Previous foraging success influences web building in the spider Stegodyphus lineatus (Eresidae) |
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Authors: | Pasquet Alain; Leborgne Raymond; Lubin Yael |
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Institution: | a
Laboratoire de Biologie et Physiologie du Comportement, URA CNRS n°1293,
UHP Nancy 1, B.P. 239, 54506 Vandoeuvre les Nancy Cedex, France,
b
Mitrani Center for Desert Ecology, Blaustein Institute for Desert Research,
Ben Gurion University, Sede Boker Campus, 84993 Israel |
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Abstract: | Stegodyphus lineatus (Eresidae) is a desert spider that buildsan
aerial capture web on bushes in the Negev desert in southernIsrael. Web
building for spiders is costly in energy, time,and risk of predation. Spiders
should trade-off these costswith the benefits in terms of prey capture. We
tested the hypothesisthat the previous foraging success of the spider
influencesthe effort invested in foraging. Specifically, we asked whetheran
increase in food intake causes spiders to reduce web renewalactivity and web
size. Alternatively, time constraints on foragingand development, resulting
from a short growing season, couldinduce spiders to continue foraging even
when supplemented withprey. The cost of web building was measured as time and
massloss. To build an average size web (about 150 cm2), we
calculatedthat a spider requires 6 h and that spiders lose 3%-7% of their
weight.In field experiments, spiders responded differently to food
supplementationin 2 different years. In 1994, they improved their condition
comparedto individuals whose webs were removed to reduce foraging
opportunitiesand compared to control spiders. In 1995, spiders tested earlier
inthe season than the previous year did not improve their conditionin
response to prey supplementation. Nonetheless, in both years,
food-supplementedspiders built significantly smaller webs than food-deprived
andcontrol spiders. This result was confirmed in a laboratory experiment
whereprey intake was controlled. We conclude that for S. lineatus
immediateforaging risks outweigh the potential time constraints on
foraging. |
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Keywords: | Eresidae food supplementation optimal foraging spiders Stegodyphus lineatus web building |
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