Search results for "Predation"
showing 10 items of 589 documents
Ontogenetic trophic segregation between two threatened smooth-hound sharks in the Central Mediterranean Sea
2020
AbstractElasmobranchs are among the species most threatened by overfishing and a large body of evidence reports their decline around the world. As they are large predators occupying the highest levels of marine food webs, their removal can alter the trophic web dynamic through predatory release effects and trophic cascade. Suitable management of threatened shark species requires a good understanding of their behaviour and feeding ecology. In this study we provide one of the first assessments of the trophic ecology of the “vulnerable” smooth-hounds Mustelus mustelus and M. punctulatus in the Central Mediterranean Sea, based on stomach contents and stable isotope analyses. Ontogenetic diet ch…
Negatively condition dependent predation cost of a positively condition dependent sexual signalling.
2006
Predation is considered as an important factor constraining the expression of sexual signals. Nevertheless, direct quantitative evidence for predation provoking significant viability costs on individuals signalling at high rates is scarce. Moreover, it is unclear whether high rate signallers are able to balance presumably increased predation costs. We examined whether a condition dependent audible sexual signal, drumming, makes Hygrolycosa rubrofasciata male spiders more prone to predation by pied flycatchers (Ficedula hypoleuca), and whether sexual signalling rate is related to escaping ability once attacked. When birds were given a choice between two spider males manipulated to drum eithe…
Behavioural and physiological effects of the trophically transmitted cestode parasite, Cyathocephalus truncatus, on its intermediate host, Gammarus p…
2007
SUMMARYSome parasites with complex life-cycles are able to manipulate the behaviour of their intermediate hosts in a way that increases their transmission to the next host. Gammarids infected by the tapeworm Cyathocephalus truncatus (Cestoda: Spathebothriidea) are known to be more predated by fish than uninfected ones, but potential behavioural manipulation by the parasite has never been investigated. In this study, we tested the hypothesis that C. truncatus is able to manipulate the behaviour of one of its intermediate hosts, Gammarus pulex (Crustacea: Amphipoda). To assess if any behavioural change was linked to other phenotypic alterations, we also measured the immunity of infected and u…
A co-invasive microsporidian parasite that reduces the predatory behaviour of its host Dikerogammarus villosus (Crustacea, Amphipoda).
2014
SUMMARYParasites are known to affect the predatory behaviour or diet of their hosts. In relation to biological invasions, parasites may significantly influence the invasiveness of the host population and/or mediate the relationships between the invader and the invaded community. Dikerogammarus villosus, a recently introduced species, has had a major impact in European rivers. Notably, its high position in trophic web and high predatory behaviour, have both facilitated its invasive success, and affected other macroinvertebrate taxa in colonized habitats. The intracellular parasite Cucumispora dikerogammari, specific to D. villosus, has successfully dispersed together with this amphipod. Data…
Trade-off between warning signal efficacy and mating success in the wood tiger moth
2011
The coloration of species can have multiple functions, such as predator avoidance and sexual signalling, that directly affect fitness. As selection should favour traits that positively affect fitness, the genes underlying the trait should reach fixation, thereby preventing the evolution of polymorphisms. This is particularly true for aposematic species that rely on coloration as a warning signal to advertise their unprofitability to predators. Nonetheless, there are numerous examples of aposematic species showing remarkable colour polymorphisms. We examined whether colour polymorphism in the wood tiger moth is maintained by trade-offs between different functions of coloration. In Finland, m…
The insectivorous batPipistrellus nathusiiuses a mixed-fuel strategy to power autumn migration
2012
In contrast to birds, bats are possibly limited in their capacity to use body fat as an energy source for long migrations. Here, we studied the fuel choice of migratoryPipistrellus nathusii(approximate weight: 8 g) by analysing the stable carbon isotope ratio (δ13CV-PDB) of breath and potential energy sources. Breathδ13CV-PDBwas intermediate betweenδ13CV-PDBof insect prey and adipocyte triacylglycerols, suggesting a mixed-fuel use ofP. nathusiiduring autumn migration. To clarify the origin of oxidized fatty acids, we performed feeding experiments with captiveP. nathusii. After an insect diet, bat breath was enriched in13C relative to the bulk and fat portion of insects, but not deviating fr…
Aposematism facilitates the diversification of parental care strategies in poison frogs
2021
AbstractMany organisms have evolved adaptations to increase the odds of survival of their offspring. Parental care has evolved several times in animals including ectotherms. In amphibians, ~ 10% of species exhibit parental care. Among these, poison frogs (Dendrobatidae) are well-known for their extensive care, which includes egg guarding, larval transport, and specialized tadpole provisioning with trophic eggs. At least one third of dendrobatids displaying aposematism by exhibiting warning coloration that informs potential predators about the presence of defensive skin toxins. Aposematism has a central role in poison frog diversification, including diet specialization, and visual and acoust…
Experiments on a Prey Predators System
2003
The paper describes a prey-predators system devoted to perform experiments on concurrent complex environment. The problem has be treated as an optimization problem. The prey goal is to escape from the predators reaching its lair, while predators want to capture the prey. At the end of the 19th century, Pareto found an optimal solutions for decision problems regarding more than one criterion at the same time. In most cases this ‘Pareto-set’ cannot be determined analytically or the computation time could be exponential. In such cases, evolutionary Algorithms (EA) are powerful optimization tools capable of finding optimal solutions of multi-modal problems. Here, both prey and predators learn i…
Feeding Habits of Trisopterus minutus capelanus (Gadidae) Off the Eastern Coast of Spain (Western Mediterranean)
2001
. The stomach contents of poor cod, Trisopterus minutus capelanus (Lacepede), were taken at monthly intervals off the eastern coast of the Gulf of Valencia (Spain). A total of 1276 were analyzed to determine diet according to fish size and season. The basic food consists of crustaceans (Mysidacea and Decapoda) and teleosts. Feeding habits varied with size: decapods and fishes were more abundant in the stomachs of larger specimens. Little seasonal variation in food habits was recorded.
Diet of Risso's dolphin (<i>Grampus griseus</i>) in the western Mediterranean Sea
2006
The diet of Risso’s dolphin in the Mediterranean is described based on 15 animals stranded between 40°25’N 00°32’W and 37°35’N 00°45’E from April 1987 to January 2003. The prey were mainly oceanic cephalopods. Pelagic octopods, especially A. argo, were the most abundant (mean = 41.28%; SD±34.32). Species belonging to the families Ommastrephidae, Histioteuthidae and Onychoteuthidae were also frequent components of its diet. The bathymetric distribution of cephalopods shows that Risso’s dolphin preferentially feeds on the middle slope (600 to 800 m depth) in the Mediterranean.