The costs of moving for a diurnally cryptic araneid spider.
In orb web spiders that recycle webs and thus minimize the material
costs of web relocation, the characteristics of their temporal movement
patterns between web sites can be used to examine otherwise hidden
costs. Previous studies have shown that one such cost is the extra risk
from predation. An unusually long average residence time at web sites is
one indicator of cost. In some cases the pattern of movements also
appears to be indicative of high costs, similar to those experienced by
spiders that do not recycle web proteins. Nocturnal Poltys noblei Smith
2006 (Araneidae) spiders are heavily reliant on good camouflage in their
exposed daytime hiding positions. Thus the risk of moving to an unknown
site where the spider may not match its background may impose a large
cost on relocation. The temporal pattern and frequency of relocations of
P. noblei in northern Sydney are compared to those reported for other
orb web species. Poltys noblei,on average, is found to have a long
residence period, and the pattern of movement of larger individuals in
this species is found to be random. These data support the idea that
moving is costly for this species. Finally, the seasonal timing of
movements is examined for P. noblei. It is found that most spiders
relocate in spring but it is unknown if this is to seek a better web
site or for the spider to avoid predation.
Keywords: Web site tenacity, Poltys, seasonality, camouflage, material costs, predation
Spatial behavior in animals
Spiders (Physiological aspects)
Animal ecology (Research)
|Author:||Smith, Helen M.|
|Publication:||Name: Journal of Arachnology Publisher: American Arachnological Society Audience: Academic Format: Magazine/Journal Subject: Biological sciences; Zoology and wildlife conservation Copyright: COPYRIGHT 2009 American Arachnological Society ISSN: 0161-8202|
|Issue:||Date: Jan, 2009 Source Volume: 37 Source Issue: 1|
|Topic:||Event Code: 310 Science & research Canadian Subject Form: Animal spatial behaviour|
|Geographic:||Geographic Scope: Australia Geographic Code: 8AUST Australia|
Spiders have often been used as model organisms when examining
facets of predator-prey interactions and optimal foraging theory, both
as predators (e.g., Olive 1982; Janetos 1982a) and as prey (e.g.,
Rypstra 1984; Wise & Chen 1999). Web building spiders have
especially attracted the attention of researchers, in part because many
are relatively easy to find and work with in the field and in the
laboratory. Some rebuild all or part of their webs almost daily and so
have the potential to react quickly to applied stimuli. A variety of
models and ingenious measurement techniques have allowed researchers to
estimate aspects of the cost of web construction with respect to the
expenditure of silk and energy (e.g., Tanaka 1989; Nakata & Ushimaru
When a spider moves to a new web site there are potential costs from loss of hunting time, risks in entering an area of unknown quality with possible predators, as well as the costs in silk production and energy expenditure. For spiders that build materially expensive webs and do not recycle silk proteins, the high cost of silk and associated energy investment appears correlated to long web site residence times (Janetos 1982a; Tanaka 1989). In many orb web building species in the families Araneidae, Tetragnathidae, and Nephilidae ingestion of most of the web occurs before the spider moves away from a web site. The silk proteins, therefore, are largely recycled (Peakall 1971 in Janetos 1982a). This minimization of material costs has allowed researchers to focus on the other factors that affect orb web spiders' decisions to move, such as the effects of disturbance (e.g., Enders 1976) or prey abundance (McNett & Rypstra 1997). Two sources of information have most frequently been utilized: the temporal pattern of the movements and the frequency of relocation.
Temporal pattern of movements.--Janetos (1982a) showed that orb web building spiders with relatively low material costs of relocation may show 