I investigated the effect of turbidity on the foraging behaviour of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the laboratory. Specifically, I examined a behavioural "tradeoff" between visual ability and "perceived" risk. I assessed visual ability by measuring the reaction distance of juvenile Chinook to planktonic Artemia prey. I found Chinook exhibited a log-linear decline in reaction distance with increasing turbidity. To determine the effects of turbidity and microhabitat on foraging rate, I conducted separate experiments for surface (Drosophila), planktonic (Artemia), and benthic (Tubifex) prey across a range of turbidity levels (0, 25, 50, 100, 200, 400, 800 mg•L⁻¹). Foraging rates were reduced at higher turbidity conditions for all three prey. However, for surface and benthic prey, foraging rates were also low in clear water; highest rates were attained at intermediate turbidity levels (50-200 mg•L⁻¹). The degree to which intermediate turbidities were associated with higher foraging rates was size-dependent. Smaller individuals (150-57 mm FL) exhibited relatively higher foraging rates in clear conditions than did larger individuals. However, planktonic foraging rates by juveniles were consistently high in clear water, regardless of fish size. In experiments manipulating light level independent of turbidity, I allowed salmon to forage under conditions which were either turbid, or clear but with light intensity correspondingly reduced. Foraging rates were similar between the two treatments for planktonic prey, but differed for benthic and surface prey. Generally, foraging rates exhibited by juvenile Chinook salmon could not be explained on the basis of visual ability alone. I suggest that young salmon also exhibited foraging behaviour consistent with their perception of risk to predation. In arena experiments, juvenile Chinook distributed themselves randomly in turbid conditions; in clear conditions they associated with the bottom. When bird and fish predator models were introduced the fish altered their spatial distribution, occupying deeper regions regardless of turbidity. However, their response in turbid conditions was less marked and lasted for a shorter time. Turbidity apparently mitigated the perceived risk of predation in juvenile Chinook. I developed a conceptual tradeoff model that predicted the general effect of turbidity on foraging behaviour. Assuming differences in either prey quality or perceived risk of predation in three microhabitats (surface, water column, bottom), the model resolved the apparent dissimilarities between planktonic and other foraging behaviours. Perceived risk of Chinook to predation was significantly different between surface and water column microhabitats. When exposed to a non-visual "fixed-risk" stimulus (sound), salmon apparently perceived less risk as turbidity increased. I conclude that in turbid waters juvenile salmon exhibit foraging behaviour in a manner consistent with a tradeoff between their visual ability and perceived risk. / Science, Faculty of / Zoology, Department of / Graduate

Various aspects of downstream migratory behavior of sockeye salmon fry (pncorhynchus nerka) were examined in a series of field and laboratory experiments. The field work at the Department of tie Environment (Fisheries and Marine Service) Fulton Eiver spawning channels, Babine Lake, British Columbia, was concerned with the predation by rainbow trout (Salmo gairdneri) and whitefish (Prosopium williamsoni) on sockeye fry with various kinds of prior experience. The laboratory studies focused on the effects of exposure to light on the behavior of emerging and recently emerged fry. The results showed that : (1) the number of fry moving downstream varies throughout the nightly migration period; (2) the presence cf predators modifies the movement pattern of migrating fry, such that the fry tend to move downstream over a more concentrated time period; (3) fry response to predators tends not to be predator-specific, migrating fry respond similarly to different species of predators; (4) emergent fry are not all similar in their migratory behavior, some tend to migrate rapidly (fast migrants), while others migrate at a slower rate (slow migrants); (5) generally fry with prior experience to predators displayed different migratory behavior compared to fast and slow migrants; and (6) subjecting newly-emerged fry to increasing time periods of light treatment and fry densities, alters behavior patterns. It is concluded that fry commencing downstream movement are not all similar in their migratory behavior. Begardless of the basis for the behavioral difference between fast and slow migrants, the presence of predators modifies and enhances downstream movement. Further, subjecting premigratory fry to light, alters downstream movement and behavioral interactions between fry. / Science, Faculty of / Zoology, Department of / Unknown

Orientador: Luís Felipe de Toledo Ramos Pereira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-24T04:49:15Z (GMT). No. of bitstreams: 1 RochaLima_AnaBeatrizCarollo_M.pdf: 4483469 bytes, checksum: 075bff58acd826eaa3ec36949ad8f85c (MD5) Previous issue date: 2013 / Resumo: A família Brachycephalidae compreende dois gêneros e 52 espécies. O gênero Brachycephalus apresenta, em sua maioria, espécies tóxicas e de coloração conspícua, enquanto o gênero Ischnocnema possui muitas espécies polimórficas e crípticas quanto a sua coloração dorsal. No primeiro capítulo foi realizado um experimento com modelos de plasticina para testar se os padrões coloridos e brilhantes do gênero Brachycephalus estão relacionados com aposematismo. Além disso, foi testada a hipótese alóctone/autóctone, que prediz que os predadores vão responder mais fortemente a um padrão autóctone do que a um alóctone, dado que eles supostamente são ingênuos ao padrão introduzido e/ou experientes quanto ao padrão autóctone. O experimento foi realizado em duas localidades de Mata Atlântica no estado de São Paulo, Brasil, onde ocorrem tanto espécies camufladas quanto conspícuas de Brachycephalidae. Foram encontradas diferenças na intensidade de ataque entre os modelos crípticos e vistosos, suportando a hipótese de que a coloração conspícua de Brachycephalus é sinal de sua toxicidade. No segundo capítulo foi investigado como fatores ambientais e espaciais afetam os padrões de coloração de espécies do complexo de Ischnocnema guentheri-henselii e I. parva, comparando populações em diferentes latitudes depositadas no acervo de quatro coleções científicas. Os diferentes padrões foram plotados em mapas e, através de análises de agrupamento, foram detectadas diferenças na proporção da frequência dos padrões nas populações situadas no limite meridional da ocorrência das espécies. A segregação de populações abaixo da latitude -24º é coincidente com variações morfológicas observadas em outras espécies, ou mesmo com limites de distribuição de espécies irmãs de anuros. Assim, é evidente que esta região caracteriza-se por forte promotora de diversificação e o clima pode ser uma das explicações para nossos resultados. Desta forma os resultados desta dissertação sugerem que a predação pode estar exercendo pressão no gênero Brachycephalus e que fatores climáticos e geológicos podem estar influenciando a coloração no gênero Ischnocnema / Abstract: Brachycephalidae family comprises two genera and 52 species. Brachycephalus genus presents mostly toxic species with conspicuous coloration, while Ischnocnema genus has many polymorphic and cryptic species as their dorsal coloration. In the first chapter we conducted an experimental essay, with plasticine frog simulacra to test if the bright colorful patterns of Brachycephalus species are related to aposematism. Furthermore, we tested the allochthonous/autochthonous hypothesis, which predicts that predators will respond strongly to an autochthonous pattern than to an allochthonous one, as they supposedly are naïve to this introduced pattern and/or experienced to the autochthonous pattern. The experiment was made in two Atlantic forest sites in the state of São Paulo, Brazil, where both cryptic and conspicuous Brachycephalidae species occur. We found differences in predation attack between cryptic and conspicuous simulacra, supporting that the conspicuous coloration of Brachycephalus is a sign of their toxicity. In the second chapter we investigated how environmental and spatial factors affect color patterns of species complex Ischnocnema guentheri-henselii and I. parva comparing populations at different latitudes deposited in four scientific collections. Different patterns were plotted on maps and, through cluster analysis, differences were detected in the ratio of the frequency of patterns in populations located in the southern limit of species occurrences. The segregation of populations below -24 º latitude coincides with morphological variations observed in other species, or even distribution limits sister species of frogs. Thus, it is clear that this region is characterized by a strong promoter of diversification and the weather can be one of the explanations for our study. Thus, the results of this dissertation suggest that predation may be exerting pressure on the Brachycephalus genus and geological and climatic factors may be influencing the coloration in the Ischnocnema genus / Mestrado / Biodiversidade Animal / Mestra em Biologia Animal

Coral reefs are priority habitats which are vulnerable to natural and anthropogenic disturbances. These can cause phase shifts from coral habitat to degraded algal-dominated states – and consequent changes in the distribution, abundance and activity of associated fish species. In the eastern Red Sea, human-induced reef degradation is likely to increase with planned development of the Saudi Arabian coast and the changing climate. The present study therefore investigates the ecological effects of coral-algal phase shifts in reef-associated fish communities, using naturally occurring within-reef benthic zones as proxies for levels of habitat health - with a focus on how these responses differ temporally. These zones were dominated by: hard coral (coral zone), coral and turf algae (transition zone), and macroalgal canopies (algal zone). Six inshore reef areas, were studied in periods with low and high densities of Sargassum in the algal zones (May and November respectively). Community composition was assessed via visual census and predation activity predicted using two proxies: in situ experiments and biomass of carnivores. In both periods, we observed distinct fish communities in each zone - with reduced species richness, Shannon-Wiener diversity and predation intensity, from the coral to the algal zones. Decreases in the abundance and biomass of fish also occurred from the coral to algal zones in May but a spike, as well as a shift in community composition, occurred in the algal zone in November. This shift is attributed to the vast increases in grazer biomass, predominantly Siganus luridus, associated with the November bloom of Sargassum canopies. The present study established, the composition and functioning of Red Sea fish communities is spatially and temporally affected by increased macroalgal dominance. This finding supports the need for herbivorous fish to be made a conservation priority in the management and conservation of reef systems in order to prevent phase shifts to algal dominated states. We conclude that if Red Sea reefs are allowed to shift to alternate states, depending on the density of macroalgal canopies, reefs may support high biomass and abundance of fish but the functioning of the fish community will be altered and the diversity lost.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / It is widely reported that snakes can be major predators of avian nests, but the use of a single avian prey type by competing species has rarely been examined. This study aimed to investigate predation of a single food resource by the sympatric snakes Naja nivea and Dispholidus typus. Specifically, I aimed to 1) identify factors influencing snake presence in sociable weaver colonies and 2) quantify snake predation and potential differences in the consumption of prey by the two competing snakes. I used repeated visual surveys of sociable weavers to obtain presence-absence data of cape cobra and boomslang in sociable weaver colonies over an entire breeding season. I related the presence-absence data of the two snake species to spatially- and temporally-variable factors using principal component analyses (PCA) and multiple logistic regression analyses. The presence of snakes in sociable weaver colonies is primarily influenced by temporal factors, but spatial factors also play a role.

Flera vadare har på strandängar och liknande lokaler i södra Sverige haft en längre tid med svåra eller oroväckande populationsminskningar. Habitatförluster och habitatförändringar såväl som predation har setts vara bidragande faktorer. I detta arbete ligger fokus på hur årets häckningssäsong kan ha förhållit sig till just predationen i Trönninge ängar naturreservat strax söder om Halmstad. Där har nyligen införts predatorkontroll som en del av skötseln av reservatet. Bristen på predatorkontroll tros ha varit en av orsakerna till vadarnas framgångslösa häckning vid tidigare inventering. Ytterligare satsningar har gjorts på habitatstrukturen som bland annat har inneburit en förbättrad/utökad vattenmiljö. Jag har, mellan slutet av april och början av juni, utfört en revirkartering av häckande vadare samt studerat predatornärvaro och predatoraktivitet, av bland annat gråkråka (Corvus corone cornix), ormvråk (Buteo buteo) och rödräv (Vulpes vulpes), med hjälp av två olika metoder. Revirkarteringen resulterade i att jag fann sex häckande arter och hos fem av dessa hade ungar kläckts, med olika framgång, vid undersökningens avslut 10:e juni. Den sammanlagda bilden av predatorundersökningen visar att predationstrycket hade varken ökat eller minskat mot slutet av säsongen. Dock sågs gråkråkorna minska i antal med båda metoderna, detta som förmodad följd av framgångsrik skyddsjakt. Närvaron av predatorer utgjordes främst av tre arter och nästan samma uppsättning av tre arter stod för den huvudsakliga aktiviteten. Denna aktivitet från predatorer mättes med hjälp av tofsvipornas (Vanellus vanellus) typiska försvarsbeteende som innebär stötande flyganfall mot närgångna hot. Sammanfattningsvis har häckningsframgången varit god med hänsyn till tidigare inventering, och detta som förmodat resultat av de nya satsningarna i området. Tofsviporna har häckat med särskilt gott resultat och kan troligen ses öka i antal nästkommande säsong. / <p>Olle Liedberg</p>

Osämja mellan människan och rovdjuren har funnits sedan vi slutade jaga och började bruka jorden och bedriva lantbruk. En av de absolut viktigaste faktorerna som bestämmer vart en art förekommer, hur stark en stam är och hur den förändras över tiden, är predation. I svensk historia har både rådjurs (Capreolus capreolus) och rödräven (Vulpes vulpes) båda populationer varit nära nationell utrotning. Syftet med uppsatsen är att ta reda på om räven har någon påverkan på rådjurspopulationen. Detta görs genom att analysera avskjutningsstatistik från viltdata.nu i tre olika län med liknande klimat och innehåller samma arter av predatorer. Analysen gjordes med korrelationsanalys. Dock var det inget utav resultaten som visade någon signifikans. Dessa olika resultat i de olika län tyder på att det finns andra faktorer än räven som påverkar rådjurspopulationen. / A conflict between humans and predators has existed since man stopped hunting and started with agriculture instead. We know today that one of the most important factors influencing the distribution and abundance of a species is predation. Over the last two? centuries, both the roe deer (Capreolus capreolus) population and the red fox (Vulpes vulpes) population have been very close to extinction in Sweden. The purpose of this study was to determine if the red fox population affects the roe deer population. This was done by analyzing hunting statistics from viltdata.nu in three different regions with similar climate and with the same type of carnivores. The analysis was performed using correlation analysis. None of the relationships between roe deer and the fox in the three different areas was significant. This indicates that there are factors other than predation by fox that influence the deer population.

The importance of Trait Mediated Indirect Interactions (TMII) is increasingly being recognized. TMII are interactions between two species via a change in trait (behavioural, morphological, but not numerical) over a third one, which together cause ecological dynamics. Marine food webs have complex interactions, but TMII have not yet received great appreciation or application in marine conservation and management models. This article is a review about the different ways in which TMII can affect marine ecological dynamics. I summarize known examples of Behaviourally Mediated Indirect Interactions, Physiologically Mediated Indirect Interactions, and other types of indirect interactions such as initiated or mediated by parasites, in order to provide a better understanding about their functioning. I found that TMII are omnipresent in marine ecosystems and occur at all trophic levels, spanning from macro- to microorganisms. Furthermore, it includes many different taxa and guilds, and the mechanisms are highly diverse. Some of them enhance Density Mediated Effects, while others counteract them. Sometimes this results in the effects opposite of those expected, and often they extend further in the food web. Understanding of TMII is likely to be beneficial for marine conservation and management, due to the role of humans causing them or suffering its effects.

The emergence of the eukaryotic cell was one of the key events that paved the path to the vast variety of complex life visible all around us. A pivotal event in the process of eukaryogenesis was an endosymbiosis of two prokaryotic cells which in time resulted in the mitochondria. Phagocytosis, which is the process in which  larger cells envelope and digest smaller cells is one of the feasible explanations for how one cell came to be within another. It is common in eukaryotes, however, no contemporary examples of prokaryotes practicing phagocytosis exist. But phagocytosis had to evolve at some point, so how did it happen? This thesis gives an attempt to determine what conditions facilitate the evolution of phagocytosis. In this endeavour, we constructed chemostatic models for two different population structures where secondary consumers are subject to an invasion by a mutant with predatory capabilities. The different population structures are denoted as "competition" and "cross-feeding". By using random parameter sampling we show that the predator has a higher likelihood to invade in the cross-feeding environment. We also showed using adaptive dynamics that a mutant that is able to invade and replace its predecessor favours evolving towards a higher predation strategy in the cross-feeding case whereas in competition  such behaviour is less clear and a more balanced strategy seems preferable.

Mule deer (Odocoileus hemionus) populations are influenced by multiple factors, including interspecific competition and predation. Interspecific competition can affect resource acquisition and survival through altering space use and access to preferred habitat. Mule deer in some areas alter space use in the presence of competing species, including bison (Bison bison), cattle (Box taurus), elk (Cervus canadensis), and feral horses (Equus caballus), however the influence of competition on survival of mule deer during specific life history stages, such as birthing and rearing of neonates, is largely unknown. In addition to competition, predation can influence mule deer populations and even limit population growth by reducing recruitment of neonates into the adult population. The effects of predation may increase within a complex predator community, as predator species differ in hunting strategies, which may influence timing of predation events. We investigated the effects of interspecific competition on space use by mule deer during birthing and rearing of young (Chapter 1) and analyzed temporal patterns of predator kills of neonate mule deer in a complex predator community (Chapter 2). We hypothesized that mule deer would avoid competing ungulate species during birth and rearing of young, and that survival of neonate mule deer would decrease in areas of with increased likelihood of competition. We also hypothesized that timing of kills and habitat characteristics of kill sites would differ by predator species due to different hunting strategies. We captured 98 neonate mule deer and fit them with mortality-sensing radiocollars to test our hypotheses. We did not observe any evidence of competitive interactions between mule deer and other ungulate species. Further, we observed a positive association between space use by mule deer and elk following parturition. We also observed an increase in probability of survival for neonate mule deer in areas with higher probability of use by elk (Hazard ratio= 0.185, SE=0.497). We observed differences in timing of kills among predator species (p=0.026), however habitat characteristics of kill sites did not differ for those species. It appears that resource availability and climatic conditions influence space use by mule deer more strongly than space use by competing species. Further, timing of kills of neonate mule deer differ by predator species, which may lead to an additive effect of predation within a complex predator community.