Search results for "Predator"
showing 10 items of 349 documents
Fishless-stream mayflies express behavioural flexibility in response to predatory fish
1996
The fish avoidance behaviour of nymphs of the grazing mayfly Baetis rhodani (Ephemerop- tera) was examined. The nymphs originated from a fishless stream. To study their responses to the addition of predator cues, nymphs were exposed to (1) chemical cues from a caged fish, or (2) a freely moving diurnal fish (European minnow, Phoxinus phoxinus). The nymphs immediately increased their refuge use when exposed to a live fish, whereas chemical cues alone did not cause any avoidance responses. In a second experiment, the eVects of (1) fish chemicals and (2) a fish model plus fish chemicals on the diel refuge use patterns of Baetis nymphs were examined. In the presence of a fish model, more nymphs…
Can large branchiopods shape microcrustacean communities in Mediterranean temporary wetlands?
2011
It was recently suggested that large branchiopods may play a keystone role in temporary aquatic habitats. Using a microcosm experiment manipulating microcrustacean communities of Mediterranean temporary wetlands (Camargue, Southern France), we tested the following hypotheses: (i) large branchiopods (the notostracan Triops cancriformis and the anostracan Chirocephalus diaphanus) can limit microcrustacean densities through both competition and predation; (ii) notostracans create high suspended-matter concentrations through bioturbation, which can negatively impact microcrustaceans; and (iii) the outcome of these biotic interactions is more detrimental at high salinities. We found a strong pr…
Behavioural responses of voles to simulated risk of predation by a native and an alien mustelid: an odour manipulation experiment
2010
Context. Potential mammalian prey commonly use the odours of their co-evolved predators to manage their risks of predation. But when the risk comes from an unknown source of predation, odours might not be perceived as dangerous, and anti-predator responses may fail, except possibly if the alien predator is of the same archetype as a native predator. Aims. In the present study we examined anti-predator behavioural responses of voles from the outer archipelagos of the Baltic Sea, south-western Finland, where they have had no resident mammalian predators in recent history. Methods. We investigated responses of field voles (Microtus agrestis) to odours of native least weasels (Mustela nivalis)…
UV reflecting vole scent marks attract a passerine, the great grey shrike Lanius excubitor
2002
Diurnal raptors have been shown to use ultraviolet vision and UV-reflecting vole scent marks to find suitable hunting areas. We studied if a passerine species, the great grey shrike Lanius excubitor that uses voles as its primary food, may also detect prey-patches in the same way. We conducted a laboratory experiment with ten shrikes. Each individual shrike had four options to choose from: (1) scent marks with UV light, (2) scent marks without UV light, (3) clean arena with UV light, and (4) clean arena without UV light. The birds preferred the scent-marked arena with UV light as measured by the number of scans and the time spent above it. Therefore, we suggest that great grey shrike probab…
The role of lantern fish (Myctophidae) in the life-cycle of cetacean parasites from western Mediterranean waters
2015
Myctophids (lantern fish) and cephalopods play a key role in trophic webs from the continental slope and oceanic waters linking the zooplankton to top predators. Many cetaceans feed on both lantern fish and cephalopods, and such prey would thus be expected to bridge the trophic gap in the life-cycles of helminths infecting cetaceans. However, information on the life-cycles of most of these helminths is extremely scanty. We examined the parasite fauna of myctophids and cephalopods in two areas from the western Mediterranean where at least 21 helminth taxa from cetaceans have been reported and both cetacean diversity and abundance is high. A total of 1012 individuals of 8 lantern fish species…
THERMOREGULATION CONSTRAINS EFFECTIVE WARNING SIGNAL EXPRESSION
2009
Evolution of conspicuous signals may be constrained if animal coloration has nonsignaling as well as signaling functions. In aposematic wood tiger moth (Parasemia plantaginis) larvae, the size of a warning signal (orange patch on black body) varies phenotypically and genetically. Although a large warning signal is favored as an antipredator defense, we hypothesized that thermoregulation may constrain the signal size in colder habitats. To test this hypothesis, we conducted a factorial rearing experiment with two selection lines for larval coloration (small and large signal) and with two temperature manipulations (high and low temperature environment). Temperature constrained the size and br…
Life-history constraints and warning signal expression in an arctiid moth
2007
Summary 1 Traditionally, large pattern elements in conspicuous warning signals are assumed to be selected by predation because increasing signal strength enhances education and avoidance of predators. However, variation in the colour pattern of a warningly coloured species often exists even within a location, and many warning signals have relatively small pattern elements. This suggests that there must be opposing selection pressures that can constrain warning signal expression, resulting in variation in warning signals as well as suboptimal signals for predator education. 2 We quantified the variation in the warning signal of Parasemia plantaginis-moth larvae. With a full-sib rearing exper…
Responses of microbial-feeding nematodes to organic matter distribution and predation in experimental soil habitat
2001
Abstract Soils are spatially heterogeneous environments, a condition which is likely to affect the structure and function of soil food webs. To study the influence of soil organic matter distribution on decomposer food webs, we established microcosms that contained either: (1) large patches of initially sterile humus-litter mixture placed within sterile sand matrix (creating a large-patch habitat; LPH); or (2) blend of sand and humus-litter mixture (creating a small-patch habitat; SPH). Ten species of bacteria and ten species of fungi, and two bacterial-feeding ( Acrobeloides tricornis , Caenorhabditis elegans ) and two fungal-feeding ( Aphelenchus avenae , Aphelenchoides sp.) nematodes wer…
Modelling the evolution of cognitive styles.
2019
Abstract Individuals consistently differ in behaviour, exhibiting so-called personalities. In many species, individuals differ also in their cognitive abilities. When personalities and cognitive abilities occur in distinct combinations, they can be described as ‘cognitive styles’. Both empirical and theoretical investigations produced contradicting or mixed results regarding the complex interplay between cognitive styles and environmental conditions. Here we use individual-based simulations to show that, under just slightly different environmental conditions, different cognitive styles exist and under a variety of conditions, can also co-exist. Co-existences are based on individual speciali…
Predator mimicry, not conspicuousness, explains the efficacy of butterfly eyespots
2015
Large conspicuous eyespots on butterfly wings have been shown to deter predators. This has been traditionally explained by mimicry of vertebrate eyes, but recently the classic eye-mimicry hypothesis has been challenged. It is proposed that the conspicuousness of the eyespot, not mimicry, is what causes aversion due to sensory biases, neophobia or sensory overloads. We conducted an experiment to directly test whether the eye-mimicry or the conspicuousness hypothesis better explain eyespot efficacy. We used great tits ( Parus major ) as model predator, and tested their reaction towards animated images on a computer display. Birds were tested against images of butterflies without eyespots, wi…