Elsevier

Animal Behaviour

Volume 120, October 2016, Pages 115-121
Animal Behaviour

Cost of complex behaviour and its implications in antipredator defence in orb-web spiders

https://doi.org/10.1016/j.anbehav.2016.07.034Get rights and content

Highlights

  • We found time cost of complex behaviour in spider web building.

  • Thread-laying speed was lower in complex than simple webs.

  • We also found an ecological implication of complex behaviour.

  • Spiders built less complex webs after being exposed to predator stimuli.

  • Time cost of complex behaviour mediates food–safety trade-offs.

Complex behaviour may incur a cost. We assumed here that web-building behaviour for two species of orb-web spider, Cyclosa argenteoalba and Eriophora sagana, was more complex when their webs were asymmetric from top to bottom than when their webs were symmetric. The rationale for this assumption was that, while spiders have to adjust their spiral building behaviour in different web sectors to build asymmetric webs, they do not have to make these adjustments for symmetric webs. To estimate the costs involved in building more asymmetric webs, we measured the time taken for spiders to build orb-webs with various up-down size asymmetries and used this as a measure of the complexity of web-building behaviour. The results showed that the spiders required more time to lay the spiral threads as their webs became more asymmetric even when the length of spiral threads was the same, suggesting a time cost of processing complex information. Furthermore, we found that spiders built more symmetric webs when they perceived a risk of predation, perhaps to reduce the web-building time during which they are more vulnerable. This suggests that the cost of behavioural complexity may mediate the outcome of interspecific interactions and thus may be ecologically important.

Section snippets

Time Cost of Building Asymmetric Webs

We used Cyclosa argenteoalba to examine the effect of web asymmetry on the time required for laying the capture spirals. Cyclosa argenteoalba is a diurnal orb-web spider, which is common in suburbs and rural areas in Japan. Adult females are approximately 5–6 mm long and weigh 5–20 mg. The spider builds its web around dawn and collapses the web at the end of the day, rebuilding it on a daily basis. From 4 May to 7 August 2008, we collected C. argenteoalba adult females in and around the campus of

Time Cost of Building Asymmetric Webs

The coefficients of constrained regression were significantly positive for the spider weight and absolute value of AI, and significantly negative for observation date (Table 1). On average, the spider took 1860.2 s ± 600.5 SD to construct a capture spiral. While web asymmetry was significantly correlated with spiral spacing asymmetry (r49 = 0.579, N = 51, P < 0.001), the correlation between web asymmetry and the number of U-turns was not significant (r49 = 0.192, N = 51, P = 0.531).

Effect of Predator Cue on Web Asymmetry

In C. argenteoalba, the

Discussion

The observations of web-building behaviour of C. argenteoalba revealed that the time taken for capture spiral construction took longer when the web asymmetry was larger, the spider was heavier, the spiral length was longer and the observation was conducted earlier in the season (i.e. mean temperature was lower). The effects of spider weight, spiral length and observation date were not surprising because spiders have to move greater distances to lay longer spirals, heavy spiders move slower, and

Acknowledgments

We thank Chiharu Wako for her help in measuring web parameters. This work was partly supported by Japan Society for the Promotion of Science grants-in-aid for Scientific Research (C) (no. 20570025, 23570037, and 26440251).

References (35)

  • F. Vollrath

    Analysis and interpretation of orb spider exploration and web-building behaviour

    Advances in the Study of Behavior

    (1992)
  • B. Winkens et al.

    Randomized clinical trials with a pre- and a post-treatment measurement: Repeated measures versus ANCOVA models

    Contemporary Clinical Trials

    (2007)
  • A. ap Rhisiart et al.

    Design features of the orb web of the spider, Araneus diadematus

    Behavioral Ecology

    (1994)
  • E.A. Bernays et al.

    Specialists make faster decisions than generalists: Experiments with aphids

    Proceedings of the Royal Society B: Biological Sciences

    (1999)
  • L. Chittka et al.

    Visual search and the importance of time in complex decision making by bees

    Arthropod-Plant Interactions

    (2007)
  • J.L. Cloudsley-Thompson

    A review of the anti-predator devices of spiders

    Bulletin of the British Arachnological Society

    (1995)
  • W.G. Eberhard

    A new view of orb webs: Multiple trap designs in a single structure

    Biological Journal of the Linnean Society

    (2014)
  • Cited by (0)

    View full text