- Unidirectional and transitive predatory relationships of spider species in one-on-one encounters (Arachnida; Araneae)
- Nieuwsbrief Spined
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- Faculty of Science (FNWI)
- Swammerdam Institute for Life Sciences (SILS)
Inter-specific predation (‘inter-specific araneophagy’) among spiders is very common in the field.
We investigated the transitivity (defined hereafter) of inter-specific predatory dominance relationships among 60 spider species belonging to 16 families in the laboratory in one-on-one encounters between specimens of unlike species (dyads). Inter-specific predatory dominance (killing-dominance) of one over another species was only assigned if the killing specimen was smaller than the killed specimen (smaller prosoma and shorter and thinner first legs of the killing than of the killed specimen, while disregarding opisthosoma (abdomen) size). The transitivity of predatory-dominance-relationships was statistically significant (as demonstrated in our earlier study on much fewer species). The definition of transitivity of dominance relationships among three different species is that species A shows dominance over species C if A is dominant over B and B dominant over C.
The inter-specific dominance (predatory) relationships were not only significantly transitive, but also significantly unidirectional (as in the pioneer studies of the ‘peck-right’ order among individuals of the same species in fowl and fish groups).
An example of an unidirectional killing(predatory)dominance-relationship between two different species is that smaller specimens of species A have the power to kill larger specimens of species B, whereas smaller specimens of species B cannot kill larger specimens of species A (definition of unidirectionality in the case of only two involved species). We are not aware of published accounts on the statistical significance of the unidirectionality of the inter-specific predatory relationships among spiders in the field or in the laboratory.
Highly-killing-dominant species of spiders showed shorter killing(predation)-latency times than less dominant species in the laboratory. Hence, the high dominance of a particular species could be predicted from its short killing-latency-time.
The stickiness of the spin-threads, some predatory techniques (with or without using threads and/or wrapping up of the prey), and morpholgical characteristics of the legs are discussed in an attempt to explain the high dominance of a few of the highly dominant investigated species.
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