ORCID Profile
0000-0002-6715-7294
Current Organisations
University of Jyväskylä
,
University of Veterinary Medicine Vienna
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Publisher: Cold Spring Harbor Laboratory
Date: 29-05-2022
DOI: 10.1101/2022.05.28.493811
Abstract: Chemical defences often vary within and between populations both in quantity and quality, which is puzzling if prey survival is dependent on the strength of the defence. We investigated the within-and between-population variability in chemical defence of the wood tiger moth ( Arctia plantaginis ). The major components of its defences, SBMP (2-sec-butyl-3-methoxypyrazine) and IBMP (2-isobutyl-3-methoxypyrazine) are volatiles that deter bird attacks. We expected the variation to reflect populations’ predation pressures and early-life conditions. To understand the role of the methoxypyrazines, we experimentally manipulated synthetic SBMP and IBMP and tested the birds’ reactions. We found a considerable variation in methoxypyrazine amounts and composition, both from wild-caught and laboratory-raised male moths. In agreement with the “cost of defence” hypothesis, the moths raised in the laboratory had a higher amount of pyrazines. We found that SBMP is more effective at higher concentrations and that IBMP is more effective only in combination with SBMP and at lower concentrations. Our results fit findings from the wild: the amount of SBMP was higher in the populations with higher predation pressure. Altogether, this suggests that, regarding pyrazine concentration, more is not always better, and highlights the importance of testing the efficacy of chemical defence and its components with relevant predators, rather than relying only on results from chemical analyses.
Publisher: The Royal Society
Date: 06-2014
Abstract: Aposematic signal variation is a paradox: predators are better at learning and retaining the association between conspicuousness and unprofitability when signal variation is low. Movement patterns and variable colour patterns are linked in non-aposematic species: striped patterns generate illusions of altered speed and direction when moving linearly, affecting predators' tracking ability blotched patterns benefit instead from unpredictable pauses and random movement. We tested whether the extensive colour-pattern variation in an aposematic frog is linked to movement, and found that in iduals moving directionally and faster have more elongated patterns than in iduals moving randomly and slowly. This may help explain the paradox of polymorphic aposematism: variable warning signals may reduce protection, but predator defence might still be effective if specific behaviours are tuned to specific signals. The interacting effects of behavioural and morphological traits may be a key to the evolution of warning signals.
Publisher: Springer Science and Business Media LLC
Date: 22-06-2013
Publisher: Springer Science and Business Media LLC
Date: 07-05-2015
DOI: 10.1007/S10071-015-0874-0
Abstract: Several antipredator strategies are related to prey colouration. Some colour patterns can create visual illusions during movement (such as motion dazzle), making it difficult for a predator to capture moving prey successfully. Experimental evidence about motion dazzle, however, is still very scarce and comes only from studies using human predators capturing moving prey items in computer games. We tested a motion dazzle effect using for the first time natural predators (wild great tits, Parus major). We used artificial prey items bearing three different colour patterns: uniform brown (control), black with elongated yellow pattern and black with interrupted yellow pattern. The last two resembled colour patterns of the aposematic, polymorphic dart-poison frog Dendrobates tinctorius. We specifically tested whether an elongated colour pattern could create visual illusions when combined with straight movement. Our results, however, do not support this hypothesis. We found no differences in the number of successful attacks towards prey items with different patterns (elongated/interrupted) moving linearly. Nevertheless, both prey types were significantly more difficult to catch compared to the uniform brown prey, indicating that both colour patterns could provide some benefit for a moving in idual. Surprisingly, no effect of background (complex vs. plain) was found. This is the first experiment with moving prey showing that some colour patterns can affect avian predators' ability to capture moving prey, but the mechanisms lowering the capture rate are still poorly understood.
Publisher: University of Chicago Press
Date: 03-2009
DOI: 10.1086/596528
Abstract: Apostatic (frequency- or density-dependent) selection, aposematic signals, and mate choice behavior generally require that the mean prey or potential mate density m value be high enough (above a threshold T) to result in sufficient encounter rates for the searcher to learn or retain the association between conspicuous signals and prey unprofitability, to forage apostatically, or to choose among mates. This assumes that all searchers experience m >T, which implicitly assumes an even dispersion of targets among searcher territories. Uneven dispersion generates new phenomena. If m T) is greater than the increase in the percentage of territories that are favorable. The relationship is reversed when m >T. In both cases, because as few as 10% of the territories can contain 80% of the targets, only a few territory holders may account for most of the selection on most of the target population accidents of experience in only a few searchers can have unexpectedly large effects on the target population. This also provides an explanation for high searcher behavior variation (personalities): in iduals from favorable territories will behave differently in behavioral experiments than those from unfavorable territories, at least with respect to similar kinds of targets. These effects will generate spatial heterogeneity in natural and sexual selection in what are otherwise uniform environments.
Publisher: The Royal Society
Date: 09-2017
Abstract: Much of what we know about human colour perception has come from psychophysical studies conducted in tightly-controlled laboratory settings. An enduring challenge, however, lies in extrapolating this knowledge to the noisy conditions that characterize our actual visual experience. Here we combine statistical models of visual perception with empirical data to explore how chromatic (hue/saturation) and achromatic (luminant) information underpins the detection and classification of stimuli in a complex forest environment. The data best support a simple linear model of stimulus detection as an additive function of both luminance and saturation contrast. The strength of each predictor is modest yet consistent across gross variation in viewing conditions, which accords with expectation based upon general primate psychophysics. Our findings implicate simple visual cues in the guidance of perception amidst natural noise, and highlight the potential for informing human vision via a fusion between psychophysical modelling and real-world behaviour.
No related grants have been discovered for Bibiana Rojas.