Do predator energy demands or previous exposure influence protection by aposematic coloration of prey?

2017

Petr Veselý, Barbora Ernestová, Oldřich Nedvěd, Roman Fuchs

DOI: 10.1093/cz/zow057


Abstract: Growing evidence exists that aposematic and toxic prey may be included in a predator’s diet when the predator experiences physiological stress. The tree sparrow Passer montanus is known to have a significant portion of aposematic and toxic ladybirds in its natural diet. Here, we present experiments testing the attack and eating rate of the tree sparrow toward the invasive aposematic harlequin ladybird Harmonia axyridis. We wondered whether the sparrow’s ability to prey on native ladybirds predisposes them to also prey on harlequin ladybirds. We compared the attack and eating rates of tree sparrows of particular age and/or experience classes to test for any changes during ontogeny (hand-reared × young wild-caught ×adult wild-caught) and with differing perceived levels of physiological stress (summer adult × winter adult). Winter adult tree sparrows commonly attacked and ate the offered ladybirds with no evidence of disgust or metabolic difficulties after ingestion. Naïve and wild immature tree sparrows attacked the ladybirds but hesitated to eat them. Adult tree sparrows caught in the summer avoided attacking the ladybirds. These results suggest that tree sparrows are able to cope with chemicals ingested along with the ladybirds. This pre-adaptation enables them to include ladybirds in their diet; though they commonly do this only in times of shortage in insect availability (winter). Young sparrows showed avoidance toward the chemical protection of the ladybirds.


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Five species of passerine bird differ in their ability to detect Batesian mimics

2016

Alena Turini, Petr Veselý, Roman Fuchs

DOI: 10.1111/bij.12708


Abstract:

Multiple predators affect the evolution of aposematic signals in nature and these predators may substantially differ in terms of ecological and cognitive parameters. However, most experimental studies testing the evolution of Batesian mimics use only a single species of predator (usually the great tit or a domestic chick). Therefore, in the present study, we experimentally tested the responses of five passerine predators to an artificially made Batesian mimic (a cockroach equipped with the warning pattern of the red firebug) with respect to their dietary ecology. Half of the individuals of each species were fed on unmodified roaches before the experiment, whereas the other half were fed with mealworms and thus had no previous experience with roaches. We found that Batesian mimics were better protected than inconspicuous prey against inexperienced great tits and robins alone. The other three bird species showed high level of neophobia; therefore, the effect of warning coloration could not be assessed. We also found that experienced birds attacked a greater number of Batesian mimics compared to inexperienced individuals of all tested species, with the exception of blackcaps. In the great tits, robins, and blue tits, a significant number of experienced birds attacked the Batesian mimic, which was possibly the result of a learned search image for a roach. Our results suggest that using a limited array of predators to describe evolutionary processes forming the diversity of antipredatory strategies of the prey may be biased and need not describe the situation occurring in nature.


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Low Ability of Great Tits to Discriminate Similarly Inconspicuous Edible and Inedible Prey

2016

Zuzana Karlíková, Petr Veselý, Jana Beránková, Roman Fuchs

DOI: 10.1111/eth.12454


Abstract:

Numerous studies have shown warning coloration to facilitate the discrimination of edible and inedible prey. However, inedible insect species may possess cryptic coloration as well. It has been shown that some other visual features (especially characteristic body shape) are sufficient for the recognition of some insect taxa (e.g. ladybirds, ants, wasps). We tested the ability of wild-caught great tits (Parus major) to discriminate between the identically coloured edible (roach – Blaptica dubia) and the inedible (firebug – Pyrrhocoris apterus) as prey according to subtle peripheral visual traits (shape of legs and antennae, body posture, and means of locomotion). Both prey species were offered either simultaneously or alternately. The ability of the birds to learn was tested by means of fourteen trial repetitions in two sessions. In general, great tits were not able to learn to discriminate between firebugs and roaches by subtle shape cues alone during the two sessions. However, multivariate analysis of individual bird behaviour showed that they adopted one of three different attitudes to the presented prey. Most of the birds never attacked any or always attacked both prey. In addition, a small proportion of the birds was able to discriminate between the two prey types and attacked only roaches. Nevertheless, firebugs survived most of the attacks, which suggests that in case of chemically protected prey, the evolution of conspicuous coloration is not always the best/only option.


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