in the Brazilian coast, 53 Priority Areas for Conservation were used by humpback whales. The frequencies were higher inside the PACs than outside (p<0,001). And from 73 UCs recorded, 13 Conservation Units were used by humpback whales and the frequencies were lower inside the CU’s than outside (p<0,001). We concluded that the PACs identified, areas not yet protected, are representative considering the movement of humpback whales. However, CU’s are still poorly representative for humpback whales conservation considering the low frequency of occurrence of whales in these areas already managed. Satellite telemetry studies are useful to assess the representativeness of Priority and Protected Areas in the conservation of humpback whales indirectly, contributing to strategies for management of the species in Brazilian waters.
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Spatial Ecology of Inter- and Post-nesting Green Turtles (Chelonia mydas) on Bioko Island, Equatorial GuineaEmily K Mettler (6620087) 10 June 2019 (has links)
<p>Effective conservation
strategies for sea turtles require knowledge of animal movements and protection
of biologically important habitats and life history stages. For breeding adult
sea turtles, understanding both their inshore and pelagic spatial patterns is
imperative to the successful protection of the species and the accurate
identification of their vulnerabilities. This study provides insight into the inter-nesting,
post-nesting, and foraging movements of green sea turtles (<i>Chelonia mydas</i>) that nest on Bioko Island, Equatorial Guinea, by
using satellite telemetry to track green turtles (n=12) during two nesting
seasons (2017-18, 2018-19), and as they migrated to foraging grounds after the
nesting season. These tracks were fit with a switching state space model to
characterize movements, and then analyzed in relation to environmental and
anthropogenic factors. Dive depth data was also used to determine utilization
patterns within the water column. The 12 tagged turtles migrated for an average
of 1064 km to two distinct foraging grounds, with 10 migrating west for an
average of 1115 km to the coastal waters of Ghana, and 2 migrating south for an
average of 1563 km to the coastal waters of Angola. Migrating turtles used both
direct, pelagic migration strategies, and biphasal, coastal strategies, which
included intermittent foraging throughout migrations. Dive depths varied
depending on behavior, with an average of 19.3 m during inter-nesting, 12.6 m
during migration and 8.5 m during foraging. Knowledge of inter-nesting habitat
use, migration patterns, and foraging ground locations will be critical for the
development of marine conservation management plans in the Gulf of Guinea and
aide in sea turtle conservation efforts throughout the area. Additionally, spatial
and dive depth data can inform zonal fishing regulators and provide information
needed for modifications to fishing practices and gear that is most likely to
reduce sea turtle bycatch. These data will provide a more complete
understanding of marine areas critical to sea turtle conservation and aide in
sustainable economic development in the Gulf of Guinea.</p><br>
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Health, disease, mortality and survival in wild and rehabilitated harbor seals (Phoca vitulina) in San Francisco Bay and along the central California coastGreig, Denise J. January 2011 (has links)
Conventional methods for health assessment of wild-caught and stranded seals were used to describe the disease status of harbor seals in California. Clinical chemistry, infectious disease prevalence, immune function, and contaminant data were collected to evaluate harbor seal health with data collected from three groups of seals. Wild-caught seals of all ages were sampled at two locations: San Francisco Bay (a heavily urbanized estuary) and Tomales Bay (a less developed control site). Stranded seals entered rehabilitation from a more extensive portion of the California coast which included the locations where seals were caught. Hematology reference intervals were generated to provide a baseline for health assessment among the seals. Individual variability in blood variables among seals was affected by age, sex, location, and girth. Disease surveillance focused on pathogens known to cause lesions in harbor seals, zoonoses, and those with terrestrial sources. Specific pathogens of interest were E coli, Clostridium perfringens, Vibrio spp, Campylobacter spp, Salmonella, Giardia, Cryptosporidium, avian influenza virus, Brucella, Leptospira spp., Toxoplasma gondii, Sarcocystis neurona, and Neospora caninum, Leptospira spp, and phocine and canine distemper virus. There was evidence of exposure to all pathogens except for phocine distemper virus. Simple measures of immune response were used to evaluate the immune function of harbor seal pups in rehabilitation that had evidence of previous bacterial infection. The swelling response to a subcutaneous injection of phytohemagglutinin (PHA) was positively associated with growth rate, possibly illustrating the energetic trade-offs between growth and immunity. Blubber contaminant concentrations (PCBs, DDTs, PBDEs, CHLDs, and HCHs) in harbor seal pups were grouped by extent of suckling and strand location. The ratio of PCB:DDT was increased in San Francisco Bay and decreased in Monterey Bay compared with other locations along the coast. Pups that weaned in the wild, lost weight and then stranded had the highest contaminant levels, equivalent to the concentrations detected in stranded adult harbor seals. Dispersal and survival were monitored by satellite telemetry in harbor seal pups released from rehabilitation and recently weaned wild-caught pups to assess the effect of condition, health, and contaminant levels on survival probability. Increased contaminant levels and decreased thyroxine (T4) were associated with decreased survival probability. Increased mass, particularly among the rehabilitated pups, was associated with increased survival probability. This study demonstrates that health and survival of harbor seals pups along the central California coast are impacted by human activities such as contaminant disposal, pathogen pollution and boat traffic, although the variability in individual health measures requires carefully designed studies to detect these effects.
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Modelling space-use and habitat preference from wildlife telemetry dataAarts, Geert January 2007 (has links)
Management and conservation of populations of animals requires information on where they are, why they are there, and where else they could be. These objectives are typically approached by collecting data on the animals’ use of space, relating these to prevailing environmental conditions and employing these relations to predict usage at other geographical regions. Technical advances in wildlife telemetry have accomplished manifold increases in the amount and quality of available data, creating the need for a statistical framework that can use them to make population-level inferences for habitat preference and space-use. This has been slow-in-coming because wildlife telemetry data are, by definition, spatio-temporally autocorrelated, unbalanced, presence-only observations of behaviorally complex animals, responding to a multitude of cross-correlated environmental variables. I review the evolution of techniques for the analysis of space-use and habitat preference, from simple hypothesis tests to modern modeling techniques and outline the essential features of a framework that emerges naturally from these foundations. Within this framework, I discuss eight challenges, inherent in the spatial analysis of telemetry data and, for each, I propose solutions that can work in tandem. Specifically, I propose a logistic, mixed-effects approach that uses generalized additive transformations of the environmental covariates and is fitted to a response data-set comprising the telemetry and simulated observations, under a case-control design. I apply this framework to non-trivial case-studies using data from satellite-tagged grey seals (Halichoerus grypus) foraging off the east and west coast of Scotland, and northern gannets (Morus Bassanus) from Bass Rock. I find that sea bottom depth and sediment type explain little of the variation in gannet usage, but grey seals from different regions strongly prefer coarse sediment types, the ideal burrowing habitat of sandeels, their preferred prey. The results also suggest that prey aggregation within the water column might be as important as horizontal heterogeneity. More importantly, I conclude that, despite the complex behavior of the study species, flexible empirical models can capture the environmental relationships that shape population distributions.
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