Prey-capture strategies in sympatric web-building spiders

Abstract

Arthropods in several orders use traps to capture prey. Such trap-building predators expend most of their foraging energy prior to any prey contact. Nevertheless, relative investments in trap construction and actual prey capture may vary among trap builders, and they are likely to face a trade-off between building very effective but energetically costly traps and building less effective traps requiring faster reaction times when attacking prey. We analysed this trade-off in a field experiment by comparing the prey capture behaviour of four different sympatric web-building spiders (Araneae: Araneidae, Nephilidae, Tetragnathidae, Theridiidae) with the retention times of five different prey types in the webs of these spiders. Retention times differed greatly among webs and among prey types. The vertical orb webs retained prey longer than the horizontal orb web and the sheet web, and active prey escaped more quickly than less active prey. Among spiders with orb webs, the spider with the web that retained prey for the shortest time was the fastest to capture prey, thus confirming the expected trade-off between building long-retaining webs and attacking slowly versus building short-retaining webs and attacking more rapidly. The sheet web, however, neither retained prey for an appreciable period of time nor facilitated rapid prey capture. We suggest that this low capture effectiveness of sheet webs is compensated by their lower maintenance costs.

The hub as a launching platform: rapid movements of the spider Leucauge mariana (Araneae: Tetragnathidae) as it turns to attack prey

“…The median of the total time to reach the prey in L. mariana (time between prey impact and the spider's legs contacting the prey) was only 0.53 s; the minimum was 0.21 s. These are substantially quicker responses than the mean of about 1.5 s reported for a combination of L. mariana and L. venusta (Walckenaer 1842) by Zschokke et al (2006), perhaps because the prey in the present study were smaller (2.75 vs. mean of 14.4 mg in the Zschokke et al study) and thus elicited less cautious approaches. The responses of other species of orb weavers are in general slower, with means ranging from 1.7 to 8.7 s (Lubin 1973;Witt et al 1978;Zschokke et al 2006;R. Suter pers.…”

“…The angle she turned tended to be the minimum rather than the maximum needed (the leading leg I was more than twice as likely as the trailing leg I to grasp the correct radius), perhaps an additional feature designed to increase attack speed. In sum, we speculate that raw speed probably plays an important role in the predatory strategy of L. mariana (see also Zschokke et al 2006). This gives reason to analyze the leg movements that were used to turn at the hub in terms of their effects on the speed of the spider's turn.…”

“…Speed of turns.-Compared with the webs of many orb weavers, those of L. mariana probably retain prey relatively briefly (Zschokke et al 2006). Their orbs are relatively openmeshed, weak, and horizontal, and, compared with the spider's body size, have relatively small amounts of sticky material on sticky spiral lines (Opell 2002).…”

Upside-down spiders build upside-down orb webs: web asymmetry, spider orientation and running speed in Cyclosa

“…Because orb webs hold prey in most cases only temporarily (e.g. Eberhard 1986;Zschokke et al 2006), predation success will be lower if the spider takes more time to reach prey. This implies that the spider should shape its web and orient itself in such a way that the average time to reach the prey trapped anywhere in the web is minimized.…”

Attention focusing in a sit-and-wait forager: a spider controls its prey-detection ability in different web sectors by adjusting thread tension

“…Predation behaviour starts when the spider becomes aware of intercepted prey trapped in the web, and tries to locate it by plucking radii (Díaz-Fleischer 2005). When the prey is detected the spider moves to it and capture follows if the web retains the prey long enough; but the prey sometimes escapes before the spider reaches them (Zschokke et al 2006). Do orb-web spiders focus their attention on limited web areas when waiting for prey?…”