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Sat Nov 01 09:36:19 SAST 2014

Prey's nutritional value affects wolf spider foraging: study

Times LIVE | 09 November, 2012 08:18
A Wolf spider. File picture.
Image by: Valerius Geng/ Wikimedia Commons

Researchers have found that wolf spiders tend to kill more and leave more of their prey behind when fed highly nutritious flies.

The researchers, whose work can be read in the free online scientific journal PloS One, were interested in finding out if spiders modify how much they eat based on how nutritious their prey was.

In order to test this, they got a few female spiders from the Ecology Research Center at Miami University, Butler County, Ohio, and placed them in separate plastic containers.

They then cultured some vestigial-winged fruit flies.

"Studies have shown that Diptera are an important component in the diet of wolf spiders and the nutritional content of Diptera can vary substantially in the field. In addition, there is a well-established approach to altering the nutritional content of Drosophila by adjusting the media in which they are cultured and the resulting differences directly affect the growth, performance, and behaviour of Pardosa species," the researchers said.

They then set up three experiments, one where the spiders were fed on similar food for a few weeks before the tests, on in which the spiders had been fed with flies of differing quality for a few weeks, and one where the spiders could select between high quality and low quality flies

The spiders with similar nutritional histories killed about the same number of high quality flies as low quality, but they were more likely to leave a corpse with the high quality flies, according to the researchers.

The spiders who were fed on nutritious flies for a few weeks first, killed more flies than the ones that had been eating less nutritious flies.

When given a choice between flies, however, the spiders on a high quality diet surprised researchers.

"Surprisingly, wolf spiders were also able to discriminate between prey based solely on their nutrient content, which suggests that prey choice in field situations occurs on a finer scale than is typically considered."

"However, only spiders on the high quality diet selected among prey types and no parsimonious explanation would allow us to postulate that predator diet would shift their relative reliance on, or sensitivity to, prey activity while foraging," the researchers said.

"Our study demonstrates the need for a more explicit integration of prey nutritional composition and predator dietary history into the metrics of foraging, such as the functional response," the researchers concluded.

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