 at each site is depicted in Fig. 2. All spiders were used for the calculations, which therefore include movements due to conspecific interference.
Long-term observations of residence time.--The mean residence time for all spiders is 4.80 recording periods (40.75 days), SD = 5.57, n = 218. The longest recorded residence is 31 recording periods (approximately 263 days) (Fig. 3a). When Small and Large residence times are compared, the distribution of residence times is found to be significantly different between the two size classes (P = 0.012). The mean residence times are 3.77 sampling periods, (32 days), for Small spiders (SD = 4.51, n = 138), and 6.59 sampling periods (56 days), for Large spiders (SD = 6.69, n = 80). Most aggregated spiders were omitted in calculating these figures; hence movements due to conspecific interference are minimal.
The distribution of residence times of Small spiders is significantly different from the random hypothesis (0.05 > P > 0.025) (Fig. 3b). This is not the case for the Large spiders; the distribution of residency times for these is not significantly different from random (0.5 > P > 0.1) (Fig. 3c). For the complete data set see Smith 2006b.
Seasonality of spider relocations.--Summer and autumn are shown to be the peak seasons for beginning a period of residence (Table 2a); spring and summer are the peak seasons for leaving (Table 2b). Winter is a period of relatively low mobility, at least for spiders arriving into a new web site.
The average residence time of 24.9 nights for P. noblei (spiders of all instars) in the short-term observations is just slightly shorter than the residence time of adult females of Cyclosa octotuberculata Karsch 1879 (26.3 days, Nakata & Ushimaru 2004). The residence time of a wide variety of spiders is shown in Table 1 in order of increasing length, and both of these species fit in towards the bottom of the table, i.e. they have long average residence periods. The figures for Poltys were calculated in a similar way to the majority of the species shown here, from the rate of departure of spiders from web sites over several consecutive nights of observation. The major difference between the short-term results for Poltys and most of the other studies included here is the wide range of instars represented in the current studies and the inclusion of some spiders known to have experienced interactions with conspecifics. The overall figure from the long-term transects (all ages) is rather longer at 40.75 nights and is only second to the residence times of N. clavipes spiderlings among the silk recycling species in these examples. These Nephila were protected from predators in enclosures and provided with abundant prey, however, which is hardly a natural situation, and there are similar caveats for the long-term transect results for Poltys, discussed below. Nephila clavipes and P. noblei (Large spiders), have been shown to have an essentially random pattern of relocation from web sites (Vollrath & Houston 1986; Smith this paper); the pattern of relocation of the other orb web species at the bottom of the table has not been tested. These characteristics of long residence period and random relocation pattern suggest some hidden high cost of moving may be present for each species in comparison to the presumed freely moving spiders at the top of Table 1.
[FIGURE 2 OMITTED]
The risk of predation, or expenditure of energy associated with avoiding such a fate, has previously been suggested to be this hidden cost for the diurnal species with long residence periods. For Nephila there is a direct risk after relocating due to the lack of protection usually afforded by an extensive barrier web (labyrinth) at an established site (Vollrath 1985). In the case of C. octotuberculata, the spider hides among debris and egg sacs that are incorporated in a line across its web. The line of debris is taken by the spider when it relocates and although this protects the spider after arrival at a new site, carrying such a burden takes more energy and time (Nakata & Ushimaru 2004). In the s