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Habitat use and foraging success of Roseate and Common Terns feeding in flocks in the Azores; Uso del hábitat y éxito en la búsqueda de alimento en bandos del charrán rosado y charrán común en Azores

Monticelli, David; Ramos, Jaime A.; Pereira, José
Fonte: Spanish Society of Ornithology Publicador: Spanish Society of Ornithology
Tipo: Artigo de Revista Científica
ENG
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Aims: To study the foraging ecology of roseate terns and common terns in the Azores sub-tropical wa- ters where the former species is relatively abundant compared to congeners. In particular, we asked whether foraging behaviour differed between both species, which factors determined individual success at forag- ing-flocks, and how did our findings compare with previous studies of Atlantic populations in North Amer- ica (temperate), and Caribbean (tropical). Location: Ponta das Contendas (38°39’N, 27°05’W), Terceira Island, Azores. Methods: Foraging-flocks were characterized and compared in terms of species (single- or mixed- species), size (no. of individuals), type of habitat (inshore, exposed coast, deep blue water), and presence- absence of biotic effects. We used a generalized linear model (GLM) approach to study the effect of se- lected factors (species, habitat, biotic effect, cloud cover, wind speed, and their interactions) on individual foraging parameters at these flocks (number of dives min-1, number of aborted dives min-1, number of prey caught min -1). Results: Both tern species were most often observed in mixed-flocks in the exposed coast habitat, but roseate terns were also prone to feed in mono-specific flocks over blue water. Only one quarter of the to- tal number of flocks recorded was in the presence of biotic effects...

Behavioral suites mediate group-level foraging dynamics in communities of tropical stingless bees

LICHTENBERG, E. M.; IMPERATRIZ-FONSECA, V. L.; NIEH, J. C.
Fonte: BIRKHAUSER VERLAG AG Publicador: BIRKHAUSER VERLAG AG
Tipo: Artigo de Revista Científica
ENG
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Competition for floral resources is a key force shaping pollinator communities, particularly among social bees. The ability of social bees to recruit nestmates for group foraging is hypothesized to be a major factor in their ability to dominate rich resources such as mass-flowering trees. We tested the role of group foraging in attaining dominance by stingless bees, eusocial tropical pollinators that exhibit high diversity in foraging strategies. We provide the first experimental evidence that meliponine group foraging strategies, large colony sizes and aggressive behavior form a suite of traits that enable colonies to improve dominance of rich resources. Using a diverse assemblage of Brazilian stingless bee species and an array of artificial ""flowers"" that provided a sucrose reward, we compared species` dominance and visitation under unrestricted foraging conditions and with experimental removal of group-foraging species. Dominance does not vary with individual body size, but rather with foraging group size. Species that recruit larger numbers of nestmates (Scaptotrigona aff. depilis, Trigona hyalinata, Trigona spinipes) dominated both numerically (high local abundance) and behaviorally (controlling feeders). Removal of group-foraging species increased feeding opportunities for solitary foragers (Frieseomelitta varia...

O período juvenil em macacos-prego (Sapajus sp.): ontogenia das relações sociais e do forrageamento; The juvenile period in tufted capuchin monkeys (Sapajus sp.): ontogeny of social relationships and foraging behavior

Winandy, Mariana Mascarenhas
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 08/05/2012 PT
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Primatas apresentam maturação tardia em relação a outros mamíferos, com infância e, particularmente, juventude prolongadas. Duas hipóteses para explicar esta característica da ordem são a hipótese da necessidade de aprendizagem, que aponta a necessidade de aquisição de habilidades sociais ou de forrageamento como fator-chave, e a hipótese de aversão a riscos, segundo a qual primatas apresentam crescimento lento de modo a reduzir suas taxas metabólicas, uma vez que sofrem com a competição por alimento com indivíduos adultos devido à baixa posição hierárquica ou a uma menor eficiência no forrageamento. O presente trabalho analisou o desenvolvimento comportamental de jovens macacos-prego (Sapajus sp.) de um grupo que vive em semi-liberdade no Parque Ecológico do Tietê, São Paulo, de outubro de 2007 a maio de 2010. Os dados foram obtidos com os métodos Focal de Varredura e Todas as Ocorrências. Os resultados mostram uma hierarquia de dominância, de modo geral, herdada da mãe entre as fêmeas e dependente de idade entre os machos. O grande número de indivíduos com pouca participação em interações agonísticas e de díades sem relações de dominância e o baixo número de coalizões, que envolveram principalmente indivíduos dominantes...

Mosaicos sucessionais em florestas tropicais: efeitos sobre o forrageio e deposição de fezes pela anta Tapirus terrestris (Perissodactyla: Tapiridae); Successional mosaics in tropical forests: effects on foraging and dung deposition by tapirs Tapirus terrestris (Perissodactyla: Tapiridae)

Luca, Juliana Ranzani de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/08/2012 PT
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Grandes mamíferos herbívoros exercem papel fundamental para a função e estrutura dos ecossistemas terrestres, através principalmente da herbivoria e da deposição de fezes e urina, que influenciam a germinação e crescimento de plantas, a composição e diversidade de comunidades vegetais, a ciclagem e translocação de nutrientes, o estoque de carbono e a freqüência de distúrbios como o fogo. Entretanto, em florestas tropicais, o papel de grandes mamíferos herbívoros foi pouco estudado até o momento. De acordo com a Teoria de Forrageio Ótimo, a seleção de recursos alimentares é resultado do balanço entre o ganho energético e o gasto com a procura, captura e ingestão do alimento. Na escala da paisagem, um dos processos que pode gerar manchas com diferentes qualidades nutricionais para herbívoros é a sucessão da vegetação. Estádios iniciais de sucessão, por serem dominados por espécies de plantas de baixa estatura e crescimento rápido, com folhas tenras, alto conteúdo de nitrogênio, poucos compostos secundários e mais palatáveis, deveriam ser preferidos por grandes mamíferos herbívoros. No entanto, para herbívoros podadores, que incluem frutos na dieta, a disponibilidade destes itens, que são mais nutritivos que a folhagem...

Aspectos temporais da organização coletiva do forrageamento em formigas saúvas (Atta sexdens rubropilosa); Temporal aspects of collective organization of foraging in leaf-cutting ants (Atta sexdens rubropilosa)

Toledo, Marcelo Arruda Fiuza de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/03/2013 PT
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Ao observarmos uma trilha de forrageamento de formigas saúvas parece bastante claro que ela consiste no tráfego de muitos indivíduos que buscam alimento numa mesma fonte e o trazem para a colônia. No entanto, a organização presente numa trilha vai muito além do fato de que formigas operárias transportam folhas para o ninho. Desde os mecanismos de formação e manutenção de trilhas baseados no recrutamento e em retroalimentação positiva da marcação feromonal, até a forma com que formigas de tamanhos diferentes se dividem entre as tarefas de corte, transporte e patrulhamento, as trilhas de forrageamento exibem uma organização muito sofisticada, que reflete a complexidade característica dos de organismos eussociais. Neste cenário, é particularmente desafiador identificar a relação entre os comportamentos individuais, característicos de formigas de um dado morfotipo, e os padrões globais coletivos observados na colônia, como por exemplo, o padrão temporal da atividade de forrageamento. No caso de formigas Atta sexdens, apesar de ser reconhecida a importância do polimorfismo na divisão de tarefas, não foi investigado o seu papel na determinação do padrão temporal com que as tarefas são realizadas. Esta questão é especialmente interessante no caso das trilhas...

Soldiers initiate foraging activities in the subterranean termite, Heterotermes tenuis

Casarin, Fabiana Elaine; Costa-Leonardob, Ana Maria; Arab, Alberto
Fonte: Univ Arizona Publicador: Univ Arizona
Tipo: Artigo de Revista Científica Formato: 5
ENG
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Caste polyethism has been recorded in some termite species, however the foraging behavior of subterranean termites remains poorly known. Heterotermes tenuis Hagen (Isoptera: Rhinotermitidae) is a subterranean termite that is native to Brazil and is an agricultural and urban pest. The aim of this study was to investigate which caste acts as scouts when searching for food sources and determinate the percentages of each caste present in the foraging territories of field colonies of H. tenuis. Our results showed no significant differences among the caste proportions present in the foraging territories of the three colonies studied in the field. Laboratory experiments showed that minor soldiers were the most frequent initiators of foraging activities. This result suggests that the exploratory phase of the foraging behavior may be regulated by the number of soldiers present in the foraging territories of each colony.

Estimates of Foraging Population and Territory of Heterotermes tenuis Colonies using Mark-Release-Recapture (Isoptera: Rhinotermitidae)

Costa-Leonardo, Ana Maria; Casarin, Fabiana Elaine; Ferreira Jr., João
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 807-814
ENG
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Heterotermes tenuis is an important economic pest in São Paulo state. Foraging populations of three field colonies of H. tenuis located on a University campus (UNESP, Rio Claro, SP, Brazil) were characterized. Foraging populations of H. tenuis colonies were calculated using four cycles of a mark-release-recapture program with a weighted mean method. The foraging population sizes of three colonies: A, B and C were 389,313±14,907; 265,589 ±12,635; and 641,600∓12,127; respectively. Foraging biomasses were 0.77 kg in the colony A, 0.51 kg in the colony B and 1.17 kg in colony C. Mean worker biomass was approximately 1.9 mg. Foraging territories occupied an area ranging from 70 m2 to 131 m2 per colony. The maximum linear foraging distance traveled by H. tenuis was 28m.

Epigenetics and behavioural plasticity: drosophila euchromatin histone metiltransferase and foraging

Anreiter, Ina
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2012 ENG
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37.13%
A thesis submitted in fulfillment of the requirements for the degree of Masters in Molecular Genetics and Biomedicine; The foraging gene in D. melanogaster underlies a natural polymorphism with two variants called rover and sitter. These variants differ in a suite of phenotypes which are plastic when exposed to varying environmental parameters. Although the phenotypic differences between rovers and sitters are evident, the underlying molecular mechanisms involved are not completely understood. Recently, a histone methyltransferase (EHMT) was found to methylate histones at the foraging promoter region, suggesting a possible interaction of these two genes. This work provides strong evidence that EHMT significantly affects several phenotypic traits linked to the foraging gene. EHMT is needed for the plastic response to food-deprivation seen in larval feeding behaviour, evident as food-deprived larvae lacking EHMT show the same behaviour as fed larva, while larva with functional EHMT significantly reduce their path-lengths when food-deprived. Furthermore, the loss of functional EHMT affects sitter but not rover adult foraging behaviour in food-deprived flies, suggesting an epigenetic interaction between EHMT and the foraging alleles. EHMT mutants also have higher fat storage levels and survive longer during starvation. And finally...

Foraging behavior of the queenless ant Dinoponera quadriceps Santschi (Hymenoptera: Formicidae)

Araújo,Arrilton; Rodrigues,Zenilde
Fonte: Sociedade Entomológica do Brasil Publicador: Sociedade Entomológica do Brasil
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2006 EN
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The search for and ingestion of food are essential to all animals, which spend most of their lives looking for nutritional sources, more than other activities such as mating, intra-specific disputes or escaping from predators. The present study aims to describe and quantify several aspects of foraging behavior, diet and food transport in the queenless ant Dinoponera quadriceps Santschi in a secondary Atlantic forest, Northeastern Brazil. Three colonies were randomly selected at a distance of at least 50 m from one another. On leaving the colony, worker ants were followed until their return, with no nutritional provision or interference with their activities. Activities were recorded using focal time sampling with instantaneous recording every minute for 10 consecutive minutes. Each colony was observed 1 day/week, for at least 6 h/day resulting in 53.8h of direct observation of the workers. Foraging activities, success in transporting food, type of food, cleaning and interaction among the workers were recorded. Foraging was always individual, with no occurrence of recruitment. Diet was composed mainly of arthropods, mostly insects. The collection of small fruits (Eugenia sp.) was also observed. Foraging time was greater when workers transported food to the colony...

A Phylogenetic Perspective on Foraging Mode Evolution and Habitat Use in West Indian Anolis Lizards

Lara, Ada Chamizo; Johnson, Michele A.; Revell, Liam J.; Leal, Manuel; Rodríguez Schettino, Lourdes; Losos, Jonathan
Fonte: Elsevier Publicador: Elsevier
EN_US
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Although many descriptive studies of foraging mode have been performed, the factors that underlie the evolution of foraging mode remain poorly understood. To test the hypothesis that foraging mode evolution is affected by habitat use, we analysed two data sets including 31 species of West Indian Anolis lizards. In this genus, the same suite of habitat specialists (or ecomorphs) has evolved on four islands, providing the replication necessary to evaluate the generality of the relationship between foraging mode and habitat use. Using habitat and behavioural data, we conducted phylogenetic comparative analyses to determine whether species of the same ecomorph have evolved similar foraging behaviour and whether differences in foraging mode are associated with differences in habitat use. We found that Anolis species show substantial variation in foraging behaviour, including differences in movement and eating rates. Furthermore, variation among ecomorphs indicates that foraging behaviour is related to habitat use, although the specific environmental factors driving foraging divergence are unclear. Our results show that foraging mode is an evolutionarily labile trait that is influenced by evolution of habitat use.; Organismic and Evolutionary Biology

Seasonal and colony differences in the foraging ecology of New Zealand fur seals (Arctocephalus forsteri).

Baylis, Alastair Martin Mitri
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
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The New Zealand fur seal (Arctocephalus forsteri) is the most abundant fur seal species in the Australian-New Zealand region. Approximately 85 % of Australia’s population of New Zealand fur seals reside in the state of South Australia. As a result of their abundance and size, it has been estimated that the New Zealand fur seal population in South Australia consumes the greatest biomass of resources of all marine mammal and seabird species. However, despite the importance of New Zealand fur seals as top predators, our understanding of their foraging ecology in South Australia is limited. In order to better understand the habitat utilized and the diet of New Zealand fur seals, this study explores the foraging ecology of lactating seals from four primary colonies in South Australia, which account for ~ 78 % of the Australian population. These colonies are Cape Gantheaume (36о04’S, 137о27’E) and Cape du Couedic (36о03’S, 136о42’E) on Kangaroo Island; North Neptune Island (35о13’S, 136о03’E) and Liguanea Island (34о59’S, 135о37’E). I start this study by assessing the seasonal variation in foraging location and dive behaviour of lactating New Zealand fur seals from Cape Gantheaume. 18 seals were fitted with satellite transmitters and time depth recorders (TDRs). The presence of thermoclines (derived from TDRs)...

Foraging behaviour and habitat use of a short-ranging seabird, the crested tern

McLeay, L.; Page, B.; Goldsworthy, S.; Paton, D.; Teixeira, C.; Burch, P.; Ward, T.
Fonte: Inter-research Publicador: Inter-research
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
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We used satellite tracking technology on the crested tern Sterna bergii, a seabird weighing <400 g. GPS units weighing <22 g were deployed on adult terns brooding young chicks. Individuals typically commuted to foraging grounds <40 km from the colony where their travel speeds slowed to ≤10 km h–1, presumably as prey encounter rates increased. Individuals undertook trips up to 4 h 17 min in length and 118 km in distance, and trip duration was positively correlated with the maximum distance and total distance traveled. Foraging behaviour, examined in relation to habitat characteristics (benthic habitat type, depth, sea surface temperature [SST], chlorophyll a [chl a]), was typically associated with warm (19 to 21°C), shallow (<20 m depth) waters that were relatively high in chl a (>0.5 mg m–3). The most well-supported model (generalised linear mixed model) of foraging behaviour indicated a positive relationship between time spent at sea, distance travelled and chl a, suggesting individuals spent relatively more time foraging at greater distances from the colony in zones of higher primary production. The timing and location of crested tern breeding may be linked to the 2-fold increase in primary production near Troubridge Island over the austral summer. Individual differences in the length (distance and duration) of foraging trips may reflect either prior knowledge of where prey aggregations exist...

The foraging ecology of the short-tailed shearwater puffinus tenuirostris.

Einoder, Luke D.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010
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The short-tailed shearwater Puffinus tenuirostris is one of the world’s most abundant seabirds, with a population of around 23 million breeding birds. Despite this abundance we have a limited understanding of their role in the marine ecosystem. This is largely due to the many uncertainties surrounding the trophic interactions, resource requirements and foraging ecology of this wide ranging pelagic seabird. I studied the movement of adults during the short trip (ST) and long trip (LT) component of their dual foraging strategy to determine how they use their marine habitat. ST were primarily confined to neritic (continental shelf) waters 30 to 100 km from their colony, and maximum depth gauges revealed that birds reached a depth of 21 ± 13 m (SD). Analysis of the time spent in area by 39 individuals performing ST revealed that 18 birds employed area restricted searches within circles of a diameter of 14 ± 3 km (SE). Prey returns from area restricted search flights were predominated by bony fish, whereas prey diversity increased for non-area restricted search flights, with more krill and cephalopods. Thus, direct flights were performed when birds were exploiting prey patches dominated by fish, in contrast to the more varied diet returned when birds covered greater distances. LT flights were highly variable ranging from 11 - 32 days duration...

In situ measures of foraging success and prey encounter reveal marine habitat-dependent search strategies

Thums, M.; Bradshaw, C.; Hindell, M.
Fonte: Ecological Soc Amer Publicador: Ecological Soc Amer
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
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Predators are thought to reduce travel speed and increase turning rate in areas where resources are relatively more abundant, a behavior termed ‘‘area-restricted search.’’ However, evidence for this is rare, and few empirical data exist for large predators. Animals exhibiting foraging site fidelity could also be spatially aware of suitable feeding areas based on prior experience; changes in movement patterns might therefore arise from the anticipation of higher prey density. We tested the hypothesis that regions of area-restricted search were associated with a higher number of daily speed spikes (a proxy for potential prey encounter rate) and foraging success in southern elephant seals (Mirounga leonina), a species exhibiting both area-restricted searches and high interannual foraging site fidelity. We used onshore morphological measurements and diving data from archival tags deployed during winter foraging trips. Foraging success was inferred from in situ changes in relative lipid content derived from measured changes in buoyancy, and first-passage time analysis was used to identify area-restricted search behavior. Seals exhibited relatively direct southerly movement on average, with intensive search behavior predominantly located at the distal end of tracks. The probability of being in search mode was positively related to changes in relative lipid content; thus...

The life history characters, reproductive constraints and foraging strategies of a neritic seabird, the crested tern.

McLeay, Lachlan J.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010
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This thesis examines the functional relationships between the diet, foraging behaviour and life history traits of crested tern populations in South Australia between 2004 and 2008. Diet analyses indicated that crested terns are a generalist predator on surface-schooling fishes. Clupeiform fish (Australian anchovy Engraulis australis, sardine Sardinops sagax) comprised a large component of the diet of crested terns. Ontogenetic differences in prey size indicated that adults selected small prey for their chicks during early provisioning but increased the size and rate of prey delivered throughout the breeding season as chicks grew. Adults also selected higher quality prey for their chicks compared to what they consumed themselves. Chick and adult diets may have reflected spatial differences in the species composition of prey assemblages near colonies and a North-South gradient in prey size. I also investigated the provisioning patterns of crested terns and how reproductive timing and adult body condition affect the growth and survival of crested tern chicks. Provisioning rates were related to the daily mass change of chicks, and chick growth was correlated with asymptotic mass, suggesting that prey availability and adult foraging proficiency influences fledgling size. Parental ‘quality’ affected reproductive performance. Adults with good body condition hatched chicks earlier and early breeding was positively related to hatchling mass...

Alternate foraging strategies and population structure of adult female Australian sea lions.

Lowther, Andrew Damon
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
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Otariid seals pose several challenges in collecting behavioural data due because of the geographical decoupling of breeding habitat (terrestrial) and foraging grounds (aquatic). Additionally, life history traits such as breeding chronology and moult state constrain the temporal window over which data can be collected. Expensive telemetry devices coupled with logistical difficulties and the biology of animals often limits the ability to answer questions concerning the role of seasonal or life-history differences in foraging ecology. However, quantifying individual behavioural specialisations such as foraging behaviour that may impede gene flow is an essential prerequisite to understanding population structure. Several unusual life history traits of the IUCN Red Listed (threatened) Australian sea lion Neophoca cinerea are interesting from an ecological, evolutionary and conservation standpoint. Australian sea lions are endemic to the southern and western coastline of Australia, distributed over approximately 70 breeding colonies with 86% of all breeding occurring in South Australia. Most notably, a unique 17.5month breeding chronology and asynchronous breeding between spatially-close colonies has been proposed to be an adaptive response to a low-quality foraging environment that has little or no seasonality. Contrary to this...

Individual foraging site fidelity in lactating New Zealand fur seals: Continental shelf vs. oceanic habitats

Baylis, A.; Page, B.; McKenzie, J.; Goldsworthy, S.
Fonte: Soc Marine Mammalogy Publicador: Soc Marine Mammalogy
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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Wide-ranging marine central place foragers often exhibit foraging site fidelity to oceanographic features over differing spatial scales (i.e., localized coastal upwellings and oceanic fronts). Few studies have tested how the degree of site fidelity to foraging areas varies in relation to the type of ocean features used. In order to determine how foraging site fidelity varied between continental shelf and oceanic foraging habitats, 31 lactating New Zealand fur seals (Arctocephalus australis forsteri1) were satellite tracked over consecutive foraging trips (14–108 d). Thirty-seven foraging trips were recorded from 11 females that foraged on the continental shelf, in a region associated with a coastal upwelling, while 65 foraging trips were recorded from 20 females that foraged in oceanic waters. There were no significant differences in the mean bearings (to maximum distance) of individual's consecutive foraging trips, suggesting individual fidelity to foraging areas. However, overlap in area and time spent in area varied considerably between continental shelf and oceanic foragers. Females that foraged on the continental shelf had significantly greater overlap in consecutive foraging trips when compared to females that foraged in oceanic waters (overlap in 5 × 5 km grid cells visited on consecutive trips 55.9%± 20.4% and 13.4%± 7.6%...

Does vigilance always covary negatively with group size? Effects of foraging strategy

Barbosa, Andrés
Fonte: Springer Publicador: Springer
Tipo: Artículo Formato: 24576 bytes; application/msword
ENG
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The possible effects of foraging strategy on the relationship between vigilance and group size were studied in three species of waders with different foraging strategies. I predict that (1) pause–travel species should show no relationship between scanning and group size, because these species scan for prey as well as for predators; (2) continuous-tactile foraging species should show a positive relationship between flock size and vigilance level, because in their large groups vigilance towards other birds could be used to avoid interference and aggression; and (3) continuous-visual searching species should show the general pattern of decreasing vigilance when group size increases as predicted by both the 'many eyes' and the 'predatory risk' hypotheses. Results support the predictions for the influence of foraging strategy on the relationship between vigilance level and group size. The mutual exclusion of foraging and scanning can determine the importance of the 'many eyes' hypothesis. Such exclusion seems to be determined by foraging strategy. The influence of foraging on scanning must be taken into account in future studies on the group-size effect; Financial support was provided by a MNCN-CSIC-CAM predoctoral grant and partly by Caja Madrid during field work. I have been supported by a contract from the Ministry of Science and Technology under the project PB98-0506 during writing.; Peer reviewed

Activity patterns and foraging behaviour of Audouin's gulls at the Ebro Delta, NW Mediterranean; Patrones de actividad y comportamiento de caza en la gaviota de Audouin en el delta del Ebro, Mediterráneo occidental

Oro, Daniel; Ruiz, Xavier; Mañosa, Santi
Fonte: CSIC - Instituto de Ciencias del Mar (ICM) Publicador: CSIC - Instituto de Ciencias del Mar (ICM)
Tipo: Artículo Formato: 252557 bytes; application/pdf
ENG
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Publicación online disponible en: http://www.icm.csic.es/scimar/index.php; [EN] Twenty Audoui´s gulls, Larus audouinii, breeding in the Ebro Delta (NW Mediterranean) were radio-tracked in 1998 to study their foraging behaviour and activity patterns. Some detrimental effects of tagging on the breeding success of the birds were detected, especially when both members of the pair were tagged. The results were actually constrained by the low number of locations due to natural breeding failure and failure in tag emission, as well as the adverse effect of tagging. However, through a combination of aircraft surveys at sea and a fixed station for automatic tracking of the presence of the birds at the colony, novel individual-based information of home ranges and activity patterns was obtained. Trawler fishing activity seemed to influence both the foraging range and habitat use: while trawlers operated, gulls overlapped their fishing grounds with vessels, probably to scavenge on discards. Very few locations were obtained during a trawling moratorium period, although they were all recorded in coastal bays and terrestrial habitats. During the trawling activity period, gulls ranged over a minimum convex polygon area of 2900 km2. Gulls were tracked up to 40 km from the colony...

Foraging Ecology and Maternal Transmission of Foraging Specializations of Bottlenose Dolphins (Tursiops truncatus)

Weiss, Jessica
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' Project Formato: 1056700 bytes; application/pdf
Publicado em //2004; 2004 EN_US
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Bottlenose dolphins use a variety of foraging specializations to detect and pursue prey. Like other mammals, individual dolphins may use specialized foraging techniques that are shaped in response to habitat or particular prey resources. The long duration of the mother-calf bond presents an opportunity for mothers to transmit such specializations to their calves, and cases of observational learning by dolphins are well known from captive colonies. This study explored how specializations may influence choices of habitat use and on how such specializations may spread within a community. A focal follow technique was used to document the foraging behavior of five resident females and their calves from June-August 2003 in Sarasota, FL. Females significantly differed in their selection of foraging habitats. Three of the five focal females used known foraging specializations, kerplunking and barrier feeding, and exhibited a preference for only one type. Females also increased the use of foraging habitats associated with their preferred foraging specializations. Limited observations, as well as anecdotal evidence from past studies, suggest that maternal transmission may play a role in the spread of kerplunking and barrier feeding within a community. Findings suggest that the use of foraging specializations is associated with foraging habitat preferences in Sarasota Bay as well as support the importance of incorporating knowledge of social behavior into the management structure for bottlenose dolphins. Many questions still remain concerning the prey specificity...